endian(3) - Linux manual page (original) (raw)
endian(3) Library Functions 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 orderLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <endian.h>**
**uint16_t htobe16(uint16_t** _host16bits_**);**
**uint16_t htole16(uint16_t** _host16bits_**);**
**uint16_t be16toh(uint16_t** _bigendian16bits_**);**
**uint16_t le16toh(uint16_t** _littleendian16bits_**);**
**uint32_t htobe32(uint32_t** _host32bits_**);**
**uint32_t htole32(uint32_t** _host32bits_**);**
**uint32_t be32toh(uint32_t** _bigendian32bits_**);**
**uint32_t le32toh(uint32_t** _littleendian32bits_**);**
**uint64_t htobe64(uint64_t** _host64bits_**);**
**uint64_t htole64(uint64_t** _host64bits_**);**
**uint64_t be64toh(uint64_t** _bigendian64bits_**);**
**uint64_t le64toh(uint64_t** _littleendian64bits_**);**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_SOURCEDESCRIPTION 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 "htobe_nn_" convert from host
byte order to big-endian order.
The functions with names of the form "htole_nn_" convert from host
byte order to little-endian order.
The functions with names of the form "be_nn_toh" convert from big-
endian order to host byte order.
The functions with names of the form "le_nn_toh" convert from
little-endian order to host byte order.VERSIONS top
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 top
None.HISTORY top
glibc 2.9.
These functions are similar to the older [byteorder(3)](../man3/byteorder.3.html) family of
functions. For example, **be32toh**() is identical to **ntohl**().
The advantage of the [byteorder(3)](../man3/byteorder.3.html) 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 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) = 0x11223344Program 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 top
[bswap(3)](../man3/bswap.3.html), [byteorder(3)](../man3/byteorder.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 endian(3)
Pages that refer to this page:bswap(3), byteorder(3)