prism/util/pm_memchr.c

   1 #include "prism/util/pm_memchr.h"
   2
   3 #define PRISM_MEMCHR_TRAILING_BYTE_MINIMUM 0x40
   4
   5 /**
   6  * We need to roll our own memchr to handle cases where the encoding changes and
   7  * we need to search for a character in a buffer that could be the trailing byte
   8  * of a multibyte character.
   9  */
  10 void *
  11 pm_memchr(const void *memory, int character, size_t number, bool encoding_changed, const pm_encoding_t *encoding) {
  12     if (encoding_changed && encoding->multibyte && character >= PRISM_MEMCHR_TRAILING_BYTE_MINIMUM) {
  13         const uint8_t *source = (const uint8_t *) memory;
  14         size_t index = 0;
  15
  16         while (index < number) {
  17             if (source[index] == character) {
  18                 return (void *) (source + index);
  19             }
  20
  21             size_t width = encoding->char_width(source + index, (ptrdiff_t) (number - index));
  22             if (width == 0) {
  23                 return NULL;
  24             }
  25
  26             index += width;
  27         }
  28
  29         return NULL;
  30     } else {
  31         return memchr(memory, character, number);
  32     }
  33 }
  34
  35 #undef PRISM_MEMCHR_TRAILING_BYTE_MINIMUM