C++ Auto update program

Question

I'm having problems with an auto-update program of mine

It's supposed to download & save an update from a website, but the problem is(And I'm sure that this happens alot yet I couldn't phrase the keywords that would get me the answer on google) it saves the .exe data it receives not as it's supposed to. It saves the bytes in acsi... let me illustrate that:

Offset      0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F

00000000   4D 5A 90 00 03 00 00 00  04 00 00 00 FF FF 00 00   MZ          ÿÿ  
00000010   B8 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00   ¸       @       
00000020   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00                   
00000030   00 00 00 00 00 00 00 00  00 00 00 00 B0 00 00 00               °   

This data, (which is the correct data) Looks like this in the new program:

Offset      0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F

00000000   0D 0A 34 44 35 41 39 30  30 30 30 33 30 30 30 30     4D5A9000030000
00000010   30 30 30 34 30 30 30 30  30 30 46 46 46 46 30 30   0004000000FFFF00
00000020   30 30 42 38 30 30 30 30  30 30 30 30 30 30 30 30   00B8000000000000
00000030   30 30 34 30 30 30 30 30  30 30 30 30 30 30 30 30   0040000000000000

As you can see it writes the codebytes as ascii values... This is the code I'm using

The receiving part:

char   szRecvBuff[10000] = "" ;
string szRecvHolder = "" ;      
int    iLastCharacter = 0;

    recv(Socket, szRecvBuff, sizeof(szRecvBuff), 0);

    szRecvHolder = szRecvBuff;

    iLastCharacter = szRecvHolder.find_last_of("\n");
    if(iLastCharacter < szRecvHolder.size() && iLastCharacter > 0 ){
    szRecvHolder.erase(iLastCharacter);
    }
  return szRecvHolder;
}
...
...
{
...
...
Recv();
string Edat = Recv();
std::ofstream put("Eprog.exe", ios::hex );
put <<  Edat.c_str();
put.close();

Does anyone know how to go about it, I've tried using google, but I couldn't phrase a question that would give me proper results

Answer 1

确保以二进制模式打开输出文件：

std::ofstream put("Eprog.exe", ios::binary | ios::hex );

Answer 2

The bigger problem I see with your code is that when you call to Edat.c_str() you're giving presumably a const char* to the stream. This pointer has no information on how much to write to the stream, so it has to stop, by convention, at the first ' \\0 '.

You should instead use the write() call and use a raw char buffer.

Answer 3

I've solved the problem, instead of trying to make the compiler interpret the values as hex I've simply made an lookup table containing all 256 possible bytes.

unsigned char Table[] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x5B, 0x5C, 0x5D, 0x5E, 0x5F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C, 0x7D, 0x7E, 0x7F, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, 0x9E, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF, 0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF, 0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE, 0xDF, 0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF };



int GetIndexNumber(string str){
unsigned long rint = NULL;
unsigned long size = str.size() - 2;
unsigned long fi[sizeof(str)];
unsigned long mul;

for( int i = 0; i != 2; i++){
    if( str.at(i+2) == '0' ) fi[i] = 0;
    if( str.at(i+2) == '1' ) fi[i] = 1;
    if( str.at(i+2) == '2' ) fi[i] = 2;
    if( str.at(i+2) == '3' ) fi[i] = 3;
    if( str.at(i+2) == '4' ) fi[i] = 4;
    if( str.at(i+2) == '5' ) fi[i] = 5;
    if( str.at(i+2) == '6' ) fi[i] = 6;
    if( str.at(i+2) == '7' ) fi[i] = 7;
    if( str.at(i+2) == '8' ) fi[i] = 8;
    if( str.at(i+2) == '9' ) fi[i] = 9;
    if( str.at(i+2) == 'A' ) fi[i] = 10;
    if( str.at(i+2) == 'B' ) fi[i] = 11;
    if( str.at(i+2) == 'C' ) fi[i] = 12;
    if( str.at(i+2) == 'D' ) fi[i] = 13;
    if( str.at(i+2) == 'E' ) fi[i] = 14;
    if( str.at(i+2) == 'F' ) fi[i] = 15;
}

for(int i = 0; i != 2 ; i++){
    mul = (1 * pow(16, (double)size-1));
    size--;
    rint += ( mul * fi[i]);
}
return rint;
}

Recv();
string Edat = Recv();
Edat += Recv();
cout<<Edat.c_str()<<endl<<endl;

unsigned char buffer[10000] = "";

for( int i = 0; i <= Edat.size(); i++){
    int PlaceHolder = Edat.find_first_of("0x");
    if(PlaceHolder <= Edat.size() && PlaceHolder > 0){ 
        string tmpstr = Edat.substr(PlaceHolder, 4);
        int TableNumber = GetIndexNumber(tmpstr);
         buffer[i] = Table[TableNumber];
    }
    Edat.replace(PlaceHolder, 4, "");
}

std::ofstream put("Eprog.exe", ios::binary);
put.write((char *)buffer, sizeof(buffer));
put.close(); 

return 0; 
}