src/quvi/strepl.c

   1 /*
   2 * Copyright (C) 2009 Toni Gundogdu.
   3 * Copyright (C) Laird Shaw.
   4 *
   5 * Public domain.
   6 *
   7 * http://creativeandcritical.net/sites/default/files/replacebench.c
   8 */
   9
  10 /*
  11 * Changes to the original code:
  12 *   - This revision _releases_ the source string
  13 *   - Rename "replace_opt" -> "strepl"
  14 *   - Minor style changes
  15 */
  16
  17 #include "config.h"
  18
  19 #include <stdlib.h>
  20 #include <stddef.h>
  21 #include <string.h>
  22
  23 char *strepl(const char *str, const char *old, const char *new)
  24 {
  25   size_t oldlen, count, retlen, newlen;
  26   const char *p, *q;
  27   char *ret, *r;
  28
  29   oldlen = strlen(old);
  30   newlen = strlen(new);
  31
  32   if (oldlen != newlen)
  33     {
  34       for (count = 0, p = str; (q = strstr(p, old)) != 0; p = q + oldlen)
  35         count++;
  36       retlen = p - str + strlen(p) + count * (newlen - oldlen);
  37     }
  38   else
  39     retlen = strlen(str);
  40
  41   if ((ret = malloc(retlen + 1)) == 0)
  42     return 0;
  43
  44   for (r = ret, p = str; (q = strstr(p, old)) != 0; p = q + oldlen)
  45     {
  46 #ifdef HAVE_PTRDIFF_T
  47       ptrdiff_t l = q - p;
  48 #else
  49       long l = q - p;
  50 #endif
  51       memcpy(r, p, l);
  52       r += l;
  53       memcpy(r, new, newlen);
  54       r += newlen;
  55     }
  56   strcpy(r, p);
  57
  58   /* See the notes above. */
  59   free((void *)str);
  60
  61   return (ret);
  62 }
  63
  64 /* vim: set ts=2 sw=2 tw=72 expandtab: */