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ENDIAN(3)                                                               Linux Programmer's Manual                                                              ENDIAN(3)

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

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
       These functions were added to glibc in version 2.9.

CONFORMING TO
       These  functions  are  nonstandard.  Similar functions are present on the BSDs, where the required header file is <sys/endian.h> instead of <endian.h>.  Unfortu‐
       nately, 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").

NOTES
       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 de‐
       signed 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(int argc, char *argv[])
       {
           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)

GNU                                                                            2021-03-22                                                                      ENDIAN(3)