## NAME

`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

## SYNOPSIS

```
#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`);

## DESCRIPTION

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.

## SEE ALSO

## STANDARDS

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.

## HISTORY

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”).

## BUGS

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