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>BYTEORDER(3) System Library Functions Manual BYTEORDER(3)
NAME
htonl, htons, ntohl, ntohs, htobe32, htobe16, betoh32, betoh16, htole32,
htole16, letoh32, letoh16, swap32, swap16 - convert values between dif-
ferent byte orderings
SYNOPSIS
#include <sys/types.h>
#include <machine/endian.h>
u_int32_t
htonl(u_int32_t host32);
u_int16_t
htons(u_int16_t host16);
u_int32_t
ntohl(u_int32_t net32);
u_int16_t
ntohs(u_int16_t net16);
u_int32_t
htobe32(u_int32_t host32);
u_int16_t
htobe16(u_int16_t host16);
u_int32_t
betoh32(u_int32_t big32);
u_int16_t
betoh16(u_int16_t big16);
u_int32_t
htole32(u_int32_t host32);
u_int16_t
htole16(u_int16_t host16);
u_int32_t
letoh32(u_int32_t little32);
u_int16_t
letoh16(u_int16_t little16);
u_int32_t
swap32(u_int32_t val32);
u_int16_t
swap16(u_int16_t val16);
DESCRIPTION
These routines convert 16- and 32-bit quantities between different byte
orderings. The ``swap'' functions reverse the byte ordering of the given
quantity, the others converts either from/to the native byte order used
by the host to/from either little- or big-endian (a.k.a network) order.
Apart from the swap functions, the names can be described by this form:
{src-order}to{dst-order}{size}. Both {src-order} and {dst-order} can
take the following forms:
h Host order.
n Network order (big-endian).
be Big-endian (most significant byte first).
le Little-endian (least significant byte first).
One of the specified orderings must be `h'. {size} will take these
forms:
l Long (32-bit, used in conjunction with forms involving `n').
s Short (16-bit, used in conjunction with forms involving `n').
16
16-bit.
32
32-bit.
The swap functions are of the form: swap{size}.
Names involving `n' convert quantities between network byte order and
host byte order. The last letter (`s' or `l') is a mnemonic for the tra-
ditional names for such quantities, short and long, respectively. Today,
the C concept of short and long integers need not coincide with this tra-
ditional misunderstanding. On machines which have a byte order which is
the same as the network order, routines are defined as null macros.
The functions involving either ``be'', ``le'', or ``swap'' use the num-
bers 16 and 32 for specifying the bitwidth of the quantities they operate
on. Currently all supported architectures are either big- or little-
endian so either the ``be'' or ``le'' variants are implemented as null
macros.
The routines mentioned above which have either {src-order} or {dst-order}
set to `n' are most often used in conjunction with Internet addresses and
ports as returned by gethostbyname(3) and getservent(3).
SEE ALSO
gethostbyname(3), getservent(3)
HISTORY
The byteorder functions appeared in 4.2BSD.
BUGS
On the vax, alpha, i386, and so far mips, bytes are handled backwards
from most everyone else in the world. This is not expected to be fixed
in the near future.
BSD June 4, 1993 BSD
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