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1556 mateusz.vi 1 
/*
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 * replacement for a couple of libc functions
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 */
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#include <i86.h>
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#include <stddef.h>
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#include "libc.h"
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size_t strlen(const char *s) {
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  size_t res = 0;
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  while (s[res] != 0) res++;
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  return(res);
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}
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void bzero(void *ptr, size_t len) {
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  while (len > 0) ((char *)ptr)[--len] = 0;
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}
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/* TODO this function does not handle overlapping strings well! */
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void far *_fmemmove(void far *dst, const void far *src, size_t len) {
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  while (len-- > 0) {
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    ((char far *)dst)[len] = ((char far *)src)[len];
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  }
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  return(dst);
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}
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unsigned short mdr_dos_fopen(const char *fname, unsigned short *fhandle) {
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  unsigned short res = 0;
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  unsigned short handle = 0;
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  unsigned short fname_seg = FP_SEG(fname);
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  unsigned short fname_off = FP_OFF(fname);
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  _asm {
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    push cx
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    push dx
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    mov ax, 0x3d00
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    mov dx, fname_off
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    xor cl, cl
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    push ds
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    mov ds, fname_seg
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    int 0x21
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    pop ds
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    jc err
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    mov handle, ax
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    jmp done
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    err:
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    mov res, ax
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    done:
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    pop dx
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    pop cx
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  }
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  *fhandle = handle;
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  return(res);
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}
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unsigned short mdr_dos_fclose(unsigned short handle) {
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  unsigned short res = 0;
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  _asm {
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    push bx
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    mov ah, 0x3e
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    mov bx, handle
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    int 0x21
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    jnc done
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    mov res, ax
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    done:
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    pop bx
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  }
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  return(res);
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}
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unsigned short _dos_freemem(unsigned short segn) {
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  unsigned short res = 0;
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  _asm {
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    push es
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    mov ah, 0x49
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    mov es, segn
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    int 0x21
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    pop es
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    jnc done
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    mov res, ax
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    done:
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  }
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  return(res);
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}
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unsigned short mdr_dos_allocmem(unsigned short siz) {
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  unsigned short segnum = 0;
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  _asm {
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    push bx
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    mov ah, 0x48
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    mov bx, siz
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    int 0x21
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    jc done
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    mov segnum, ax
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    done:
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    pop bx
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  }
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  return(segnum);
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}
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unsigned short mdr_dos_resizeblock(unsigned short siz, unsigned short segn, unsigned short *maxsiz) {
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  unsigned short resbx = 0;
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  unsigned short res = 0;
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  _asm {
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    push bx
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    push es
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    mov ah, 0x4a
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    mov bx, siz
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    mov es, segn
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    int 0x21
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    jnc done
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    mov resbx, bx
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    mov res, ax
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    done:
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    pop es
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    pop bx
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  }
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  *maxsiz = resbx;
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  return(res);
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}
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unsigned short mdr_dos_read(unsigned short handle, void far *buf, unsigned short count, unsigned short *bytes) {
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  unsigned short res = 0;
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  unsigned short resax = 0;
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  unsigned short buf_off = FP_OFF(buf);
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  unsigned short buf_seg = FP_SEG(buf);
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  _asm {
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    push bx,
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    push cx
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    push dx
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    mov ah, 0x3f
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    mov bx, handle
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    mov cx, count
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    mov dx, buf_off
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    push ds
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    mov ds, buf_seg
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    int 0x21
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    pop ds
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    jnc done
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    mov res, ax
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    done:
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    mov resax, ax
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    pop dx
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    pop cx
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    pop bx
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  }
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  *bytes = resax;
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  return(res);
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}
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unsigned short mdr_dos_write(unsigned short handle, const void far *buf, unsigned short count, unsigned short *bytes) {
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  unsigned short res = 0;
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  unsigned short resax = 0;
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  unsigned short buf_seg = FP_SEG(buf);
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  unsigned short buf_off = FP_OFF(buf);
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  _asm {
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    push bx
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    push cx
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    push dx
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    mov ah, 0x40
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    mov bx, handle
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    mov cx, count
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    mov dx, buf_off
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    push ds
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    mov ds, buf_seg
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    int 0x21
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    pop ds
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    jnc done
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    mov res, ax
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    done:
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    mov resax, ax
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    pop dx
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    pop cx
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    pop bx
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  }
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  *bytes = resax;
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  return(res);
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}