`htobe64`

,

`htobe32`

,

`htobe16`

,

`be64toh`

,

`be32toh`

,

`be16toh`

,

`betoh64`

,

`betoh32`

,

`betoh16`

,

`htole64`

,

`htole32`

,

`htole16`

,

`le64toh`

,

`le32toh`

,

`le16toh`

,

`letoh64`

,

`letoh32`

,

`letoh16`

,

`swap64`

,

`swap32`

,

`swap16`

—

convert values between different byte orderings

```
#include
<endian.h>
```

`uint64_t`
`htobe64`

(

`uint64_t
host64`);

`uint32_t`
`htobe32`

(

`uint32_t
host32`);

`uint16_t`
`htobe16`

(

`uint16_t
host16`);

`uint64_t`
`be64toh`

(

`uint64_t
big64`);

`uint32_t`
`be32toh`

(

`uint32_t
big32`);

`uint16_t`
`be16toh`

(

`uint16_t
big16`);

`uint64_t`
`betoh64`

(

`uint64_t
big64`);

`uint32_t`
`betoh32`

(

`uint32_t
big32`);

`uint16_t`
`betoh16`

(

`uint16_t
big16`);

`uint64_t`
`htole64`

(

`uint64_t
host64`);

`uint32_t`
`htole32`

(

`uint32_t
host32`);

`uint16_t`
`htole16`

(

`uint16_t
host16`);

`uint64_t`
`letoh64`

(

`uint64_t
little64`);

`uint64_t`
`le64toh`

(

`uint64_t
little64`);

`uint32_t`
`le32toh`

(

`uint32_t
little32`);

`uint16_t`
`le16toh`

(

`uint16_t
little16`);

`uint32_t`
`letoh32`

(

`uint32_t
little32`);

`uint16_t`
`letoh16`

(

`uint16_t
little16`);

`uint64_t`
`swap64`

(

`uint64_t
val64`);

`uint32_t`
`swap32`

(

`uint32_t
val32`);

`uint16_t`
`swap16`

(

`uint16_t
val16`);

These routines convert 16, 32 and 64-bit quantities between different byte
orderings. The “swap” functions reverse the byte ordering of the
given quantity; the others convert 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 containing “be” convert
between host and big-endian (most significant byte first) order of the given
quantity, while the names containing “le” convert between host
and little-endian (least significant byte first) order of the given quantity.

All these functions use the numbers 16, 32, or 64 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.

htonl(3)
The

`htobe64`

(),

`htobe32`

(),

`htobe16`

(),

`be64toh`

(),

`be32toh`

(),

`be16toh`

(),

`htole64`

(),

`htole32`

(),

`htole16`

(),

`le64toh`

(),

`le32toh`

(), and

`le16toh`

() functions are expected to conform
to a future version of

IEEE Std 1003.1
(“POSIX.1”). The other functions are extensions that
should not be used when portability is required.

The

`swap{size}`

and

`{src-order}to{dst-order}{size}`

functions
appeared in

4.2BSD. The

`{src-order}{size}to{dst-order}`

functions
appeared in

OpenBSD 5.6. A subset of them was
submitted for standardization after

IEEE Std
1003.1-2008 (“POSIX.1”).

The perceived antagonism between ‘host’ and
‘network’ byte order does not allow PDP-11 users to sleep
soundly at night.