port/stdio/fread.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1988 AT&T */
/*    All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include "lint.h"
#include "file64.h"
#include "mtlib.h"
#include <stdio.h>
#include <stddef.h>
#include <values.h>
#include <memory.h>
#include <thread.h>
#include <synch.h>
#include <errno.h>
#include <sys/types.h>
#include "stdiom.h"
#include "mse.h"

size_t
fread(void *ptr, size_t size, size_t count, FILE *iop)
{
    ssize_t s;
    int c;
    char *dptr = (char *)ptr;
    rmutex_t *lk;

    FLOCKFILE(lk, iop);

    _SET_ORIENTATION_BYTE(iop);

    /* is it a readable stream */
    if (!(iop->_flag & (_IOREAD | _IORW))) {
        iop->_flag |= _IOERR;
        errno = EBADF;
        FUNLOCKFILE(lk);
        return (0);
    }

    if (iop->_flag & _IOEOF) {
        FUNLOCKFILE(lk);
        return (0);
    }

    /* These checks are here to avoid the multiply */
    if (count == 1)
        s = size;
    else if (size == 1)
        s = count;
    else
        s = size * count;

    while (s > 0) {
        if (iop->_cnt < s) {
            if (iop->_cnt > 0) {
                (void) memcpy((void*)dptr, iop->_ptr,
                    iop->_cnt);
                dptr += iop->_cnt;
                s -= iop->_cnt;
            }
            /*
             * filbuf clobbers _cnt & _ptr,
             * so don't waste time setting them.
             */
            if ((c = __filbuf(iop)) == EOF)
                break;
            *dptr++ = (char)c;
            s--;
        }
        if (iop->_cnt >= s) {
            char *tmp = (char *)iop->_ptr;
            switch (s) {
            case 8:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 7:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 6:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 5:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 4:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 3:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 2:
                *dptr++ = *tmp++;
                /*FALLTHRU*/
            case 1:
                *dptr++ = *tmp++;
                break;
            default:
                (void) memcpy((void*)dptr, iop->_ptr,
                    (size_t)s);
            }
            iop->_ptr += s;
            iop->_cnt -= s;
            FUNLOCKFILE(lk);
            return (count);
        }
    }
    FUNLOCKFILE(lk);
    return (size != 0 ? count - ((s + size - 1) / size) : 0);
}