libc/stdio/findfp.c

/*	$OpenBSD: findfp.c,v 1.15 2013/12/17 16:33:27 deraadt Exp $ */
/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "local.h"
#include "glue.h"
#include "private/thread_private.h"

#define ALIGNBYTES (sizeof(uintptr_t) - 1)
#define ALIGN(p) (((uintptr_t)(p) + ALIGNBYTES) &~ ALIGNBYTES)

int	__sdidinit;

#define	NDYNAMIC 10		/* add ten more whenever necessary */

#define	std(flags, file) \
	{0,0,0,flags,file,{0,0},0,__sF+file,__sclose,__sread,__sseek,__swrite, \
	    {(unsigned char *)(__sFext+file), 0},NULL,0,{0},{0},{0,0},0,0}

				/* the usual - (stdin + stdout + stderr) */
static FILE usual[FOPEN_MAX - 3];
static struct __sfileext usualext[FOPEN_MAX - 3];
static struct glue uglue = { 0, FOPEN_MAX - 3, usual };
static struct glue *lastglue = &uglue;
_THREAD_PRIVATE_MUTEX(__sfp_mutex);

static struct __sfileext __sFext[3];

// __sF is exported for backwards compatibility. Until M, we didn't have symbols
// for stdin/stdout/stderr; they were macros accessing __sF.
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 };

FILE* stdin = &__sF[0];
FILE* stdout = &__sF[1];
FILE* stderr = &__sF[2];

static struct glue *
moreglue(int n)
{
	struct glue *g;
	FILE *p;
	struct __sfileext *pext;
	static FILE empty;
	char *data;

	data = malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE)
	    + n * sizeof(struct __sfileext));
	if (data == NULL)
		return (NULL);
	g = (struct glue *)data;
	p = (FILE *)ALIGN(data + sizeof(*g));
	pext = (struct __sfileext *)
	    (ALIGN(data + sizeof(*g)) + n * sizeof(FILE));
	g->next = NULL;
	g->niobs = n;
	g->iobs = p;
	while (--n >= 0) {
		*p = empty;
		_FILEEXT_SETUP(p, pext);
		p++;
		pext++;
	}
	return (g);
}

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

	if (!__sdidinit)
		__sinit();

	_THREAD_PRIVATE_MUTEX_LOCK(__sfp_mutex);
	for (g = &__sglue; g != NULL; g = g->next) {
		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
			if (fp->_flags == 0)
				goto found;
	}

	/* release lock while mallocing */
	_THREAD_PRIVATE_MUTEX_UNLOCK(__sfp_mutex);
	if ((g = moreglue(NDYNAMIC)) == NULL)
		return (NULL);
	_THREAD_PRIVATE_MUTEX_LOCK(__sfp_mutex);
	lastglue->next = g;
	lastglue = g;
	fp = g->iobs;
found:
	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
	_THREAD_PRIVATE_MUTEX_UNLOCK(__sfp_mutex);
	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->_lb._base = NULL;	/* no line buffer */
	fp->_lb._size = 0;
	_FILEEXT_INIT(fp);
	return (fp);
}

/*
 * exit() and abort() call _cleanup() through the callback registered
 * with __atexit_register_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)
{
	/* (void) _fwalk(fclose); */
	(void) _fwalk(__sflush);		/* `cheating' */
}

/*
 * __sinit() is called whenever stdio's internal variables must be set up.
 */
void
__sinit(void)
{
	_THREAD_PRIVATE_MUTEX(__sinit_mutex);

	_THREAD_PRIVATE_MUTEX_LOCK(__sinit_mutex);
	if (__sdidinit) {
		/* bail out if caller lost the race */
		_THREAD_PRIVATE_MUTEX_UNLOCK(__sinit_mutex);
		return;
	}

	/* Initialize stdin/stdout/stderr (for the recursive mutex). http://b/18208568. */
	for (size_t i = 0; i < 3; ++i) {
		_FILEEXT_SETUP(__sF+i, __sFext+i);
	}
	/* Initialize the pre-allocated (but initially unused) streams. */
	for (size_t i = 0; i < FOPEN_MAX - 3; ++i) {
		_FILEEXT_SETUP(usual+i, usualext+i);
	}

	/* make sure we clean up on exit */
	__atexit_register_cleanup(_cleanup); /* conservative */
	__sdidinit = 1;

	_THREAD_PRIVATE_MUTEX_UNLOCK(__sinit_mutex);
}