xref: /csrg-svn/lib/libc/stdio/findfp.c (revision 46074)

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)findfp.c	5.8 (Berkeley) 01/20/91";
#endif /* LIBC_SCCS and not lint */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include "local.h"
#include "glue.h"

int	__sdidinit;

#define NSTATIC	20	/* stdin + stdout + stderr + the usual */
#define	NDYNAMIC 10	/* add ten more whenever necessary */

#define	std(flags, file) \
	{0,0,0,flags,file,{0},0,__sF+file,__sread,__swrite,__sseek,__sclose}
/*	 p r w flags file _bf z  cookie    read    write    seek    close */

static FILE usual[NSTATIC - 3];	/* the usual */
static struct glue uglue = { 0, NSTATIC - 3, usual };

FILE __sF[3] = {
	std(__SRD, STDIN_FILENO),		/* stdin */
	std(__SWR, STDOUT_FILENO),		/* stdout */
	std(__SWR|__SNBF, STDERR_FILENO)	/* stderr */
};
struct glue __sglue = { &uglue, 3, __sF };

static struct glue *
moreglue(n)
	register int n;
{
	register struct glue *g;
	register FILE *p;
	static FILE empty;

	g = (struct glue *)malloc(sizeof(*g) + n * sizeof(FILE));
	if (g == NULL)
		return (NULL);
	p = (FILE *)(g + 1);
	g->next = NULL;
	g->niobs = n;
	g->iobs = p;
	while (--n >= 0)
		*p++ = empty;
	return (g);
}

/*
 * Find a free FILE for fopen et al.
 */
FILE *
__sfp()
{
	register FILE *fp;
	register int n;
	register struct glue *g;

	if (!__sdidinit)
		__sinit();
	for (g = &__sglue;; g = g->next) {
		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
			if (fp->_flags == 0)
				goto found;
		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
			break;
	}
	return (NULL);
found:
	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
	fp->_p = NULL;		/* no current pointer */
	fp->_w = 0;		/* nothing to read or write */
	fp->_r = 0;
	fp->_bf._base = NULL;	/* no buffer */
	fp->_bf._size = 0;
	fp->_lbfsize = 0;	/* not line buffered */
	fp->_file = -1;		/* no file */
/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
	fp->_ub._base = NULL;	/* no ungetc buffer */
	fp->_ub._size = 0;
	fp->_lb._base = NULL;	/* no line buffer */
	fp->_lb._size = 0;
	return (fp);
}

/*
 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
 * but documented historically for certain applications.  Bad applications.
 */
f_prealloc()
{
	int n = getdtablesize() - NSTATIC + 20;		/* 20 for slop */
	register struct glue *g;

	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
		/* void */;
	if (n > 0)
		g->next = moreglue(n);
}

/*
 * exit() calls _cleanup() through *__cleanup, set whenever we
 * open or buffer a file.  This chicanery is done so that programs
 * that do not use stdio need not link it all in.
 *
 * The name `_cleanup' is, alas, fairly well known outside stdio.
 */
void
_cleanup()
{
	/* (void) _fwalk(fclose); */
	(void) _fwalk(__sflush);		/* `cheating' */
}

/*
 * __sinit() is called whenever stdio's internal variables must be set up.
 */
void
__sinit()
{
	/* make sure we clean up on exit */
	__cleanup = _cleanup;		/* conservative */
	__sdidinit = 1;
}