[十万个为什么] [lua] 自定义byte_buffer

#include "lprefix.h"

#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"

#define BYTE_BUFFER_META_TABLE_NAME  "byte_buffer*"

#define GET_BYTE_BUFFER(L) ((byte_buffer_t*)luaL_checkudata(L, 1, BYTE_BUFFER_META_TABLE_NAME))

// ---------------------------------------------------------------------------
typedef struct byte_buffer_t byte_buffer_t;

struct byte_buffer_t
{
	int 	m_size;

	uint8_t  m_buffer[0];
};

// 创建自定义类型byte_buffer_t
// ---------------------------------------------------------------------------
static int byte_buffer_new(lua_State* L)
{
	int size = luaL_checkinteger(L, 1);

	if (size <= 0)
	{
		return 0;
	}

	byte_buffer_t* bf = (byte_buffer_t*)lua_newuserdatauv(L, 4+size, 0);
	if (bf == NULL)
	{
		return 0;
	}

	bf->m_size = size;

	luaL_setmetatable(L, BYTE_BUFFER_META_TABLE_NAME);

	return 1;
}

// ---------------------------------------------------------------------------
static int bf_meta_len(lua_State* L)
{
	byte_buffer_t* bf = GET_BYTE_BUFFER(L);
	lua_pushinteger(L, bf->m_size);
	return 1;
}

// ---------------------------------------------------------------------------
static int bf_meta_tostring(lua_State* L)
{
	byte_buffer_t* bf = GET_BYTE_BUFFER(L);
	lua_pushfstring(L, "byte_buffer(%d)@%p", bf->m_size, bf);
	return 1;
}

// ---------------------------------------------------------------------------
static int bf_get(lua_State* L)
{
	byte_buffer_t* bf = GET_BYTE_BUFFER(L);
	int index = luaL_checkinteger(L, 2);
	if (index >= 0 && index < bf->m_size)
	{
		lua_pushinteger(L, bf->m_buffer[index]);
		return 1;
	}
	return 0;
}

// ---------------------------------------------------------------------------
static int bf_set(lua_State* L)
{
	byte_buffer_t* bf = GET_BYTE_BUFFER(L);
	int index = luaL_checkinteger(L, 2);
	int value = luaL_checkinteger(L, 3);
	if (index >= 0 && index < bf->m_size)
	{
		bf->m_buffer[index] = value&0xFF;
		lua_pushboolean(L, 1);
		return 1;
	}
	return 0;
}

// ---------------------------------------------------------------------------
static const luaL_Reg byte_buffer_func[] =
{
	{"new", byte_buffer_new},
	{NULL, NULL},
};

// ---------------------------------------------------------------------------
static const luaL_Reg bf_meta_func[] =
{
	{"__index", NULL},  /* placeholder */
	{"__len", bf_meta_len},
	{"__tostring", bf_meta_tostring},
	{NULL, NULL},
};

// ---------------------------------------------------------------------------
static const luaL_Reg bf_func[] =
{
	{"len", bf_meta_len},
	{"get", bf_get},
	{"set", bf_set},
	{NULL, NULL},
};

// ---------------------------------------------------------------------------
LUAMOD_API int luaopen_byte_buffer(lua_State *L);

LUAMOD_API int luaopen_byte_buffer(lua_State *L)
{
	// 创建 byte_bufer = {...}
	luaL_newlib(L, byte_buffer_func);

	// 创建 bf_meta = {..}
	luaL_newmetatable(L, BYTE_BUFFER_META_TABLE_NAME);
	luaL_setfuncs(L, bf_meta_func, 0);

	// 创建bf = {...}
	luaL_newlibtable(L, bf_func);
	luaL_setfuncs(L, bf_func, 0);

	// 设置buf_meta.__index = bf
	lua_setfield(L, -2, "__index");

	lua_pop(L, 1);

	return 1;
}