A program example to mark an executable with an md5 hash

//
//  A program example to mark an executable with a specified unique identification number
//  Written By: MadMouse
////////////////////////////////////////////////////////////////////////////////////////////
// example implementation
////////////////////////////////////////////////////////////////////////////////////////////
/*  #include <unistd.h>
    main()
    {
        static const char poop[] = "\xDE\xAD\xBE\xEF!ca419c121f43ab9c91a23e5cb727cef6";
        puts((char*)poop+5);
    }
*/
////////////////////////////////////////////////////////////////////////////////////////////
// Example run:
////////////////////////////////////////////////////////////////////////////////////////////
// [user@n0 identifier]$ gcc test.c -o test
// [user@n0 identifier]$ ./test
// ca419c121f43ab9c91a23e5cb727cef6
// [user@n0 identifier]$ g++ identifier.cc -o identifier
// [user@n0 identifier]$ ./identifier test $(date|md5sum)
// Writting version after magic sequence
// Old: ca419c121f43ab9c91a23e5cb727cef6
// New: e68658eacedafb864fbf1b3484781c1e
// [user@n0 identifier]$ ./test
// e68658eacedafb864fbf1b3484781c1e
// [user@n0 identifier]$

#include <cstring>
#include <fstream>
#include <iostream>
#include <stdlib.h>

typedef unsigned char BYTE;

// Get the size of a file
long getfilesize(FILE *file)
{
    long end;
    fseek(file, 0L, SEEK_END);
    end = ftell(file);
    fseek(file, 0L, SEEK_SET);
    return end;
}

void usage(const char* name)
{
    std::cout << "Usage: " << name << " <file> <md5hash>" << std::endl;
    exit(1);
}

int main(int argc,const char** argv)
{
    if(argc != 4) usage(argv[0]);
    else if(strlen(argv[2])<32) usage(argv[0]);

    FILE* file = NULL;  // declare a file pointer
    BYTE* buffer;   // buffer for file

    std::cout << "Writting version after magic sequence" << std::endl;
    if ((file = fopen(argv[1], "rb")) == NULL)  // open the file for reading
    {
        std::cout << "Could not open file..." << std::endl;
        return 1;       // return fail
    }

    long fsize = getfilesize(file); // get the size of the exe
    buffer = new BYTE[fsize];       // allocate space to store exe in mem
    fread(buffer, fsize, 1, file);  // read the exe into memory

    long counter=0; // counter... lol
    for(;counter<fsize;++counter)   // count through the file in memory
    {
        // if we find the magic sequence
        if(buffer[counter]==0xDE&&buffer[counter+1]==0xAD&&buffer[counter+2]==0xBE&&buffer[counter+3]==0xEF&&buffer[counter+4]=='!')
        {
            std::cout << "Old: " <<(BYTE*) buffer+(counter+5) << std::endl;
            break;
        }
    }
    fclose(file);       // close the file
    if(counter==fsize)
    {
        std::cerr << "We did not find the magic number..." << std::endl;
        return 1;
    }
    for(unsigned int i=0;i<=strlen(argv[2]);++i)
    {
        buffer[(counter+5)+i]=argv[2][i];
        if ((file = fopen(argv[1], "wb")) == NULL)  // open the file for writing
        {
            delete[] buffer;    // free buffer
            std::cout << "Failed to write to file..." << std::endl;
            return 1;       // return fail
        }
    }

    fwrite(buffer,sizeof(BYTE),fsize,file);  // write the new identifier
    std::cout<<"New: " << argv[2] << std::endl;
    delete[] buffer;    // free the buffer
    fclose(file);       // close the file
    return 0;        // return success
}