endian

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  in-
       teger 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-en-
       dian 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  <en-
       dian.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 "be-
       toh32" is "be32toh").

NOTES
       These  functions  are similar to the older byteorder(3) family of func-
       tions.  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.

EXAMPLE
       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 = 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));

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       bswap(3), byteorder(3)

COLOPHON
       This  page  is  part of release 5.05 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU                               2019-03-06                         ENDIAN(3)