Subversion Repositories SvarDOS

/*

 * a variety of helper functions

 * Copyright (C) 2021 Mateusz Viste

 */

#include <i86.h>    /* MK_FP() */

#include "helpers.h"

/* case-insensitive comparison of strings, returns non-zero on equality */

int imatch(const char *s1, const char *s2) {

  for (;;) {

    char c1, c2;

    c1 = *s1;

    c2 = *s2;

    if ((c1 >= 'a') && (c1 <= 'z')) c1 -= ('a' - 'A');

    if ((c2 >= 'a') && (c2 <= 'z')) c2 -= ('a' - 'A');

    /* */

    if (c1 != c2) return(0);

    if (c1 == 0) return(1);

    s1++;

    s2++;

  }

}

/* returns zero if s1 starts with s2 */

int strstartswith(const char *s1, const char *s2) {

  while (*s2 != 0) {

    if (*s1 != *s2) return(-1);

    s1++;

    s2++;

  }

  return(0);

}

/* outputs a NULL-terminated string to stdout */

void output_internal(const char *s, unsigned short nl) {

  _asm {

    mov ah, 0x02 /* AH=9 - write character in DL to stdout */

    mov si, s

    cld          /* clear DF so lodsb increments SI */

    NEXTBYTE:

    lodsb /* load byte from DS:SI into AL, SI++ */

    mov dl, al

    or al, 0  /* is al == 0? */

    jz DONE

    int 0x21

    jmp NEXTBYTE

    DONE:

    or nl, 0

    jz FINITO

    /* print out a CR/LF trailer if nl set */

    mov dl, 0x0D /* CR */

    int 0x21

    mov dl, 0x0A /* LF */

    int 0x21

    FINITO:

  }

}

/* find first matching files using a FindFirst DOS call

 * returns 0 on success or a DOS err code on failure */

unsigned short findfirst(struct DTA *dta, const char *pattern, unsigned short attr) {

  unsigned short res = 0;

  _asm {

    /* set DTA location */

    mov ah, 0x1a

    mov dx, dta

    int 0x21

    /* */

    mov ah, 0x4e    /* FindFirst */

    mov dx, pattern

    mov cx, attr

    int 0x21        /* CF set on error + err code in AX, DTA filled with FileInfoRec on success */

    jnc DONE

    mov [res], ax

    DONE:

  }

  return(res);

}

/* find next matching, ie. continues an action intiated by findfirst() */

unsigned short findnext(struct DTA *dta) {

  unsigned short res = 0;

  _asm {

    mov ah, 0x4f    /* FindNext */

    mov dx, dta

    int 0x21        /* CF set on error + err code in AX, DTA filled with FileInfoRec on success */

    jnc DONE

    mov [res], ax

    DONE:

  }

  return(res);

}

/* print s string and wait for a single key press from stdin. accepts only

 * key presses defined in the c ASCIIZ string. returns offset of pressed key

 * in string. keys in c MUST BE UPPERCASE! */

unsigned short askchoice(const char *s, const char *c) {

  unsigned short res;

  char key = 0;

  AGAIN:

  output(s);

  output(" ");

  _asm {

    push ax

    push dx

    mov ax, 0x0c01 /* clear input buffer and execute getchar (INT 21h,AH=1) */

    int 0x21

    /* if AL == 0 then this is an extended character */

    test al, al

    jnz GOTCHAR

    mov ah, 0x08   /* read again to flush extended char from input buffer */

    int 0x21

    xor al, al     /* all extended chars are ignored */

    GOTCHAR:       /* received key is in AL now */

    mov [key], al  /* save key */

    /* print a cr/lf */

    mov ah, 0x02

    mov dl, 0x0D

    int 0x21

    mov dl, 0x0A

    int 0x21

    pop dx

    pop ax

  }

  /* ucase() result */

  if ((key >= 'a') && (key <= 'z')) key -= ('a' - 'A');

  /* is there a match? */

  for (res = 0; c[res] != 0; res++) if (c[res] == key) return(res);

  goto AGAIN;

}

/* converts a path to its canonic representation, returns 0 on success

 * or DOS err on failure (invalid drive) */

unsigned short file_truename(const char *src, char *dst) {

  unsigned short res = 0;

  _asm {

    push es

    mov ah, 0x60  /* query truename, DS:SI=src, ES:DI=dst */

    push ds

    pop es

    mov si, src

    mov di, dst

    int 0x21

    jnc DONE

    mov [res], ax

    DONE:

    pop es

  }

  return(res);

}

/* returns DOS attributes of file, or -1 on error */

int file_getattr(const char *fname) {

  int res = -1;

  _asm {

    mov ax, 0x4300  /* query file attributes, fname at DS:DX */

    mov dx, fname

    int 0x21        /* CX=attributes if CF=0, otherwise AX=errno */

    jc DONE

    mov [res], cx

    DONE:

  }

  return(res);

}

/* returns screen's width (in columns) */

unsigned short screen_getwidth(void) {

  /* BIOS 0040:004A = word containing screen width in text columns */

  unsigned short far *scrw = MK_FP(0x40, 0x4a);

  return(*scrw);

}

/* returns screen's height (in rows) */

unsigned short screen_getheight(void) {

  /* BIOS 0040:0084 = byte containing maximum valid row value (EGA ONLY) */

  unsigned char far *scrh = MK_FP(0x40, 0x84);

  if (*scrh == 0) return(25);  /* pre-EGA adapter */

  return(*scrh + 1);

}

/* displays the "Press any key to continue" msg and waits for a keypress */

void press_any_key(void) {

  output("Press any key to continue...");

  _asm {

    mov ah, 0x08  /* no echo console input */

    int 0x21      /* pressed key in AL now (0 for extended keys) */

    test al, al

    jnz DONE

    int 0x21      /* executed ah=8 again to read the rest of extended key */

    DONE:

    /* output CR/LF */

    mov ah, 0x02

    mov dl, 0x0D

    int 0x21

    mov dl, 0x0A

    int 0x21

  }

}

/* validate a drive (A=0, B=1, etc). returns 1 if valid, 0 otherwise */

int isdrivevalid(unsigned char drv) {

  _asm {

    mov ah, 0x19  /* query default (current) disk */

    int 0x21      /* drive in AL (0=A, 1=B, etc) */

    mov ch, al    /* save current drive to ch */

    /* try setting up the drive as current */

    mov ah, 0x0E   /* select default drive */

    mov dl, [drv]  /* 0=A, 1=B, etc */

    int 0x21

    /* this call does not set CF on error, I must check cur drive to look for success */

    mov ah, 0x19  /* query default (current) disk */

    int 0x21      /* drive in AL (0=A, 1=B, etc) */

    mov [drv], 1  /* preset result as success */

    cmp al, dl    /* is eq? */

    je DONE

    mov [drv], 0  /* fail */

    jmp FAILED

    DONE:

    /* set current drive back to what it was initially */

    mov ah, 0x0E

    mov dl, ch

    int 0x21

    FAILED:

  }

  return(drv);

}

/* converts a 8+3 filename into 11-bytes FCB format (MYFILE  EXT) */

void file_fname2fcb(char *dst, const char *src) {

  unsigned short i;

  /* fill dst with 11 spaces and a NULL terminator */

  for (i = 0; i < 12; i++) dst[i] = ' ';

  dst[12] = 0;

  /* copy fname until dot (.) or 8 characters */

  for (i = 0; i < 8; i++) {

    if ((src[i] == '.') || (src[i] == 0)) break;

    dst[i] = src[i];

  }

  /* advance src until extension or end of string */

  src += i;

  for (;;) {

    if (*src == '.') {

      src++; /* next character is extension */

      break;

    }

    if (*src == 0) break;

  }

  /* copy extension to dst (3 chars max) */

  dst += 8;

  for (i = 0; i < 3; i++) {

    if (src[i] == 0) break;

    dst[i] = src[i];

  }

}

/* converts a 11-bytes FCB filename (MYFILE  EXT) into 8+3 format (MYFILE.EXT) */

void file_fcb2fname(char *dst, const char *src) {

  unsigned short i, end = 0;

  for (i = 0; i < 8; i++) {

    dst[i] = src[i];

    if (dst[i] != ' ') end = i + 1;

  }

  /* is there an extension? */

  if (src[8] == ' ') {

    dst[end] = 0;

  } else { /* found extension: copy it until first space */

    dst[end++] = '.';

    for (i = 8; i < 11; i++) {

      if (src[i] == ' ') break;

      dst[end++] = src[i];

    }

    dst[end] = 0;

  }

}

/* converts an ASCIIZ string into an unsigned short. returns 0 on success. */

int atouns(unsigned short *r, const char *s) {

  int err = 0;

  _asm {

    mov si, s

    xor ax, ax  /* general purpose register */

    xor cx, cx  /* contains the result */

    mov bx, 10  /* used as a multiplicative step */

    NEXTBYTE:

    xchg cx, ax /* move result into cx temporarily */

    lodsb  /* AL = DS:[SI++] */

    /* is AL 0? if so we're done */

    test al, al

    jz DONE

    /* validate that AL is in range '0'-'9' */

    sub al, '0'

    jc FAIL   /* neg result */

    cmp al, 9

    jg FAIL

    /* restore result into AX (CX contains the new digit) */

    xchg cx, ax

    /* multiply result by 10 and add cl */

    mul bx    /* DX AX = AX * BX(10) */

    jc FAIL   /* overflow */

    add ax, cx

    /* if CF then overflow occured (overflow part lands in DX) */

    jnc NEXTBYTE

    FAIL:

    inc [err]

    DONE: /* save result (CX) into indirect memory address r */

    mov bx, [r]

    mov [bx], cx

  }

  return(err);

}