/* Copyright (C) 2008, 2009 Free Software Foundation, Inc.
   Contributed by Janne Blomqvist

This file is part of the GNU Fortran runtime library (libgfortran).

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

Libgfortran 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 General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */


#include "io.h"
#include <string.h>
#include <stdlib.h>


void
fbuf_init (gfc_unit * u, size_t len)
{
  if (len == 0)
    len = 512;			/* Default size.  */

  u->fbuf = get_mem (sizeof (fbuf));
  u->fbuf->buf = get_mem (len);
  u->fbuf->len = len;
  u->fbuf->act = u->fbuf->flushed = u->fbuf->pos = 0;
}


void
fbuf_reset (gfc_unit * u)
{
  u->fbuf->act = u->fbuf->flushed = u->fbuf->pos = 0;
}


void
fbuf_destroy (gfc_unit * u)
{
  if (u->fbuf == NULL)
    return;
  if (u->fbuf->buf)
    free_mem (u->fbuf->buf);
  free_mem (u->fbuf);
}


/* Return a pointer to the current position in the buffer, and increase
   the pointer by len. Makes sure that the buffer is big enough, 
   reallocating if necessary. If the buffer is not big enough, there are
   three cases to consider:
   1. If we haven't flushed anything, realloc
   2. If we have flushed enough that by discarding the flushed bytes
      the request fits into the buffer, do that.
   3. Else allocate a new buffer, memcpy unflushed active bytes from old
      buffer. */

char *
fbuf_alloc (gfc_unit * u, size_t len)
{
  size_t newlen;
  char *dest;
  if (u->fbuf->pos + len > u->fbuf->len)
    {
      if (u->fbuf->flushed == 0)
	{
	  /* Round up to nearest multiple of the current buffer length.  */
	  newlen = ((u->fbuf->pos + len) / u->fbuf->len + 1) * u->fbuf->len;
	  dest = realloc (u->fbuf->buf, newlen);
	  if (dest == NULL)
	    return NULL;
	  u->fbuf->buf = dest;
	  u->fbuf->len = newlen;
	}
      else if (u->fbuf->act - u->fbuf->flushed + len < u->fbuf->len)
	{
	  memmove (u->fbuf->buf, u->fbuf->buf + u->fbuf->flushed,
		   u->fbuf->act - u->fbuf->flushed);
	  u->fbuf->act -= u->fbuf->flushed;
	  u->fbuf->pos -= u->fbuf->flushed;
	  u->fbuf->flushed = 0;
	}
      else
	{
	  /* Most general case, flushed != 0, request doesn't fit.  */
	  newlen = ((u->fbuf->pos - u->fbuf->flushed + len)
		    / u->fbuf->len + 1) * u->fbuf->len;
	  dest = get_mem (newlen);
	  memcpy (dest, u->fbuf->buf + u->fbuf->flushed,
		  u->fbuf->act - u->fbuf->flushed);
	  u->fbuf->act -= u->fbuf->flushed;
	  u->fbuf->pos -= u->fbuf->flushed;
	  u->fbuf->flushed = 0;
	  u->fbuf->buf = dest;
	  u->fbuf->len = newlen;
	}
    }

  dest = u->fbuf->buf + u->fbuf->pos;
  u->fbuf->pos += len;
  if (u->fbuf->pos > u->fbuf->act)
    u->fbuf->act = u->fbuf->pos;
  return dest;
}




int
fbuf_flush (gfc_unit * u, int record_done)
{
  int status;
  size_t nbytes;

  if (!u->fbuf)
    return 0;
  if (u->fbuf->act - u->fbuf->flushed != 0)
    {
      if (record_done)
        nbytes = u->fbuf->act - u->fbuf->flushed;
      else	
        nbytes = u->fbuf->pos - u->fbuf->flushed;	
      status = swrite (u->s, u->fbuf->buf + u->fbuf->flushed, &nbytes);
      u->fbuf->flushed += nbytes;
    }
  else
    status = 0;
  if (record_done)
    fbuf_reset (u);
  return status;
}


int
fbuf_seek (gfc_unit * u, gfc_offset off)
{
  gfc_offset pos = u->fbuf->pos + off;
  /* Moving to the left past the flushed marked would imply moving past
     the left tab limit, which is never allowed. So return error if
     that is attempted.  */
  if (pos < (gfc_offset) u->fbuf->flushed)
    return -1;
  u->fbuf->pos = pos;
  return 0;
}