1 | =head1 NAME
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2 |
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3 | perlxs - XS language reference manual
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4 |
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5 | =head1 DESCRIPTION
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6 |
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7 | =head2 Introduction
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8 |
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9 | XS is an interface description file format used to create an extension
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10 | interface between Perl and C code (or a C library) which one wishes
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11 | to use with Perl. The XS interface is combined with the library to
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12 | create a new library which can then be either dynamically loaded
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13 | or statically linked into perl. The XS interface description is
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14 | written in the XS language and is the core component of the Perl
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15 | extension interface.
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16 |
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17 | An B<XSUB> forms the basic unit of the XS interface. After compilation
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18 | by the B<xsubpp> compiler, each XSUB amounts to a C function definition
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19 | which will provide the glue between Perl calling conventions and C
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20 | calling conventions.
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21 |
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22 | The glue code pulls the arguments from the Perl stack, converts these
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23 | Perl values to the formats expected by a C function, call this C function,
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24 | transfers the return values of the C function back to Perl.
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25 | Return values here may be a conventional C return value or any C
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26 | function arguments that may serve as output parameters. These return
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27 | values may be passed back to Perl either by putting them on the
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28 | Perl stack, or by modifying the arguments supplied from the Perl side.
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29 |
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30 | The above is a somewhat simplified view of what really happens. Since
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31 | Perl allows more flexible calling conventions than C, XSUBs may do much
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32 | more in practice, such as checking input parameters for validity,
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33 | throwing exceptions (or returning undef/empty list) if the return value
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34 | from the C function indicates failure, calling different C functions
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35 | based on numbers and types of the arguments, providing an object-oriented
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36 | interface, etc.
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37 |
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38 | Of course, one could write such glue code directly in C. However, this
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39 | would be a tedious task, especially if one needs to write glue for
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40 | multiple C functions, and/or one is not familiar enough with the Perl
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41 | stack discipline and other such arcana. XS comes to the rescue here:
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42 | instead of writing this glue C code in long-hand, one can write
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43 | a more concise short-hand I<description> of what should be done by
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44 | the glue, and let the XS compiler B<xsubpp> handle the rest.
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45 |
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46 | The XS language allows one to describe the mapping between how the C
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47 | routine is used, and how the corresponding Perl routine is used. It
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48 | also allows creation of Perl routines which are directly translated to
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49 | C code and which are not related to a pre-existing C function. In cases
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50 | when the C interface coincides with the Perl interface, the XSUB
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51 | declaration is almost identical to a declaration of a C function (in K&R
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52 | style). In such circumstances, there is another tool called C<h2xs>
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53 | that is able to translate an entire C header file into a corresponding
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54 | XS file that will provide glue to the functions/macros described in
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55 | the header file.
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56 |
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57 | The XS compiler is called B<xsubpp>. This compiler creates
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58 | the constructs necessary to let an XSUB manipulate Perl values, and
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59 | creates the glue necessary to let Perl call the XSUB. The compiler
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60 | uses B<typemaps> to determine how to map C function parameters
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61 | and output values to Perl values and back. The default typemap
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62 | (which comes with Perl) handles many common C types. A supplementary
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63 | typemap may also be needed to handle any special structures and types
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64 | for the library being linked.
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65 |
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66 | A file in XS format starts with a C language section which goes until the
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67 | first C<MODULE =Z<>> directive. Other XS directives and XSUB definitions
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68 | may follow this line. The "language" used in this part of the file
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69 | is usually referred to as the XS language. B<xsubpp> recognizes and
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70 | skips POD (see L<perlpod>) in both the C and XS language sections, which
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71 | allows the XS file to contain embedded documentation.
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72 |
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73 | See L<perlxstut> for a tutorial on the whole extension creation process.
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74 |
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75 | Note: For some extensions, Dave Beazley's SWIG system may provide a
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76 | significantly more convenient mechanism for creating the extension
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77 | glue code. See http://www.swig.org/ for more information.
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78 |
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79 | =head2 On The Road
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80 |
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81 | Many of the examples which follow will concentrate on creating an interface
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82 | between Perl and the ONC+ RPC bind library functions. The rpcb_gettime()
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83 | function is used to demonstrate many features of the XS language. This
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84 | function has two parameters; the first is an input parameter and the second
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85 | is an output parameter. The function also returns a status value.
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86 |
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87 | bool_t rpcb_gettime(const char *host, time_t *timep);
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88 |
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89 | From C this function will be called with the following
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90 | statements.
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91 |
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92 | #include <rpc/rpc.h>
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93 | bool_t status;
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94 | time_t timep;
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95 | status = rpcb_gettime( "localhost", &timep );
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96 |
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97 | If an XSUB is created to offer a direct translation between this function
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98 | and Perl, then this XSUB will be used from Perl with the following code.
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99 | The $status and $timep variables will contain the output of the function.
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100 |
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101 | use RPC;
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102 | $status = rpcb_gettime( "localhost", $timep );
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103 |
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104 | The following XS file shows an XS subroutine, or XSUB, which
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105 | demonstrates one possible interface to the rpcb_gettime()
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106 | function. This XSUB represents a direct translation between
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107 | C and Perl and so preserves the interface even from Perl.
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108 | This XSUB will be invoked from Perl with the usage shown
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109 | above. Note that the first three #include statements, for
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110 | C<EXTERN.h>, C<perl.h>, and C<XSUB.h>, will always be present at the
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111 | beginning of an XS file. This approach and others will be
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112 | expanded later in this document.
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113 |
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114 | #include "EXTERN.h"
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115 | #include "perl.h"
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116 | #include "XSUB.h"
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117 | #include <rpc/rpc.h>
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118 |
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119 | MODULE = RPC PACKAGE = RPC
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120 |
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121 | bool_t
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122 | rpcb_gettime(host,timep)
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123 | char *host
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124 | time_t &timep
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125 | OUTPUT:
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126 | timep
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127 |
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128 | Any extension to Perl, including those containing XSUBs,
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129 | should have a Perl module to serve as the bootstrap which
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130 | pulls the extension into Perl. This module will export the
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131 | extension's functions and variables to the Perl program and
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132 | will cause the extension's XSUBs to be linked into Perl.
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133 | The following module will be used for most of the examples
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134 | in this document and should be used from Perl with the C<use>
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135 | command as shown earlier. Perl modules are explained in
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136 | more detail later in this document.
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137 |
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138 | package RPC;
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139 |
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140 | require Exporter;
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141 | require DynaLoader;
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142 | @ISA = qw(Exporter DynaLoader);
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143 | @EXPORT = qw( rpcb_gettime );
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144 |
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145 | bootstrap RPC;
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146 | 1;
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147 |
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148 | Throughout this document a variety of interfaces to the rpcb_gettime()
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149 | XSUB will be explored. The XSUBs will take their parameters in different
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150 | orders or will take different numbers of parameters. In each case the
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151 | XSUB is an abstraction between Perl and the real C rpcb_gettime()
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152 | function, and the XSUB must always ensure that the real rpcb_gettime()
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153 | function is called with the correct parameters. This abstraction will
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154 | allow the programmer to create a more Perl-like interface to the C
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155 | function.
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156 |
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157 | =head2 The Anatomy of an XSUB
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158 |
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159 | The simplest XSUBs consist of 3 parts: a description of the return
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160 | value, the name of the XSUB routine and the names of its arguments,
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161 | and a description of types or formats of the arguments.
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162 |
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163 | The following XSUB allows a Perl program to access a C library function
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164 | called sin(). The XSUB will imitate the C function which takes a single
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165 | argument and returns a single value.
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166 |
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167 | double
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168 | sin(x)
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169 | double x
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170 |
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171 | Optionally, one can merge the description of types and the list of
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172 | argument names, rewriting this as
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173 |
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174 | double
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175 | sin(double x)
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176 |
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177 | This makes this XSUB look similar to an ANSI C declaration. An optional
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178 | semicolon is allowed after the argument list, as in
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179 |
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180 | double
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181 | sin(double x);
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182 |
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183 | Parameters with C pointer types can have different semantic: C functions
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184 | with similar declarations
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185 |
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186 | bool string_looks_as_a_number(char *s);
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187 | bool make_char_uppercase(char *c);
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188 |
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189 | are used in absolutely incompatible manner. Parameters to these functions
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190 | could be described B<xsubpp> like this:
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191 |
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192 | char * s
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193 | char &c
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194 |
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195 | Both these XS declarations correspond to the C<char*> C type, but they have
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196 | different semantics, see L<"The & Unary Operator">.
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197 |
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198 | It is convenient to think that the indirection operator
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199 | C<*> should be considered as a part of the type and the address operator C<&>
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200 | should be considered part of the variable. See L<"The Typemap">
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201 | for more info about handling qualifiers and unary operators in C types.
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202 |
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203 | The function name and the return type must be placed on
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204 | separate lines and should be flush left-adjusted.
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205 |
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206 | INCORRECT CORRECT
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207 |
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208 | double sin(x) double
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209 | double x sin(x)
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210 | double x
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211 |
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212 | The rest of the function description may be indented or left-adjusted. The
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213 | following example shows a function with its body left-adjusted. Most
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214 | examples in this document will indent the body for better readability.
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215 |
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216 | CORRECT
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217 |
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218 | double
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219 | sin(x)
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220 | double x
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221 |
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222 | More complicated XSUBs may contain many other sections. Each section of
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223 | an XSUB starts with the corresponding keyword, such as INIT: or CLEANUP:.
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224 | However, the first two lines of an XSUB always contain the same data:
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225 | descriptions of the return type and the names of the function and its
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226 | parameters. Whatever immediately follows these is considered to be
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227 | an INPUT: section unless explicitly marked with another keyword.
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228 | (See L<The INPUT: Keyword>.)
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229 |
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230 | An XSUB section continues until another section-start keyword is found.
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231 |
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232 | =head2 The Argument Stack
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233 |
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234 | The Perl argument stack is used to store the values which are
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235 | sent as parameters to the XSUB and to store the XSUB's
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236 | return value(s). In reality all Perl functions (including non-XSUB
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237 | ones) keep their values on this stack all the same time, each limited
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238 | to its own range of positions on the stack. In this document the
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239 | first position on that stack which belongs to the active
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240 | function will be referred to as position 0 for that function.
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241 |
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242 | XSUBs refer to their stack arguments with the macro B<ST(x)>, where I<x>
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243 | refers to a position in this XSUB's part of the stack. Position 0 for that
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244 | function would be known to the XSUB as ST(0). The XSUB's incoming
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245 | parameters and outgoing return values always begin at ST(0). For many
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246 | simple cases the B<xsubpp> compiler will generate the code necessary to
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247 | handle the argument stack by embedding code fragments found in the
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248 | typemaps. In more complex cases the programmer must supply the code.
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249 |
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250 | =head2 The RETVAL Variable
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251 |
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252 | The RETVAL variable is a special C variable that is declared automatically
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253 | for you. The C type of RETVAL matches the return type of the C library
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254 | function. The B<xsubpp> compiler will declare this variable in each XSUB
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255 | with non-C<void> return type. By default the generated C function
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256 | will use RETVAL to hold the return value of the C library function being
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257 | called. In simple cases the value of RETVAL will be placed in ST(0) of
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258 | the argument stack where it can be received by Perl as the return value
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259 | of the XSUB.
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260 |
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261 | If the XSUB has a return type of C<void> then the compiler will
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262 | not declare a RETVAL variable for that function. When using
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263 | a PPCODE: section no manipulation of the RETVAL variable is required, the
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264 | section may use direct stack manipulation to place output values on the stack.
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265 |
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266 | If PPCODE: directive is not used, C<void> return value should be used
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267 | only for subroutines which do not return a value, I<even if> CODE:
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268 | directive is used which sets ST(0) explicitly.
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269 |
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270 | Older versions of this document recommended to use C<void> return
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271 | value in such cases. It was discovered that this could lead to
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272 | segfaults in cases when XSUB was I<truly> C<void>. This practice is
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273 | now deprecated, and may be not supported at some future version. Use
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274 | the return value C<SV *> in such cases. (Currently C<xsubpp> contains
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275 | some heuristic code which tries to disambiguate between "truly-void"
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276 | and "old-practice-declared-as-void" functions. Hence your code is at
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277 | mercy of this heuristics unless you use C<SV *> as return value.)
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278 |
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279 | =head2 Returning SVs, AVs and HVs through RETVAL
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280 |
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281 | When you're using RETVAL to return an C<SV *>, there's some magic
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282 | going on behind the scenes that should be mentioned. When you're
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283 | manipulating the argument stack using the ST(x) macro, for example,
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284 | you usually have to pay special attention to reference counts. (For
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285 | more about reference counts, see L<perlguts>.) To make your life
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286 | easier, the typemap file automatically makes C<RETVAL> mortal when
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287 | you're returning an C<SV *>. Thus, the following two XSUBs are more
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288 | or less equivalent:
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289 |
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290 | void
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291 | alpha()
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292 | PPCODE:
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293 | ST(0) = newSVpv("Hello World",0);
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294 | sv_2mortal(ST(0));
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295 | XSRETURN(1);
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296 |
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297 | SV *
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298 | beta()
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299 | CODE:
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300 | RETVAL = newSVpv("Hello World",0);
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301 | OUTPUT:
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302 | RETVAL
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303 |
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304 | This is quite useful as it usually improves readability. While
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305 | this works fine for an C<SV *>, it's unfortunately not as easy
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306 | to have C<AV *> or C<HV *> as a return value. You I<should> be
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307 | able to write:
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308 |
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309 | AV *
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310 | array()
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311 | CODE:
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312 | RETVAL = newAV();
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313 | /* do something with RETVAL */
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314 | OUTPUT:
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315 | RETVAL
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316 |
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317 | But due to an unfixable bug (fixing it would break lots of existing
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318 | CPAN modules) in the typemap file, the reference count of the C<AV *>
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319 | is not properly decremented. Thus, the above XSUB would leak memory
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320 | whenever it is being called. The same problem exists for C<HV *>.
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321 |
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322 | When you're returning an C<AV *> or a C<HV *>, you have make sure
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323 | their reference count is decremented by making the AV or HV mortal:
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324 |
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325 | AV *
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326 | array()
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327 | CODE:
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328 | RETVAL = newAV();
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329 | sv_2mortal((SV*)RETVAL);
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330 | /* do something with RETVAL */
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331 | OUTPUT:
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332 | RETVAL
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333 |
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334 | And also remember that you don't have to do this for an C<SV *>.
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335 |
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336 | =head2 The MODULE Keyword
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337 |
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338 | The MODULE keyword is used to start the XS code and to specify the package
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339 | of the functions which are being defined. All text preceding the first
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340 | MODULE keyword is considered C code and is passed through to the output with
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341 | POD stripped, but otherwise untouched. Every XS module will have a
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342 | bootstrap function which is used to hook the XSUBs into Perl. The package
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343 | name of this bootstrap function will match the value of the last MODULE
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344 | statement in the XS source files. The value of MODULE should always remain
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345 | constant within the same XS file, though this is not required.
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346 |
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347 | The following example will start the XS code and will place
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348 | all functions in a package named RPC.
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349 |
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350 | MODULE = RPC
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351 |
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352 | =head2 The PACKAGE Keyword
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353 |
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354 | When functions within an XS source file must be separated into packages
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355 | the PACKAGE keyword should be used. This keyword is used with the MODULE
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356 | keyword and must follow immediately after it when used.
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357 |
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358 | MODULE = RPC PACKAGE = RPC
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359 |
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360 | [ XS code in package RPC ]
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361 |
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362 | MODULE = RPC PACKAGE = RPCB
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363 |
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364 | [ XS code in package RPCB ]
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365 |
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366 | MODULE = RPC PACKAGE = RPC
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367 |
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368 | [ XS code in package RPC ]
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369 |
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370 | The same package name can be used more than once, allowing for
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371 | non-contiguous code. This is useful if you have a stronger ordering
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372 | principle than package names.
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373 |
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374 | Although this keyword is optional and in some cases provides redundant
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375 | information it should always be used. This keyword will ensure that the
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376 | XSUBs appear in the desired package.
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377 |
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378 | =head2 The PREFIX Keyword
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379 |
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380 | The PREFIX keyword designates prefixes which should be
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381 | removed from the Perl function names. If the C function is
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382 | C<rpcb_gettime()> and the PREFIX value is C<rpcb_> then Perl will
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383 | see this function as C<gettime()>.
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384 |
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385 | This keyword should follow the PACKAGE keyword when used.
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386 | If PACKAGE is not used then PREFIX should follow the MODULE
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387 | keyword.
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388 |
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389 | MODULE = RPC PREFIX = rpc_
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390 |
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391 | MODULE = RPC PACKAGE = RPCB PREFIX = rpcb_
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392 |
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393 | =head2 The OUTPUT: Keyword
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394 |
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395 | The OUTPUT: keyword indicates that certain function parameters should be
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396 | updated (new values made visible to Perl) when the XSUB terminates or that
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397 | certain values should be returned to the calling Perl function. For
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398 | simple functions which have no CODE: or PPCODE: section,
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399 | such as the sin() function above, the RETVAL variable is
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400 | automatically designated as an output value. For more complex functions
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401 | the B<xsubpp> compiler will need help to determine which variables are output
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402 | variables.
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403 |
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404 | This keyword will normally be used to complement the CODE: keyword.
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405 | The RETVAL variable is not recognized as an output variable when the
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406 | CODE: keyword is present. The OUTPUT: keyword is used in this
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407 | situation to tell the compiler that RETVAL really is an output
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408 | variable.
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409 |
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410 | The OUTPUT: keyword can also be used to indicate that function parameters
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411 | are output variables. This may be necessary when a parameter has been
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412 | modified within the function and the programmer would like the update to
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413 | be seen by Perl.
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414 |
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415 | bool_t
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416 | rpcb_gettime(host,timep)
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417 | char *host
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418 | time_t &timep
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419 | OUTPUT:
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420 | timep
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421 |
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422 | The OUTPUT: keyword will also allow an output parameter to
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423 | be mapped to a matching piece of code rather than to a
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424 | typemap.
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425 |
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426 | bool_t
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427 | rpcb_gettime(host,timep)
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428 | char *host
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429 | time_t &timep
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430 | OUTPUT:
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431 | timep sv_setnv(ST(1), (double)timep);
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432 |
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433 | B<xsubpp> emits an automatic C<SvSETMAGIC()> for all parameters in the
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434 | OUTPUT section of the XSUB, except RETVAL. This is the usually desired
|
---|
435 | behavior, as it takes care of properly invoking 'set' magic on output
|
---|
436 | parameters (needed for hash or array element parameters that must be
|
---|
437 | created if they didn't exist). If for some reason, this behavior is
|
---|
438 | not desired, the OUTPUT section may contain a C<SETMAGIC: DISABLE> line
|
---|
439 | to disable it for the remainder of the parameters in the OUTPUT section.
|
---|
440 | Likewise, C<SETMAGIC: ENABLE> can be used to reenable it for the
|
---|
441 | remainder of the OUTPUT section. See L<perlguts> for more details
|
---|
442 | about 'set' magic.
|
---|
443 |
|
---|
444 | =head2 The NO_OUTPUT Keyword
|
---|
445 |
|
---|
446 | The NO_OUTPUT can be placed as the first token of the XSUB. This keyword
|
---|
447 | indicates that while the C subroutine we provide an interface to has
|
---|
448 | a non-C<void> return type, the return value of this C subroutine should not
|
---|
449 | be returned from the generated Perl subroutine.
|
---|
450 |
|
---|
451 | With this keyword present L<The RETVAL Variable> is created, and in the
|
---|
452 | generated call to the subroutine this variable is assigned to, but the value
|
---|
453 | of this variable is not going to be used in the auto-generated code.
|
---|
454 |
|
---|
455 | This keyword makes sense only if C<RETVAL> is going to be accessed by the
|
---|
456 | user-supplied code. It is especially useful to make a function interface
|
---|
457 | more Perl-like, especially when the C return value is just an error condition
|
---|
458 | indicator. For example,
|
---|
459 |
|
---|
460 | NO_OUTPUT int
|
---|
461 | delete_file(char *name)
|
---|
462 | POSTCALL:
|
---|
463 | if (RETVAL != 0)
|
---|
464 | croak("Error %d while deleting file '%s'", RETVAL, name);
|
---|
465 |
|
---|
466 | Here the generated XS function returns nothing on success, and will die()
|
---|
467 | with a meaningful error message on error.
|
---|
468 |
|
---|
469 | =head2 The CODE: Keyword
|
---|
470 |
|
---|
471 | This keyword is used in more complicated XSUBs which require
|
---|
472 | special handling for the C function. The RETVAL variable is
|
---|
473 | still declared, but it will not be returned unless it is specified
|
---|
474 | in the OUTPUT: section.
|
---|
475 |
|
---|
476 | The following XSUB is for a C function which requires special handling of
|
---|
477 | its parameters. The Perl usage is given first.
|
---|
478 |
|
---|
479 | $status = rpcb_gettime( "localhost", $timep );
|
---|
480 |
|
---|
481 | The XSUB follows.
|
---|
482 |
|
---|
483 | bool_t
|
---|
484 | rpcb_gettime(host,timep)
|
---|
485 | char *host
|
---|
486 | time_t timep
|
---|
487 | CODE:
|
---|
488 | RETVAL = rpcb_gettime( host, &timep );
|
---|
489 | OUTPUT:
|
---|
490 | timep
|
---|
491 | RETVAL
|
---|
492 |
|
---|
493 | =head2 The INIT: Keyword
|
---|
494 |
|
---|
495 | The INIT: keyword allows initialization to be inserted into the XSUB before
|
---|
496 | the compiler generates the call to the C function. Unlike the CODE: keyword
|
---|
497 | above, this keyword does not affect the way the compiler handles RETVAL.
|
---|
498 |
|
---|
499 | bool_t
|
---|
500 | rpcb_gettime(host,timep)
|
---|
501 | char *host
|
---|
502 | time_t &timep
|
---|
503 | INIT:
|
---|
504 | printf("# Host is %s\n", host );
|
---|
505 | OUTPUT:
|
---|
506 | timep
|
---|
507 |
|
---|
508 | Another use for the INIT: section is to check for preconditions before
|
---|
509 | making a call to the C function:
|
---|
510 |
|
---|
511 | long long
|
---|
512 | lldiv(a,b)
|
---|
513 | long long a
|
---|
514 | long long b
|
---|
515 | INIT:
|
---|
516 | if (a == 0 && b == 0)
|
---|
517 | XSRETURN_UNDEF;
|
---|
518 | if (b == 0)
|
---|
519 | croak("lldiv: cannot divide by 0");
|
---|
520 |
|
---|
521 | =head2 The NO_INIT Keyword
|
---|
522 |
|
---|
523 | The NO_INIT keyword is used to indicate that a function
|
---|
524 | parameter is being used only as an output value. The B<xsubpp>
|
---|
525 | compiler will normally generate code to read the values of
|
---|
526 | all function parameters from the argument stack and assign
|
---|
527 | them to C variables upon entry to the function. NO_INIT
|
---|
528 | will tell the compiler that some parameters will be used for
|
---|
529 | output rather than for input and that they will be handled
|
---|
530 | before the function terminates.
|
---|
531 |
|
---|
532 | The following example shows a variation of the rpcb_gettime() function.
|
---|
533 | This function uses the timep variable only as an output variable and does
|
---|
534 | not care about its initial contents.
|
---|
535 |
|
---|
536 | bool_t
|
---|
537 | rpcb_gettime(host,timep)
|
---|
538 | char *host
|
---|
539 | time_t &timep = NO_INIT
|
---|
540 | OUTPUT:
|
---|
541 | timep
|
---|
542 |
|
---|
543 | =head2 Initializing Function Parameters
|
---|
544 |
|
---|
545 | C function parameters are normally initialized with their values from
|
---|
546 | the argument stack (which in turn contains the parameters that were
|
---|
547 | passed to the XSUB from Perl). The typemaps contain the
|
---|
548 | code segments which are used to translate the Perl values to
|
---|
549 | the C parameters. The programmer, however, is allowed to
|
---|
550 | override the typemaps and supply alternate (or additional)
|
---|
551 | initialization code. Initialization code starts with the first
|
---|
552 | C<=>, C<;> or C<+> on a line in the INPUT: section. The only
|
---|
553 | exception happens if this C<;> terminates the line, then this C<;>
|
---|
554 | is quietly ignored.
|
---|
555 |
|
---|
556 | The following code demonstrates how to supply initialization code for
|
---|
557 | function parameters. The initialization code is eval'd within double
|
---|
558 | quotes by the compiler before it is added to the output so anything
|
---|
559 | which should be interpreted literally [mainly C<$>, C<@>, or C<\\>]
|
---|
560 | must be protected with backslashes. The variables $var, $arg,
|
---|
561 | and $type can be used as in typemaps.
|
---|
562 |
|
---|
563 | bool_t
|
---|
564 | rpcb_gettime(host,timep)
|
---|
565 | char *host = (char *)SvPV($arg,PL_na);
|
---|
566 | time_t &timep = 0;
|
---|
567 | OUTPUT:
|
---|
568 | timep
|
---|
569 |
|
---|
570 | This should not be used to supply default values for parameters. One
|
---|
571 | would normally use this when a function parameter must be processed by
|
---|
572 | another library function before it can be used. Default parameters are
|
---|
573 | covered in the next section.
|
---|
574 |
|
---|
575 | If the initialization begins with C<=>, then it is output in
|
---|
576 | the declaration for the input variable, replacing the initialization
|
---|
577 | supplied by the typemap. If the initialization
|
---|
578 | begins with C<;> or C<+>, then it is performed after
|
---|
579 | all of the input variables have been declared. In the C<;>
|
---|
580 | case the initialization normally supplied by the typemap is not performed.
|
---|
581 | For the C<+> case, the declaration for the variable will include the
|
---|
582 | initialization from the typemap. A global
|
---|
583 | variable, C<%v>, is available for the truly rare case where
|
---|
584 | information from one initialization is needed in another
|
---|
585 | initialization.
|
---|
586 |
|
---|
587 | Here's a truly obscure example:
|
---|
588 |
|
---|
589 | bool_t
|
---|
590 | rpcb_gettime(host,timep)
|
---|
591 | time_t &timep; /* \$v{timep}=@{[$v{timep}=$arg]} */
|
---|
592 | char *host + SvOK($v{timep}) ? SvPV($arg,PL_na) : NULL;
|
---|
593 | OUTPUT:
|
---|
594 | timep
|
---|
595 |
|
---|
596 | The construct C<\$v{timep}=@{[$v{timep}=$arg]}> used in the above
|
---|
597 | example has a two-fold purpose: first, when this line is processed by
|
---|
598 | B<xsubpp>, the Perl snippet C<$v{timep}=$arg> is evaluated. Second,
|
---|
599 | the text of the evaluated snippet is output into the generated C file
|
---|
600 | (inside a C comment)! During the processing of C<char *host> line,
|
---|
601 | $arg will evaluate to C<ST(0)>, and C<$v{timep}> will evaluate to
|
---|
602 | C<ST(1)>.
|
---|
603 |
|
---|
604 | =head2 Default Parameter Values
|
---|
605 |
|
---|
606 | Default values for XSUB arguments can be specified by placing an
|
---|
607 | assignment statement in the parameter list. The default value may
|
---|
608 | be a number, a string or the special string C<NO_INIT>. Defaults should
|
---|
609 | always be used on the right-most parameters only.
|
---|
610 |
|
---|
611 | To allow the XSUB for rpcb_gettime() to have a default host
|
---|
612 | value the parameters to the XSUB could be rearranged. The
|
---|
613 | XSUB will then call the real rpcb_gettime() function with
|
---|
614 | the parameters in the correct order. This XSUB can be called
|
---|
615 | from Perl with either of the following statements:
|
---|
616 |
|
---|
617 | $status = rpcb_gettime( $timep, $host );
|
---|
618 |
|
---|
619 | $status = rpcb_gettime( $timep );
|
---|
620 |
|
---|
621 | The XSUB will look like the code which follows. A CODE:
|
---|
622 | block is used to call the real rpcb_gettime() function with
|
---|
623 | the parameters in the correct order for that function.
|
---|
624 |
|
---|
625 | bool_t
|
---|
626 | rpcb_gettime(timep,host="localhost")
|
---|
627 | char *host
|
---|
628 | time_t timep = NO_INIT
|
---|
629 | CODE:
|
---|
630 | RETVAL = rpcb_gettime( host, &timep );
|
---|
631 | OUTPUT:
|
---|
632 | timep
|
---|
633 | RETVAL
|
---|
634 |
|
---|
635 | =head2 The PREINIT: Keyword
|
---|
636 |
|
---|
637 | The PREINIT: keyword allows extra variables to be declared immediately
|
---|
638 | before or after the declarations of the parameters from the INPUT: section
|
---|
639 | are emitted.
|
---|
640 |
|
---|
641 | If a variable is declared inside a CODE: section it will follow any typemap
|
---|
642 | code that is emitted for the input parameters. This may result in the
|
---|
643 | declaration ending up after C code, which is C syntax error. Similar
|
---|
644 | errors may happen with an explicit C<;>-type or C<+>-type initialization of
|
---|
645 | parameters is used (see L<"Initializing Function Parameters">). Declaring
|
---|
646 | these variables in an INIT: section will not help.
|
---|
647 |
|
---|
648 | In such cases, to force an additional variable to be declared together
|
---|
649 | with declarations of other variables, place the declaration into a
|
---|
650 | PREINIT: section. The PREINIT: keyword may be used one or more times
|
---|
651 | within an XSUB.
|
---|
652 |
|
---|
653 | The following examples are equivalent, but if the code is using complex
|
---|
654 | typemaps then the first example is safer.
|
---|
655 |
|
---|
656 | bool_t
|
---|
657 | rpcb_gettime(timep)
|
---|
658 | time_t timep = NO_INIT
|
---|
659 | PREINIT:
|
---|
660 | char *host = "localhost";
|
---|
661 | CODE:
|
---|
662 | RETVAL = rpcb_gettime( host, &timep );
|
---|
663 | OUTPUT:
|
---|
664 | timep
|
---|
665 | RETVAL
|
---|
666 |
|
---|
667 | For this particular case an INIT: keyword would generate the
|
---|
668 | same C code as the PREINIT: keyword. Another correct, but error-prone example:
|
---|
669 |
|
---|
670 | bool_t
|
---|
671 | rpcb_gettime(timep)
|
---|
672 | time_t timep = NO_INIT
|
---|
673 | CODE:
|
---|
674 | char *host = "localhost";
|
---|
675 | RETVAL = rpcb_gettime( host, &timep );
|
---|
676 | OUTPUT:
|
---|
677 | timep
|
---|
678 | RETVAL
|
---|
679 |
|
---|
680 | Another way to declare C<host> is to use a C block in the CODE: section:
|
---|
681 |
|
---|
682 | bool_t
|
---|
683 | rpcb_gettime(timep)
|
---|
684 | time_t timep = NO_INIT
|
---|
685 | CODE:
|
---|
686 | {
|
---|
687 | char *host = "localhost";
|
---|
688 | RETVAL = rpcb_gettime( host, &timep );
|
---|
689 | }
|
---|
690 | OUTPUT:
|
---|
691 | timep
|
---|
692 | RETVAL
|
---|
693 |
|
---|
694 | The ability to put additional declarations before the typemap entries are
|
---|
695 | processed is very handy in the cases when typemap conversions manipulate
|
---|
696 | some global state:
|
---|
697 |
|
---|
698 | MyObject
|
---|
699 | mutate(o)
|
---|
700 | PREINIT:
|
---|
701 | MyState st = global_state;
|
---|
702 | INPUT:
|
---|
703 | MyObject o;
|
---|
704 | CLEANUP:
|
---|
705 | reset_to(global_state, st);
|
---|
706 |
|
---|
707 | Here we suppose that conversion to C<MyObject> in the INPUT: section and from
|
---|
708 | MyObject when processing RETVAL will modify a global variable C<global_state>.
|
---|
709 | After these conversions are performed, we restore the old value of
|
---|
710 | C<global_state> (to avoid memory leaks, for example).
|
---|
711 |
|
---|
712 | There is another way to trade clarity for compactness: INPUT sections allow
|
---|
713 | declaration of C variables which do not appear in the parameter list of
|
---|
714 | a subroutine. Thus the above code for mutate() can be rewritten as
|
---|
715 |
|
---|
716 | MyObject
|
---|
717 | mutate(o)
|
---|
718 | MyState st = global_state;
|
---|
719 | MyObject o;
|
---|
720 | CLEANUP:
|
---|
721 | reset_to(global_state, st);
|
---|
722 |
|
---|
723 | and the code for rpcb_gettime() can be rewritten as
|
---|
724 |
|
---|
725 | bool_t
|
---|
726 | rpcb_gettime(timep)
|
---|
727 | time_t timep = NO_INIT
|
---|
728 | char *host = "localhost";
|
---|
729 | C_ARGS:
|
---|
730 | host, &timep
|
---|
731 | OUTPUT:
|
---|
732 | timep
|
---|
733 | RETVAL
|
---|
734 |
|
---|
735 | =head2 The SCOPE: Keyword
|
---|
736 |
|
---|
737 | The SCOPE: keyword allows scoping to be enabled for a particular XSUB. If
|
---|
738 | enabled, the XSUB will invoke ENTER and LEAVE automatically.
|
---|
739 |
|
---|
740 | To support potentially complex type mappings, if a typemap entry used
|
---|
741 | by an XSUB contains a comment like C</*scope*/> then scoping will
|
---|
742 | be automatically enabled for that XSUB.
|
---|
743 |
|
---|
744 | To enable scoping:
|
---|
745 |
|
---|
746 | SCOPE: ENABLE
|
---|
747 |
|
---|
748 | To disable scoping:
|
---|
749 |
|
---|
750 | SCOPE: DISABLE
|
---|
751 |
|
---|
752 | =head2 The INPUT: Keyword
|
---|
753 |
|
---|
754 | The XSUB's parameters are usually evaluated immediately after entering the
|
---|
755 | XSUB. The INPUT: keyword can be used to force those parameters to be
|
---|
756 | evaluated a little later. The INPUT: keyword can be used multiple times
|
---|
757 | within an XSUB and can be used to list one or more input variables. This
|
---|
758 | keyword is used with the PREINIT: keyword.
|
---|
759 |
|
---|
760 | The following example shows how the input parameter C<timep> can be
|
---|
761 | evaluated late, after a PREINIT.
|
---|
762 |
|
---|
763 | bool_t
|
---|
764 | rpcb_gettime(host,timep)
|
---|
765 | char *host
|
---|
766 | PREINIT:
|
---|
767 | time_t tt;
|
---|
768 | INPUT:
|
---|
769 | time_t timep
|
---|
770 | CODE:
|
---|
771 | RETVAL = rpcb_gettime( host, &tt );
|
---|
772 | timep = tt;
|
---|
773 | OUTPUT:
|
---|
774 | timep
|
---|
775 | RETVAL
|
---|
776 |
|
---|
777 | The next example shows each input parameter evaluated late.
|
---|
778 |
|
---|
779 | bool_t
|
---|
780 | rpcb_gettime(host,timep)
|
---|
781 | PREINIT:
|
---|
782 | time_t tt;
|
---|
783 | INPUT:
|
---|
784 | char *host
|
---|
785 | PREINIT:
|
---|
786 | char *h;
|
---|
787 | INPUT:
|
---|
788 | time_t timep
|
---|
789 | CODE:
|
---|
790 | h = host;
|
---|
791 | RETVAL = rpcb_gettime( h, &tt );
|
---|
792 | timep = tt;
|
---|
793 | OUTPUT:
|
---|
794 | timep
|
---|
795 | RETVAL
|
---|
796 |
|
---|
797 | Since INPUT sections allow declaration of C variables which do not appear
|
---|
798 | in the parameter list of a subroutine, this may be shortened to:
|
---|
799 |
|
---|
800 | bool_t
|
---|
801 | rpcb_gettime(host,timep)
|
---|
802 | time_t tt;
|
---|
803 | char *host;
|
---|
804 | char *h = host;
|
---|
805 | time_t timep;
|
---|
806 | CODE:
|
---|
807 | RETVAL = rpcb_gettime( h, &tt );
|
---|
808 | timep = tt;
|
---|
809 | OUTPUT:
|
---|
810 | timep
|
---|
811 | RETVAL
|
---|
812 |
|
---|
813 | (We used our knowledge that input conversion for C<char *> is a "simple" one,
|
---|
814 | thus C<host> is initialized on the declaration line, and our assignment
|
---|
815 | C<h = host> is not performed too early. Otherwise one would need to have the
|
---|
816 | assignment C<h = host> in a CODE: or INIT: section.)
|
---|
817 |
|
---|
818 | =head2 The IN/OUTLIST/IN_OUTLIST/OUT/IN_OUT Keywords
|
---|
819 |
|
---|
820 | In the list of parameters for an XSUB, one can precede parameter names
|
---|
821 | by the C<IN>/C<OUTLIST>/C<IN_OUTLIST>/C<OUT>/C<IN_OUT> keywords.
|
---|
822 | C<IN> keyword is the default, the other keywords indicate how the Perl
|
---|
823 | interface should differ from the C interface.
|
---|
824 |
|
---|
825 | Parameters preceded by C<OUTLIST>/C<IN_OUTLIST>/C<OUT>/C<IN_OUT>
|
---|
826 | keywords are considered to be used by the C subroutine I<via
|
---|
827 | pointers>. C<OUTLIST>/C<OUT> keywords indicate that the C subroutine
|
---|
828 | does not inspect the memory pointed by this parameter, but will write
|
---|
829 | through this pointer to provide additional return values.
|
---|
830 |
|
---|
831 | Parameters preceded by C<OUTLIST> keyword do not appear in the usage
|
---|
832 | signature of the generated Perl function.
|
---|
833 |
|
---|
834 | Parameters preceded by C<IN_OUTLIST>/C<IN_OUT>/C<OUT> I<do> appear as
|
---|
835 | parameters to the Perl function. With the exception of
|
---|
836 | C<OUT>-parameters, these parameters are converted to the corresponding
|
---|
837 | C type, then pointers to these data are given as arguments to the C
|
---|
838 | function. It is expected that the C function will write through these
|
---|
839 | pointers.
|
---|
840 |
|
---|
841 | The return list of the generated Perl function consists of the C return value
|
---|
842 | from the function (unless the XSUB is of C<void> return type or
|
---|
843 | C<The NO_OUTPUT Keyword> was used) followed by all the C<OUTLIST>
|
---|
844 | and C<IN_OUTLIST> parameters (in the order of appearance). On the
|
---|
845 | return from the XSUB the C<IN_OUT>/C<OUT> Perl parameter will be
|
---|
846 | modified to have the values written by the C function.
|
---|
847 |
|
---|
848 | For example, an XSUB
|
---|
849 |
|
---|
850 | void
|
---|
851 | day_month(OUTLIST day, IN unix_time, OUTLIST month)
|
---|
852 | int day
|
---|
853 | int unix_time
|
---|
854 | int month
|
---|
855 |
|
---|
856 | should be used from Perl as
|
---|
857 |
|
---|
858 | my ($day, $month) = day_month(time);
|
---|
859 |
|
---|
860 | The C signature of the corresponding function should be
|
---|
861 |
|
---|
862 | void day_month(int *day, int unix_time, int *month);
|
---|
863 |
|
---|
864 | The C<IN>/C<OUTLIST>/C<IN_OUTLIST>/C<IN_OUT>/C<OUT> keywords can be
|
---|
865 | mixed with ANSI-style declarations, as in
|
---|
866 |
|
---|
867 | void
|
---|
868 | day_month(OUTLIST int day, int unix_time, OUTLIST int month)
|
---|
869 |
|
---|
870 | (here the optional C<IN> keyword is omitted).
|
---|
871 |
|
---|
872 | The C<IN_OUT> parameters are identical with parameters introduced with
|
---|
873 | L<The & Unary Operator> and put into the C<OUTPUT:> section (see
|
---|
874 | L<The OUTPUT: Keyword>). The C<IN_OUTLIST> parameters are very similar,
|
---|
875 | the only difference being that the value C function writes through the
|
---|
876 | pointer would not modify the Perl parameter, but is put in the output
|
---|
877 | list.
|
---|
878 |
|
---|
879 | The C<OUTLIST>/C<OUT> parameter differ from C<IN_OUTLIST>/C<IN_OUT>
|
---|
880 | parameters only by the initial value of the Perl parameter not
|
---|
881 | being read (and not being given to the C function - which gets some
|
---|
882 | garbage instead). For example, the same C function as above can be
|
---|
883 | interfaced with as
|
---|
884 |
|
---|
885 | void day_month(OUT int day, int unix_time, OUT int month);
|
---|
886 |
|
---|
887 | or
|
---|
888 |
|
---|
889 | void
|
---|
890 | day_month(day, unix_time, month)
|
---|
891 | int &day = NO_INIT
|
---|
892 | int unix_time
|
---|
893 | int &month = NO_INIT
|
---|
894 | OUTPUT:
|
---|
895 | day
|
---|
896 | month
|
---|
897 |
|
---|
898 | However, the generated Perl function is called in very C-ish style:
|
---|
899 |
|
---|
900 | my ($day, $month);
|
---|
901 | day_month($day, time, $month);
|
---|
902 |
|
---|
903 | =head2 The C<length(NAME)> Keyword
|
---|
904 |
|
---|
905 | If one of the input arguments to the C function is the length of a string
|
---|
906 | argument C<NAME>, one can substitute the name of the length-argument by
|
---|
907 | C<length(NAME)> in the XSUB declaration. This argument must be omitted when
|
---|
908 | the generated Perl function is called. E.g.,
|
---|
909 |
|
---|
910 | void
|
---|
911 | dump_chars(char *s, short l)
|
---|
912 | {
|
---|
913 | short n = 0;
|
---|
914 | while (n < l) {
|
---|
915 | printf("s[%d] = \"\\%#03o\"\n", n, (int)s[n]);
|
---|
916 | n++;
|
---|
917 | }
|
---|
918 | }
|
---|
919 |
|
---|
920 | MODULE = x PACKAGE = x
|
---|
921 |
|
---|
922 | void dump_chars(char *s, short length(s))
|
---|
923 |
|
---|
924 | should be called as C<dump_chars($string)>.
|
---|
925 |
|
---|
926 | This directive is supported with ANSI-type function declarations only.
|
---|
927 |
|
---|
928 | =head2 Variable-length Parameter Lists
|
---|
929 |
|
---|
930 | XSUBs can have variable-length parameter lists by specifying an ellipsis
|
---|
931 | C<(...)> in the parameter list. This use of the ellipsis is similar to that
|
---|
932 | found in ANSI C. The programmer is able to determine the number of
|
---|
933 | arguments passed to the XSUB by examining the C<items> variable which the
|
---|
934 | B<xsubpp> compiler supplies for all XSUBs. By using this mechanism one can
|
---|
935 | create an XSUB which accepts a list of parameters of unknown length.
|
---|
936 |
|
---|
937 | The I<host> parameter for the rpcb_gettime() XSUB can be
|
---|
938 | optional so the ellipsis can be used to indicate that the
|
---|
939 | XSUB will take a variable number of parameters. Perl should
|
---|
940 | be able to call this XSUB with either of the following statements.
|
---|
941 |
|
---|
942 | $status = rpcb_gettime( $timep, $host );
|
---|
943 |
|
---|
944 | $status = rpcb_gettime( $timep );
|
---|
945 |
|
---|
946 | The XS code, with ellipsis, follows.
|
---|
947 |
|
---|
948 | bool_t
|
---|
949 | rpcb_gettime(timep, ...)
|
---|
950 | time_t timep = NO_INIT
|
---|
951 | PREINIT:
|
---|
952 | char *host = "localhost";
|
---|
953 | STRLEN n_a;
|
---|
954 | CODE:
|
---|
955 | if( items > 1 )
|
---|
956 | host = (char *)SvPV(ST(1), n_a);
|
---|
957 | RETVAL = rpcb_gettime( host, &timep );
|
---|
958 | OUTPUT:
|
---|
959 | timep
|
---|
960 | RETVAL
|
---|
961 |
|
---|
962 | =head2 The C_ARGS: Keyword
|
---|
963 |
|
---|
964 | The C_ARGS: keyword allows creating of XSUBS which have different
|
---|
965 | calling sequence from Perl than from C, without a need to write
|
---|
966 | CODE: or PPCODE: section. The contents of the C_ARGS: paragraph is
|
---|
967 | put as the argument to the called C function without any change.
|
---|
968 |
|
---|
969 | For example, suppose that a C function is declared as
|
---|
970 |
|
---|
971 | symbolic nth_derivative(int n, symbolic function, int flags);
|
---|
972 |
|
---|
973 | and that the default flags are kept in a global C variable
|
---|
974 | C<default_flags>. Suppose that you want to create an interface which
|
---|
975 | is called as
|
---|
976 |
|
---|
977 | $second_deriv = $function->nth_derivative(2);
|
---|
978 |
|
---|
979 | To do this, declare the XSUB as
|
---|
980 |
|
---|
981 | symbolic
|
---|
982 | nth_derivative(function, n)
|
---|
983 | symbolic function
|
---|
984 | int n
|
---|
985 | C_ARGS:
|
---|
986 | n, function, default_flags
|
---|
987 |
|
---|
988 | =head2 The PPCODE: Keyword
|
---|
989 |
|
---|
990 | The PPCODE: keyword is an alternate form of the CODE: keyword and is used
|
---|
991 | to tell the B<xsubpp> compiler that the programmer is supplying the code to
|
---|
992 | control the argument stack for the XSUBs return values. Occasionally one
|
---|
993 | will want an XSUB to return a list of values rather than a single value.
|
---|
994 | In these cases one must use PPCODE: and then explicitly push the list of
|
---|
995 | values on the stack. The PPCODE: and CODE: keywords should not be used
|
---|
996 | together within the same XSUB.
|
---|
997 |
|
---|
998 | The actual difference between PPCODE: and CODE: sections is in the
|
---|
999 | initialization of C<SP> macro (which stands for the I<current> Perl
|
---|
1000 | stack pointer), and in the handling of data on the stack when returning
|
---|
1001 | from an XSUB. In CODE: sections SP preserves the value which was on
|
---|
1002 | entry to the XSUB: SP is on the function pointer (which follows the
|
---|
1003 | last parameter). In PPCODE: sections SP is moved backward to the
|
---|
1004 | beginning of the parameter list, which allows C<PUSH*()> macros
|
---|
1005 | to place output values in the place Perl expects them to be when
|
---|
1006 | the XSUB returns back to Perl.
|
---|
1007 |
|
---|
1008 | The generated trailer for a CODE: section ensures that the number of return
|
---|
1009 | values Perl will see is either 0 or 1 (depending on the C<void>ness of the
|
---|
1010 | return value of the C function, and heuristics mentioned in
|
---|
1011 | L<"The RETVAL Variable">). The trailer generated for a PPCODE: section
|
---|
1012 | is based on the number of return values and on the number of times
|
---|
1013 | C<SP> was updated by C<[X]PUSH*()> macros.
|
---|
1014 |
|
---|
1015 | Note that macros C<ST(i)>, C<XST_m*()> and C<XSRETURN*()> work equally
|
---|
1016 | well in CODE: sections and PPCODE: sections.
|
---|
1017 |
|
---|
1018 | The following XSUB will call the C rpcb_gettime() function
|
---|
1019 | and will return its two output values, timep and status, to
|
---|
1020 | Perl as a single list.
|
---|
1021 |
|
---|
1022 | void
|
---|
1023 | rpcb_gettime(host)
|
---|
1024 | char *host
|
---|
1025 | PREINIT:
|
---|
1026 | time_t timep;
|
---|
1027 | bool_t status;
|
---|
1028 | PPCODE:
|
---|
1029 | status = rpcb_gettime( host, &timep );
|
---|
1030 | EXTEND(SP, 2);
|
---|
1031 | PUSHs(sv_2mortal(newSViv(status)));
|
---|
1032 | PUSHs(sv_2mortal(newSViv(timep)));
|
---|
1033 |
|
---|
1034 | Notice that the programmer must supply the C code necessary
|
---|
1035 | to have the real rpcb_gettime() function called and to have
|
---|
1036 | the return values properly placed on the argument stack.
|
---|
1037 |
|
---|
1038 | The C<void> return type for this function tells the B<xsubpp> compiler that
|
---|
1039 | the RETVAL variable is not needed or used and that it should not be created.
|
---|
1040 | In most scenarios the void return type should be used with the PPCODE:
|
---|
1041 | directive.
|
---|
1042 |
|
---|
1043 | The EXTEND() macro is used to make room on the argument
|
---|
1044 | stack for 2 return values. The PPCODE: directive causes the
|
---|
1045 | B<xsubpp> compiler to create a stack pointer available as C<SP>, and it
|
---|
1046 | is this pointer which is being used in the EXTEND() macro.
|
---|
1047 | The values are then pushed onto the stack with the PUSHs()
|
---|
1048 | macro.
|
---|
1049 |
|
---|
1050 | Now the rpcb_gettime() function can be used from Perl with
|
---|
1051 | the following statement.
|
---|
1052 |
|
---|
1053 | ($status, $timep) = rpcb_gettime("localhost");
|
---|
1054 |
|
---|
1055 | When handling output parameters with a PPCODE section, be sure to handle
|
---|
1056 | 'set' magic properly. See L<perlguts> for details about 'set' magic.
|
---|
1057 |
|
---|
1058 | =head2 Returning Undef And Empty Lists
|
---|
1059 |
|
---|
1060 | Occasionally the programmer will want to return simply
|
---|
1061 | C<undef> or an empty list if a function fails rather than a
|
---|
1062 | separate status value. The rpcb_gettime() function offers
|
---|
1063 | just this situation. If the function succeeds we would like
|
---|
1064 | to have it return the time and if it fails we would like to
|
---|
1065 | have undef returned. In the following Perl code the value
|
---|
1066 | of $timep will either be undef or it will be a valid time.
|
---|
1067 |
|
---|
1068 | $timep = rpcb_gettime( "localhost" );
|
---|
1069 |
|
---|
1070 | The following XSUB uses the C<SV *> return type as a mnemonic only,
|
---|
1071 | and uses a CODE: block to indicate to the compiler
|
---|
1072 | that the programmer has supplied all the necessary code. The
|
---|
1073 | sv_newmortal() call will initialize the return value to undef, making that
|
---|
1074 | the default return value.
|
---|
1075 |
|
---|
1076 | SV *
|
---|
1077 | rpcb_gettime(host)
|
---|
1078 | char * host
|
---|
1079 | PREINIT:
|
---|
1080 | time_t timep;
|
---|
1081 | bool_t x;
|
---|
1082 | CODE:
|
---|
1083 | ST(0) = sv_newmortal();
|
---|
1084 | if( rpcb_gettime( host, &timep ) )
|
---|
1085 | sv_setnv( ST(0), (double)timep);
|
---|
1086 |
|
---|
1087 | The next example demonstrates how one would place an explicit undef in the
|
---|
1088 | return value, should the need arise.
|
---|
1089 |
|
---|
1090 | SV *
|
---|
1091 | rpcb_gettime(host)
|
---|
1092 | char * host
|
---|
1093 | PREINIT:
|
---|
1094 | time_t timep;
|
---|
1095 | bool_t x;
|
---|
1096 | CODE:
|
---|
1097 | ST(0) = sv_newmortal();
|
---|
1098 | if( rpcb_gettime( host, &timep ) ){
|
---|
1099 | sv_setnv( ST(0), (double)timep);
|
---|
1100 | }
|
---|
1101 | else{
|
---|
1102 | ST(0) = &PL_sv_undef;
|
---|
1103 | }
|
---|
1104 |
|
---|
1105 | To return an empty list one must use a PPCODE: block and
|
---|
1106 | then not push return values on the stack.
|
---|
1107 |
|
---|
1108 | void
|
---|
1109 | rpcb_gettime(host)
|
---|
1110 | char *host
|
---|
1111 | PREINIT:
|
---|
1112 | time_t timep;
|
---|
1113 | PPCODE:
|
---|
1114 | if( rpcb_gettime( host, &timep ) )
|
---|
1115 | PUSHs(sv_2mortal(newSViv(timep)));
|
---|
1116 | else{
|
---|
1117 | /* Nothing pushed on stack, so an empty
|
---|
1118 | * list is implicitly returned. */
|
---|
1119 | }
|
---|
1120 |
|
---|
1121 | Some people may be inclined to include an explicit C<return> in the above
|
---|
1122 | XSUB, rather than letting control fall through to the end. In those
|
---|
1123 | situations C<XSRETURN_EMPTY> should be used, instead. This will ensure that
|
---|
1124 | the XSUB stack is properly adjusted. Consult L<perlapi> for other
|
---|
1125 | C<XSRETURN> macros.
|
---|
1126 |
|
---|
1127 | Since C<XSRETURN_*> macros can be used with CODE blocks as well, one can
|
---|
1128 | rewrite this example as:
|
---|
1129 |
|
---|
1130 | int
|
---|
1131 | rpcb_gettime(host)
|
---|
1132 | char *host
|
---|
1133 | PREINIT:
|
---|
1134 | time_t timep;
|
---|
1135 | CODE:
|
---|
1136 | RETVAL = rpcb_gettime( host, &timep );
|
---|
1137 | if (RETVAL == 0)
|
---|
1138 | XSRETURN_UNDEF;
|
---|
1139 | OUTPUT:
|
---|
1140 | RETVAL
|
---|
1141 |
|
---|
1142 | In fact, one can put this check into a POSTCALL: section as well. Together
|
---|
1143 | with PREINIT: simplifications, this leads to:
|
---|
1144 |
|
---|
1145 | int
|
---|
1146 | rpcb_gettime(host)
|
---|
1147 | char *host
|
---|
1148 | time_t timep;
|
---|
1149 | POSTCALL:
|
---|
1150 | if (RETVAL == 0)
|
---|
1151 | XSRETURN_UNDEF;
|
---|
1152 |
|
---|
1153 | =head2 The REQUIRE: Keyword
|
---|
1154 |
|
---|
1155 | The REQUIRE: keyword is used to indicate the minimum version of the
|
---|
1156 | B<xsubpp> compiler needed to compile the XS module. An XS module which
|
---|
1157 | contains the following statement will compile with only B<xsubpp> version
|
---|
1158 | 1.922 or greater:
|
---|
1159 |
|
---|
1160 | REQUIRE: 1.922
|
---|
1161 |
|
---|
1162 | =head2 The CLEANUP: Keyword
|
---|
1163 |
|
---|
1164 | This keyword can be used when an XSUB requires special cleanup procedures
|
---|
1165 | before it terminates. When the CLEANUP: keyword is used it must follow
|
---|
1166 | any CODE:, PPCODE:, or OUTPUT: blocks which are present in the XSUB. The
|
---|
1167 | code specified for the cleanup block will be added as the last statements
|
---|
1168 | in the XSUB.
|
---|
1169 |
|
---|
1170 | =head2 The POSTCALL: Keyword
|
---|
1171 |
|
---|
1172 | This keyword can be used when an XSUB requires special procedures
|
---|
1173 | executed after the C subroutine call is performed. When the POSTCALL:
|
---|
1174 | keyword is used it must precede OUTPUT: and CLEANUP: blocks which are
|
---|
1175 | present in the XSUB.
|
---|
1176 |
|
---|
1177 | See examples in L<"The NO_OUTPUT Keyword"> and L<"Returning Undef And Empty Lists">.
|
---|
1178 |
|
---|
1179 | The POSTCALL: block does not make a lot of sense when the C subroutine
|
---|
1180 | call is supplied by user by providing either CODE: or PPCODE: section.
|
---|
1181 |
|
---|
1182 | =head2 The BOOT: Keyword
|
---|
1183 |
|
---|
1184 | The BOOT: keyword is used to add code to the extension's bootstrap
|
---|
1185 | function. The bootstrap function is generated by the B<xsubpp> compiler and
|
---|
1186 | normally holds the statements necessary to register any XSUBs with Perl.
|
---|
1187 | With the BOOT: keyword the programmer can tell the compiler to add extra
|
---|
1188 | statements to the bootstrap function.
|
---|
1189 |
|
---|
1190 | This keyword may be used any time after the first MODULE keyword and should
|
---|
1191 | appear on a line by itself. The first blank line after the keyword will
|
---|
1192 | terminate the code block.
|
---|
1193 |
|
---|
1194 | BOOT:
|
---|
1195 | # The following message will be printed when the
|
---|
1196 | # bootstrap function executes.
|
---|
1197 | printf("Hello from the bootstrap!\n");
|
---|
1198 |
|
---|
1199 | =head2 The VERSIONCHECK: Keyword
|
---|
1200 |
|
---|
1201 | The VERSIONCHECK: keyword corresponds to B<xsubpp>'s C<-versioncheck> and
|
---|
1202 | C<-noversioncheck> options. This keyword overrides the command line
|
---|
1203 | options. Version checking is enabled by default. When version checking is
|
---|
1204 | enabled the XS module will attempt to verify that its version matches the
|
---|
1205 | version of the PM module.
|
---|
1206 |
|
---|
1207 | To enable version checking:
|
---|
1208 |
|
---|
1209 | VERSIONCHECK: ENABLE
|
---|
1210 |
|
---|
1211 | To disable version checking:
|
---|
1212 |
|
---|
1213 | VERSIONCHECK: DISABLE
|
---|
1214 |
|
---|
1215 | =head2 The PROTOTYPES: Keyword
|
---|
1216 |
|
---|
1217 | The PROTOTYPES: keyword corresponds to B<xsubpp>'s C<-prototypes> and
|
---|
1218 | C<-noprototypes> options. This keyword overrides the command line options.
|
---|
1219 | Prototypes are enabled by default. When prototypes are enabled XSUBs will
|
---|
1220 | be given Perl prototypes. This keyword may be used multiple times in an XS
|
---|
1221 | module to enable and disable prototypes for different parts of the module.
|
---|
1222 |
|
---|
1223 | To enable prototypes:
|
---|
1224 |
|
---|
1225 | PROTOTYPES: ENABLE
|
---|
1226 |
|
---|
1227 | To disable prototypes:
|
---|
1228 |
|
---|
1229 | PROTOTYPES: DISABLE
|
---|
1230 |
|
---|
1231 | =head2 The PROTOTYPE: Keyword
|
---|
1232 |
|
---|
1233 | This keyword is similar to the PROTOTYPES: keyword above but can be used to
|
---|
1234 | force B<xsubpp> to use a specific prototype for the XSUB. This keyword
|
---|
1235 | overrides all other prototype options and keywords but affects only the
|
---|
1236 | current XSUB. Consult L<perlsub/Prototypes> for information about Perl
|
---|
1237 | prototypes.
|
---|
1238 |
|
---|
1239 | bool_t
|
---|
1240 | rpcb_gettime(timep, ...)
|
---|
1241 | time_t timep = NO_INIT
|
---|
1242 | PROTOTYPE: $;$
|
---|
1243 | PREINIT:
|
---|
1244 | char *host = "localhost";
|
---|
1245 | STRLEN n_a;
|
---|
1246 | CODE:
|
---|
1247 | if( items > 1 )
|
---|
1248 | host = (char *)SvPV(ST(1), n_a);
|
---|
1249 | RETVAL = rpcb_gettime( host, &timep );
|
---|
1250 | OUTPUT:
|
---|
1251 | timep
|
---|
1252 | RETVAL
|
---|
1253 |
|
---|
1254 | If the prototypes are enabled, you can disable it locally for a given
|
---|
1255 | XSUB as in the following example:
|
---|
1256 |
|
---|
1257 | void
|
---|
1258 | rpcb_gettime_noproto()
|
---|
1259 | PROTOTYPE: DISABLE
|
---|
1260 | ...
|
---|
1261 |
|
---|
1262 | =head2 The ALIAS: Keyword
|
---|
1263 |
|
---|
1264 | The ALIAS: keyword allows an XSUB to have two or more unique Perl names
|
---|
1265 | and to know which of those names was used when it was invoked. The Perl
|
---|
1266 | names may be fully-qualified with package names. Each alias is given an
|
---|
1267 | index. The compiler will setup a variable called C<ix> which contain the
|
---|
1268 | index of the alias which was used. When the XSUB is called with its
|
---|
1269 | declared name C<ix> will be 0.
|
---|
1270 |
|
---|
1271 | The following example will create aliases C<FOO::gettime()> and
|
---|
1272 | C<BAR::getit()> for this function.
|
---|
1273 |
|
---|
1274 | bool_t
|
---|
1275 | rpcb_gettime(host,timep)
|
---|
1276 | char *host
|
---|
1277 | time_t &timep
|
---|
1278 | ALIAS:
|
---|
1279 | FOO::gettime = 1
|
---|
1280 | BAR::getit = 2
|
---|
1281 | INIT:
|
---|
1282 | printf("# ix = %d\n", ix );
|
---|
1283 | OUTPUT:
|
---|
1284 | timep
|
---|
1285 |
|
---|
1286 | =head2 The OVERLOAD: Keyword
|
---|
1287 |
|
---|
1288 | Instead of writing an overloaded interface using pure Perl, you
|
---|
1289 | can also use the OVERLOAD keyword to define additional Perl names
|
---|
1290 | for your functions (like the ALIAS: keyword above). However, the
|
---|
1291 | overloaded functions must be defined with three parameters (except
|
---|
1292 | for the nomethod() function which needs four parameters). If any
|
---|
1293 | function has the OVERLOAD: keyword, several additional lines
|
---|
1294 | will be defined in the c file generated by xsubpp in order to
|
---|
1295 | register with the overload magic.
|
---|
1296 |
|
---|
1297 | Since blessed objects are actually stored as RV's, it is useful
|
---|
1298 | to use the typemap features to preprocess parameters and extract
|
---|
1299 | the actual SV stored within the blessed RV. See the sample for
|
---|
1300 | T_PTROBJ_SPECIAL below.
|
---|
1301 |
|
---|
1302 | To use the OVERLOAD: keyword, create an XS function which takes
|
---|
1303 | three input parameters ( or use the c style '...' definition) like
|
---|
1304 | this:
|
---|
1305 |
|
---|
1306 | SV *
|
---|
1307 | cmp (lobj, robj, swap)
|
---|
1308 | My_Module_obj lobj
|
---|
1309 | My_Module_obj robj
|
---|
1310 | IV swap
|
---|
1311 | OVERLOAD: cmp <=>
|
---|
1312 | { /* function defined here */}
|
---|
1313 |
|
---|
1314 | In this case, the function will overload both of the three way
|
---|
1315 | comparison operators. For all overload operations using non-alpha
|
---|
1316 | characters, you must type the parameter without quoting, seperating
|
---|
1317 | multiple overloads with whitespace. Note that "" (the stringify
|
---|
1318 | overload) should be entered as \"\" (i.e. escaped).
|
---|
1319 |
|
---|
1320 | =head2 The FALLBACK: Keyword
|
---|
1321 |
|
---|
1322 | In addition to the OVERLOAD keyword, if you need to control how
|
---|
1323 | Perl autogenerates missing overloaded operators, you can set the
|
---|
1324 | FALLBACK keyword in the module header section, like this:
|
---|
1325 |
|
---|
1326 | MODULE = RPC PACKAGE = RPC
|
---|
1327 |
|
---|
1328 | FALLBACK: TRUE
|
---|
1329 | ...
|
---|
1330 |
|
---|
1331 | where FALLBACK can take any of the three values TRUE, FALSE, or
|
---|
1332 | UNDEF. If you do not set any FALLBACK value when using OVERLOAD,
|
---|
1333 | it defaults to UNDEF. FALLBACK is not used except when one or
|
---|
1334 | more functions using OVERLOAD have been defined. Please see
|
---|
1335 | L<overload/Fallback> for more details.
|
---|
1336 |
|
---|
1337 | =head2 The INTERFACE: Keyword
|
---|
1338 |
|
---|
1339 | This keyword declares the current XSUB as a keeper of the given
|
---|
1340 | calling signature. If some text follows this keyword, it is
|
---|
1341 | considered as a list of functions which have this signature, and
|
---|
1342 | should be attached to the current XSUB.
|
---|
1343 |
|
---|
1344 | For example, if you have 4 C functions multiply(), divide(), add(),
|
---|
1345 | subtract() all having the signature:
|
---|
1346 |
|
---|
1347 | symbolic f(symbolic, symbolic);
|
---|
1348 |
|
---|
1349 | you can make them all to use the same XSUB using this:
|
---|
1350 |
|
---|
1351 | symbolic
|
---|
1352 | interface_s_ss(arg1, arg2)
|
---|
1353 | symbolic arg1
|
---|
1354 | symbolic arg2
|
---|
1355 | INTERFACE:
|
---|
1356 | multiply divide
|
---|
1357 | add subtract
|
---|
1358 |
|
---|
1359 | (This is the complete XSUB code for 4 Perl functions!) Four generated
|
---|
1360 | Perl function share names with corresponding C functions.
|
---|
1361 |
|
---|
1362 | The advantage of this approach comparing to ALIAS: keyword is that there
|
---|
1363 | is no need to code a switch statement, each Perl function (which shares
|
---|
1364 | the same XSUB) knows which C function it should call. Additionally, one
|
---|
1365 | can attach an extra function remainder() at runtime by using
|
---|
1366 |
|
---|
1367 | CV *mycv = newXSproto("Symbolic::remainder",
|
---|
1368 | XS_Symbolic_interface_s_ss, __FILE__, "$$");
|
---|
1369 | XSINTERFACE_FUNC_SET(mycv, remainder);
|
---|
1370 |
|
---|
1371 | say, from another XSUB. (This example supposes that there was no
|
---|
1372 | INTERFACE_MACRO: section, otherwise one needs to use something else instead of
|
---|
1373 | C<XSINTERFACE_FUNC_SET>, see the next section.)
|
---|
1374 |
|
---|
1375 | =head2 The INTERFACE_MACRO: Keyword
|
---|
1376 |
|
---|
1377 | This keyword allows one to define an INTERFACE using a different way
|
---|
1378 | to extract a function pointer from an XSUB. The text which follows
|
---|
1379 | this keyword should give the name of macros which would extract/set a
|
---|
1380 | function pointer. The extractor macro is given return type, C<CV*>,
|
---|
1381 | and C<XSANY.any_dptr> for this C<CV*>. The setter macro is given cv,
|
---|
1382 | and the function pointer.
|
---|
1383 |
|
---|
1384 | The default value is C<XSINTERFACE_FUNC> and C<XSINTERFACE_FUNC_SET>.
|
---|
1385 | An INTERFACE keyword with an empty list of functions can be omitted if
|
---|
1386 | INTERFACE_MACRO keyword is used.
|
---|
1387 |
|
---|
1388 | Suppose that in the previous example functions pointers for
|
---|
1389 | multiply(), divide(), add(), subtract() are kept in a global C array
|
---|
1390 | C<fp[]> with offsets being C<multiply_off>, C<divide_off>, C<add_off>,
|
---|
1391 | C<subtract_off>. Then one can use
|
---|
1392 |
|
---|
1393 | #define XSINTERFACE_FUNC_BYOFFSET(ret,cv,f) \
|
---|
1394 | ((XSINTERFACE_CVT(ret,))fp[CvXSUBANY(cv).any_i32])
|
---|
1395 | #define XSINTERFACE_FUNC_BYOFFSET_set(cv,f) \
|
---|
1396 | CvXSUBANY(cv).any_i32 = CAT2( f, _off )
|
---|
1397 |
|
---|
1398 | in C section,
|
---|
1399 |
|
---|
1400 | symbolic
|
---|
1401 | interface_s_ss(arg1, arg2)
|
---|
1402 | symbolic arg1
|
---|
1403 | symbolic arg2
|
---|
1404 | INTERFACE_MACRO:
|
---|
1405 | XSINTERFACE_FUNC_BYOFFSET
|
---|
1406 | XSINTERFACE_FUNC_BYOFFSET_set
|
---|
1407 | INTERFACE:
|
---|
1408 | multiply divide
|
---|
1409 | add subtract
|
---|
1410 |
|
---|
1411 | in XSUB section.
|
---|
1412 |
|
---|
1413 | =head2 The INCLUDE: Keyword
|
---|
1414 |
|
---|
1415 | This keyword can be used to pull other files into the XS module. The other
|
---|
1416 | files may have XS code. INCLUDE: can also be used to run a command to
|
---|
1417 | generate the XS code to be pulled into the module.
|
---|
1418 |
|
---|
1419 | The file F<Rpcb1.xsh> contains our C<rpcb_gettime()> function:
|
---|
1420 |
|
---|
1421 | bool_t
|
---|
1422 | rpcb_gettime(host,timep)
|
---|
1423 | char *host
|
---|
1424 | time_t &timep
|
---|
1425 | OUTPUT:
|
---|
1426 | timep
|
---|
1427 |
|
---|
1428 | The XS module can use INCLUDE: to pull that file into it.
|
---|
1429 |
|
---|
1430 | INCLUDE: Rpcb1.xsh
|
---|
1431 |
|
---|
1432 | If the parameters to the INCLUDE: keyword are followed by a pipe (C<|>) then
|
---|
1433 | the compiler will interpret the parameters as a command.
|
---|
1434 |
|
---|
1435 | INCLUDE: cat Rpcb1.xsh |
|
---|
1436 |
|
---|
1437 | =head2 The CASE: Keyword
|
---|
1438 |
|
---|
1439 | The CASE: keyword allows an XSUB to have multiple distinct parts with each
|
---|
1440 | part acting as a virtual XSUB. CASE: is greedy and if it is used then all
|
---|
1441 | other XS keywords must be contained within a CASE:. This means nothing may
|
---|
1442 | precede the first CASE: in the XSUB and anything following the last CASE: is
|
---|
1443 | included in that case.
|
---|
1444 |
|
---|
1445 | A CASE: might switch via a parameter of the XSUB, via the C<ix> ALIAS:
|
---|
1446 | variable (see L<"The ALIAS: Keyword">), or maybe via the C<items> variable
|
---|
1447 | (see L<"Variable-length Parameter Lists">). The last CASE: becomes the
|
---|
1448 | B<default> case if it is not associated with a conditional. The following
|
---|
1449 | example shows CASE switched via C<ix> with a function C<rpcb_gettime()>
|
---|
1450 | having an alias C<x_gettime()>. When the function is called as
|
---|
1451 | C<rpcb_gettime()> its parameters are the usual C<(char *host, time_t *timep)>,
|
---|
1452 | but when the function is called as C<x_gettime()> its parameters are
|
---|
1453 | reversed, C<(time_t *timep, char *host)>.
|
---|
1454 |
|
---|
1455 | long
|
---|
1456 | rpcb_gettime(a,b)
|
---|
1457 | CASE: ix == 1
|
---|
1458 | ALIAS:
|
---|
1459 | x_gettime = 1
|
---|
1460 | INPUT:
|
---|
1461 | # 'a' is timep, 'b' is host
|
---|
1462 | char *b
|
---|
1463 | time_t a = NO_INIT
|
---|
1464 | CODE:
|
---|
1465 | RETVAL = rpcb_gettime( b, &a );
|
---|
1466 | OUTPUT:
|
---|
1467 | a
|
---|
1468 | RETVAL
|
---|
1469 | CASE:
|
---|
1470 | # 'a' is host, 'b' is timep
|
---|
1471 | char *a
|
---|
1472 | time_t &b = NO_INIT
|
---|
1473 | OUTPUT:
|
---|
1474 | b
|
---|
1475 | RETVAL
|
---|
1476 |
|
---|
1477 | That function can be called with either of the following statements. Note
|
---|
1478 | the different argument lists.
|
---|
1479 |
|
---|
1480 | $status = rpcb_gettime( $host, $timep );
|
---|
1481 |
|
---|
1482 | $status = x_gettime( $timep, $host );
|
---|
1483 |
|
---|
1484 | =head2 The & Unary Operator
|
---|
1485 |
|
---|
1486 | The C<&> unary operator in the INPUT: section is used to tell B<xsubpp>
|
---|
1487 | that it should convert a Perl value to/from C using the C type to the left
|
---|
1488 | of C<&>, but provide a pointer to this value when the C function is called.
|
---|
1489 |
|
---|
1490 | This is useful to avoid a CODE: block for a C function which takes a parameter
|
---|
1491 | by reference. Typically, the parameter should be not a pointer type (an
|
---|
1492 | C<int> or C<long> but not an C<int*> or C<long*>).
|
---|
1493 |
|
---|
1494 | The following XSUB will generate incorrect C code. The B<xsubpp> compiler will
|
---|
1495 | turn this into code which calls C<rpcb_gettime()> with parameters C<(char
|
---|
1496 | *host, time_t timep)>, but the real C<rpcb_gettime()> wants the C<timep>
|
---|
1497 | parameter to be of type C<time_t*> rather than C<time_t>.
|
---|
1498 |
|
---|
1499 | bool_t
|
---|
1500 | rpcb_gettime(host,timep)
|
---|
1501 | char *host
|
---|
1502 | time_t timep
|
---|
1503 | OUTPUT:
|
---|
1504 | timep
|
---|
1505 |
|
---|
1506 | That problem is corrected by using the C<&> operator. The B<xsubpp> compiler
|
---|
1507 | will now turn this into code which calls C<rpcb_gettime()> correctly with
|
---|
1508 | parameters C<(char *host, time_t *timep)>. It does this by carrying the
|
---|
1509 | C<&> through, so the function call looks like C<rpcb_gettime(host, &timep)>.
|
---|
1510 |
|
---|
1511 | bool_t
|
---|
1512 | rpcb_gettime(host,timep)
|
---|
1513 | char *host
|
---|
1514 | time_t &timep
|
---|
1515 | OUTPUT:
|
---|
1516 | timep
|
---|
1517 |
|
---|
1518 | =head2 Inserting POD, Comments and C Preprocessor Directives
|
---|
1519 |
|
---|
1520 | C preprocessor directives are allowed within BOOT:, PREINIT: INIT:, CODE:,
|
---|
1521 | PPCODE:, POSTCALL:, and CLEANUP: blocks, as well as outside the functions.
|
---|
1522 | Comments are allowed anywhere after the MODULE keyword. The compiler will
|
---|
1523 | pass the preprocessor directives through untouched and will remove the
|
---|
1524 | commented lines. POD documentation is allowed at any point, both in the
|
---|
1525 | C and XS language sections. POD must be terminated with a C<=cut> command;
|
---|
1526 | C<xsubpp> will exit with an error if it does not. It is very unlikely that
|
---|
1527 | human generated C code will be mistaken for POD, as most indenting styles
|
---|
1528 | result in whitespace in front of any line starting with C<=>. Machine
|
---|
1529 | generated XS files may fall into this trap unless care is taken to
|
---|
1530 | ensure that a space breaks the sequence "\n=".
|
---|
1531 |
|
---|
1532 | Comments can be added to XSUBs by placing a C<#> as the first
|
---|
1533 | non-whitespace of a line. Care should be taken to avoid making the
|
---|
1534 | comment look like a C preprocessor directive, lest it be interpreted as
|
---|
1535 | such. The simplest way to prevent this is to put whitespace in front of
|
---|
1536 | the C<#>.
|
---|
1537 |
|
---|
1538 | If you use preprocessor directives to choose one of two
|
---|
1539 | versions of a function, use
|
---|
1540 |
|
---|
1541 | #if ... version1
|
---|
1542 | #else /* ... version2 */
|
---|
1543 | #endif
|
---|
1544 |
|
---|
1545 | and not
|
---|
1546 |
|
---|
1547 | #if ... version1
|
---|
1548 | #endif
|
---|
1549 | #if ... version2
|
---|
1550 | #endif
|
---|
1551 |
|
---|
1552 | because otherwise B<xsubpp> will believe that you made a duplicate
|
---|
1553 | definition of the function. Also, put a blank line before the
|
---|
1554 | #else/#endif so it will not be seen as part of the function body.
|
---|
1555 |
|
---|
1556 | =head2 Using XS With C++
|
---|
1557 |
|
---|
1558 | If an XSUB name contains C<::>, it is considered to be a C++ method.
|
---|
1559 | The generated Perl function will assume that
|
---|
1560 | its first argument is an object pointer. The object pointer
|
---|
1561 | will be stored in a variable called THIS. The object should
|
---|
1562 | have been created by C++ with the new() function and should
|
---|
1563 | be blessed by Perl with the sv_setref_pv() macro. The
|
---|
1564 | blessing of the object by Perl can be handled by a typemap. An example
|
---|
1565 | typemap is shown at the end of this section.
|
---|
1566 |
|
---|
1567 | If the return type of the XSUB includes C<static>, the method is considered
|
---|
1568 | to be a static method. It will call the C++
|
---|
1569 | function using the class::method() syntax. If the method is not static
|
---|
1570 | the function will be called using the THIS-E<gt>method() syntax.
|
---|
1571 |
|
---|
1572 | The next examples will use the following C++ class.
|
---|
1573 |
|
---|
1574 | class color {
|
---|
1575 | public:
|
---|
1576 | color();
|
---|
1577 | ~color();
|
---|
1578 | int blue();
|
---|
1579 | void set_blue( int );
|
---|
1580 |
|
---|
1581 | private:
|
---|
1582 | int c_blue;
|
---|
1583 | };
|
---|
1584 |
|
---|
1585 | The XSUBs for the blue() and set_blue() methods are defined with the class
|
---|
1586 | name but the parameter for the object (THIS, or "self") is implicit and is
|
---|
1587 | not listed.
|
---|
1588 |
|
---|
1589 | int
|
---|
1590 | color::blue()
|
---|
1591 |
|
---|
1592 | void
|
---|
1593 | color::set_blue( val )
|
---|
1594 | int val
|
---|
1595 |
|
---|
1596 | Both Perl functions will expect an object as the first parameter. In the
|
---|
1597 | generated C++ code the object is called C<THIS>, and the method call will
|
---|
1598 | be performed on this object. So in the C++ code the blue() and set_blue()
|
---|
1599 | methods will be called as this:
|
---|
1600 |
|
---|
1601 | RETVAL = THIS->blue();
|
---|
1602 |
|
---|
1603 | THIS->set_blue( val );
|
---|
1604 |
|
---|
1605 | You could also write a single get/set method using an optional argument:
|
---|
1606 |
|
---|
1607 | int
|
---|
1608 | color::blue( val = NO_INIT )
|
---|
1609 | int val
|
---|
1610 | PROTOTYPE $;$
|
---|
1611 | CODE:
|
---|
1612 | if (items > 1)
|
---|
1613 | THIS->set_blue( val );
|
---|
1614 | RETVAL = THIS->blue();
|
---|
1615 | OUTPUT:
|
---|
1616 | RETVAL
|
---|
1617 |
|
---|
1618 | If the function's name is B<DESTROY> then the C++ C<delete> function will be
|
---|
1619 | called and C<THIS> will be given as its parameter. The generated C++ code for
|
---|
1620 |
|
---|
1621 | void
|
---|
1622 | color::DESTROY()
|
---|
1623 |
|
---|
1624 | will look like this:
|
---|
1625 |
|
---|
1626 | color *THIS = ...; // Initialized as in typemap
|
---|
1627 |
|
---|
1628 | delete THIS;
|
---|
1629 |
|
---|
1630 | If the function's name is B<new> then the C++ C<new> function will be called
|
---|
1631 | to create a dynamic C++ object. The XSUB will expect the class name, which
|
---|
1632 | will be kept in a variable called C<CLASS>, to be given as the first
|
---|
1633 | argument.
|
---|
1634 |
|
---|
1635 | color *
|
---|
1636 | color::new()
|
---|
1637 |
|
---|
1638 | The generated C++ code will call C<new>.
|
---|
1639 |
|
---|
1640 | RETVAL = new color();
|
---|
1641 |
|
---|
1642 | The following is an example of a typemap that could be used for this C++
|
---|
1643 | example.
|
---|
1644 |
|
---|
1645 | TYPEMAP
|
---|
1646 | color * O_OBJECT
|
---|
1647 |
|
---|
1648 | OUTPUT
|
---|
1649 | # The Perl object is blessed into 'CLASS', which should be a
|
---|
1650 | # char* having the name of the package for the blessing.
|
---|
1651 | O_OBJECT
|
---|
1652 | sv_setref_pv( $arg, CLASS, (void*)$var );
|
---|
1653 |
|
---|
1654 | INPUT
|
---|
1655 | O_OBJECT
|
---|
1656 | if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVMG) )
|
---|
1657 | $var = ($type)SvIV((SV*)SvRV( $arg ));
|
---|
1658 | else{
|
---|
1659 | warn( \"${Package}::$func_name() -- $var is not a blessed SV reference\" );
|
---|
1660 | XSRETURN_UNDEF;
|
---|
1661 | }
|
---|
1662 |
|
---|
1663 | =head2 Interface Strategy
|
---|
1664 |
|
---|
1665 | When designing an interface between Perl and a C library a straight
|
---|
1666 | translation from C to XS (such as created by C<h2xs -x>) is often sufficient.
|
---|
1667 | However, sometimes the interface will look
|
---|
1668 | very C-like and occasionally nonintuitive, especially when the C function
|
---|
1669 | modifies one of its parameters, or returns failure inband (as in "negative
|
---|
1670 | return values mean failure"). In cases where the programmer wishes to
|
---|
1671 | create a more Perl-like interface the following strategy may help to
|
---|
1672 | identify the more critical parts of the interface.
|
---|
1673 |
|
---|
1674 | Identify the C functions with input/output or output parameters. The XSUBs for
|
---|
1675 | these functions may be able to return lists to Perl.
|
---|
1676 |
|
---|
1677 | Identify the C functions which use some inband info as an indication
|
---|
1678 | of failure. They may be
|
---|
1679 | candidates to return undef or an empty list in case of failure. If the
|
---|
1680 | failure may be detected without a call to the C function, you may want to use
|
---|
1681 | an INIT: section to report the failure. For failures detectable after the C
|
---|
1682 | function returns one may want to use a POSTCALL: section to process the
|
---|
1683 | failure. In more complicated cases use CODE: or PPCODE: sections.
|
---|
1684 |
|
---|
1685 | If many functions use the same failure indication based on the return value,
|
---|
1686 | you may want to create a special typedef to handle this situation. Put
|
---|
1687 |
|
---|
1688 | typedef int negative_is_failure;
|
---|
1689 |
|
---|
1690 | near the beginning of XS file, and create an OUTPUT typemap entry
|
---|
1691 | for C<negative_is_failure> which converts negative values to C<undef>, or
|
---|
1692 | maybe croak()s. After this the return value of type C<negative_is_failure>
|
---|
1693 | will create more Perl-like interface.
|
---|
1694 |
|
---|
1695 | Identify which values are used by only the C and XSUB functions
|
---|
1696 | themselves, say, when a parameter to a function should be a contents of a
|
---|
1697 | global variable. If Perl does not need to access the contents of the value
|
---|
1698 | then it may not be necessary to provide a translation for that value
|
---|
1699 | from C to Perl.
|
---|
1700 |
|
---|
1701 | Identify the pointers in the C function parameter lists and return
|
---|
1702 | values. Some pointers may be used to implement input/output or
|
---|
1703 | output parameters, they can be handled in XS with the C<&> unary operator,
|
---|
1704 | and, possibly, using the NO_INIT keyword.
|
---|
1705 | Some others will require handling of types like C<int *>, and one needs
|
---|
1706 | to decide what a useful Perl translation will do in such a case. When
|
---|
1707 | the semantic is clear, it is advisable to put the translation into a typemap
|
---|
1708 | file.
|
---|
1709 |
|
---|
1710 | Identify the structures used by the C functions. In many
|
---|
1711 | cases it may be helpful to use the T_PTROBJ typemap for
|
---|
1712 | these structures so they can be manipulated by Perl as
|
---|
1713 | blessed objects. (This is handled automatically by C<h2xs -x>.)
|
---|
1714 |
|
---|
1715 | If the same C type is used in several different contexts which require
|
---|
1716 | different translations, C<typedef> several new types mapped to this C type,
|
---|
1717 | and create separate F<typemap> entries for these new types. Use these
|
---|
1718 | types in declarations of return type and parameters to XSUBs.
|
---|
1719 |
|
---|
1720 | =head2 Perl Objects And C Structures
|
---|
1721 |
|
---|
1722 | When dealing with C structures one should select either
|
---|
1723 | B<T_PTROBJ> or B<T_PTRREF> for the XS type. Both types are
|
---|
1724 | designed to handle pointers to complex objects. The
|
---|
1725 | T_PTRREF type will allow the Perl object to be unblessed
|
---|
1726 | while the T_PTROBJ type requires that the object be blessed.
|
---|
1727 | By using T_PTROBJ one can achieve a form of type-checking
|
---|
1728 | because the XSUB will attempt to verify that the Perl object
|
---|
1729 | is of the expected type.
|
---|
1730 |
|
---|
1731 | The following XS code shows the getnetconfigent() function which is used
|
---|
1732 | with ONC+ TIRPC. The getnetconfigent() function will return a pointer to a
|
---|
1733 | C structure and has the C prototype shown below. The example will
|
---|
1734 | demonstrate how the C pointer will become a Perl reference. Perl will
|
---|
1735 | consider this reference to be a pointer to a blessed object and will
|
---|
1736 | attempt to call a destructor for the object. A destructor will be
|
---|
1737 | provided in the XS source to free the memory used by getnetconfigent().
|
---|
1738 | Destructors in XS can be created by specifying an XSUB function whose name
|
---|
1739 | ends with the word B<DESTROY>. XS destructors can be used to free memory
|
---|
1740 | which may have been malloc'd by another XSUB.
|
---|
1741 |
|
---|
1742 | struct netconfig *getnetconfigent(const char *netid);
|
---|
1743 |
|
---|
1744 | A C<typedef> will be created for C<struct netconfig>. The Perl
|
---|
1745 | object will be blessed in a class matching the name of the C
|
---|
1746 | type, with the tag C<Ptr> appended, and the name should not
|
---|
1747 | have embedded spaces if it will be a Perl package name. The
|
---|
1748 | destructor will be placed in a class corresponding to the
|
---|
1749 | class of the object and the PREFIX keyword will be used to
|
---|
1750 | trim the name to the word DESTROY as Perl will expect.
|
---|
1751 |
|
---|
1752 | typedef struct netconfig Netconfig;
|
---|
1753 |
|
---|
1754 | MODULE = RPC PACKAGE = RPC
|
---|
1755 |
|
---|
1756 | Netconfig *
|
---|
1757 | getnetconfigent(netid)
|
---|
1758 | char *netid
|
---|
1759 |
|
---|
1760 | MODULE = RPC PACKAGE = NetconfigPtr PREFIX = rpcb_
|
---|
1761 |
|
---|
1762 | void
|
---|
1763 | rpcb_DESTROY(netconf)
|
---|
1764 | Netconfig *netconf
|
---|
1765 | CODE:
|
---|
1766 | printf("Now in NetconfigPtr::DESTROY\n");
|
---|
1767 | free( netconf );
|
---|
1768 |
|
---|
1769 | This example requires the following typemap entry. Consult the typemap
|
---|
1770 | section for more information about adding new typemaps for an extension.
|
---|
1771 |
|
---|
1772 | TYPEMAP
|
---|
1773 | Netconfig * T_PTROBJ
|
---|
1774 |
|
---|
1775 | This example will be used with the following Perl statements.
|
---|
1776 |
|
---|
1777 | use RPC;
|
---|
1778 | $netconf = getnetconfigent("udp");
|
---|
1779 |
|
---|
1780 | When Perl destroys the object referenced by $netconf it will send the
|
---|
1781 | object to the supplied XSUB DESTROY function. Perl cannot determine, and
|
---|
1782 | does not care, that this object is a C struct and not a Perl object. In
|
---|
1783 | this sense, there is no difference between the object created by the
|
---|
1784 | getnetconfigent() XSUB and an object created by a normal Perl subroutine.
|
---|
1785 |
|
---|
1786 | =head2 The Typemap
|
---|
1787 |
|
---|
1788 | The typemap is a collection of code fragments which are used by the B<xsubpp>
|
---|
1789 | compiler to map C function parameters and values to Perl values. The
|
---|
1790 | typemap file may consist of three sections labelled C<TYPEMAP>, C<INPUT>, and
|
---|
1791 | C<OUTPUT>. An unlabelled initial section is assumed to be a C<TYPEMAP>
|
---|
1792 | section. The INPUT section tells
|
---|
1793 | the compiler how to translate Perl values
|
---|
1794 | into variables of certain C types. The OUTPUT section tells the compiler
|
---|
1795 | how to translate the values from certain C types into values Perl can
|
---|
1796 | understand. The TYPEMAP section tells the compiler which of the INPUT and
|
---|
1797 | OUTPUT code fragments should be used to map a given C type to a Perl value.
|
---|
1798 | The section labels C<TYPEMAP>, C<INPUT>, or C<OUTPUT> must begin
|
---|
1799 | in the first column on a line by themselves, and must be in uppercase.
|
---|
1800 |
|
---|
1801 | The default typemap in the C<lib/ExtUtils> directory of the Perl source
|
---|
1802 | contains many useful types which can be used by Perl extensions. Some
|
---|
1803 | extensions define additional typemaps which they keep in their own directory.
|
---|
1804 | These additional typemaps may reference INPUT and OUTPUT maps in the main
|
---|
1805 | typemap. The B<xsubpp> compiler will allow the extension's own typemap to
|
---|
1806 | override any mappings which are in the default typemap.
|
---|
1807 |
|
---|
1808 | Most extensions which require a custom typemap will need only the TYPEMAP
|
---|
1809 | section of the typemap file. The custom typemap used in the
|
---|
1810 | getnetconfigent() example shown earlier demonstrates what may be the typical
|
---|
1811 | use of extension typemaps. That typemap is used to equate a C structure
|
---|
1812 | with the T_PTROBJ typemap. The typemap used by getnetconfigent() is shown
|
---|
1813 | here. Note that the C type is separated from the XS type with a tab and
|
---|
1814 | that the C unary operator C<*> is considered to be a part of the C type name.
|
---|
1815 |
|
---|
1816 | TYPEMAP
|
---|
1817 | Netconfig *<tab>T_PTROBJ
|
---|
1818 |
|
---|
1819 | Here's a more complicated example: suppose that you wanted C<struct
|
---|
1820 | netconfig> to be blessed into the class C<Net::Config>. One way to do
|
---|
1821 | this is to use underscores (_) to separate package names, as follows:
|
---|
1822 |
|
---|
1823 | typedef struct netconfig * Net_Config;
|
---|
1824 |
|
---|
1825 | And then provide a typemap entry C<T_PTROBJ_SPECIAL> that maps underscores to
|
---|
1826 | double-colons (::), and declare C<Net_Config> to be of that type:
|
---|
1827 |
|
---|
1828 |
|
---|
1829 | TYPEMAP
|
---|
1830 | Net_Config T_PTROBJ_SPECIAL
|
---|
1831 |
|
---|
1832 | INPUT
|
---|
1833 | T_PTROBJ_SPECIAL
|
---|
1834 | if (sv_derived_from($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")) {
|
---|
1835 | IV tmp = SvIV((SV*)SvRV($arg));
|
---|
1836 | $var = INT2PTR($type, tmp);
|
---|
1837 | }
|
---|
1838 | else
|
---|
1839 | croak(\"$var is not of type ${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\")
|
---|
1840 |
|
---|
1841 | OUTPUT
|
---|
1842 | T_PTROBJ_SPECIAL
|
---|
1843 | sv_setref_pv($arg, \"${(my $ntt=$ntype)=~s/_/::/g;\$ntt}\",
|
---|
1844 | (void*)$var);
|
---|
1845 |
|
---|
1846 | The INPUT and OUTPUT sections substitute underscores for double-colons
|
---|
1847 | on the fly, giving the desired effect. This example demonstrates some
|
---|
1848 | of the power and versatility of the typemap facility.
|
---|
1849 |
|
---|
1850 | The INT2PTR macro (defined in perl.h) casts an integer to a pointer,
|
---|
1851 | of a given type, taking care of the possible different size of integers
|
---|
1852 | and pointers. There are also PTR2IV, PTR2UV, PTR2NV macros,
|
---|
1853 | to map the other way, which may be useful in OUTPUT sections.
|
---|
1854 |
|
---|
1855 | =head2 Safely Storing Static Data in XS
|
---|
1856 |
|
---|
1857 | Starting with Perl 5.8, a macro framework has been defined to allow
|
---|
1858 | static data to be safely stored in XS modules that will be accessed from
|
---|
1859 | a multi-threaded Perl.
|
---|
1860 |
|
---|
1861 | Although primarily designed for use with multi-threaded Perl, the macros
|
---|
1862 | have been designed so that they will work with non-threaded Perl as well.
|
---|
1863 |
|
---|
1864 | It is therefore strongly recommended that these macros be used by all
|
---|
1865 | XS modules that make use of static data.
|
---|
1866 |
|
---|
1867 | The easiest way to get a template set of macros to use is by specifying
|
---|
1868 | the C<-g> (C<--global>) option with h2xs (see L<h2xs>).
|
---|
1869 |
|
---|
1870 | Below is an example module that makes use of the macros.
|
---|
1871 |
|
---|
1872 | #include "EXTERN.h"
|
---|
1873 | #include "perl.h"
|
---|
1874 | #include "XSUB.h"
|
---|
1875 |
|
---|
1876 | /* Global Data */
|
---|
1877 |
|
---|
1878 | #define MY_CXT_KEY "BlindMice::_guts" XS_VERSION
|
---|
1879 |
|
---|
1880 | typedef struct {
|
---|
1881 | int count;
|
---|
1882 | char name[3][100];
|
---|
1883 | } my_cxt_t;
|
---|
1884 |
|
---|
1885 | START_MY_CXT
|
---|
1886 |
|
---|
1887 | MODULE = BlindMice PACKAGE = BlindMice
|
---|
1888 |
|
---|
1889 | BOOT:
|
---|
1890 | {
|
---|
1891 | MY_CXT_INIT;
|
---|
1892 | MY_CXT.count = 0;
|
---|
1893 | strcpy(MY_CXT.name[0], "None");
|
---|
1894 | strcpy(MY_CXT.name[1], "None");
|
---|
1895 | strcpy(MY_CXT.name[2], "None");
|
---|
1896 | }
|
---|
1897 |
|
---|
1898 | int
|
---|
1899 | newMouse(char * name)
|
---|
1900 | char * name;
|
---|
1901 | PREINIT:
|
---|
1902 | dMY_CXT;
|
---|
1903 | CODE:
|
---|
1904 | if (MY_CXT.count >= 3) {
|
---|
1905 | warn("Already have 3 blind mice");
|
---|
1906 | RETVAL = 0;
|
---|
1907 | }
|
---|
1908 | else {
|
---|
1909 | RETVAL = ++ MY_CXT.count;
|
---|
1910 | strcpy(MY_CXT.name[MY_CXT.count - 1], name);
|
---|
1911 | }
|
---|
1912 |
|
---|
1913 | char *
|
---|
1914 | get_mouse_name(index)
|
---|
1915 | int index
|
---|
1916 | CODE:
|
---|
1917 | dMY_CXT;
|
---|
1918 | RETVAL = MY_CXT.lives ++;
|
---|
1919 | if (index > MY_CXT.count)
|
---|
1920 | croak("There are only 3 blind mice.");
|
---|
1921 | else
|
---|
1922 | RETVAL = newSVpv(MY_CXT.name[index - 1]);
|
---|
1923 |
|
---|
1924 |
|
---|
1925 | B<REFERENCE>
|
---|
1926 |
|
---|
1927 | =over 5
|
---|
1928 |
|
---|
1929 | =item MY_CXT_KEY
|
---|
1930 |
|
---|
1931 | This macro is used to define a unique key to refer to the static data
|
---|
1932 | for an XS module. The suggested naming scheme, as used by h2xs, is to
|
---|
1933 | use a string that consists of the module name, the string "::_guts"
|
---|
1934 | and the module version number.
|
---|
1935 |
|
---|
1936 | #define MY_CXT_KEY "MyModule::_guts" XS_VERSION
|
---|
1937 |
|
---|
1938 | =item typedef my_cxt_t
|
---|
1939 |
|
---|
1940 | This struct typedef I<must> always be called C<my_cxt_t> -- the other
|
---|
1941 | C<CXT*> macros assume the existence of the C<my_cxt_t> typedef name.
|
---|
1942 |
|
---|
1943 | Declare a typedef named C<my_cxt_t> that is a structure that contains
|
---|
1944 | all the data that needs to be interpreter-local.
|
---|
1945 |
|
---|
1946 | typedef struct {
|
---|
1947 | int some_value;
|
---|
1948 | } my_cxt_t;
|
---|
1949 |
|
---|
1950 | =item START_MY_CXT
|
---|
1951 |
|
---|
1952 | Always place the START_MY_CXT macro directly after the declaration
|
---|
1953 | of C<my_cxt_t>.
|
---|
1954 |
|
---|
1955 | =item MY_CXT_INIT
|
---|
1956 |
|
---|
1957 | The MY_CXT_INIT macro initialises storage for the C<my_cxt_t> struct.
|
---|
1958 |
|
---|
1959 | It I<must> be called exactly once -- typically in a BOOT: section.
|
---|
1960 |
|
---|
1961 | =item dMY_CXT
|
---|
1962 |
|
---|
1963 | Use the dMY_CXT macro (a declaration) in all the functions that access
|
---|
1964 | MY_CXT.
|
---|
1965 |
|
---|
1966 | =item MY_CXT
|
---|
1967 |
|
---|
1968 | Use the MY_CXT macro to access members of the C<my_cxt_t> struct. For
|
---|
1969 | example, if C<my_cxt_t> is
|
---|
1970 |
|
---|
1971 | typedef struct {
|
---|
1972 | int index;
|
---|
1973 | } my_cxt_t;
|
---|
1974 |
|
---|
1975 | then use this to access the C<index> member
|
---|
1976 |
|
---|
1977 | dMY_CXT;
|
---|
1978 | MY_CXT.index = 2;
|
---|
1979 |
|
---|
1980 | =back
|
---|
1981 |
|
---|
1982 | =head1 EXAMPLES
|
---|
1983 |
|
---|
1984 | File C<RPC.xs>: Interface to some ONC+ RPC bind library functions.
|
---|
1985 |
|
---|
1986 | #include "EXTERN.h"
|
---|
1987 | #include "perl.h"
|
---|
1988 | #include "XSUB.h"
|
---|
1989 |
|
---|
1990 | #include <rpc/rpc.h>
|
---|
1991 |
|
---|
1992 | typedef struct netconfig Netconfig;
|
---|
1993 |
|
---|
1994 | MODULE = RPC PACKAGE = RPC
|
---|
1995 |
|
---|
1996 | SV *
|
---|
1997 | rpcb_gettime(host="localhost")
|
---|
1998 | char *host
|
---|
1999 | PREINIT:
|
---|
2000 | time_t timep;
|
---|
2001 | CODE:
|
---|
2002 | ST(0) = sv_newmortal();
|
---|
2003 | if( rpcb_gettime( host, &timep ) )
|
---|
2004 | sv_setnv( ST(0), (double)timep );
|
---|
2005 |
|
---|
2006 | Netconfig *
|
---|
2007 | getnetconfigent(netid="udp")
|
---|
2008 | char *netid
|
---|
2009 |
|
---|
2010 | MODULE = RPC PACKAGE = NetconfigPtr PREFIX = rpcb_
|
---|
2011 |
|
---|
2012 | void
|
---|
2013 | rpcb_DESTROY(netconf)
|
---|
2014 | Netconfig *netconf
|
---|
2015 | CODE:
|
---|
2016 | printf("NetconfigPtr::DESTROY\n");
|
---|
2017 | free( netconf );
|
---|
2018 |
|
---|
2019 | File C<typemap>: Custom typemap for RPC.xs.
|
---|
2020 |
|
---|
2021 | TYPEMAP
|
---|
2022 | Netconfig * T_PTROBJ
|
---|
2023 |
|
---|
2024 | File C<RPC.pm>: Perl module for the RPC extension.
|
---|
2025 |
|
---|
2026 | package RPC;
|
---|
2027 |
|
---|
2028 | require Exporter;
|
---|
2029 | require DynaLoader;
|
---|
2030 | @ISA = qw(Exporter DynaLoader);
|
---|
2031 | @EXPORT = qw(rpcb_gettime getnetconfigent);
|
---|
2032 |
|
---|
2033 | bootstrap RPC;
|
---|
2034 | 1;
|
---|
2035 |
|
---|
2036 | File C<rpctest.pl>: Perl test program for the RPC extension.
|
---|
2037 |
|
---|
2038 | use RPC;
|
---|
2039 |
|
---|
2040 | $netconf = getnetconfigent();
|
---|
2041 | $a = rpcb_gettime();
|
---|
2042 | print "time = $a\n";
|
---|
2043 | print "netconf = $netconf\n";
|
---|
2044 |
|
---|
2045 | $netconf = getnetconfigent("tcp");
|
---|
2046 | $a = rpcb_gettime("poplar");
|
---|
2047 | print "time = $a\n";
|
---|
2048 | print "netconf = $netconf\n";
|
---|
2049 |
|
---|
2050 |
|
---|
2051 | =head1 XS VERSION
|
---|
2052 |
|
---|
2053 | This document covers features supported by C<xsubpp> 1.935.
|
---|
2054 |
|
---|
2055 | =head1 AUTHOR
|
---|
2056 |
|
---|
2057 | Originally written by Dean Roehrich <F<roehrich@cray.com>>.
|
---|
2058 |
|
---|
2059 | Maintained since 1996 by The Perl Porters <F<perlbug@perl.org>>.
|
---|