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Annotation of prex-old/usr/lib/libc/stdio/fseek.c, Revision 1.1.1.1

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: }