NAME

       htobe16,  htole16, be16toh, le16toh, htobe32, htole32, be32toh, le32toh, htobe64, htole64,
       be64toh, le64toh - convert values between host and big-/little-endian byte order

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <endian.h>

       uint16_t htobe16(uint16_t host_16bits);
       uint16_t htole16(uint16_t host_16bits);
       uint16_t be16toh(uint16_t big_endian_16bits);
       uint16_t le16toh(uint16_t little_endian_16bits);

       uint32_t htobe32(uint32_t host_32bits);
       uint32_t htole32(uint32_t host_32bits);
       uint32_t be32toh(uint32_t big_endian_32bits);
       uint32_t le32toh(uint32_t little_endian_32bits);

       uint64_t htobe64(uint64_t host_64bits);
       uint64_t htole64(uint64_t host_64bits);
       uint64_t be64toh(uint64_t big_endian_64bits);
       uint64_t le64toh(uint64_t little_endian_64bits);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       htobe16(), htole16(), be16toh(), le16toh(), htobe32(), htole32(), be32toh(), le32toh(),
       htobe64(), htole64(), be64toh(), le64toh():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           In glibc up to and including 2.19:
               _BSD_SOURCE

DESCRIPTION

       These  functions  convert the byte encoding of integer values from the byte order that the
       current CPU (the "host") uses, to and from little-endian and big-endian byte order.

       The number, nn, in the name of each function indicates the size of integer handled by  the
       function, either 16, 32, or 64 bits.

       The  functions with names of the form "htobenn" convert from host byte order to big-endian
       order.

       The functions with names of the form "htolenn" convert from host  byte  order  to  little-
       endian order.

       The  functions with names of the form "benntoh" convert from big-endian order to host byte
       order.

       The functions with names of the form "lenntoh" convert from little-endian  order  to  host
       byte order.

VERSIONS

       Similar   functions   are  present  on  the  BSDs,  where  the  required  header  file  is
       <sys/endian.h> instead of <endian.h>.  Unfortunately, NetBSD, FreeBSD, and  glibc  haven't
       followed  the  original  OpenBSD  naming  convention  for  these functions, whereby the nn
       component always appears at the end of the function name (thus, for  example,  in  NetBSD,
       FreeBSD, and glibc, the equivalent of OpenBSDs "betoh32" is "be32toh").

STANDARDS

       None.

HISTORY

       glibc 2.9.

       These  functions  are similar to the older byteorder(3) family of functions.  For example,
       be32toh() is identical to ntohl().

       The advantage of the byteorder(3) functions is that they are standard functions  available
       on  all  UNIX systems.  On the other hand, the fact that they were designed for use in the
       context of TCP/IP means that they lack the 64-bit and little-endian variants described  in
       this page.

EXAMPLES

       The  program  below  display  the results of converting an integer from host byte order to
       both little-endian and big-endian byte order.  Since host byte  order  is  either  little-
       endian or big-endian, only one of these conversions will have an effect.  When we run this
       program on a little-endian system such as x86-32, we see the following:

           $ ./a.out
           x.u32 = 0x44332211
           htole32(x.u32) = 0x44332211
           htobe32(x.u32) = 0x11223344

   Program source

       #include <endian.h>
       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(void)
       {
           union {
               uint32_t u32;
               uint8_t arr[4];
           } x;

           x.arr[0] = 0x11;     /* Lowest-address byte */
           x.arr[1] = 0x22;
           x.arr[2] = 0x33;
           x.arr[3] = 0x44;     /* Highest-address byte */

           printf("x.u32 = %#x\n", x.u32);
           printf("htole32(x.u32) = %#x\n", htole32(x.u32));
           printf("htobe32(x.u32) = %#x\n", htobe32(x.u32));

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       bswap(3), byteorder(3)