libc/string/memmem.c

   1 /*
   2  * Copyright (C) 2002     Manuel Novoa III
   3  * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
   4  *
   5  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
   6  */
   7
   8 #include "_string.h"
   9
  10 #ifdef __USE_GNU
  11 void *memmem(const void *haystack, size_t haystacklen,
  12                      const void *needle, size_t needlelen)
  13 {
  14         register const char *ph;
  15         register const char *pn;
  16         const char *plast;
  17         size_t n;
  18
  19         if (needlelen == 0) {
  20                 return (void *) haystack;
  21         }
  22
  23         if (haystacklen >= needlelen) {
  24                 ph = (const char *) haystack;
  25                 pn = (const char *) needle;
  26                 plast = ph + (haystacklen - needlelen);
  27
  28                 do {
  29                         n = 0;
  30                         while (ph[n] == pn[n]) {
  31                                 if (++n == needlelen) {
  32                                         return (void *) ph;
  33                                 }
  34                         }
  35                 } while (++ph <= plast);
  36         }
  37
  38         return NULL;
  39 }
  40 #endif