Byte Order Macros: GLib Reference Manual

Byte Order Macros

Byte Order Macros — a portable way to convert between different byte orders

Functions

#define	g_htonl()
#define	g_htons()
#define	g_ntohl()
#define	g_ntohs()
#define	GINT_FROM_BE()
#define	GINT_FROM_LE()
#define	GINT_TO_BE()
#define	GINT_TO_LE()
#define	GUINT_FROM_BE()
#define	GUINT_FROM_LE()
#define	GUINT_TO_BE()
#define	GUINT_TO_LE()
#define	GLONG_FROM_BE()
#define	GLONG_FROM_LE()
#define	GLONG_TO_BE()
#define	GLONG_TO_LE()
#define	GULONG_FROM_BE()
#define	GULONG_FROM_LE()
#define	GULONG_TO_BE()
#define	GULONG_TO_LE()
#define	GSIZE_FROM_BE()
#define	GSIZE_FROM_LE()
#define	GSIZE_TO_BE()
#define	GSIZE_TO_LE()
#define	GSSIZE_FROM_BE()
#define	GSSIZE_FROM_LE()
#define	GSSIZE_TO_BE()
#define	GSSIZE_TO_LE()
#define	GINT16_FROM_BE()
#define	GINT16_FROM_LE()
#define	GINT16_TO_BE()
#define	GINT16_TO_LE()
#define	GUINT16_FROM_BE()
#define	GUINT16_FROM_LE()
#define	GUINT16_TO_BE()
#define	GUINT16_TO_LE()
#define	GINT32_FROM_BE()
#define	GINT32_FROM_LE()
#define	GINT32_TO_BE()
#define	GINT32_TO_LE()
#define	GUINT32_FROM_BE()
#define	GUINT32_FROM_LE()
#define	GUINT32_TO_BE()
#define	GUINT32_TO_LE()
#define	GINT64_FROM_BE()
#define	GINT64_FROM_LE()
#define	GINT64_TO_BE()
#define	GINT64_TO_LE()
#define	GUINT64_FROM_BE()
#define	GUINT64_FROM_LE()
#define	GUINT64_TO_BE()
#define	GUINT64_TO_LE()
#define	GUINT16_SWAP_BE_PDP()
#define	GUINT16_SWAP_LE_BE()
#define	GUINT16_SWAP_LE_PDP()
#define	GUINT32_SWAP_BE_PDP()
#define	GUINT32_SWAP_LE_BE()
#define	GUINT32_SWAP_LE_PDP()
#define	GUINT64_SWAP_LE_BE()

Types and Values

#define	G_BYTE_ORDER
#define	G_LITTLE_ENDIAN
#define	G_BIG_ENDIAN
#define	G_PDP_ENDIAN

Includes

#include <glib.h>

Description

These macros provide a portable way to determine the host byte order and to convert values between different byte orders.

The byte order is the order in which bytes are stored to create larger data types such as the gint and glong values. The host byte order is the byte order used on the current machine.

Some processors store the most significant bytes (i.e. the bytes that hold the largest part of the value) first. These are known as big-endian processors. Other processors (notably the x86 family) store the most significant byte last. These are known as little-endian processors.

Finally, to complicate matters, some other processors store the bytes in a rather curious order known as PDP-endian. For a 4-byte word, the 3rd most significant byte is stored first, then the 4th, then the 1st and finally the 2nd.

Obviously there is a problem when these different processors communicate with each other, for example over networks or by using binary file formats. This is where these macros come in. They are typically used to convert values into a byte order which has been agreed on for use when communicating between different processors. The Internet uses what is known as 'network byte order' as the standard byte order (which is in fact the big-endian byte order).

Note that the byte order conversion macros may evaluate their arguments multiple times, thus you should not use them with arguments which have side-effects.

Functions

g_htonl()

#define             g_htonl(val)

Converts a 32-bit integer value from host to network byte order.

Parameters

val

a 32-bit integer value in host byte order

Returns

val converted to network byte order

g_htons()

#define             g_htons(val)

Converts a 16-bit integer value from host to network byte order.

Parameters

val

a 16-bit integer value in host byte order

Returns

val converted to network byte order

g_ntohl()

#define             g_ntohl(val)

Converts a 32-bit integer value from network to host byte order.

Parameters

val

a 32-bit integer value in network byte order

Returns

val converted to host byte order.

g_ntohs()

#define             g_ntohs(val)

Converts a 16-bit integer value from network to host byte order.

Parameters

val

a 16-bit integer value in network byte order

Returns

val converted to host byte order

GINT_FROM_BE()

#define GINT_FROM_BE(val) (GINT_TO_BE (val))

Converts a gint value from big-endian to host byte order.

Parameters

val

a gint value in big-endian byte order

Returns

val converted to host byte order

GINT_FROM_LE()

#define GINT_FROM_LE(val) (GINT_TO_LE (val))

Converts a gint value from little-endian to host byte order.

Parameters

val

a gint value in little-endian byte order

Returns

val converted to host byte order

GINT_TO_BE()

#define GINT_TO_BE(val)		((gint) GINT32_TO_BE (val))

Converts a gint value from host byte order to big-endian.

Parameters

val

a gint value in host byte order

Returns

val converted to big-endian byte order

GINT_TO_LE()

#define GINT_TO_LE(val)		((gint) GINT32_TO_LE (val))

Converts a gint value from host byte order to little-endian.

Parameters

val

a gint value in host byte order

Returns

val converted to little-endian byte order

GUINT_FROM_BE()

#define GUINT_FROM_BE(val) (GUINT_TO_BE (val))

Converts a guint value from big-endian to host byte order.

Parameters

val

a guint value in big-endian byte order

Returns

val converted to host byte order

GUINT_FROM_LE()

#define GUINT_FROM_LE(val) (GUINT_TO_LE (val))

Converts a guint value from little-endian to host byte order.

Parameters

val

a guint value in little-endian byte order

Returns

val converted to host byte order

GUINT_TO_BE()

#define GUINT_TO_BE(val) ((guint) GUINT32_TO_BE (val))

Converts a guint value from host byte order to big-endian.

Parameters

val

a guint value in host byte order

Returns

val converted to big-endian byte order

GUINT_TO_LE()

#define GUINT_TO_LE(val) ((guint) GUINT32_TO_LE (val))

Converts a guint value from host byte order to little-endian.

Parameters

val

a guint value in host byte order

Returns

val converted to little-endian byte order.

GLONG_FROM_BE()

#define GLONG_FROM_BE(val) (GLONG_TO_BE (val))

Converts a glong value from big-endian to the host byte order.

Parameters

val

a glong value in big-endian byte order

Returns

val converted to host byte order

GLONG_FROM_LE()

#define GLONG_FROM_LE(val) (GLONG_TO_LE (val))

Converts a glong value from little-endian to host byte order.

Parameters

val

a glong value in little-endian byte order

Returns

val converted to host byte order

GLONG_TO_BE()

#define GLONG_TO_BE(val) ((glong) GINT64_TO_BE (val))

Converts a glong value from host byte order to big-endian.

Parameters

val

a glong value in host byte order

Returns

val converted to big-endian byte order

GLONG_TO_LE()

#define GLONG_TO_LE(val) ((glong) GINT64_TO_LE (val))

Converts a glong value from host byte order to little-endian.

Parameters

val

a glong value in host byte order

Returns

val converted to little-endian

GULONG_FROM_BE()

#define GULONG_FROM_BE(val) (GULONG_TO_BE (val))

Converts a gulong value from big-endian to host byte order.

Parameters

val

a gulong value in big-endian byte order

Returns

val converted to host byte order

GULONG_FROM_LE()

#define GULONG_FROM_LE(val) (GULONG_TO_LE (val))

Converts a gulong value from little-endian to host byte order.

Parameters

val

a gulong value in little-endian byte order

Returns

val converted to host byte order

GULONG_TO_BE()

#define GULONG_TO_BE(val) ((gulong) GUINT64_TO_BE (val))

Converts a gulong value from host byte order to big-endian.

Parameters

val

a gulong value in host byte order

Returns

val converted to big-endian

GULONG_TO_LE()

#define GULONG_TO_LE(val) ((gulong) GUINT64_TO_LE (val))

Converts a gulong value from host byte order to little-endian.

Parameters

val

a gulong value in host byte order

Returns

val converted to little-endian

GSIZE_FROM_BE()

#define GSIZE_FROM_BE(val) (GSIZE_TO_BE (val))

Converts a gsize value from big-endian to the host byte order.

Parameters

val

a gsize value in big-endian byte order

Returns

val converted to host byte order

GSIZE_FROM_LE()

#define GSIZE_FROM_LE(val) (GSIZE_TO_LE (val))

Converts a gsize value from little-endian to host byte order.

Parameters

val

a gsize value in little-endian byte order

Returns

val converted to host byte order

GSIZE_TO_BE()

#define GSIZE_TO_BE(val) ((gsize) GUINT64_TO_BE (val))

Converts a gsize value from host byte order to big-endian.

Parameters

val

a gsize value in host byte order

Returns

val converted to big-endian byte order

GSIZE_TO_LE()

#define GSIZE_TO_LE(val) ((gsize) GUINT64_TO_LE (val))

Converts a gsize value from host byte order to little-endian.

Parameters

val

a gsize value in host byte order

Returns

val converted to little-endian

GSSIZE_FROM_BE()

#define GSSIZE_FROM_BE(val) (GSSIZE_TO_BE (val))

Converts a gssize value from big-endian to host byte order.

Parameters

val

a gssize value in big-endian byte order

Returns

val converted to host byte order

GSSIZE_FROM_LE()

#define GSSIZE_FROM_LE(val) (GSSIZE_TO_LE (val))

Converts a gssize value from little-endian to host byte order.

Parameters

val

a gssize value in little-endian byte order

Returns

val converted to host byte order

GSSIZE_TO_BE()

#define GSSIZE_TO_BE(val) ((gssize) GINT64_TO_BE (val))

Converts a gssize value from host byte order to big-endian.

Parameters

val

a gssize value in host byte order

Returns

val converted to big-endian

GSSIZE_TO_LE()

#define GSSIZE_TO_LE(val) ((gssize) GINT64_TO_LE (val))

Converts a gssize value from host byte order to little-endian.

Parameters

val

a gssize value in host byte order

Returns

val converted to little-endian

GINT16_FROM_BE()

#define GINT16_FROM_BE(val) (GINT16_TO_BE (val))

Converts a gint16 value from big-endian to host byte order.

Parameters

val

a gint16 value in big-endian byte order

Returns

val converted to host byte order

GINT16_FROM_LE()

#define GINT16_FROM_LE(val) (GINT16_TO_LE (val))

Converts a gint16 value from little-endian to host byte order.

Parameters

val

a gint16 value in little-endian byte order

Returns

val converted to host byte order

GINT16_TO_BE()

#define GINT16_TO_BE(val) ((gint16) GUINT16_SWAP_LE_BE (val))

Converts a gint16 value from host byte order to big-endian.

Parameters

val

a gint16 value in host byte order

Returns

val converted to big-endian

GINT16_TO_LE()

#define GINT16_TO_LE(val) ((gint16) (val))

Converts a gint16 value from host byte order to little-endian.

Parameters

val

a gint16 value in host byte order

Returns

val converted to little-endian

GUINT16_FROM_BE()

#define GUINT16_FROM_BE(val) (GUINT16_TO_BE (val))

Converts a guint16 value from big-endian to host byte order.

Parameters

val

a guint16 value in big-endian byte order

Returns

val converted to host byte order

GUINT16_FROM_LE()

#define GUINT16_FROM_LE(val) (GUINT16_TO_LE (val))

Converts a guint16 value from little-endian to host byte order.

Parameters

val

a guint16 value in little-endian byte order

Returns

val converted to host byte order

GUINT16_TO_BE()

#define GUINT16_TO_BE(val) (GUINT16_SWAP_LE_BE (val))

Converts a guint16 value from host byte order to big-endian.

Parameters

val

a guint16 value in host byte order

Returns

val converted to big-endian

GUINT16_TO_LE()

#define GUINT16_TO_LE(val) ((guint16) (val))

Converts a guint16 value from host byte order to little-endian.

Parameters

val

a guint16 value in host byte order

Returns

val converted to little-endian

GINT32_FROM_BE()

#define GINT32_FROM_BE(val) (GINT32_TO_BE (val))

Converts a gint32 value from big-endian to host byte order.

Parameters

val

a gint32 value in big-endian byte order

Returns

val converted to host byte order

GINT32_FROM_LE()

#define GINT32_FROM_LE(val) (GINT32_TO_LE (val))

Converts a gint32 value from little-endian to host byte order.

Parameters

val

a gint32 value in little-endian byte order

Returns

val converted to host byte order

GINT32_TO_BE()

#define GINT32_TO_BE(val) ((gint32) GUINT32_SWAP_LE_BE (val))

Converts a gint32 value from host byte order to big-endian.

Parameters

val

a gint32 value in host byte order

Returns

val converted to big-endian

GINT32_TO_LE()

#define GINT32_TO_LE(val) ((gint32) (val))

Converts a gint32 value from host byte order to little-endian.

Parameters

val

a gint32 value in host byte order

Returns

val converted to little-endian

GUINT32_FROM_BE()

#define GUINT32_FROM_BE(val) (GUINT32_TO_BE (val))

Converts a guint32 value from big-endian to host byte order.

Parameters

val

a guint32 value in big-endian byte order

Returns

val converted to host byte order

GUINT32_FROM_LE()

#define GUINT32_FROM_LE(val) (GUINT32_TO_LE (val))

Converts a guint32 value from little-endian to host byte order.

Parameters

val

a guint32 value in little-endian byte order

Returns

val converted to host byte order

GUINT32_TO_BE()

#define GUINT32_TO_BE(val) (GUINT32_SWAP_LE_BE (val))

Converts a guint32 value from host byte order to big-endian.

Parameters

val

a guint32 value in host byte order

Returns

val converted to big-endian

GUINT32_TO_LE()

#define GUINT32_TO_LE(val) ((guint32) (val))

Converts a guint32 value from host byte order to little-endian.

Parameters

val

a guint32 value in host byte order

Returns

val converted to little-endian

GINT64_FROM_BE()

#define GINT64_FROM_BE(val) (GINT64_TO_BE (val))

Converts a gint64 value from big-endian to host byte order.

Parameters

val

a gint64 value in big-endian byte order

Returns

val converted to host byte order

GINT64_FROM_LE()

#define GINT64_FROM_LE(val) (GINT64_TO_LE (val))

Converts a gint64 value from little-endian to host byte order.

Parameters

val

a gint64 value in little-endian byte order

Returns

val converted to host byte order

GINT64_TO_BE()

#define GINT64_TO_BE(val) ((gint64) GUINT64_SWAP_LE_BE (val))

Converts a gint64 value from host byte order to big-endian.

Parameters

val

a gint64 value in host byte order

Returns

val converted to big-endian

GINT64_TO_LE()

#define GINT64_TO_LE(val) ((gint64) (val))

Converts a gint64 value from host byte order to little-endian.

Parameters

val

a gint64 value in host byte order

Returns

val converted to little-endian

GUINT64_FROM_BE()

#define GUINT64_FROM_BE(val) (GUINT64_TO_BE (val))

Converts a guint64 value from big-endian to host byte order.

Parameters

val

a guint64 value in big-endian byte order

Returns

val converted to host byte order

GUINT64_FROM_LE()

#define GUINT64_FROM_LE(val) (GUINT64_TO_LE (val))

Converts a guint64 value from little-endian to host byte order.

Parameters

val

a guint64 value in little-endian byte order

Returns

val converted to host byte order

GUINT64_TO_BE()

#define GUINT64_TO_BE(val) (GUINT64_SWAP_LE_BE (val))

Converts a guint64 value from host byte order to big-endian.

Parameters

val

a guint64 value in host byte order

Returns

val converted to big-endian

GUINT64_TO_LE()

#define GUINT64_TO_LE(val) ((guint64) (val))

Converts a guint64 value from host byte order to little-endian.

Parameters

val

a guint64 value in host byte order

Returns

val converted to little-endian

GUINT16_SWAP_BE_PDP()

#define GUINT16_SWAP_BE_PDP(val) (GUINT16_SWAP_LE_BE (val))

Converts a guint16 value between big-endian and pdp-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint16 value in big-endian or pdp-endian byte order

Returns

val converted to the opposite byte order

GUINT16_SWAP_LE_BE()

#    define GUINT16_SWAP_LE_BE(val) (GUINT16_SWAP_LE_BE_IA32 (val))

Converts a guint16 value between little-endian and big-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint16 value in little-endian or big-endian byte order

Returns

val converted to the opposite byte order

GUINT16_SWAP_LE_PDP()

#define GUINT16_SWAP_LE_PDP(val) ((guint16) (val))

Converts a guint16 value between little-endian and pdp-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint16 value in little-endian or pdp-endian byte order

Returns

val converted to the opposite byte order

GUINT32_SWAP_BE_PDP()

#define             GUINT32_SWAP_BE_PDP(val)

Converts a guint32 value between big-endian and pdp-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint32 value in big-endian or pdp-endian byte order

Returns

val converted to the opposite byte order

GUINT32_SWAP_LE_BE()

#    define GUINT32_SWAP_LE_BE(val) ((guint32) __builtin_bswap32 ((guint32) (val)))

Converts a guint32 value between little-endian and big-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint32 value in little-endian or big-endian byte order

Returns

val converted to the opposite byte order

GUINT32_SWAP_LE_PDP()

#define             GUINT32_SWAP_LE_PDP(val)

Converts a guint32 value between little-endian and pdp-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint32 value in little-endian or pdp-endian byte order

Returns

val converted to the opposite byte order

GUINT64_SWAP_LE_BE()

#    define GUINT64_SWAP_LE_BE(val) ((guint64) __builtin_bswap64 ((guint64) (val)))

Converts a guint64 value between little-endian and big-endian byte order. The conversion is symmetric so it can be used both ways.

Parameters

val

a guint64 value in little-endian or big-endian byte order

Returns

val converted to the opposite byte order

Types and Values

G_BYTE_ORDER

#define G_BYTE_ORDER G_LITTLE_ENDIAN

The host byte order. This can be either G_LITTLE_ENDIAN or G_BIG_ENDIAN (support for G_PDP_ENDIAN may be added in future.)

G_LITTLE_ENDIAN

#define G_LITTLE_ENDIAN 1234

Specifies one of the possible types of byte order. See G_BYTE_ORDER.

G_BIG_ENDIAN

#define G_BIG_ENDIAN    4321

Specifies one of the possible types of byte order. See G_BYTE_ORDER.

G_PDP_ENDIAN

#define G_PDP_ENDIAN    3412		/* unused, need specific PDP check */

Specifies one of the possible types of byte order (currently unused). See G_BYTE_ORDER.