stdio/common/findiop.c

	findiop.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 1987 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984 AT&T */
/*        All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"  /* from S5R2 1.2 */

/*LINTLIBRARY*/
#include <stdio.h>
#include <errno.h>
#include "iob.h"

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

extern  char    *calloc();

static unsigned char sbuf[NSTATIC][_SBFSIZ];
unsigned char (*_smbuf)[_SBFSIZ] = sbuf;
static  FILE    **iobglue;
static  FILE    **endglue;

/*
 * 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;
    register FILE *fp;

    if(iobglue == NULL) {
        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);
}

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

    nfiles = getdtablesize();

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

    if((_smbuf = (unsigned char (*)[_SBFSIZ])malloc(nfiles * sizeof *_smbuf)) == NULL) {
        free((char *)iobglue);
        iobglue = NULL;
        return(0);
    }

    endglue = iobglue + nfiles;

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

    return(1);
}

f_prealloc()
{
    register FILE **iov;
    register FILE *fp;

    if(iobglue == NULL && _f_morefiles() == 0)
        return;

    for(iov = iobglue; iov < endglue; iov++)
        if(*iov == NULL)
            *iov = (FILE *)calloc(1, sizeof **iov);
}

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

    if(function == NULL)
        return;

    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);
    }
}