Lua third-party byte stream serialization and deserialization module --lpack

Recent research luasocket, Ready to use all lua To implement a lightweight framework , Used to make some tools 、 Simple game server , And as a network library used in cocos2dx in .

A perfect network library will inevitably encounter sticky packets 、 Half a package of questions ,luasocket No exception , Because the network part is lua, Formulation of the agreement and buff There is no suitable scheme for the analysis of , I don't want to be in C++ To encapsulate the interface , Later, I checked some information on the Internet , Find out lua There is also a binary packaged extension library ——lpack, After understanding, I found that it is still very easy to use , I decided to use it to do buff analysis , To solve sticking 、 Half a package of questions .

First you need to download lpack Source code , The address is lpack Download address , Then decompress , There are lpack.c and makefile file .
Then there's compilation lpack, There are two ways to compile and initialize lpack

1. take lpack.c Add it to the source code of the host program , And then you initialize it lua Call the initialization function :

luaopen_pack(lua_state);

2. take lpack Translate it into dll(so), And then in lua It calls :

require("lpack")

And then say lpack The interface of ,lpack The extension library provides two interfaces ,pack and unpack. But there are two ways to call , Use macros (USE_GLOBALS) To control , The first is to use the global interface (pack/unpack), The other is to insert these two interfaces into string In my space (string.pack/string.unpack).

lpack Specific usage of

1. Packaging interface pack Use , The global name is easy to confuse lua Self function unpack, Use string.pack many , You can also modify the source code and function name .

--luapack The interface name modified for me 
local _ss = luapack(">P", " China asd")

local _ss2 = luapack(">h", 500)
_ss = _ss.._ss2
print(_ss, #_ss)

-- The results 
 China asd        9
 China asd       11

2. Unpacking interface unpack Use

--luaunpack The interface name modified for me 
-- Usage mode 1
local ne, value = luaunpack(_ss, ">P")
print(ne, value)

_ss = string.sub(_ss, ne, #_ss)
local ne, value = luaunpack(_ss, ">h")
print(ne, value)

-- The results 
10       China asd
3       500

-- Usage mode 2
local ne, value1, value2 = luaunpack(_ss, ">Ph")
print(ne, value, value2)

-- The results 
12       China asd 500

Package variable type definitions

    #define OP_ZSTRING  'z'     // An empty string 
    #define OP_BSTRING  'p'     // The length is less than 2^8 String 
    #define OP_WSTRING  'P'     // The length is less than 2^16 String 
    #define OP_SSTRING  'a'     // The length is less than 2^32/64 String */
    #define OP_STRING   'A'     // Specify the length string 
    #define OP_FLOAT    'f'     /* float */
    #define OP_DOUBLE   'd'     /* double */
    #define OP_NUMBER   'n'     /* Lua number */
    #define OP_CHAR     'c'     /* char */
    #define OP_BYTE     'b'     /* byte = unsigned char */
    #define OP_SHORT    'h'     /* short */
    #define OP_USHORT   'H'     /* unsigned short */
    #define OP_INT      'i'     /* int */
    #define OP_UINT     'I'     /* unsigned int */
    #define OP_LONG     'l'     /* long */
    #define OP_ULONG    'L'     /* unsigned long */

Packed byte order , Divided into the following 3 Kind of

    #define OP_LITTLEENDIAN '<'     /* little endian */
    #define OP_BIGENDIAN    '>'     /* big endian */
    #define OP_NATIVE       '='     /* native endian */

Project examples

function parcel_method:read_ussd_buff()
    local buf = string.sub(self.buffer, self.pos,#self.buffer)
    local pos,hex_value
    local str_buffer = ""
    for index =1,#buf,2 do
        pos, hex_value = string.unpack(buf,"<h")
        -- log.debug("ussd hex_value=%d",hex_value)
        if hex_value > 0 and hex_value < 128 then  -- Input parameter must be ASCII code 
            local str_chr = string.char(hex_value)
            str_buffer = str_buffer .. str_chr
        end
        buf = string.sub(buf,pos)
        -- print(string.unpack(str,">h"))
    end

    self.pos = self.pos + pos - 1

    -- log.debug("ussd " .. str_buffer)
    return str_buffer
end

Okay , How to use it here lpack It's already clear , Then you can use lpack Characteristic design of buff To parse the network byte stream .