Subversion Repositories SvarDOS

/* This file is part of the SvarCOM project and is published under the terms

 * of the MIT license.

 *

 * Copyright (C) 2021-2024 Mateusz Viste

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER

 * DEALINGS IN THE SOFTWARE.

 */

/*

 * a variety of helper functions

 */

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

#include <stdio.h>  /* sprintf() */

#include <string.h> /* memcpy() */

#include "svarlang.lib\svarlang.h"

#include "env.h"

#include "rmodinit.h"

#include "helpers.h"

void dos_get_date(unsigned short *y, unsigned char *m, unsigned char *d) {

  /* get cur date */

  _asm {

    mov ah, 0x2a  /* DOS 1+ -- Query DOS Date */

    int 0x21      /* CX=year DH=month DL=day */

    mov bx, y

    mov [bx], cx

    mov bx, m

    mov [bx], dh

    mov bx, d

    mov [bx], dl

  }

}

void dos_get_time(unsigned char *h, unsigned char *m, unsigned char *s) {

  _asm {

    mov ah, 0x2c  /* DOS 1+ -- Query DOS Time */

    int 0x21      /* CH=hour CL=minutes DH=seconds DL=1/100sec */

    mov bx, h

    mov [bx], ch

    mov bx, m

    mov [bx], cl

    mov bx, s

    mov [bx], dh

  }

}

/* case-insensitive comparison of strings, compares up to maxlen characters.

 * returns non-zero on equality. */

int imatchlim(const char *s1, const char *s2, unsigned short maxlen) {

  while (maxlen--) {

    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) break;

    s1++;

    s2++;

  }

  return(1);

}

/* 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 handle (1=stdout 2=stderr) */

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

  const static unsigned char *crlf = "\r\n";

  _asm {

    push ds

    pop es         /* make sure es=ds (scasb uses es) */

    /* get length of s into CX */

    mov ax, 0x4000 /* ah=DOS "write to file" and AL=0 for NULL matching */

    mov dx, s      /* set dx to string (required for later) */

    mov di, dx     /* set di to string (for NULL matching) */

    mov cx, 0xffff /* preset cx to 65535 (-1) */

    cld            /* clear DF so scasb increments DI */

    repne scasb    /* cmp al, es:[di], inc di, dec cx until match found */

    /* CX contains (65535 - strlen(s)) now */

    not cx         /* reverse all bits so I get (strlen(s) + 1) */

    dec cx         /* this is CX length */

    jz WRITEDONE   /* do nothing for empty strings */

    /* output by writing to stdout */

    /* mov ah, 0x40 */  /* DOS 2+ -- write to file via handle */

    xor bh, bh

    mov bl, handle /* set handle (1=stdout 2=stderr) */

    /* mov cx, xxx */ /* write CX bytes */

    /* mov dx, s   */ /* DS:DX is the source of bytes to "write" */

    int 0x21

    WRITEDONE:

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

    test byte ptr [nl], 0xff

    jz FINITO

    /* bx still contains handle */

    mov ah, 0x40 /* "write to file" */

    mov cx, 2

    mov dx, crlf

    int 0x21

    FINITO:

  }

}

void nls_output_internal(unsigned short id, unsigned char nl, unsigned char handle) {

  const char *NOTFOUND = "NLS_STRING_NOT_FOUND";

  const char *ptr = svarlang_strid(id);

  if ((ptr == NULL) || (ptr[0]) == 0) ptr = NOTFOUND;

  output_internal(ptr, nl, handle);

}

/* output DOS error e to stdout, if stdout is redirected then *additionally*

 * also to stderr */

void nls_outputnl_doserr(unsigned short e) {

  static char errstr[16];

  const char *ptr = NULL;

  unsigned char redirflag = 0;

  /* find string in nls block */

  if (e < 0xff) ptr = svarlang_strid(0xff00 | e);

  /* if not found, use a fallback */

  if ((ptr == NULL) || (ptr[0] == 0)) {

    sprintf(errstr, "DOS ERR %u", e);

    ptr = errstr;

  }

  /* display to stdout */

  output_internal(ptr, 1, hSTDOUT);

  /* is stdout redirected? */

  _asm {

    push bx

    push dx

    mov ax, 0x4400   /* query device flags */

    mov bx, 1        /* stdout */

    int 0x21

    /* CF set on error and AX filled with DOS error,

     * returns flags in DX on succes:

     *  bit 7 reset if handle points to a file, set if handle points to a device  */

    jc FAIL

    mov redirflag, dl

    and redirflag, 128

    FAIL:

    pop dx

    pop bx

  }

  if (redirflag == 0) output_internal(ptr, 1, hSTDERR);

}

/* 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);

}

static unsigned char _dos_getkey_noecho(void);

#pragma aux _dos_getkey_noecho = \

"mov ax, 0x0c08" /* clear input buffer and execute getchar (INT 21h,AH=8) */  \

"int 0x21"                                                                    \

"test al, al"    /* if AL == 0 then this is an extended character */          \

"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 */                              \

modify [ah]                                                                   \

value [al]

/* 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! ENTER chooses the FIRST choice */

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

  unsigned short res;

  char cstr[2] = {0,0};

  char key = 0;

  output(s);

  output(" ");

  output("(");

  for (res = 0; c[res] != 0; res++) {

    if (res != 0) output("/");

    cstr[0] = c[res];

    output(cstr);

  }

  output(") ");

  AGAIN:

  key = _dos_getkey_noecho();

  if (key == '\r') key = c[0]; /* ENTER is synonym for the first key */

  /* 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) {

      cstr[0] = key;

      output(cstr);

      output("\r\n");

      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) {

  nls_output(15, 1); /* 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 < 11; i++) dst[i] = ' ';

  dst[11] = 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.

 * on error, result will contain all valid digits that were read until

 * error occurred (0 on overflow or if parsing failed immediately) */

int atous(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   /* invalid character detected */

    cmp al, 9

    jg FAIL   /* invalid character detected */

    /* 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 OVERFLOW  /* overflow */

    add ax, cx

    /* if CF is set then overflow occurred (overflow part lands in DX) */

    jnc NEXTBYTE

    OVERFLOW:

    xor cx, cx  /* make sure result is zeroed in case overflow occured */

    FAIL:

    inc [err]

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

    mov bx, [r]

    mov [bx], cx

  }

  return(err);

}

/* appends a backslash if path is a directory

 * returns the (possibly updated) length of path */

unsigned short path_appendbkslash_if_dir(char *path) {

  unsigned short len;

  int attr;

  for (len = 0; path[len] != 0; len++);

  if (len == 0) return(0);

  if (path[len - 1] == '\\') return(len);

  /* */

  attr = file_getattr(path);

  if ((attr > 0) && (attr & DOS_ATTR_DIR)) {

    path[len++] = '\\';

    path[len] = 0;

  }

  return(len);

}

/* get current path drive d (A=1, B=2, etc - 0 is "current drive")

 * returns 0 on success, doserr otherwise */

unsigned short curpathfordrv(char *buff, unsigned char d) {

  unsigned short r = 0;

  _asm {

    /* is d == 0? then I need to resolve current drive */

    cmp byte ptr [d], 0

    jne GETCWD

    /* resolve cur drive */

    mov ah, 0x19  /* get current default drive */

    int 0x21      /* al = drive (00h = A:, 01h = B:, etc) */

    inc al        /* convert to 1=A, 2=B, etc */

    mov [d], al

    GETCWD:

    /* prepend buff with drive:\ */

    mov si, buff

    mov dl, [d]

    mov [si], dl

    add byte ptr [si], 'A' - 1

    inc si

    mov [si], ':'

    inc si

    mov [si], '\\'

    inc si

    mov ah, 0x47      /* get current directory of drv DL into DS:SI */

    int 0x21

    jnc DONE

    mov [r], ax       /* copy result from ax */

    DONE:

  }

  return(r);

}

/* fills a nls_patterns struct with current NLS patterns, returns 0 on success, DOS errcode otherwise */

unsigned short nls_getpatterns(struct nls_patterns *p) {

  unsigned short r = 0;

  _asm {

    mov ax, 0x3800  /* DOS 2+ -- Get Country Info for current country */

    mov dx, p       /* DS:DX points to the CountryInfoRec buffer */

    int 0x21

    jnc DONE

    mov [r], ax     /* copy DOS err code to r */

    DONE:

  }

  return(r);

}

/* computes a formatted date based on NLS patterns found in p

 * returns length of result */

unsigned short nls_format_date(char *s, unsigned short yr, unsigned char mo, unsigned char dy, const struct nls_patterns *p) {

  unsigned short items[3];

  /* preset date/month/year in proper order depending on date format */

  switch (p->dateformat) {

    case 0:  /* USA style: m d y */

      items[0] = mo;

      items[1] = dy;

      items[2] = yr;

      break;

    case 1:  /* EU style: d m y */

      items[0] = dy;

      items[1] = mo;

      items[2] = yr;

      break;

    case 2:  /* Japan-style: y m d */

    default:

      items[0] = yr;

      items[1] = mo;

      items[2] = dy;

      break;

  }

  /* compute the string */

  return(sprintf(s, "%02u%s%02u%s%02u", items[0], p->datesep, items[1], p->datesep, items[2]));

}

/* computes a formatted time based on NLS patterns found in p, sc are ignored if set 0xff

 * returns length of result */

unsigned short nls_format_time(char *s, unsigned char ho, unsigned char mn, unsigned char sc, const struct nls_patterns *p) {

  char ampm = 0;

  unsigned short res;

  if (p->timefmt == 0) {

    if (ho == 12) {

      ampm = 'p';

    } else if (ho > 12) {

      ho -= 12;

      ampm = 'p';

    } else { /* ho < 12 */

      if (ho == 0) ho = 12;

      ampm = 'a';

    }

    res = sprintf(s, "%2u", ho);

  } else {

    res = sprintf(s, "%02u", ho);

  }

  /* append separator and minutes */

  res += sprintf(s + res, "%s%02u", p->timesep, mn);

  /* if seconds provided, append them, too */

  if (sc != 0xff) res += sprintf(s + res, "%s%02u", p->timesep, sc);

  /* finally append AM/PM char */

  if (ampm != 0) s[res++] = ampm;

  s[res] = 0;

  return(res);

}

/* computes a formatted integer number based on NLS patterns found in p

 * returns length of result */

unsigned short nls_format_number(char *s, unsigned long num, const struct nls_patterns *p) {

  unsigned short sl = 0, i;

  unsigned char thcount = 0;

  /* write the value (reverse) with thousand separators (if any defined) */

  do {

    if ((thcount == 3) && (p->thousep[0] != 0)) {

      s[sl++] = p->thousep[0];

      thcount = 0;

    }

    s[sl++] = '0' + num % 10;

    num /= 10;

    thcount++;

  } while (num > 0);

  /* terminate the string */

  s[sl] = 0;

  /* reverse the string now (has been built in reverse) */

  for (i = sl / 2 + (sl & 1); i < sl; i++) {

    thcount = s[i];

    s[i] = s[sl - (i + 1)];   /* abc'de  if i=3 then ' <-> c */

    s[sl - (i + 1)] = thcount;

  }

  return(sl);

}

/* capitalize an ASCIZ string following country-dependent rules */

void nls_strtoup(char *buff) {

  unsigned short errcode = 0;

  /* requires DOS 4+ */

  _asm {

    push ax

    push dx

    mov ax, 0x6522 /* country-dependent capitalize string (DOS 4+) */

    mov dx, buff   /* DS:DX -> string to capitalize */

    int 0x21

    jnc DONE

    mov errcode, ax /* set errcode on failure */

    DONE:

    pop dx

    pop ax

  }

  /* rely on OpenWatcom's strupr() if DOS has no NLS support */

  if (errcode != 0) strupr(buff);

}

/* reload nls ressources from svarcom.lng into svarlang_mem and rmod */

void nls_langreload(char *buff, unsigned short rmodseg) {

  const char far *dosdir;

  const char far *lang;

  static unsigned short lastlang;

  unsigned short dosdirlen;

  unsigned short rmodenvseg = *(unsigned short far *)MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);

  unsigned char far *rmodcritmsg = MK_FP(rmodseg, RMOD_OFFSET_CRITMSG);

  int i;

  /* look up the LANG env variable, upcase it and copy to lang */

  lang = env_lookup_val(rmodenvseg, "LANG");

  if ((lang == NULL) || (lang[0] == 0)) return;

  _fmemcpy(buff, lang, 2);

  buff[2] = 0;

  /* check if there is need to reload at all */

  if (memcmp(&lastlang, buff, 2) == 0) return;

  buff[4] = 0;

  dosdir = env_lookup_val(rmodenvseg, "DOSDIR");

  if (dosdir == NULL) return;

  _fstrcpy(buff + 4, dosdir);

  dosdirlen = strlen(buff + 4);

  if (buff[4 + dosdirlen - 1] == '\\') dosdirlen--;

  memcpy(buff + 4 + dosdirlen, "\\SVARCOM.LNG", 13);

  /* try loading %DOSDIR%\SVARCOM.LNG */

  if (svarlang_load(buff + 4, buff) != 0) {

    /* failed! try %DOSDIR%\BIN\SVARCOM.LNG */

    memcpy(buff + 4 + dosdirlen, "\\BIN\\SVARCOM.LNG", 17);

    if (svarlang_load(buff + 4, buff) != 0) return;

  }

  _fmemcpy(&lastlang, lang, 2);

  /* update RMOD's critical handler with new strings */

  for (i = 0; i < 7; i++) {

    int len;

    len = strlen(svarlang_str(3, i));

    if (len > 15) len = 15;

    _fmemcpy(rmodcritmsg + (i * 16), svarlang_str(3, i), len);

    _fmemcpy(rmodcritmsg + (i * 16) + len, "$", 1);

  }

  /* The ARIF string is special: always 4 bytes long and no $ terminator */

  _fmemcpy(rmodcritmsg + (7 * 16), svarlang_str(3,9), 4);

}

/* locates executable fname in path and fill res with result. returns 0 on success,

 * -1 on failed match and -2 on failed match + "don't even try with other paths"

 * extptr is filled with a ptr to the extension in fname (NULL if no extension) */

int lookup_cmd(char *res, const char *fname, const char *path, const char **extptr) {

  unsigned short lastbslash = 0;

  unsigned short i, len;

  unsigned char explicitpath = 0;

  const char *exec_ext[] = {"COM", "EXE", "BAT", NULL};

  /* does the original fname has an explicit path prefix or explicit ext? */

  *extptr = NULL;

  for (i = 0; fname[i] != 0; i++) {

    switch (fname[i]) {

      case ':':

      case '\\':

        explicitpath = 1;

        *extptr = NULL; /* extension is the last dot AFTER all path delimiters */

        break;

      case '.':

        *extptr = fname + i + 1;

        break;

    }

  }

  /* if explicit ext found, make sure it is executable */

  if (*extptr != NULL) {

    for (i = 0; exec_ext[i] != NULL; i++) if (imatch(*extptr, exec_ext[i])) break;

    if (exec_ext[i] == NULL) return(-2); /* bad extension - don't try running it ever */

  }

  /* normalize filename */

  if (file_truename(fname, res) != 0) return(-2);

  /* printf("truename: %s\r\n", res); */

  /* figure out where the command starts */

  for (len = 0; res[len] != 0; len++) {

    switch (res[len]) {

      case '?':   /* abort on any wildcard character */

      case '*':

        return(-2);

      case '\\':

        lastbslash = len;

        break;

    }

  }

  /* printf("lastbslash=%u\r\n", lastbslash); */

  /* if no path prefix was found in fname (no colon or backslash) AND we have

   * a path arg, then assemble path+filename */

  if ((!explicitpath) && (path != NULL) && (path[0] != 0)) {

    i = strlen(path);

    if (path[i - 1] != '\\') i++; /* add a byte for inserting a bkslash after path */

    /* move the filename at the place where path will end */

    memmove(res + i, res + lastbslash + 1, len - lastbslash);

    /* copy path in front of the filename and make sure there is a bkslash sep */

    memmove(res, path, i);

    res[i - 1] = '\\';

  }

  /* if no extension was initially provided, try matching COM, EXE, BAT */

  if (*extptr == NULL) {

    int attr;

    len = strlen(res);

    res[len++] = '.';

    for (i = 0; exec_ext[i] != NULL; i++) {

      strcpy(res + len, exec_ext[i]);

      /* printf("? '%s'\r\n", res); */

      *extptr = exec_ext[i];

      attr = file_getattr(res);

      if (attr < 0) continue; /* file not found */

      if (attr & DOS_ATTR_DIR) continue; /* this is a directory */