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

NAME         top

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

SYNOPSIS         top

       #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:
           In glibc up to and including 2.19:

DESCRIPTION         top

       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         top

       These functions were added to glibc in version 2.9.

CONFORMING TO         top

       These functions are nonstandard.  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").

NOTES         top

       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

EXAMPLE         top

       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>

       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 = 0x%x\n", x.u32);
           printf("htole32(x.u32) = 0x%x\n", htole32(x.u32));
           printf("htobe32(x.u32) = 0x%x\n", htobe32(x.u32));


SEE ALSO         top

       bswap(3), byteorder(3)

COLOPHON         top

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GNU                              2016-10-08                        ENDIAN(3)