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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | VERSIONS | STANDARDS | HISTORY | EXAMPLES | SEE ALSO |
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endian(3) Library Functions Manual endian(3)
htobe16, htole16, be16toh, le16toh, htobe32, htole32, be32toh,
le32toh, htobe64, htole64, be64toh, le64toh - convert values
between host and big-/little-endian byte order
Standard C library (libc, -lc)
#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
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.
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").
None.
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.
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);
}
bswap(3), byteorder(3)
Linux man-pages (unreleased) 2024-05-02 endian(3)
Pages that refer to this page: bswap(3), byteorder(3)
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HTML rendering created 2024-06-21 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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