C++ Checking if data has specified string

Question

So I am trying to check if a string is within a 'block' of memory. So here is a made up memory address 0x00343211 where I start and want to start checking from.

What I am trying to do is write the data from 0x00343211 to 0x00343211 + 900 into a char array and then check if within that char array there is a string that I am looking for.

So this is what I have tried already

char dataBuf[1000] = { 0 };
memcpy((void*)dataBuf,(void*)0x00343211,900);
if(strstr(dataBuf,"ACTIVE") != NULL)
{
    //I want to check if the string "ACTIVE" is
    //within the random data that I have written into dataBuf
}

But this does not seem to be working.

Just loop through the memory address, and if the character is "A", check if the next memory addresses consists of the remaining characters? Not hard to do right? — KarelG, Apr 20 '17 at 08:31
@KarelG Yes but I am doing this in a hook that is executed each frame. So doing it in a loop like that would be pretty slow and/or cause the program to run pretty slow, no? — rflxdev, Apr 20 '17 at 08:32
Possibly related: http://stackoverflow.com/q/36878017/1938163 — Marco A., Apr 20 '17 at 08:39
@reflexdev how's that slow? The process is same as searching for a string in a large string. Both performs the same way. Your databuffer is 1000 characters. That's not a problem. You don't have to do advanced stuff like using vectors or something else ... — KarelG, Apr 20 '17 at 08:44
why do you copy instead of using `strstr` directly on your mem address? — Andriy Tylychko, Apr 20 '17 at 09:49
please specify how exactly it doesn't work. `strstr` returns `nullptr` or something else? — Andriy Tylychko, Apr 20 '17 at 09:50
Do as AndyT says. Also, I would set a breakpoint and single-step through the code. Ensure that you have the correct memory address. — Sam Hobbs, Apr 20 '17 at 17:18
Also, note that you are allocating 1000 characters and copying 900. — Sam Hobbs, Apr 20 '17 at 17:43

score 0 · Answer 1 · answered Apr 20 '17 at 08:52

You can use std::search directly on the memory block and pray that your compiler has an efficient implementation, like this:

#include <algorithm>
#include <string>
#include <iostream>


int main()
{
    char dataBuf[13] = { "xxxACTIVExxx" }; // block of 12 bytes + zero byte
    std::string active = "ACTIVE";

    using std::begin;
    using std::end;

    // std::search returns dataBuf+12 if no match is found
    if (std::search(dataBuf, dataBuf + 12,
        begin(active), end(active))
        != dataBuf + 12)
    {
        std::cout << "ACTIVE has been found\n";
    }
    else {
        std::cout << "ACTIVE has not been found\n";
    }


    return 0;
}

C++ Checking if data has specified string

1 Answers1