src/endianconv.c

   1 /* endinconv.c -- Endian conversions utilities.
   2  *
   3  * This functions are never called directly, but always using the macros
   4  * defined into endianconv.h, this way we define everything is a non-operation
   5  * if the arch is already little endian.
   6  *
   7  * Redis tries to encode everything as little endian (but a few things that need
   8  * to be backward compatible are still in big endian) because most of the
   9  * production environments are little endian, and we have a lot of conversions
  10  * in a few places because ziplists, intsets, zipmaps, need to be endian-neutral
  11  * even in memory, since they are serialied on RDB files directly with a single
  12  * write(2) without other additional steps.
  13  *
  14  * ----------------------------------------------------------------------------
  15  *
  16  * Copyright (c) 2011-2012, Salvatore Sanfilippo <antirez at gmail dot com>
  17  * All rights reserved.
  18  *
  19  * Redistribution and use in source and binary forms, with or without
  20  * modification, are permitted provided that the following conditions are met:
  21  *
  22  *   * Redistributions of source code must retain the above copyright notice,
  23  *     this list of conditions and the following disclaimer.
  24  *   * Redistributions in binary form must reproduce the above copyright
  25  *     notice, this list of conditions and the following disclaimer in the
  26  *     documentation and/or other materials provided with the distribution.
  27  *   * Neither the name of Redis nor the names of its contributors may be used
  28  *     to endorse or promote products derived from this software without
  29  *     specific prior written permission.
  30  *
  31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  32  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  33  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  34  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  35  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  36  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  37  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  38  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  39  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  40  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  41  * POSSIBILITY OF SUCH DAMAGE.
  42  */
  43
  44
  45 #include <stdint.h>
  46
  47 /* Toggle the 16 bit unsigned integer pointed by *p from little endian to
  48  * big endian */
  49 void memrev16(void *p) {
  50     unsigned char *x = p, t;
  51
  52     t = x[0];
  53     x[0] = x[1];
  54     x[1] = t;
  55 }
  56
  57 /* Toggle the 32 bit unsigned integer pointed by *p from little endian to
  58  * big endian */
  59 void memrev32(void *p) {
  60     unsigned char *x = p, t;
  61
  62     t = x[0];
  63     x[0] = x[3];
  64     x[3] = t;
  65     t = x[1];
  66     x[1] = x[2];
  67     x[2] = t;
  68 }
  69
  70 /* Toggle the 64 bit unsigned integer pointed by *p from little endian to
  71  * big endian */
  72 void memrev64(void *p) {
  73     unsigned char *x = p, t;
  74
  75     t = x[0];
  76     x[0] = x[7];
  77     x[7] = t;
  78     t = x[1];
  79     x[1] = x[6];
  80     x[6] = t;
  81     t = x[2];
  82     x[2] = x[5];
  83     x[5] = t;
  84     t = x[3];
  85     x[3] = x[4];
  86     x[4] = t;
  87 }
  88
  89 uint16_t intrev16(uint16_t v) {
  90     memrev16(&v);
  91     return v;
  92 }
  93
  94 uint32_t intrev32(uint32_t v) {
  95     memrev32(&v);
  96     return v;
  97 }
  98
  99 uint64_t intrev64(uint64_t v) {
 100     memrev64(&v);
 101     return v;
 102 }
 103
 104 #ifdef TESTMAIN
 105 #include <stdio.h>
 106
 107 int main(void) {
 108     char buf[32];
 109
 110     sprintf(buf,"ciaoroma");
 111     memrev16(buf);
 112     printf("%s\n", buf);
 113
 114     sprintf(buf,"ciaoroma");
 115     memrev32(buf);
 116     printf("%s\n", buf);
 117
 118     sprintf(buf,"ciaoroma");
 119     memrev64(buf);
 120     printf("%s\n", buf);
 121
 122     return 0;
 123 }
 124 #endif