// g++ -g -O2 efbbbf-strip.cpp -o efbbbf-strip.exe

#include <iostream>
using std::cout;
using std::cerr;
using std::endl;
using std::ios_base;

#include <fstream>
using std::ifstream;
using std::ofstream;

#include <string>
using std::string;

#include <cstring>
using std::strlen;

static const string EFBBBF = string("\xef\xbb\xbf");
static const unsigned int EFBBBF_LEN = 3;

bool Strip(const char* filename);

int main(int argc, char* argv[])
{
  if(argc == 1)
  {
    cerr << "Strips text files of UTF-8 byte order marks (BOM) in place." << endl;
    cerr << "  Usage: efbbbf-strip.exe <text file> [<text file> …]" << endl;
    return 1;
  }

  for(unsigned int i = 1; i < (unsigned int)argc; i++)
  {
    Strip(argv[i]);
  }
}

bool Strip(const char* filename)
{
  if ( !filename || 0 == strlen(filename) )
    return false;

  //////////////////////////////////////////////////////////
  // Read the file
  //////////////////////////////////////////////////////////

  ifstream ifile(filename);
  if( !ifile.good() )
  {
    cerr << "Unable to open " << filename << " for reading" << endl;
    return false;
  }
  
  // Reserve size to save on allocations
  ifile.seekg(0, ios_base::end);
  if( !ifile.good() )
  {
    cerr << "Failed to seek to end of " << filename << endl;
    return false;
  }

  size_t fsize = ifile.tellg();
  if( !ifile.good() )
  {
    cerr << "Failed to determine size of " << filename << endl;
    return false;
  }

  ifile.seekg(0, ios_base::beg);
  if( !ifile.good() )
  {
    cerr << "Failed to seek to beginning of " << filename << endl;
    return false;
  }

  string str, line;
  str.reserve(fsize);

  // Read the file line by line. Not sure why reading in one fell swoop failed....
  while(std::getline(ifile, line))
  {
    str += line;
    str += "\n";

    if( !ifile.good() )
      break;
  }

  ifile.close();

  //////////////////////////////////////////////////////////
  // Fix the file
  //////////////////////////////////////////////////////////

  size_t count = 0;
  string::size_type pos = 1;
  while( (pos = str.find(EFBBBF, pos)) != string::npos )
  {
     str.replace(pos, EFBBBF_LEN, "");
     count++;
  }

  if(0 == count)
  {
    cout << filename << ": no replacements" << endl;
    return true;
  }

  //////////////////////////////////////////////////////////
  // Write the file
  //////////////////////////////////////////////////////////

  ofstream ofile(filename, ios_base::out | ios_base::trunc);
  if( !ofile.good() )
  {
    cerr << "Unable to open " << filename << " for writing" << endl;
    return false;
  }

  ofile.write(str.data(), str.size());
  if( !ofile.good() )
  {
    cerr << "Failed to write " << filename << endl;
    return false;
  }

  ofile.close();

  //////////////////////////////////////////////////////////
  // Book keeping
  //////////////////////////////////////////////////////////

  cout << filename << ": " << count << " replacements" << endl;
  return true;
}