v1_1_c_overview

msgpack-c C version users guide

This document is under construction.

How to use

Include msgpack.h header file.

#include <msgpack.h>

Link msgpack library. When you use UNIX, the library name is libmsgpack.a. When you use Windows, the library name is msgpack.lib for static link and msgpack_import.lib for dynamic link.

Packing

When you pack your data, use buffers and a packer.

msgpack_sbuffer sbuf; /* buffer */
msgpack_packer pk;    /* packer */

msgpack_sbuffer_init(&sbuf); /* initialize buffer */
msgpack_packer_init(&pk, &sbuf, msgpack_sbuffer_write); /* initialize packer */

Buffers

The buffers store packed byte data. The buffers are used by packer. msgpack-c provides four buffers. sbuffer, fbuffer, zbuffer, and vrefbuffer.

sbuffer is a simple memory buffer. It uses malloc, realloc, and free. fbuffer is a file buffer. It uses FILE structure in C standard library. zbuffer is a compressing buffer using zlib. So packed data is compressed. vrefbuffer is an iovec based buffer. So packed data is stored as iovec.

Initialize, Destroy, and Write

All buffers have at least three functions. Initialize, Destroy, and Write.

Buffer	Initialize	Destroy	Write
sbuffer	msgpack_sbuffer_init	msgpack_sbuffer_destroy	msgpack_sbuffer_write
zbuffer	msgpack_zbuffer_init	msgpack_zbuffer_destroy	msgpack_zbuffer_write
vrefbuffer	msgpack_vrefbuffer_init	msgpack_vrefbuffer_destroy	msgpack_vrefbuffer_write
fbuffer	fopen	fclose	msgpack_fbuffer_write

When you initialize packer, you pass a pointer to the buffer as the second argument, and pass write function pointer as the third argument. Packer calls the write function through the pointer internally.

The buffers have additional buffer specific functions. Please check the source code.

Packer

Packer provides packing mechanism. Packer requires a buffer. In order to use packer, call msgpack_packer_init() as follows:

msgpack_sbuffer sbuf; /* buffer */
msgpack_packer pk;    /* packer */

msgpack_sbuffer_init(&sbuf); /* initialize buffer */
msgpack_packer_init(&pk, &sbuf, msgpack_sbuffer_write); /* initialize packer */

After initializing, you can call the following packing functions:

int msgpack_pack_char(msgpack_packer* pk, char d);

int msgpack_pack_signed_char(msgpack_packer* pk, signed char d);
int msgpack_pack_short(msgpack_packer* pk, short d);
int msgpack_pack_int(msgpack_packer* pk, int d);
int msgpack_pack_long(msgpack_packer* pk, long d);
int msgpack_pack_long_long(msgpack_packer* pk, long long d);
int msgpack_pack_unsigned_char(msgpack_packer* pk, unsigned char d);
int msgpack_pack_unsigned_short(msgpack_packer* pk, unsigned short d);
int msgpack_pack_unsigned_int(msgpack_packer* pk, unsigned int d);
int msgpack_pack_unsigned_long(msgpack_packer* pk, unsigned long d);
int msgpack_pack_unsigned_long_long(msgpack_packer* pk, unsigned long long d);

int msgpack_pack_uint8(msgpack_packer* pk, uint8_t d);
int msgpack_pack_uint16(msgpack_packer* pk, uint16_t d);
int msgpack_pack_uint32(msgpack_packer* pk, uint32_t d);
int msgpack_pack_uint64(msgpack_packer* pk, uint64_t d);
int msgpack_pack_int8(msgpack_packer* pk, int8_t d);
int msgpack_pack_int16(msgpack_packer* pk, int16_t d);
int msgpack_pack_int32(msgpack_packer* pk, int32_t d);
int msgpack_pack_int64(msgpack_packer* pk, int64_t d);

int msgpack_pack_fix_uint8(msgpack_packer* pk, uint8_t d);
int msgpack_pack_fix_uint16(msgpack_packer* pk, uint16_t d);
int msgpack_pack_fix_uint32(msgpack_packer* pk, uint32_t d);
int msgpack_pack_fix_uint64(msgpack_packer* pk, uint64_t d);
int msgpack_pack_fix_int8(msgpack_packer* pk, int8_t d);
int msgpack_pack_fix_int16(msgpack_packer* pk, int16_t d);
int msgpack_pack_fix_int32(msgpack_packer* pk, int32_t d);
int msgpack_pack_fix_int64(msgpack_packer* pk, int64_t d);

int msgpack_pack_float(msgpack_packer* pk, float d);
int msgpack_pack_double(msgpack_packer* pk, double d);

int msgpack_pack_nil(msgpack_packer* pk);
int msgpack_pack_true(msgpack_packer* pk);
int msgpack_pack_false(msgpack_packer* pk);

int msgpack_pack_array(msgpack_packer* pk, size_t n);

int msgpack_pack_map(msgpack_packer* pk, size_t n);

int msgpack_pack_str(msgpack_packer* pk, size_t l);
int msgpack_pack_str_body(msgpack_packer* pk, const void* b, size_t l);

int msgpack_pack_v4raw(msgpack_packer* pk, size_t l);
int msgpack_pack_v4raw_body(msgpack_packer* pk, const void* b, size_t l);

int msgpack_pack_bin(msgpack_packer* pk, size_t l);
int msgpack_pack_bin_body(msgpack_packer* pk, const void* b, size_t l);

int msgpack_pack_ext(msgpack_packer* pk, size_t l, int8_t type);
int msgpack_pack_ext_body(msgpack_packer* pk, const void* b, size_t l);

int msgpack_pack_object(msgpack_packer* pk, msgpack_object d);

Those functions are corresponding to msgpack format

To pack STR, RAW(v4 format), BIN, and EXT, call msgpack_pack_[str|v4raw|bin|ext] to provide a size and then call msgpack_pack_[str|v4raw|bin|ext]_body to provide a payload. To pack ARRAY, call msgpack_pack_array to provide the number of elements and then call any msgpack_pack_* functions the number times. To pack MAP, call msgpack_pack_map to provide the number of elements and then call any msgpack_pack_* functions the number*2 times (key and value).

When you use packer as value (not pointer), you don't need to call destroy function. Be careful that msgpack_packer_free is not a destroy function for a packer as value. It is for msgpack_packer_new. If you want to create a packer on heap, call msgpack_packer_new to create a packer and msgpack_packer_free to destroy(free) the packer.