src/endian.c

   1 #include <stdint.h>
   2
   3 /* Toggle the 16 bit unsigned integer pointed by *p from little endian to
   4  * big endian */
   5 void memrev16(void *p) {
   6     unsigned char *x = p, t;
   7
   8     t = x[0];
   9     x[0] = x[1];
  10     x[1] = t;
  11 }
  12
  13 /* Toggle the 32 bit unsigned integer pointed by *p from little endian to
  14  * big endian */
  15 void memrev32(void *p) {
  16     unsigned char *x = p, t;
  17
  18     t = x[0];
  19     x[0] = x[3];
  20     x[3] = t;
  21     t = x[1];
  22     x[1] = x[2];
  23     x[2] = t;
  24 }
  25
  26 /* Toggle the 64 bit unsigned integer pointed by *p from little endian to
  27  * big endian */
  28 void memrev64(void *p) {
  29     unsigned char *x = p, t;
  30
  31     t = x[0];
  32     x[0] = x[7];
  33     x[7] = t;
  34     t = x[1];
  35     x[1] = x[6];
  36     x[6] = t;
  37     t = x[2];
  38     x[2] = x[5];
  39     x[5] = t;
  40     t = x[3];
  41     x[3] = x[4];
  42     x[4] = t;
  43 }
  44
  45 uint16_t intrev16(uint16_t v) {
  46     memrev16(&v);
  47     return v;
  48 }
  49
  50 uint32_t intrev32(uint32_t v) {
  51     memrev32(&v);
  52     return v;
  53 }
  54
  55 uint64_t intrev64(uint64_t v) {
  56     memrev64(&v);
  57     return v;
  58 }
  59
  60 #ifdef TESTMAIN
  61 #include <stdio.h>
  62
  63 int main(void) {
  64     char buf[32];
  65
  66     sprintf(buf,"ciaoroma");
  67     memrev16(buf);
  68     printf("%s\n", buf);
  69
  70     sprintf(buf,"ciaoroma");
  71     memrev32(buf);
  72     printf("%s\n", buf);
  73
  74     sprintf(buf,"ciaoroma");
  75     memrev64(buf);
  76     printf("%s\n", buf);
  77
  78     return 0;
  79 }
  80 #endif