Annotation of prex/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: }
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