src/regexp/regsub.c

   1 /*
   2  * regsub
   3  *
   4  *      Copyright (c) 1986 by University of Toronto.
   5  *      Written by Henry Spencer.  Not derived from licensed software.
   6  *
   7  *      Permission is granted to anyone to use this software for any
   8  *      purpose on any computer system, and to redistribute it freely,
   9  *      subject to the following restrictions:
  10  *
  11  *      1. The author is not responsible for the consequences of use of
  12  *              this software, no matter how awful, even if they arise
  13  *              from defects in it.
  14  *
  15  *      2. The origin of this software must not be misrepresented, either
  16  *              by explicit claim or by omission.
  17  *
  18  *      3. Altered versions must be plainly marked as such, and must not
  19  *              be misrepresented as being the original software.
  20  */
  21 #include <stdio.h>
  22 #include "regexp.h"
  23 #include "regmagic.h"
  24
  25 #ifndef CHARBITS
  26 #define UCHARAT(p)      ((int)*(unsigned char *)(p))
  27 #else
  28 #define UCHARAT(p)      ((int)*(p)&CHARBITS)
  29 #endif
  30
  31 /*
  32  - regsub - perform substitutions after a regexp match
  33  */
  34 void
  35 regsub(prog, source, dest)
  36 regexp *prog;
  37 char *source;
  38 char *dest;
  39 {
  40         register char *src;
  41         register char *dst;
  42         register char c;
  43         register int no;
  44         register int len;
  45 /*      extern char *strncpy(); */
  46
  47         if (prog == NULL || source == NULL || dest == NULL) {
  48                 regerror("NULL parm to regsub");
  49                 return;
  50         }
  51         if (UCHARAT(prog->program) != MAGIC) {
  52                 regerror("damaged regexp fed to regsub");
  53                 return;
  54         }
  55
  56         src = source;
  57         dst = dest;
  58         while ((c = *src++) != '\0') {
  59                 if (c == '&')
  60                         no = 0;
  61                 else if (c == '\\' && '0' <= *src && *src <= '9')
  62                         no = *src++ - '0';
  63                 else
  64                         no = -1;
  65
  66                 if (no < 0)     /* Ordinary character. */
  67                         *dst++ = c;
  68                 else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {
  69                         len = prog->endp[no] - prog->startp[no];
  70                         (void) strncpy(dst, prog->startp[no], len);
  71                         dst += len;
  72                         if (len != 0 && *(dst-1) == '\0') {             /* strncpy hit NUL. */
  73                                 regerror("damaged match string");
  74                                 return;
  75                         }
  76                 }
  77         }
  78         *dst++ = '\0';
  79 }