path: root/stdio/internals.c

/* Copyright (C) 1991, 92, 93, 94, 95, 96, 97 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


/* Make sure that FP has its functions set.  */
void
__stdio_check_funcs (register FILE *fp)
{
  if (!fp->__seen)
    {
      /* Initialize the stream's info, including buffering info.
	 This may give a buffer, change I/O functions, etc.
	 If no buffer is set (and the stream is not made explicitly
	 unbuffered), we allocate a buffer below, using the bufsize
	 set by this function.  */
      extern void __stdio_init_stream __P ((FILE *));
      fp->__room_funcs = __default_room_functions;
      fp->__io_funcs = __default_io_functions;
      __stdio_init_stream (fp);
      fp->__seen = 1;
    }
}


/* Minimum size of a buffer we will allocate by default.
   If this much memory is not available,
   the stream in question will be made unbuffered instead.  */
#define	MIN_BUFSIZE	128

/* Figure out what kind of buffering (none, line, or full)
   and what buffer size to give FP.  */
static void
init_stream (register FILE *fp)
{
  __stdio_check_funcs (fp);

  if (fp->__buffer == NULL && !fp->__userbuf)
    {
      int save;

      if (fp->__bufsize == 0)
	fp->__bufsize = BUFSIZ;

      /* Try to get however many bytes of buffering __stdio_pickbuf
	 specified, but if that much memory isn't available,
	 try half as much each time until it succeeds or the buffer
	 size becomes too small to be useful.  */
      save = errno;
      while (fp->__bufsize >= MIN_BUFSIZE)
	{
	  fp->__buffer = (char *) malloc (fp->__bufsize);
	  if (fp->__buffer == NULL)
	    fp->__bufsize /= 2;
	  else
	    break;
	}
      __set_errno (save);

      if (fp->__buffer == NULL)
	{
	  /* We can't get space for the buffer, so make it unbuffered.  */
	  fp->__userbuf = 1;
	  fp->__bufsize = 0;
	}
    }

  if (fp->__bufp == NULL)
    {
      /* Set the buffer pointer to the beginning of the buffer.  */
      fp->__bufp = fp->__buffer;
      fp->__put_limit = fp->__get_limit = fp->__buffer;
    }
}


/* Determine the current file position of STREAM if it is unknown.  */
int
__stdio_check_offset (stream)
     FILE *stream;
{
  init_stream (stream);

  if (stream->__offset == (fpos_t) -1)
    {
      /* This stream's offset is unknown or unknowable.  */
      if (stream->__io_funcs.__seek == NULL)
	{
	  /* Unknowable.  */
	  __set_errno (ESPIPE);
	  return EOF;
	}
      else
	{
	  /* Unknown.  Find it out.  */
	  fpos_t pos = (fpos_t) 0;
	  if ((*stream->__io_funcs.__seek) (stream->__cookie,
					    &