compat/memmem.c

   1 #include "../git-compat-util.h"
   2
   3 void *gitmemmem(const void *haystack, size_t haystack_len,
   4                 const void *needle, size_t needle_len)
   5 {
   6         const char *begin = haystack;
   7         const char *last_possible = begin + haystack_len - needle_len;
   8         const char *tail = needle;
   9         char point;
  10
  11         /*
  12          * The first occurrence of the empty string is deemed to occur at
  13          * the beginning of the string.
  14          */
  15         if (needle_len == 0)
  16                 return (void *)begin;
  17
  18         /*
  19          * Sanity check, otherwise the loop might search through the whole
  20          * memory.
  21          */
  22         if (haystack_len < needle_len)
  23                 return NULL;
  24
  25         point = *tail++;
  26         for (; begin <= last_possible; begin++) {
  27                 if (*begin == point && !memcmp(begin + 1, tail, needle_len - 1))
  28                         return (void *)begin;
  29         }
  30
  31         return NULL;
  32 }