/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *	The President and Fellows of Harvard College.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <unistd.h>
#include <err.h>

/*
 * cp - copy a file.
 * Usage: cp oldfile newfile
 */

/* Copy one file to another. */
static void copy(const char *from, const char *to) {
  int fromfd;
  int tofd;
  char buf[1024];
  int len, wr, wrtot;

  /*
   * Open the files, and give up if they won't open
   */
  fromfd = open(from, O_RDONLY);
  if (fromfd < 0) {
    err(1, "%s", from);
  }
  tofd = open(to, O_WRONLY | O_CREAT | O_TRUNC);
  if (tofd < 0) {
    err(1, "%s", to);
  }

  /*
   * As long as we get more than zero bytes, we haven't hit EOF.
   * Zero means EOF. Less than zero means an error occurred.
   * We may read less than we asked for, though, in various cases
   * for various reasons.
   */
  while ((len = read(fromfd, buf, sizeof(buf))) > 0) {
    /*
     * Likewise, we may actually write less than we attempted
     * to. So loop until we're done.
     */
    wrtot = 0;
    while (wrtot < len) {
      wr = write(tofd, buf + wrtot, len - wrtot);
      if (wr < 0) {
        err(1, "%s", to);
      }
      wrtot += wr;
    }
  }
  /*
   * If we got a read error, print it and exit.
   */
  if (len < 0) {
    err(1, "%s", from);
  }

  if (close(fromfd) < 0) {
    err(1, "%s: close", from);
  }

  if (close(tofd) < 0) {
    err(1, "%s: close", to);
  }
}

int main(int argc, char *argv[]) {
  /*
   * Just do it.
   *
   * We don't allow the Unix model where you can do
   *    cp file1 file2 file3 destination-directory
   *
   * although this would be pretty easy to add.
   */
  if (argc != 3) {
    errx(1, "Usage: cp OLDFILE NEWFILE");
  }
  copy(argv[1], argv[2]);
  return 0;
}
