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352 mateuszvis 1 
/*
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 * a variety of helper functions
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 * Copyright (C) 2021 Mateusz Viste
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 */
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396 mateuszvis 6 
#include <i86.h>    /* MK_FP() */
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352 mateuszvis 8 
#include "helpers.h"
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10 
/* case-insensitive comparison of strings, returns non-zero on equality */
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int imatch(const char *s1, const char *s2) {
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  for (;;) {
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    char c1, c2;
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    c1 = *s1;
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    c2 = *s2;
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    if ((c1 >= 'a') && (c1 <= 'z')) c1 -= ('a' - 'A');
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    if ((c2 >= 'a') && (c2 <= 'z')) c2 -= ('a' - 'A');
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    /* */
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    if (c1 != c2) return(0);
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    if (c1 == 0) return(1);
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    s1++;
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    s2++;
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  }
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}
25 
 
26 
 
27 
/* returns zero if s1 starts with s2 */
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int strstartswith(const char *s1, const char *s2) {
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  while (*s2 != 0) {
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    if (*s1 != *s2) return(-1);
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    s1++;
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    s2++;
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  }
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  return(0);
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}
369 mateuszvis 36 
 
37 
 
38 
/* outputs a NULL-terminated string to stdout */
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void output_internal(const char *s, unsigned short nl) {
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  _asm {
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    mov ah, 0x02 /* AH=9 - write character in DL to stdout */
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    mov si, s
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    cld          /* clear DF so lodsb increments SI */
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    NEXTBYTE:
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    lodsb /* load byte from DS:SI into AL, SI++ */
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    mov dl, al
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    or al, 0  /* is al == 0? */
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    jz DONE
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    int 0x21
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    jmp NEXTBYTE
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    DONE:
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    or nl, 0
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    jz FINITO
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    /* print out a CR/LF trailer if nl set */
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    mov dl, 0x0D /* CR */
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    int 0x21
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    mov dl, 0x0A /* LF */
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    int 0x21
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    FINITO:
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  }
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}
388 mateuszvis 62 
 
63 
 
64 
/* find first matching files using a FindFirst DOS call
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 * returns 0 on success or a DOS err code on failure */
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unsigned short findfirst(struct DTA *dta, const char *pattern, unsigned short attr) {
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  unsigned short res = 0;
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  _asm {
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    /* set DTA location */
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    mov ah, 0x1a
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    mov dx, dta
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    int 0x21
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    /* */
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    mov ah, 0x4e    /* FindFirst */
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    mov dx, pattern
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    mov cx, attr
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    int 0x21        /* CF set on error + err code in AX, DTA filled with FileInfoRec on success */
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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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85 
 
86 
/* find next matching, ie. continues an action intiated by findfirst() */
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unsigned short findnext(struct DTA *dta) {
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  unsigned short res = 0;
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  _asm {
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    mov ah, 0x4f    /* FindNext */
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    mov dx, dta
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    int 0x21        /* CF set on error + err code in AX, DTA filled with FileInfoRec on success */
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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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}
392 mateuszvis 99 
 
100 
 
101 
/* print s string and wait for a single key press from stdin. accepts only
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 * key presses defined in the c ASCIIZ string. returns offset of pressed key
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 * in string. keys in c MUST BE UPPERCASE! */
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unsigned short askchoice(const char *s, const char *c) {
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  unsigned short res;
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  char key = 0;
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108 
  AGAIN:
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  output(s);
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  output(" ");
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112 
  _asm {
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    push ax
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    push dx
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    mov ax, 0x0c01 /* clear input buffer and execute getchar (INT 21h,AH=1) */
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    int 0x21
118 
    /* if AL == 0 then this is an extended character */
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    test al, al
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    jnz GOTCHAR
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    mov ah, 0x08   /* read again to flush extended char from input buffer */
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    int 0x21
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    xor al, al     /* all extended chars are ignored */
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    GOTCHAR:       /* received key is in AL now */
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    mov [key], al  /* save key */
126 
 
127 
    /* print a cr/lf */
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    mov ah, 0x02
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    mov dl, 0x0D
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    int 0x21
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    mov dl, 0x0A
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    int 0x21
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134 
    pop dx
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    pop ax
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  }
137 
 
138 
  /* ucase() result */
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  if ((key >= 'a') && (key <= 'z')) key -= ('a' - 'A');
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141 
  /* is there a match? */
142 
  for (res = 0; c[res] != 0; res++) if (c[res] == key) return(res);
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144 
  goto AGAIN;
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}
146 
 
147 
 
148 
/* converts a path to its canonic representation */
149 
void file_truename(const char *src, char *dst) {
150 
  _asm {
151 
    mov ah, 0x60  /* query truename, DS:SI=src, ES:DI=dst */
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    push ds
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    pop es
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    mov si, src
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    mov di, dst
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    int 0x21
157 
  }
158 
}
159 
 
160 
 
161 
/* returns DOS attributes of file, or -1 on error */
162 
int file_getattr(const char *fname) {
163 
  int res = -1;
164 
  _asm {
165 
    mov ax, 0x4300  /* query file attributes, fname at DS:DX */
166 
    mov dx, fname
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    int 0x21        /* CX=attributes if CF=0, otherwise AX=errno */
168 
    jc DONE
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    mov [res], cx
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    DONE:
171 
  }
172 
  return(res);
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}
396 mateuszvis 174 
 
175 
 
176 
/* returns screen's width (in columns) */
177 
unsigned short screen_getwidth(void) {
178 
  /* BIOS 0040:004A = word containing screen width in text columns */
179 
  unsigned short far *scrw = MK_FP(0x40, 0x4a);
180 
  return(*scrw);
181 
}
182 
 
183 
 
184 
/* returns screen's height (in rows) */
185 
unsigned short screen_getheight(void) {
186 
  /* BIOS 0040:0084 = byte containing maximum valid row value (EGA ONLY) */
187 
  unsigned char far *scrh = MK_FP(0x40, 0x84);
188 
  if (*scrh == 0) return(25);  /* pre-EGA adapter */
189 
  return(*scrh + 1);
190 
}
191 
 
192 
 
193 
/* displays the "Press any key to continue" msg and waits for a keypress */
194 
void press_any_key(void) {
195 
  output("Press any key to continue...");
196 
  _asm {
197 
    mov ah, 0x08  /* no echo console input */
198 
    int 0x21      /* pressed key in AL now (0 for extended keys) */
199 
    test al, al
200 
    jnz DONE
201 
    int 0x21      /* executed ah=8 again to read the rest of extended key */
202 
    DONE:
203 
    /* output CR/LF */
204 
    mov ah, 0x02
205 
    mov dl, 0x0D
206 
    int 0x21
207 
    mov dl, 0x0A
208 
    int 0x21
209 
  }
210 
}