# Byte order¶

#include <libcork/core.h>


This section contains definitions for determining the endianness of the host system, and for byte-swapping integer values of various sizes.

## Endianness detection¶

CORK_LITTLE_ENDIAN
CORK_BIG_ENDIAN
CORK_HOST_ENDIANNESS
CORK_OTHER_ENDIANNESS

The CORK_HOST_ENDIANNESS macro can be used to determine the endianness of the host system. It will be equal to either CORK_LITTLE_ENDIAN or CORK_BIG_ENDIAN. (The actual values don’t matter; you should always compare against the predefined constants.) The CORK_OTHER_endianness macro is defined to be the opposite endianness as CORK_HOST_ENDIANNESS. A common use case would be something like:

#if CORK_HOST_endianness == CORK_LITTLE_ENDIAN
/* do something to little-endian values */
#else
/* do something to big-endian values */
#endif

CORK_HOST_ENDIANNESS_NAME
CORK_OTHER_ENDIANNESS_NAME

These macros give you a human-readable name of the host’s endianness. You can use this in debugging messages.

Note

You should not use these macros to detect the endianness of the system, since we might change their definitions at some point to support localization. For that, use CORK_LITTLE_ENDIAN and CORK_BIG_ENDIAN.

## Byte swapping¶

### Swapping arbitrary expressions¶

All of the macros in this section take in an rvalue (i.e., any arbitrary expression) as a parameter. The result of the swap is returned as the value of the macro.

uint16_t CORK_SWAP_UINT16(uint16_t value)
uint32_t CORK_SWAP_UINT32(uint32_t value)
uint64_t CORK_SWAP_UINT64(uint64_t value)

These functions always perform a byte-swap, regardless of the endianness of the host system.

uint16_t CORK_UINT16_BIG_TO_HOST(uint16_t value)
uint32_t CORK_UINT32_BIG_TO_HOST(uint32_t value)
uint64_t CORK_UINT64_BIG_TO_HOST(uint64_t value)

These functions convert a big-endian (or network-endian) value into host endianness. (I.e., they only perform a swap if the current host is little-endian.)

uint16_t CORK_UINT16_HOST_TO_BIG(uint16_t value)
uint32_t CORK_UINT32_HOST_TO_BIG(uint32_t value)
uint64_t CORK_UINT64_HOST_TO_BIG(uint64_t value)

These functions convert a host-endian value into big (or network) endianness. (I.e., they only perform a swap if the current host is little-endian.)

uint16_t CORK_UINT16_LITTLE_TO_HOST(uint16_t value)
uint32_t CORK_UINT32_LITTLE_TO_HOST(uint32_t value)
uint64_t CORK_UINT64_LITTLE_TO_HOST(uint64_t value)

These functions convert a little-endian value into host endianness. (I.e., they only perform a swap if the current host is big-endian.)

uint16_t CORK_UINT16_HOST_TO_LITTLE(uint16_t value)
uint32_t CORK_UINT32_HOST_TO_LITTLE(uint32_t value)
uint64_t CORK_UINT64_HOST_TO_LITTLE(uint64_t value)

These functions convert a host-endian value into little endianness. (I.e., they only perform a swap if the current host is big-endian.)

### Swapping values in place¶

The macros in this section swap an integer in place, which means that the original value is overwritten with the result of the swap. To support this, you must pass in an lvalue as the parameter to the macro. (Note that you don’t pass in a pointer to the original value; these operations are implemented as macros, and you just need to provide a reference to the variable to be swapped.)

void CORK_SWAP_UINT16_IN_PLACE(uint16_t &value)
void CORK_SWAP_UINT32_IN_PLACE(uint32_t &value)
void CORK_SWAP_UINT64_IN_PLACE(uint64_t &value)

These functions always perform a byte-swap, regardless of the endianness of the host system.

void CORK_UINT16_BIG_TO_HOST_IN_PLACE(uint16_t &value)
void CORK_UINT32_BIG_TO_HOST_IN_PLACE(uint32_t &value)
void CORK_UINT64_BIG_TO_HOST_IN_PLACE(uint64_t &value)

These functions convert a big-endian (or network-endian) value into host endianness, and vice versa. (I.e., they only perform a swap if the current host is little-endian.)

void CORK_UINT16_HOST_TO_BIG_IN_PLACE(uint16_t &value)
void CORK_UINT32_HOST_TO_BIG_IN_PLACE(uint32_t &value)
void CORK_UINT64_HOST_TO_BIG_IN_PLACE(uint64_t &value)

These functions convert a host-endian value into big (or network) endianness. (I.e., they only perform a swap if the current host is little-endian.)

void CORK_UINT16_LITTLE_TO_HOST_IN_PLACE(uint16_t &value)
void CORK_UINT32_LITTLE_TO_HOST_IN_PLACE(uint32_t &value)
void CORK_UINT64_LITTLE_TO_HOST_IN_PLACE(uint64_t &value)

These functions convert a little-endian value into host endianness, and vice versa. (I.e., they only perform a swap if the current host is big-endian.)

void CORK_UINT16_HOST_TO_LITTLE_IN_PLACE(uint16_t &value)
void CORK_UINT32_HOST_TO_LITTLE_IN_PLACE(uint32_t &value)
void CORK_UINT64_HOST_TO_LITTLE_IN_PLACE(uint64_t &value)

These functions convert a host-endian value into little endianness. (I.e., they only perform a swap if the current host is big-endian.)