/* GNU Mailutils -- a suite of utilities for electronic mail
   Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.

   This library is free software; you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with GNU Mailutils.  If not, see <http://www.gnu.org/licenses/>. */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <mailutils/types.h>
#include <mailutils/alloc.h>
#include <mailutils/error.h>
#include <mailutils/errno.h>
#include <mailutils/stream.h>
#include <mailutils/sys/stream.h>

#define STREAMCPY_MIN_BUF_SIZE 2
#define STREAMCPY_MAX_BUF_SIZE 16384

/* Copy SIZE bytes from SRC to DST.  If SIZE is 0, copy everything up to
   EOF. */
int
mu_stream_copy (mu_stream_t dst, mu_stream_t src, mu_off_t size,
		mu_off_t *pcsz)
{
  int status;
  size_t bufsize, n;
  char *buf;
  mu_off_t total = 0;
  
  if (pcsz)
    *pcsz = 0;
  if (size == 0)
    {
      status = mu_stream_size (src, &size);
      switch (status)
	{
	case 0:
	  break;

	case ENOSYS:
	  size = 0;
	  break;

	default:
	  return status;
	}
      
      if (size)
	{
	  mu_off_t pos;
	  status = mu_stream_seek (src, 0, MU_SEEK_CUR, &pos);
	  switch (status)
	    {
	    case 0:
	      if (pos > size)
		return ESPIPE;
	      size -= pos;
	      break;
      
	    case EACCES:
	      mu_stream_clearerr (src);
	    case ENOSYS:
	      size = 0;
	      break;

	    default:
	      return status;
	    }
	}
    }

  bufsize = size;
  if (!bufsize)
    bufsize = STREAMCPY_MAX_BUF_SIZE;

  for (; (buf = malloc (bufsize)) == NULL; bufsize >>= 1)
    if (bufsize < STREAMCPY_MIN_BUF_SIZE)
      return ENOMEM;

  if (size)
    while (size)
      {
	size_t rdsize = bufsize < size ? bufsize : size;

	status = mu_stream_read (src, buf, rdsize, &n);
	if (status)
	  break;
	if (n == 0)
	  break;
	status = mu_stream_write (dst, buf, n, NULL);
	if (status)
	  break;
	size -= n;
	total += n;
      }
  else
    while ((status = mu_stream_read (src, buf, bufsize, &n)) == 0
	   && n > 0)
      {
	status = mu_stream_write (dst, buf, n, NULL);
	if (status)
	  break;
	total += n;
      }

  if (pcsz)
    *pcsz = total;
  /* FIXME: When EOF error code is implemented:
  else if (total == 0)
    status = EOF;
  */
  free (buf);
  return status;
}