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[c++] Case sorting and Variable name printing problem

 
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ulysse31
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Location: Paris
PostPosted: Tue Nov 10, 2015 11:38 am    Post subject: [c++] Case sorting and Variable name printing problem Reply with quote
Hi, I am coding a packet program for an online game.
After decryption, I analyze the decrypted packets and the program takes action accordingly, I do this with a switch..case.

Simply put, I injected a dll into the game that retrieved me all the packet names and their corresponding hexa number, they are defined as follow in my c++:

Quote:
const int S_PLAYER_CHANGE_PROF = 0xbb32;
const int C_CREST_APPLY_LIST = 0xbb79;
const int C_ADMIN_LOBBY = 0xbbce;
const int S_MOUNT_VEHICLE = 0xbbf1;


The way i filter packets that matter is this one :

Quote:
void ProcessUndecryptedPacketData(boost::asio::ip::tcp::socket &socket, uint16_t& size, uint16_t& title, std::vector <unsigned char> &vectArgument, int &length)
{
switch (title)
{
case S_PLAYER_CHANGE_PROF:
//do something..
break;
case S_MOUNT_VEHICLE
//Do somth
break;
}
}


There are over 2000 packets, a switch case code cannot go over 128 possible cases or else i get a compiler limit error.
Each time a packet is processed, I log its entirety with its hexa number.


First problem :
I know there is a way better way to do this, can someone point me in the right direction ? (switch case like i did is simply bad)


I need to log the title of the packet ie S_MOUNT_VEHICLE and not only its hexa value, I came across a macro code but it prints the variable name and here the variable name is title (because switch(title)) and what i want is to print the name of the variable to which the value of title equals the hexas..I need to log the S_MOUNT_VEHICLE string and i don't see how to do this, I've thought of a function returning a string but then i'd have too many nested cases in the function.

Any help would be greatly appreciated
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atom0s
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Joined: 25 Jan 2006
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Location: 127.0.0.1
PostPosted: Tue Nov 10, 2015 2:23 pm    Post subject: This post has 1 review(s) Reply with quote
Use a functional lookup table for the packet types. Something on the line of:
Code:

bool packet_0x1234_handler()
{
    return true;
}

std::map<int, bool (*)() const> packetHandlers =
{
    { 0x1234, packet_0x1234_handler },
    { 0x1235, packet_0x1235_handler }
};


Adjust the handler function as needed for any arguments you may want etc.

You could also use std::function if need be.
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ulysse31
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Joined: 19 Mar 2015
Posts: 324
Location: Paris
PostPosted: Wed Nov 11, 2015 3:35 pm    Post subject: Reply with quote
Thanks, I haven't had the chance to come across those c ++ tools till now, it looks pretty good.

edit : Made it work, turns out to be just perfect

Last edited by ulysse31 on Wed Nov 11, 2015 7:33 pm; edited 1 time in total
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atom0s
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PostPosted: Wed Nov 11, 2015 6:40 pm    Post subject: Reply with quote
Shrooms wrote:
oh "smartone", difference in speed between map and other methods?


Performance depends on use. If you need the utmost speed out of an STL container, use unordered_map. But keep in mind being an STL container it will come at a cost with overhead and specific setups pertaining to how the STL feels things should be handled.

In most cases its best to roll your own container to get the maximum performance out of things, but if you are just looking for a quick and dirty pre-made solution, map and unordered_map from the STL are fine.

If you want to see some testings, there are various blogs that cover it:
http://www.joshbarczak.com/blog/?p=525
http://www.codeproject.com/Articles/866996/Fast-Implementations-of-Maps-with-Integer-Keys-in
http://scottmeyers.blogspot.com/2015/09/should-you-be-using-something-instead.html


Keep in mind, results will vary based on usage, data size being stored etc. as well as your system specs.
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