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scoutos / prex-0.9.0 / usr / lib / libc / stdio / fseek.c @ 03e9c04a

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/*-
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 * Copyright (c) 1990, 1993
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 *        The Regents of the University of California.  All rights reserved.
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 *
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 * This code is derived from software contributed to Berkeley by
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 * Chris Torek.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the University nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include "local.h"
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#define        POS_ERR        (-(fpos_t)1)
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/*
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 * Seek the given file to the given offset.
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 * `Whence' must be one of the three SEEK_* macros.
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 */
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int
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fseek(fp, offset, whence)
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        FILE *fp;
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        long offset;
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        int whence;
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{
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        fpos_t curoff;
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        int havepos;
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        /* make sure stdio is set up */
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        if (!__sdidinit)
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                __sinit();
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        /*
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         * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
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         * After this, whence is either SEEK_SET or SEEK_END.
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         */
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        switch (whence) {
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        case SEEK_CUR:
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                /*
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                 * In order to seek relative to the current stream offset,
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                 * we have to first find the current stream offset a la
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                 * ftell (see ftell for details).
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                 */
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                curoff = __sseek(fp, (fpos_t)0, SEEK_CUR);
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                if (curoff == POS_ERR)
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                        return (EOF);
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                if (fp->_flags & __SRD) {
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                        curoff -= fp->_r;
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                        if (HASUB(fp))
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                                curoff -= fp->_ur;
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                } else if (fp->_flags & __SWR && fp->_p != NULL)
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                        curoff += fp->_p - fp->_bf._base;
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                offset += curoff;
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                whence = SEEK_SET;
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                havepos = 1;
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                break;
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        case SEEK_SET:
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        case SEEK_END:
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                curoff = 0;                /* XXX just to keep gcc quiet */
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                havepos = 0;
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                break;
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        default:
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                errno = EINVAL;
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                return (EOF);
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        }
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        if (fp->_bf._base == NULL)
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                __smakebuf(fp);
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        if (__sflush(fp) ||
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            __sseek(fp, (fpos_t)offset, whence) == POS_ERR) {
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                return (EOF);
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        }
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        /* success: clear EOF indicator and discard ungetc() data */
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        if (HASUB(fp))
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                FREEUB(fp);
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        fp->_p = fp->_bf._base;
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        fp->_r = 0;
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        /* fp->_w = 0; */        /* unnecessary (I think...) */
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        fp->_flags &= ~__SEOF;
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        return (0);
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}