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Annotation of prex-old/usr/lib/libc/stdio/fseek.c, Revision 1.1

1.1     ! nbrk        1: /*-
        !             2:  * Copyright (c) 1990, 1993
        !             3:  *     The Regents of the University of California.  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. Neither the name of the University nor the names of its contributors
        !            17:  *    may be used to endorse or promote products derived from this software
        !            18:  *    without specific prior written permission.
        !            19:  *
        !            20:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            21:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            22:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            23:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            24:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            25:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            26:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            27:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            28:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            29:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            30:  * SUCH DAMAGE.
        !            31:  */
        !            32:
        !            33: #include <sys/types.h>
        !            34: #include <sys/stat.h>
        !            35: #include <fcntl.h>
        !            36: #include <stdio.h>
        !            37: #include <stdlib.h>
        !            38: #include <errno.h>
        !            39: #include "local.h"
        !            40:
        !            41: #define        POS_ERR (-(fpos_t)1)
        !            42:
        !            43: /*
        !            44:  * Seek the given file to the given offset.
        !            45:  * `Whence' must be one of the three SEEK_* macros.
        !            46:  */
        !            47: int
        !            48: fseek(fp, offset, whence)
        !            49:        FILE *fp;
        !            50:        long offset;
        !            51:        int whence;
        !            52: {
        !            53:        fpos_t curoff;
        !            54:        int havepos;
        !            55:
        !            56:        /* make sure stdio is set up */
        !            57:        if (!__sdidinit)
        !            58:                __sinit();
        !            59:
        !            60:        /*
        !            61:         * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
        !            62:         * After this, whence is either SEEK_SET or SEEK_END.
        !            63:         */
        !            64:        switch (whence) {
        !            65:
        !            66:        case SEEK_CUR:
        !            67:                /*
        !            68:                 * In order to seek relative to the current stream offset,
        !            69:                 * we have to first find the current stream offset a la
        !            70:                 * ftell (see ftell for details).
        !            71:                 */
        !            72:                curoff = __sseek(fp, (fpos_t)0, SEEK_CUR);
        !            73:                if (curoff == POS_ERR)
        !            74:                        return (EOF);
        !            75:                if (fp->_flags & __SRD) {
        !            76:                        curoff -= fp->_r;
        !            77:                        if (HASUB(fp))
        !            78:                                curoff -= fp->_ur;
        !            79:                } else if (fp->_flags & __SWR && fp->_p != NULL)
        !            80:                        curoff += fp->_p - fp->_bf._base;
        !            81:
        !            82:                offset += curoff;
        !            83:                whence = SEEK_SET;
        !            84:                havepos = 1;
        !            85:                break;
        !            86:
        !            87:        case SEEK_SET:
        !            88:        case SEEK_END:
        !            89:                curoff = 0;             /* XXX just to keep gcc quiet */
        !            90:                havepos = 0;
        !            91:                break;
        !            92:
        !            93:        default:
        !            94:                errno = EINVAL;
        !            95:                return (EOF);
        !            96:        }
        !            97:
        !            98:        if (fp->_bf._base == NULL)
        !            99:                __smakebuf(fp);
        !           100:
        !           101:        if (__sflush(fp) ||
        !           102:            __sseek(fp, (fpos_t)offset, whence) == POS_ERR) {
        !           103:                return (EOF);
        !           104:        }
        !           105:        /* success: clear EOF indicator and discard ungetc() data */
        !           106:        if (HASUB(fp))
        !           107:                FREEUB(fp);
        !           108:        fp->_p = fp->_bf._base;
        !           109:        fp->_r = 0;
        !           110:        /* fp->_w = 0; */       /* unnecessary (I think...) */
        !           111:        fp->_flags &= ~__SEOF;
        !           112:        return (0);
        !           113: }