findiop.c

Algorithms for Image Processing and Computer Vision Source Code

/* This is file FINDIOP.C */
/* This file may have been modified by DJ Delorie (Jan 1991).  If so,
** these modifications are Coyright (C) 1993 DJ Delorie, 24 Kirsten Ave,
** Rochester NH, 03867-2954, USA.
*/

/*
 * Copyright (c) 1983, 1985 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)findiop.c	5.7 (Berkeley) 9/22/88";
#endif LIBC_SCCS and not lint

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>

extern int errno;

extern int _setmode(int, int);

#define active(iop)	((iop)->_flag & (_IOREAD|_IOWRT|_IORW))

#define NSTATIC	20	/* stdin + stdout + stderr + the usual */

FILE _iob[NSTATIC] = {
	{ 0, NULL, NULL, 0, _IOREAD|_IOTEXT,	0 },	/* stdin  */
	{ 0, NULL, NULL, 0, _IOWRT|_IOTEXT,	1 },	/* stdout */
	{ 0, NULL, NULL, 0, _IOWRT|_IONBF|_IOTEXT,2 },	/* stderr */
	{ 0, NULL, NULL, 0, _IOWRT|_IONBF,3 },		/* stdaux */
	{ 0, NULL, NULL, 0, _IOWRT|_IONBF,4 },		/* stdprn */
};

extern	void	*calloc();

static	char sbuf[NSTATIC];
char	*_smallbuf = sbuf;
static	FILE	**iobglue;
static	FILE	**endglue;

static int _f_morefiles();

int setmode(int handle, int newmode)
{
  FILE *f=0, **fp;
  int i;
  for (i=0; i<NSTATIC; i++)
    if (_iob[i]._file == handle)
    {
      f = _iob + i;
      goto got_it;
    }
  if (!iobglue)
    goto not_got_it;
  for (fp=iobglue; fp<endglue; fp++)
    if ((*fp)->_file == handle)
    {
      f = *fp;
      break;
    }

got_it:
  if (newmode & O_BINARY)
    f->_flag &= ~_IOTEXT;
  else
    f->_flag |= _IOTEXT;

not_got_it:
  return _setmode(handle, newmode);
}

/*
 * Find a free FILE for fopen et al.
 * We have a fixed static array of entries, and in addition
 * may allocate additional entries dynamically, up to the kernel
 * limit on the number of open files.
 * At first just check for a free slot in the fixed static array.
 * If none are available, then we allocate a structure to glue together
 * the old and new FILE entries, which are then no longer contiguous.
 */
FILE *
_findiop()
{
	register FILE **iov, *iop;

	if (iobglue == 0) {
		for (iop = _iob; iop < _iob + NSTATIC; iop++)
			if (!active(iop))
				return (iop);

		if (_f_morefiles() == 0) {
			errno = ENOMEM;
			return (NULL);
		}
	}

	iov = iobglue;
	while (*iov != NULL && active(*iov))
		if (++iov >= endglue) {
			errno = EMFILE;
			return (NULL);
		}

	if (*iov == NULL)
		*iov = (FILE *)calloc(1, sizeof **iov);

	return (*iov);
}

int
_f_morefiles()
{
	register FILE **iov;
	register FILE *fp;
	int nfiles;

	nfiles = getdtablesize();

	iobglue = (FILE **)calloc(nfiles, sizeof *iobglue);
	if (iobglue == NULL)
		return (0);

	endglue = iobglue + nfiles;

	for (fp = _iob, iov = iobglue; fp < &_iob[NSTATIC]; /* void */)
		*iov++ = fp++;

	_smallbuf = calloc(nfiles, sizeof(*_smallbuf));
	return (1);
}

void
_fwalk(function)
	register void (*function)(FILE *);
{
	register FILE **iov;
	register FILE *fp;

	if (iobglue == NULL) {
		for (fp = _iob; fp < &_iob[NSTATIC]; fp++)
			if (active(fp))
				(*function)(fp);
	} else {
		for (iov = iobglue; iov < endglue; iov++)
			if (*iov && active(*iov))
				(*function)(*iov);
	}
}