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Rev | Author | Line No. | Line |
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2 | pj | 1 | /*- |
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. All advertising materials mentioning features or use of this software |
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17 | * must display the following acknowledgement: |
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18 | * This product includes software developed by the University of |
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19 | * California, Berkeley and its contributors. |
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20 | * 4. Neither the name of the University nor the names of its contributors |
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21 | * may be used to endorse or promote products derived from this software |
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22 | * without specific prior written permission. |
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23 | * |
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24 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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25 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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26 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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27 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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28 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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29 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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30 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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31 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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32 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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33 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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34 | * SUCH DAMAGE. |
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35 | */ |
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36 | |||
37 | #if defined(LIBC_SCCS) && !defined(lint) |
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38 | #if 0 |
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39 | static char sccsid[] = "@(#)fseek.c 8.3 (Berkeley) 1/2/94"; |
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40 | #endif |
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41 | static const char rcsid[] = |
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42 | "$\Id: fseek.c,v 1.4 1996/06/22 10:33:22 jraynard Exp $"; |
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43 | #endif /* LIBC_SCCS and not lint */ |
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44 | |||
45 | #include <sys/types.h> |
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46 | #include <sys/stat.h> |
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47 | #include <fcntl.h> |
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48 | #include <stdio.h> |
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49 | #include <stdlib.h> |
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50 | #include <errno.h> |
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51 | #include "local.h" |
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52 | #ifdef _THREAD_SAFE |
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53 | #include <pthread.h> |
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54 | #include "pthread_private.h" |
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55 | #endif |
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56 | |||
57 | #define POS_ERR (-(fpos_t)1) |
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58 | |||
59 | /* |
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60 | * Seek the given file to the given offset. |
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61 | * `Whence' must be one of the three SEEK_* macros. |
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62 | */ |
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63 | int |
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64 | fseek(fp, offset, whence) |
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65 | register FILE *fp; |
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66 | long offset; |
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67 | int whence; |
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68 | { |
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69 | register fpos_t (*seekfn) __P((void *, fpos_t, int)); |
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70 | fpos_t target, curoff; |
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71 | size_t n; |
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72 | struct stat st; |
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73 | int havepos; |
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74 | |||
75 | /* make sure stdio is set up */ |
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76 | if (!__sdidinit) |
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77 | __sinit(); |
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78 | |||
79 | #ifdef _THREAD_SAFE |
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80 | _thread_flockfile(fp,__FILE__,__LINE__); |
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81 | #endif |
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82 | /* |
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83 | * Have to be able to seek. |
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84 | */ |
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85 | if ((seekfn = fp->_seek) == NULL) { |
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86 | errno = ESPIPE; /* historic practice */ |
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87 | return (EOF); |
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88 | } |
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89 | |||
90 | /* |
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91 | * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. |
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92 | * After this, whence is either SEEK_SET or SEEK_END. |
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93 | */ |
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94 | switch (whence) { |
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95 | |||
96 | case SEEK_CUR: |
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97 | /* |
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98 | * In order to seek relative to the current stream offset, |
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99 | * we have to first find the current stream offset a la |
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100 | * ftell (see ftell for details). |
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101 | */ |
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102 | if (fp->_flags & __SOFF) |
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103 | curoff = fp->_offset; |
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104 | else { |
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105 | curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR); |
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106 | if (curoff == -1) { |
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107 | #ifdef _THREAD_SAFE |
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108 | _thread_funlockfile(fp); |
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109 | #endif |
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110 | return (EOF); |
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111 | } |
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112 | } |
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113 | if (fp->_flags & __SRD) { |
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114 | curoff -= fp->_r; |
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115 | if (HASUB(fp)) |
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116 | curoff -= fp->_ur; |
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117 | } else if (fp->_flags & __SWR && fp->_p != NULL) |
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118 | curoff += fp->_p - fp->_bf._base; |
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119 | |||
120 | offset += curoff; |
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121 | whence = SEEK_SET; |
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122 | havepos = 1; |
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123 | break; |
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124 | |||
125 | case SEEK_SET: |
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126 | case SEEK_END: |
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127 | curoff = 0; /* XXX just to keep gcc quiet */ |
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128 | havepos = 0; |
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129 | break; |
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130 | |||
131 | default: |
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132 | errno = EINVAL; |
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133 | #ifdef _THREAD_SAFE |
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134 | _thread_funlockfile(fp); |
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135 | #endif |
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136 | return (EOF); |
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137 | } |
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138 | |||
139 | /* |
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140 | * Can only optimise if: |
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141 | * reading (and not reading-and-writing); |
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142 | * not unbuffered; and |
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143 | * this is a `regular' Unix file (and hence seekfn==__sseek). |
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144 | * We must check __NBF first, because it is possible to have __NBF |
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145 | * and __SOPT both set. |
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146 | */ |
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147 | if (fp->_bf._base == NULL) |
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148 | __smakebuf(fp); |
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149 | if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT)) |
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150 | goto dumb; |
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151 | if ((fp->_flags & __SOPT) == 0) { |
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152 | if (seekfn != __sseek || |
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153 | fp->_file < 0 || fstat(fp->_file, &st) || |
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154 | (st.st_mode & S_IFMT) != S_IFREG) { |
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155 | fp->_flags |= __SNPT; |
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156 | goto dumb; |
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157 | } |
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158 | fp->_blksize = st.st_blksize; |
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159 | fp->_flags |= __SOPT; |
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160 | } |
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161 | |||
162 | /* |
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163 | * We are reading; we can try to optimise. |
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164 | * Figure out where we are going and where we are now. |
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165 | */ |
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166 | if (whence == SEEK_SET) |
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167 | target = offset; |
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168 | else { |
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169 | if (fstat(fp->_file, &st)) |
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170 | goto dumb; |
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171 | target = st.st_size + offset; |
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172 | } |
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173 | |||
174 | if (!havepos) { |
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175 | if (fp->_flags & __SOFF) |
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176 | curoff = fp->_offset; |
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177 | else { |
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178 | curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR); |
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179 | if (curoff == POS_ERR) |
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180 | goto dumb; |
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181 | } |
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182 | curoff -= fp->_r; |
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183 | if (HASUB(fp)) |
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184 | curoff -= fp->_ur; |
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185 | } |
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186 | |||
187 | /* |
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188 | * Compute the number of bytes in the input buffer (pretending |
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189 | * that any ungetc() input has been discarded). Adjust current |
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190 | * offset backwards by this count so that it represents the |
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191 | * file offset for the first byte in the current input buffer. |
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192 | */ |
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193 | if (HASUB(fp)) { |
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194 | curoff += fp->_r; /* kill off ungetc */ |
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195 | n = fp->_up - fp->_bf._base; |
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196 | curoff -= n; |
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197 | n += fp->_ur; |
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198 | } else { |
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199 | n = fp->_p - fp->_bf._base; |
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200 | curoff -= n; |
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201 | n += fp->_r; |
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202 | } |
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203 | |||
204 | /* |
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205 | * If the target offset is within the current buffer, |
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206 | * simply adjust the pointers, clear EOF, undo ungetc(), |
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207 | * and return. (If the buffer was modified, we have to |
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208 | * skip this; see fgetln.c.) |
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209 | */ |
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210 | if ((fp->_flags & __SMOD) == 0 && |
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211 | target >= curoff && target < curoff + n) { |
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212 | register int o = target - curoff; |
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213 | |||
214 | fp->_p = fp->_bf._base + o; |
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215 | fp->_r = n - o; |
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216 | if (HASUB(fp)) |
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217 | FREEUB(fp); |
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218 | fp->_flags &= ~__SEOF; |
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219 | #ifdef _THREAD_SAFE |
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220 | _thread_funlockfile(fp); |
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221 | #endif |
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222 | return (0); |
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223 | } |
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224 | |||
225 | /* |
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226 | * The place we want to get to is not within the current buffer, |
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227 | * but we can still be kind to the kernel copyout mechanism. |
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228 | * By aligning the file offset to a block boundary, we can let |
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229 | * the kernel use the VM hardware to map pages instead of |
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230 | * copying bytes laboriously. Using a block boundary also |
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231 | * ensures that we only read one block, rather than two. |
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232 | */ |
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233 | curoff = target & ~(fp->_blksize - 1); |
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234 | if ((*seekfn)(fp->_cookie, curoff, SEEK_SET) == POS_ERR) |
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235 | goto dumb; |
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236 | fp->_r = 0; |
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237 | fp->_p = fp->_bf._base; |
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238 | if (HASUB(fp)) |
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239 | FREEUB(fp); |
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240 | fp->_flags &= ~__SEOF; |
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241 | n = target - curoff; |
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242 | if (n) { |
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243 | if (__srefill(fp) || fp->_r < n) |
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244 | goto dumb; |
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245 | fp->_p += n; |
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246 | fp->_r -= n; |
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247 | } |
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248 | #ifdef _THREAD_SAFE |
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249 | _thread_funlockfile(fp); |
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250 | #endif |
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251 | return (0); |
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252 | |||
253 | /* |
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254 | * We get here if we cannot optimise the seek ... just |
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255 | * do it. Allow the seek function to change fp->_bf._base. |
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256 | */ |
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257 | dumb: |
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258 | if (__sflush(fp) || |
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259 | (*seekfn)(fp->_cookie, (fpos_t)offset, whence) == POS_ERR) { |
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260 | #ifdef _THREAD_SAFE |
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261 | _thread_funlockfile(fp); |
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262 | #endif |
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263 | return (EOF); |
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264 | } |
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265 | /* success: clear EOF indicator and discard ungetc() data */ |
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266 | if (HASUB(fp)) |
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267 | FREEUB(fp); |
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268 | fp->_p = fp->_bf._base; |
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269 | fp->_r = 0; |
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270 | /* fp->_w = 0; */ /* unnecessary (I think...) */ |
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271 | fp->_flags &= ~__SEOF; |
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272 | #ifdef _THREAD_SAFE |
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273 | _thread_funlockfile(fp); |
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274 | #endif |
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275 | return (0); |
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276 | } |