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findfp.c revision 1.1 
      1 /*-
      2  * Copyright (c) 1990 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * Chris Torek.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 static char sccsid[] = "@(#)findfp.c	5.10 (Berkeley) 2/24/91";
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <unistd.h>
     42 #include <stdio.h>
     43 #include <errno.h>
     44 #include <stdlib.h>
     45 #include <string.h>
     46 #include "local.h"
     47 #include "glue.h"
     48 
     49 int	__sdidinit;
     50 
     51 #define NSTATIC	20	/* stdin + stdout + stderr + the usual */
     52 #define	NDYNAMIC 10	/* add ten more whenever necessary */
     53 
     54 #define	std(flags, file) \
     55 	{0,0,0,flags,file,{0},0,__sF+file,__sclose,__sread,__sseek,__swrite}
     56 /*	 p r w flags file _bf z  cookie      close    read    seek    write */
     57 
     58 static FILE usual[NSTATIC - 3];	/* the usual */
     59 static struct glue uglue = { 0, NSTATIC - 3, usual };
     60 
     61 FILE __sF[3] = {
     62 	std(__SRD, STDIN_FILENO),		/* stdin */
     63 	std(__SWR, STDOUT_FILENO),		/* stdout */
     64 	std(__SWR|__SNBF, STDERR_FILENO)	/* stderr */
     65 };
     66 struct glue __sglue = { &uglue, 3, __sF };
     67 
     68 static struct glue *
     69 moreglue(n)
     70 	register int n;
     71 {
     72 	register struct glue *g;
     73 	register FILE *p;
     74 	static FILE empty;
     75 
     76 	g = (struct glue *)malloc(sizeof(*g) + n * sizeof(FILE));
     77 	if (g == NULL)
     78 		return (NULL);
     79 	p = (FILE *)(g + 1);
     80 	g->next = NULL;
     81 	g->niobs = n;
     82 	g->iobs = p;
     83 	while (--n >= 0)
     84 		*p++ = empty;
     85 	return (g);
     86 }
     87 
     88 /*
     89  * Find a free FILE for fopen et al.
     90  */
     91 FILE *
     92 __sfp()
     93 {
     94 	register FILE *fp;
     95 	register int n;
     96 	register struct glue *g;
     97 
     98 	if (!__sdidinit)
     99 		__sinit();
    100 	for (g = &__sglue;; g = g->next) {
    101 		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
    102 			if (fp->_flags == 0)
    103 				goto found;
    104 		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
    105 			break;
    106 	}
    107 	return (NULL);
    108 found:
    109 	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
    110 	fp->_p = NULL;		/* no current pointer */
    111 	fp->_w = 0;		/* nothing to read or write */
    112 	fp->_r = 0;
    113 	fp->_bf._base = NULL;	/* no buffer */
    114 	fp->_bf._size = 0;
    115 	fp->_lbfsize = 0;	/* not line buffered */
    116 	fp->_file = -1;		/* no file */
    117 /*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
    118 	fp->_ub._base = NULL;	/* no ungetc buffer */
    119 	fp->_ub._size = 0;
    120 	fp->_lb._base = NULL;	/* no line buffer */
    121 	fp->_lb._size = 0;
    122 	return (fp);
    123 }
    124 
    125 /*
    126  * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
    127  * but documented historically for certain applications.  Bad applications.
    128  */
    129 f_prealloc()
    130 {
    131 	int n = getdtablesize() - NSTATIC + 20;		/* 20 for slop */
    132 	register struct glue *g;
    133 
    134 	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
    135 		/* void */;
    136 	if (n > 0)
    137 		g->next = moreglue(n);
    138 }
    139 
    140 /*
    141  * exit() calls _cleanup() through *__cleanup, set whenever we
    142  * open or buffer a file.  This chicanery is done so that programs
    143  * that do not use stdio need not link it all in.
    144  *
    145  * The name `_cleanup' is, alas, fairly well known outside stdio.
    146  */
    147 void
    148 _cleanup()
    149 {
    150 	/* (void) _fwalk(fclose); */
    151 	(void) _fwalk(__sflush);		/* `cheating' */
    152 }
    153 
    154 /*
    155  * __sinit() is called whenever stdio's internal variables must be set up.
    156  */
    157 void
    158 __sinit()
    159 {
    160 	/* make sure we clean up on exit */
    161 	__cleanup = _cleanup;		/* conservative */
    162 	__sdidinit = 1;
    163 }
    164