string.c

   1 #include <stdint.h>
   2 #include <string.h>
   3
   4 void *memchr(const void *s, int c, size_t n)
   5 {
   6     const unsigned char *b = s;
   7
   8     while (n--) {
   9         if (*(b++) == (unsigned char)c) {
  10             return (void *)(b - 1);
  11         }
  12     }
  13
  14     return NULL;
  15 }
  16
  17 int memcmp(const void *s1, const void *s2, size_t n)
  18 {
  19     int ret = 0;
  20     const unsigned char *b1 = s1, *b2 = s2;
  21
  22     while (n-- && !(ret = *(b2++) - *(b1++)));
  23
  24     return ret;
  25 }
  26
  27 void *memmove(void *d, const void *s, size_t n)
  28 {
  29     const uint8_t *s8 = s;
  30     uint8_t *d8 = d;
  31
  32     if ((uintptr_t)d < (uintptr_t)s || (uintptr_t)s + n <= (uintptr_t)d) {
  33         while (n--) {
  34             *(d8++) = *(s8++);
  35         }
  36     } else {
  37         while (n--) {
  38             d8[n] = s8[n];
  39         }
  40     }
  41
  42     return d;
  43 }
  44
  45 char *strcat(char *restrict d, const char *restrict s)
  46 {
  47     char *vd = d;
  48
  49     while (*(vd++));
  50     vd--;
  51
  52     while (*s) {
  53         *(vd++) = *(s++);
  54     }
  55     *vd = 0;
  56
  57     return d;
  58 }
  59
  60 char *strcpy(char *restrict d, const char *restrict s)
  61 {
  62     char *vd = d;
  63
  64     while (*s) {
  65         *(vd++) = *(s++);
  66     }
  67     *vd = 0;
  68
  69     return d;
  70 }
  71
  72 int strcmp(const char *s1, const char *s2)
  73 {
  74     int ret;
  75
  76     while (!(ret = (unsigned char)*(s2++) - (unsigned char)*s1)) {
  77         if (!*(s1++)) {
  78             return 0;
  79         }
  80     }
  81
  82     return ret;
  83 }