man3/bswap.3

   1 .\" Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com>
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .TH BSWAP 3 2021-06-20 "Linux man-pages (unreleased)"
   6 .SH NAME
   7 bswap_16, bswap_32, bswap_64 \- reverse order of bytes
   8 .SH LIBRARY
   9 Standard C library
  10 .RI ( libc ", " \-lc )
  11 .SH SYNOPSIS
  12 .nf
  13 .B #include <byteswap.h>
  14 .PP
  15 .BI "uint16_t bswap_16(uint16_t " x );
  16 .BI "uint32_t bswap_32(uint32_t " x );
  17 .BI "uint64_t bswap_64(uint64_t " x );
  18 .fi
  19 .SH DESCRIPTION
  20 These functions return a value in which the order of the bytes
  21 in their 2-, 4-, or 8-byte arguments is reversed.
  22 .SH RETURN VALUE
  23 These functions return the value of their argument with the bytes reversed.
  24 .SH ERRORS
  25 These functions always succeed.
  26 .SH STANDARDS
  27 These functions are GNU extensions.
  28 .SH EXAMPLES
  29 The program below swaps the bytes of the 8-byte integer supplied as
  30 its command-line argument.
  31 The following shell session demonstrates the use of the program:
  32 .PP
  33 .in +4n
  34 .EX
  35 $ \fB./a.out 0x0123456789abcdef\fP
  36 0x123456789abcdef ==> 0xefcdab8967452301
  37 .EE
  38 .in
  39 .SS Program source
  40 \&
  41 .EX
  42 #include <stdio.h>
  43 #include <stdint.h>
  44 #include <stdlib.h>
  45 #include <inttypes.h>
  46 #include <byteswap.h>
  47
  48 int
  49 main(int argc, char *argv[])
  50 {
  51     uint64_t x;
  52
  53     if (argc != 2) {
  54         fprintf(stderr, "Usage: %s <num>\en", argv[0]);
  55         exit(EXIT_FAILURE);
  56     }
  57
  58     x = strtoull(argv[1], NULL, 0);
  59     printf("%#" PRIx64 " ==> %#" PRIx64 "\en", x, bswap_64(x));
  60
  61     exit(EXIT_SUCCESS);
  62 }
  63 .EE
  64 .SH SEE ALSO
  65 .BR byteorder (3),
  66 .BR endian (3)