| 1 | ;
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| 2 | ; jmemdosa.asm
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| 3 | ;
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| 4 | ; Copyright (C) 1992, Thomas G. Lane.
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| 5 | ; This file is part of the Independent JPEG Group's software.
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| 6 | ; For conditions of distribution and use, see the accompanying README file.
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| 7 | ;
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| 8 | ; This file contains low-level interface routines to support the MS-DOS
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| 9 | ; backing store manager (jmemdos.c). Routines are provided to access disk
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| 10 | ; files through direct DOS calls, and to access XMS and EMS drivers.
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| 11 | ;
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| 12 | ; This file should assemble with Microsoft's MASM or any compatible
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| 13 | ; assembler (including Borland's Turbo Assembler). If you haven't got
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| 14 | ; a compatible assembler, better fall back to jmemansi.c or jmemname.c.
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| 15 | ;
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| 16 | ; To minimize dependence on the C compiler's register usage conventions,
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| 17 | ; we save and restore all 8086 registers, even though most compilers only
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| 18 | ; require SI,DI,DS to be preserved. Also, we use only 16-bit-wide return
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| 19 | ; values, which everybody returns in AX.
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| 20 | ;
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| 21 | ; Based on code contributed by Ge' Weijers.
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| 22 | ;
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| 23 |
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| 24 | JMEMDOSA_TXT segment byte public 'CODE'
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| 25 |
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| 26 | assume cs:JMEMDOSA_TXT
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| 27 |
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| 28 | public _jdos_open
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| 29 | public _jdos_close
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| 30 | public _jdos_seek
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| 31 | public _jdos_read
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| 32 | public _jdos_write
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| 33 | public _jxms_getdriver
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| 34 | public _jxms_calldriver
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| 35 | public _jems_available
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| 36 | public _jems_calldriver
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| 37 |
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| 38 | ;
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| 39 | ; short far jdos_open (short far * handle, char far * filename)
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| 40 | ;
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| 41 | ; Create and open a temporary file
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| 42 | ;
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| 43 | _jdos_open proc far
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| 44 | push bp ; linkage
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| 45 | mov bp,sp
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| 46 | push si ; save all registers for safety
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| 47 | push di
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| 48 | push bx
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| 49 | push cx
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| 50 | push dx
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| 51 | push es
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| 52 | push ds
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| 53 | mov cx,0 ; normal file attributes
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| 54 | lds dx,dword ptr [bp+10] ; get filename pointer
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| 55 | mov ah,3ch ; create file
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| 56 | int 21h
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| 57 | jc open_err ; if failed, return error code
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| 58 | lds bx,dword ptr [bp+6] ; get handle pointer
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| 59 | mov word ptr [bx],ax ; save the handle
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| 60 | xor ax,ax ; return zero for OK
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| 61 | open_err: pop ds ; restore registers and exit
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| 62 | pop es
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| 63 | pop dx
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| 64 | pop cx
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| 65 | pop bx
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| 66 | pop di
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| 67 | pop si
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| 68 | pop bp
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| 69 | ret
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| 70 | _jdos_open endp
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| 71 |
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| 72 |
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| 73 | ;
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| 74 | ; short far jdos_close (short handle)
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| 75 | ;
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| 76 | ; Close the file handle
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| 77 | ;
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| 78 | _jdos_close proc far
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| 79 | push bp ; linkage
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| 80 | mov bp,sp
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| 81 | push si ; save all registers for safety
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| 82 | push di
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| 83 | push bx
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| 84 | push cx
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| 85 | push dx
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| 86 | push es
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| 87 | push ds
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| 88 | mov bx,word ptr [bp+6] ; file handle
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| 89 | mov ah,3eh ; close file
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| 90 | int 21h
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| 91 | jc close_err ; if failed, return error code
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| 92 | xor ax,ax ; return zero for OK
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| 93 | close_err: pop ds ; restore registers and exit
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| 94 | pop es
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| 95 | pop dx
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| 96 | pop cx
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| 97 | pop bx
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| 98 | pop di
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| 99 | pop si
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| 100 | pop bp
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| 101 | ret
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| 102 | _jdos_close endp
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| 103 |
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| 104 |
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| 105 | ;
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| 106 | ; short far jdos_seek (short handle, long offset)
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| 107 | ;
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| 108 | ; Set file position
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| 109 | ;
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| 110 | _jdos_seek proc far
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| 111 | push bp ; linkage
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| 112 | mov bp,sp
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| 113 | push si ; save all registers for safety
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| 114 | push di
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| 115 | push bx
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| 116 | push cx
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| 117 | push dx
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| 118 | push es
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| 119 | push ds
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| 120 | mov bx,word ptr [bp+6] ; file handle
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| 121 | mov dx,word ptr [bp+8] ; LS offset
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| 122 | mov cx,word ptr [bp+10] ; MS offset
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| 123 | mov ax,4200h ; absolute seek
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| 124 | int 21h
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| 125 | jc seek_err ; if failed, return error code
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| 126 | xor ax,ax ; return zero for OK
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| 127 | seek_err: pop ds ; restore registers and exit
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| 128 | pop es
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| 129 | pop dx
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| 130 | pop cx
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| 131 | pop bx
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| 132 | pop di
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| 133 | pop si
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| 134 | pop bp
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| 135 | ret
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| 136 | _jdos_seek endp
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| 137 |
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| 138 |
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| 139 | ;
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| 140 | ; short far jdos_read (short handle, void far * buffer, unsigned short count)
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| 141 | ;
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| 142 | ; Read from file
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| 143 | ;
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| 144 | _jdos_read proc far
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| 145 | push bp ; linkage
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| 146 | mov bp,sp
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| 147 | push si ; save all registers for safety
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| 148 | push di
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| 149 | push bx
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| 150 | push cx
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| 151 | push dx
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| 152 | push es
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| 153 | push ds
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| 154 | mov bx,word ptr [bp+6] ; file handle
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| 155 | lds dx,dword ptr [bp+8] ; buffer address
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| 156 | mov cx,word ptr [bp+12] ; number of bytes
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| 157 | mov ah,3fh ; read file
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| 158 | int 21h
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| 159 | jc read_err ; if failed, return error code
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| 160 | cmp ax,word ptr [bp+12] ; make sure all bytes were read
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| 161 | je read_ok
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| 162 | mov ax,1 ; else return 1 for not OK
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| 163 | jmp short read_err
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| 164 | read_ok: xor ax,ax ; return zero for OK
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| 165 | read_err: pop ds ; restore registers and exit
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| 166 | pop es
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| 167 | pop dx
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| 168 | pop cx
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| 169 | pop bx
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| 170 | pop di
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| 171 | pop si
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| 172 | pop bp
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| 173 | ret
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| 174 | _jdos_read endp
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| 175 |
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| 176 |
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| 177 | ;
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| 178 | ; short far jdos_write (short handle, void far * buffer, unsigned short count)
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| 179 | ;
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| 180 | ; Write to file
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| 181 | ;
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| 182 | _jdos_write proc far
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| 183 | push bp ; linkage
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| 184 | mov bp,sp
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| 185 | push si ; save all registers for safety
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| 186 | push di
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| 187 | push bx
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| 188 | push cx
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| 189 | push dx
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| 190 | push es
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| 191 | push ds
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| 192 | mov bx,word ptr [bp+6] ; file handle
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| 193 | lds dx,dword ptr [bp+8] ; buffer address
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| 194 | mov cx,word ptr [bp+12] ; number of bytes
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| 195 | mov ah,40h ; write file
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| 196 | int 21h
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| 197 | jc write_err ; if failed, return error code
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| 198 | cmp ax,word ptr [bp+12] ; make sure all bytes written
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| 199 | je write_ok
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| 200 | mov ax,1 ; else return 1 for not OK
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| 201 | jmp short write_err
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| 202 | write_ok: xor ax,ax ; return zero for OK
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| 203 | write_err: pop ds ; restore registers and exit
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| 204 | pop es
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| 205 | pop dx
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| 206 | pop cx
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| 207 | pop bx
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| 208 | pop di
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| 209 | pop si
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| 210 | pop bp
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| 211 | ret
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| 212 | _jdos_write endp
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| 213 |
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| 214 |
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| 215 | ;
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| 216 | ; void far jxms_getdriver (XMSDRIVER far *)
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| 217 | ;
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| 218 | ; Get the address of the XMS driver, or NULL if not available
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| 219 | ;
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| 220 | _jxms_getdriver proc far
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| 221 | push bp ; linkage
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| 222 | mov bp,sp
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| 223 | push si ; save all registers for safety
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| 224 | push di
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| 225 | push bx
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| 226 | push cx
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| 227 | push dx
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| 228 | push es
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| 229 | push ds
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| 230 | mov ax,4300h ; call multiplex interrupt with
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| 231 | int 2fh ; a magic cookie, hex 4300
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| 232 | cmp al,80h ; AL should contain hex 80
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| 233 | je xmsavail
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| 234 | xor dx,dx ; no XMS driver available
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| 235 | xor ax,ax ; return a nil pointer
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| 236 | jmp short xmsavail_done
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| 237 | xmsavail: mov ax,4310h ; fetch driver address with
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| 238 | int 2fh ; another magic cookie
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| 239 | mov dx,es ; copy address to dx:ax
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| 240 | mov ax,bx
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| 241 | xmsavail_done: les bx,dword ptr [bp+6] ; get pointer to return value
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| 242 | mov word ptr es:[bx],ax
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| 243 | mov word ptr es:[bx+2],dx
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| 244 | pop ds ; restore registers and exit
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| 245 | pop es
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| 246 | pop dx
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| 247 | pop cx
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| 248 | pop bx
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| 249 | pop di
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| 250 | pop si
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| 251 | pop bp
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| 252 | ret
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| 253 | _jxms_getdriver endp
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| 254 |
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| 255 |
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| 256 | ;
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| 257 | ; void far jxms_calldriver (XMSDRIVER, XMScontext far *)
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| 258 | ;
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| 259 | ; The XMScontext structure contains values for the AX,DX,BX,SI,DS registers.
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| 260 | ; These are loaded, the XMS call is performed, and the new values of the
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| 261 | ; AX,DX,BX registers are written back to the context structure.
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| 262 | ;
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| 263 | _jxms_calldriver proc far
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| 264 | push bp ; linkage
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| 265 | mov bp,sp
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| 266 | push si ; save all registers for safety
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| 267 | push di
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| 268 | push bx
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| 269 | push cx
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| 270 | push dx
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| 271 | push es
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| 272 | push ds
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| 273 | les bx,dword ptr [bp+10] ; get XMScontext pointer
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| 274 | mov ax,word ptr es:[bx] ; load registers
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| 275 | mov dx,word ptr es:[bx+2]
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| 276 | mov si,word ptr es:[bx+6]
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| 277 | mov ds,word ptr es:[bx+8]
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| 278 | mov bx,word ptr es:[bx+4]
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| 279 | call dword ptr [bp+6] ; call the driver
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| 280 | mov cx,bx ; save returned BX for a sec
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| 281 | les bx,dword ptr [bp+10] ; get XMScontext pointer
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| 282 | mov word ptr es:[bx],ax ; put back ax,dx,bx
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| 283 | mov word ptr es:[bx+2],dx
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| 284 | mov word ptr es:[bx+4],cx
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| 285 | pop ds ; restore registers and exit
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| 286 | pop es
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| 287 | pop dx
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| 288 | pop cx
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| 289 | pop bx
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| 290 | pop di
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| 291 | pop si
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| 292 | pop bp
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| 293 | ret
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| 294 | _jxms_calldriver endp
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| 295 |
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| 296 |
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| 297 | ;
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| 298 | ; short far jems_available (void)
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| 299 | ;
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| 300 | ; Have we got an EMS driver? (this comes straight from the EMS 4.0 specs)
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| 301 | ;
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| 302 | _jems_available proc far
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| 303 | push si ; save all registers for safety
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| 304 | push di
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| 305 | push bx
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| 306 | push cx
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| 307 | push dx
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| 308 | push es
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| 309 | push ds
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| 310 | mov ax,3567h ; get interrupt vector 67h
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| 311 | int 21h
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| 312 | push cs
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| 313 | pop ds
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| 314 | mov di,000ah ; check offs 10 in returned seg
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| 315 | lea si,ASCII_device_name ; against literal string
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| 316 | mov cx,8
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| 317 | cld
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| 318 | repe cmpsb
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| 319 | jne no_ems
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| 320 | mov ax,1 ; match, it's there
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| 321 | jmp short avail_done
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| 322 | no_ems: xor ax,ax ; it's not there
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| 323 | avail_done: pop ds ; restore registers and exit
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| 324 | pop es
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| 325 | pop dx
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| 326 | pop cx
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| 327 | pop bx
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| 328 | pop di
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| 329 | pop si
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| 330 | ret
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| 331 |
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| 332 | ASCII_device_name db "EMMXXXX0"
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| 333 |
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| 334 | _jems_available endp
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| 335 |
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| 336 |
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| 337 | ;
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| 338 | ; void far jems_calldriver (EMScontext far *)
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| 339 | ;
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| 340 | ; The EMScontext structure contains values for the AX,DX,BX,SI,DS registers.
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| 341 | ; These are loaded, the EMS trap is performed, and the new values of the
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| 342 | ; AX,DX,BX registers are written back to the context structure.
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| 343 | ;
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| 344 | _jems_calldriver proc far
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| 345 | push bp ; linkage
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| 346 | mov bp,sp
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| 347 | push si ; save all registers for safety
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| 348 | push di
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| 349 | push bx
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| 350 | push cx
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| 351 | push dx
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| 352 | push es
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| 353 | push ds
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| 354 | les bx,dword ptr [bp+6] ; get EMScontext pointer
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| 355 | mov ax,word ptr es:[bx] ; load registers
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| 356 | mov dx,word ptr es:[bx+2]
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| 357 | mov si,word ptr es:[bx+6]
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| 358 | mov ds,word ptr es:[bx+8]
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| 359 | mov bx,word ptr es:[bx+4]
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| 360 | int 67h ; call the EMS driver
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| 361 | mov cx,bx ; save returned BX for a sec
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| 362 | les bx,dword ptr [bp+6] ; get EMScontext pointer
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| 363 | mov word ptr es:[bx],ax ; put back ax,dx,bx
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| 364 | mov word ptr es:[bx+2],dx
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| 365 | mov word ptr es:[bx+4],cx
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| 366 | pop ds ; restore registers and exit
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| 367 | pop es
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| 368 | pop dx
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| 369 | pop cx
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| 370 | pop bx
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| 371 | pop di
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| 372 | pop si
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| 373 | pop bp
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| 374 | ret
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| 375 | _jems_calldriver endp
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| 376 |
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| 377 | JMEMDOSA_TXT ends
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| 378 |
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| 379 | end
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