lua接入pb相关问题备忘

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最近接pb.c

这段代码

static int struct_unpack(lua_State *L)
{
    uint8_t format = luaL_checkinteger(L, 1);
    size_t len;
    const uint8_t* buffer = (uint8_t*)luaL_checklstring(L, 2, &len);
    size_t pos = luaL_checkinteger(L, 3);

    buffer += pos;
    uint8_t out[8];
    switch(format){
        case 'i':
            {
                lua_pushinteger(L, *(int32_t*)unpack_fixed32(buffer, out));
                break;
            }
        case 'q':
            {
                lua_pushnumber(L, (lua_Number)*(int64_t*)unpack_fixed64(buffer, out));
                break;
            }
        case 'f':
            {
                lua_pushnumber(L, (lua_Number)*(float*)unpack_fixed32(buffer, out));
                break;
            }
        case 'd':
            {
                lua_pushnumber(L, (lua_Number)*(double*)unpack_fixed64(buffer, out));
                break;
            }
        case 'I':
            {
                lua_pushnumber(L, *(uint32_t*)unpack_fixed32(buffer, out));
                break;
            }
        case 'Q':
            {
                lua_pushnumber(L, (lua_Number)*(uint64_t*)unpack_fixed64(buffer, out));
                break;
            }
        default:
            luaL_error(L, "Unknown, format");
    }
    return 1;
}

uint8_t out[8]; 这行一直接报错误错误 error C2275: “uint8_t”: 将此类型用作表达式非法 error C2146: 语法错误: 缺少“;”(在标识符“out”的前面)

按c的规范需要将变量申明放在代码开头部份。

把uint8_t out[8];移到代码段首行，问题解决。代码如下：

static int struct_unpack(lua_State *L)
{
    uint8_t out[8];
    uint8_t format = luaL_checkinteger(L, 1);
    size_t len;
    const uint8_t* buffer = (uint8_t*)luaL_checklstring(L, 2, &len);
    size_t pos = luaL_checkinteger(L, 3);

    buffer += pos;
    
    switch(format){
        case 'i':
            {
                lua_pushinteger(L, *(int32_t*)unpack_fixed32(buffer, out));
                break;
            }
        case 'q':
            {
                lua_pushnumber(L, (lua_Number)*(int64_t*)unpack_fixed64(buffer, out));
                break;
            }
        case 'f':
            {
                lua_pushnumber(L, (lua_Number)*(float*)unpack_fixed32(buffer, out));
                break;
            }
        case 'd':
            {
                lua_pushnumber(L, (lua_Number)*(double*)unpack_fixed64(buffer, out));
                break;
            }
        case 'I':
            {
                lua_pushnumber(L, *(uint32_t*)unpack_fixed32(buffer, out));
                break;
            }
        case 'Q':
            {
                lua_pushnumber(L, (lua_Number)*(uint64_t*)unpack_fixed64(buffer, out));
                break;
            }
        default:
            luaL_error(L, "Unknown, format");
    }
    return 1;
}

另外 windows下面vs编译环境提示缺少 #include <endian.h>

可加入如下代码

#ifdef WIN32
#ifndef __LITTLE_ENDIAN
#define __LITTLE_ENDIAN 1234
#define __BIG_ENDIAN 4321
#endif
#ifndef __BYTE_ORDER
#define __BYTE_ORDER __LITTLE_ENDIAN
#endif
#else
#include <endian.h>
#endif