root / prex-0.9.0 / usr / lib / libc / stdio / fseek.c @ 03e9c04a
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1 | 03e9c04a | Brad Neuman | /*-
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2 | * Copyright (c) 1990, 1993
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3 | * The Regents of the University of California. All rights reserved.
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4 | *
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5 | * This code is derived from software contributed to Berkeley by
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6 | * Chris Torek.
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7 | *
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8 | * Redistribution and use in source and binary forms, with or without
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9 | * modification, are permitted provided that the following conditions
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10 | * are met:
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11 | * 1. Redistributions of source code must retain the above copyright
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12 | * notice, this list of conditions and the following disclaimer.
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13 | * 2. Redistributions in binary form must reproduce the above copyright
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14 | * notice, this list of conditions and the following disclaimer in the
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15 | * documentation and/or other materials provided with the distribution.
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16 | * 3. Neither the name of the University nor the names of its contributors
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17 | * may be used to endorse or promote products derived from this software
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18 | * without specific prior written permission.
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19 | *
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20 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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21 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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22 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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23 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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24 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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25 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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26 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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27 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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28 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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29 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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30 | * SUCH DAMAGE.
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31 | */
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32 | |||
33 | #include <sys/types.h> |
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34 | #include <sys/stat.h> |
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35 | #include <fcntl.h> |
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36 | #include <stdio.h> |
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37 | #include <stdlib.h> |
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38 | #include <errno.h> |
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39 | #include "local.h" |
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40 | |||
41 | #define POS_ERR (-(fpos_t)1) |
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42 | |||
43 | /*
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44 | * Seek the given file to the given offset.
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45 | * `Whence' must be one of the three SEEK_* macros.
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46 | */
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47 | int
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48 | fseek(fp, offset, whence) |
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49 | FILE *fp; |
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50 | long offset;
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51 | int whence;
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52 | { |
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53 | fpos_t curoff; |
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54 | int havepos;
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55 | |||
56 | /* make sure stdio is set up */
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57 | if (!__sdidinit)
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58 | __sinit(); |
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59 | |||
60 | /*
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61 | * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
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62 | * After this, whence is either SEEK_SET or SEEK_END.
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63 | */
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64 | switch (whence) {
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65 | |||
66 | case SEEK_CUR:
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67 | /*
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68 | * In order to seek relative to the current stream offset,
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69 | * we have to first find the current stream offset a la
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70 | * ftell (see ftell for details).
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71 | */
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72 | curoff = __sseek(fp, (fpos_t)0, SEEK_CUR);
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73 | if (curoff == POS_ERR)
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74 | return (EOF); |
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75 | if (fp->_flags & __SRD) {
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76 | curoff -= fp->_r; |
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77 | if (HASUB(fp))
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78 | curoff -= fp->_ur; |
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79 | } else if (fp->_flags & __SWR && fp->_p != NULL) |
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80 | curoff += fp->_p - fp->_bf._base; |
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81 | |||
82 | offset += curoff; |
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83 | whence = SEEK_SET; |
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84 | havepos = 1;
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85 | break;
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86 | |||
87 | case SEEK_SET:
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88 | case SEEK_END:
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89 | curoff = 0; /* XXX just to keep gcc quiet */ |
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90 | havepos = 0;
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91 | break;
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92 | |||
93 | default:
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94 | errno = EINVAL; |
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95 | return (EOF); |
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96 | } |
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97 | |||
98 | if (fp->_bf._base == NULL) |
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99 | __smakebuf(fp); |
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100 | |||
101 | if (__sflush(fp) ||
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102 | __sseek(fp, (fpos_t)offset, whence) == POS_ERR) { |
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103 | return (EOF); |
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104 | } |
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105 | /* success: clear EOF indicator and discard ungetc() data */
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106 | if (HASUB(fp))
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107 | FREEUB(fp); |
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108 | fp->_p = fp->_bf._base; |
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109 | fp->_r = 0;
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110 | /* fp->_w = 0; */ /* unnecessary (I think...) */ |
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111 | fp->_flags &= ~__SEOF; |
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112 | return (0); |
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113 | } |