/*
 *---------------------------------------------------------------------
 * copyExample.cpp - demonstrate use of Linux System API to copy files
 * 
 * Jim Fawcett, Summer ShortCourse, Summer 2016
 *---------------------------------------------------------------------
 */

#include <iostream>
/*
 * The man pages say the following two headers are needed for open().
 * Apparently unistd.h includes them indirectly
 */
//#include <sys/types.h> // apparently unistd.h includes this
//#include <sys/stat.h>  // apparently unistd.h includes this
#include <fcntl.h>   // permissions
#include <unistd.h>  // universal device IO
using namespace std;

void openErr(const char* filename)
{
    std::cout << "\n  error opening file \"" << filename << "\"\n\n";
    exit(1);  
}
void opened(const char* filename)
{
    std::cout << "\n  opening file \"" << filename;
}
void exitError(const char* error)
{
  std::cout << "\n  " << error << "\n\n";
  exit(1);
}
/*
 * ----< demonstrate use of device IO >------------------------------
 */
#define BUF_SIZE 512

int main(int argc, char** argv) {
  if(argc < 2)
  {
    std::cout << "\n  please enter src and destination filenames\n\n";
    return 1;
  }
  /* open input file */
  int inFd = open(argv[1], O_RDONLY);
  if(inFd == -1)
    openErr(argv[1]);
  else
    opened(argv[1]);
  /* open output file */
  int openFlags = O_CREAT | O_WRONLY | O_TRUNC;
  mode_t filePerms = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
  int outFd = open(argv[2], openFlags, filePerms);
  if(outFd == -1)
    openErr(argv[2]);
  else
    opened(argv[2]);
  
  /* copy in to out */
  char buf[BUF_SIZE];
  size_t numRead;
  size_t count = 0;
  
  while((numRead = read(inFd, buf, BUF_SIZE)) > 0)
  {
    if(write(outFd, buf, numRead) != numRead)
      exitError("couldn't write entire buffer");
    std::cout << "\n    copying block #" << ++count << " of size " << numRead;
  }
  if(numRead == -1)
    exitError("read error");

  /* show that file sizes match */
  off_t inSize = lseek(inFd, 0, SEEK_END);
  off_t outSize = lseek(outFd, 0, SEEK_END);
  std::cout << "\n  size of source " << argv[1] << " = " << inSize;
  std::cout << "\n  size of destin " << argv[2] << " = " << outSize;

  /* clean up */
  close(inFd);
  close(outFd);
  
  std::cout << "\n\n";
  return 0;
}