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Rev 537 Rev 949
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/* This file is part of the SvarCOM project and is published under the terms
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/* This file is part of the SvarCOM project and is published under the terms
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 * of the MIT license.
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 * of the MIT license.
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 *
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 *
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 * Copyright (C) 2021 Mateusz Viste
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 * Copyright (C) 2021-2022 Mateusz Viste
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 *
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 *
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 * Permission is hereby granted, free of charge, to any person obtaining a
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 * Permission is hereby granted, free of charge, to any person obtaining a
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 * copy of this software and associated documentation files (the "Software"),
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 * copy of this software and associated documentation files (the "Software"),
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 * to deal in the Software without restriction, including without limitation
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 * to deal in the Software without restriction, including without limitation
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 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
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 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
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    *comspecptr = FP_OFF(comspecfp);
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    *comspecptr = FP_OFF(comspecfp);
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  } else {
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  } else {
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    *comspecptr = 0;
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    *comspecptr = 0;
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  }
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  }
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}
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}
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/* allocates bytes of far memory, flags it as belonging to rmod
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 * the new block can be optionally flagged as 'ident' (if not null)
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 * returns a far ptr to the allocated block, or NULL on error */
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void far *rmod_fmalloc(unsigned short bytes, unsigned short rmod_seg, char *ident) {
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  unsigned short far *owner;
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  unsigned short newseg = 0;
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  /* ask DOS for a memory block (as high as possible) */
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  _asm {
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    push bx /* save initial value in BX so I can restore it later */
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    /* get current allocation strategy and save it on stack */
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    mov ax, 0x5800
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    int 0x21
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    push ax
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    /* set strategy to 'last fit, try high then low memory' */
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    mov ax, 0x5801
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    mov bx, 0x0082
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    int 0x21
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    /* ask for a memory block and save the given segment to rmodseg */
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    mov ah, 0x48  /* Allocate Memory */
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    mov bx, bytes
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    add bx, 15    /* convert bytes to paragraphs */
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    shr bx, 1     /* bx /= 16 */
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    shr bx, 1
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    shr bx, 1
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    shr bx, 1
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    int 0x21
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    /* error handling */
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    jc FAIL
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    /* save newly allocated segment to newseg */
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    mov newseg, ax
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    FAIL:
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    /* restore initial allocation strategy */
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    mov ax, 0x5801
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    pop bx
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    int 0x21
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    pop bx /* restore BX to its initial value */
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  }
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  if (newseg == 0) return(NULL);
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  /* mark memory as "owned by rmod" */
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  owner = (void far *)(MK_FP(newseg - 1, 1));
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  *owner = rmod_seg;
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  /* set the MCB description to ident, if provided */
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  if (ident) {
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    char far *mcbdesc = MK_FP(newseg - 1, 8);
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    int i;
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    _fmemset(mcbdesc, 0, 8);
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    for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */
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      mcbdesc[i] = ident[i];
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    }
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  }
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  return(MK_FP(newseg, 0));
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}
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/* free memory previously allocated by rmod_ffmalloc() */
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void rmod_ffree(void far *ptr) {
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  unsigned short ptrseg;
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  unsigned short myseg = 0;
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  unsigned short far *owner;
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  if (ptr == NULL) return;
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  ptrseg = FP_SEG(ptr);
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  /* get my own segment */
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  _asm {
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    mov myseg, cs
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  }
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  /* mark memory in MCB as my own, otherwise DOS might refuse to free it */
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  owner = MK_FP(ptrseg - 1, 1);
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  *owner = myseg;
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  /* free the memory block */
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  _asm {
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    push es
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    mov ah, 0x49  /* Free Memory Block */
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    mov es, ptrseg
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    int 0x21
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    pop es
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  }
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}