C++ read file, search for hex, output file - c++

Question

I can't figure out why this is outputting a different file given that the start of the input file matches the first if statement. Also, if there are multiple finds, the next file name turns out to be the last file name plus the new file name together.
int main()
{
unsigned short n(0);
unsigned char y;
std::ostringstream filename;
std::ifstream input("data.dat", std::ios::binary);
input >> std::noskipws >> std::hex;
std::ofstream output;
output << std::ios::binary;
while (input.good()) {
filename.clear();
filename << n << ".dat";
output.open(filename.str());
while ( input.good() )
{
input >> y;
output << y;
if ( y == 0xFF ) {
input >> y;
output << y;
if ( y == 0xD9 ) {
input >> y;
output << y;
output.close();
break;
}
}
}
if (output.is_open())
output.close();
++n;
}
return 0;
}

Answer 1

#include <iostream> // for input/output
#include <fstream> // for file stream stuff
#include <sstream> // for ostringstream
int main()
{
unsigned short nFile = 0; // used to increment file name
std::ostringstream filename; // output filename
std::ifstream inFile; // input stream
std::ofstream outFile; // output stream
unsigned char buffer; // buffer between input and output
inFile.open("data.dat", std::ios::binary); // open input file
if ( inFile.fail() )
return 1;
while ( inFile.good() )
{
filename.str(""); // empties the stream
filename << nFile << ".dat"; // generate filename
// start the search loop
while ( inFile.good() )
{
// create a file
outFile.open(filename.str(), std::ios::binary);
if ( outFile.fail() )
return 1;
while ( inFile.good() )
{
inFile.read(reinterpret_cast<char*>(&buffer), sizeof(buffer)); // read a byte
if ( inFile.eof() )
break;
outFile.write(reinterpret_cast<char*>(&buffer), sizeof(buffer)); // write a byte
if ( buffer == 0xFF )
{
inFile.read(reinterpret_cast<char*>(&buffer), sizeof(buffer)); // read a byte
if ( inFile.eof() )
break;
outFile.write(reinterpret_cast<char*>(&buffer), sizeof(buffer)); // write a byte
if ( buffer == 0xD9 ) // full match; break loop
{
break;
}
}
}
// if search is done and file is still open, close it
if (outFile.is_open())
outFile.close();
++nFile;
}
return 0;
}
}