source: vendor/perl/5.8.8/t/op/read.t

#!./perl

# $RCSfile: read.t,v $$Revision: 4.1 $$Date: 92/08/07 18:28:17 $

BEGIN {
    chdir 't';
    @INC = '../lib';
    require './test.pl';
}
use strict;

plan tests => 2564;

open(FOO,'op/read.t') || open(FOO,'t/op/read.t') || open(FOO,':op:read.t') || die "Can't open op.read";
seek(FOO,4,0) or die "Seek failed: $!";
my $buf;
my $got = read(FOO,$buf,4);

is ($got, 4);
is ($buf, "perl");

seek (FOO,0,2) || seek(FOO,20000,0);
$got = read(FOO,$buf,4);

is ($got, 0);
is ($buf, "");

# This is true if Config is not built, or if PerlIO is enabled
# ie assume that PerlIO is present, unless we know for sure otherwise.
my $has_perlio = !eval {
    no warnings;
    require Config;
    !$Config::Config{useperlio}
};

my $tmpfile = 'Op_read.tmp';

END { 1 while unlink $tmpfile }

my (@values, @buffers) = ('', '');

foreach (65, 161, 253, 9786) {
    push @values, join "", map {chr $_} $_ .. $_ + 4;
    push @buffers, join "", map {chr $_} $_ + 5 .. $_ + 20;
}
my @offsets = (0, 3, 7, 22, -1, -3, -5, -7);
my @lengths = (0, 2, 5, 10);

foreach my $value (@values) {
    foreach my $initial_buffer (@buffers) {
        my @utf8 = 1;
        if ($value !~ tr/\0-\377//c) {
            # It's all 8 bit
            unshift @utf8, 0;
        }
      SKIP:
        foreach my $utf8 (@utf8) {
            skip "Needs :utf8 layer but no perlio", 2 * @offsets * @lengths
              if $utf8 and !$has_perlio;

            1 while unlink $tmpfile;
            open FH, ">$tmpfile" or die "Can't open $tmpfile: $!";
            binmode FH, "utf8" if $utf8;
            print FH $value;
            close FH;
            foreach my $offset (@offsets) {
                foreach my $length (@lengths) {
                    # Will read the lesser of the length of the file and the
                    # read length
                    my $will_read = $value;
                    if ($length < length $will_read) {
                        substr ($will_read, $length) = '';
                    }
                    # Going to trash this so need a copy
                    my $buffer = $initial_buffer;

                    my $expect = $buffer;
                    if ($offset > 0) {
                        # Right pad with NUL bytes
                        $expect .= "\0" x $offset;
                        substr ($expect, $offset) = '';
                    }
                    substr ($expect, $offset) = $will_read;

                    open FH, $tmpfile or die "Can't open $tmpfile: $!";
                    binmode FH, "utf8" if $utf8;
                    my $what = sprintf "%d into %d l $length o $offset",
                        ord $value, ord $buffer;
                    $what .= ' u' if $utf8;
                    $got = read (FH, $buffer, $length, $offset);
                    is ($got, length $will_read, "got $what");
                    is ($buffer, $expect, "buffer $what");
                    close FH;
                }
            }
        }
    }
}