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: }
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