[444] | 1 | /* |
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| 2 | * Copyright (c) 1990 The Regents of the University of California. |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms are permitted |
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| 6 | * provided that the above copyright notice and this paragraph are |
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| 7 | * duplicated in all such forms and that any documentation, |
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| 8 | * advertising materials, and other materials related to such |
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| 9 | * distribution and use acknowledge that the software was developed |
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| 10 | * by the University of California, Berkeley. The name of the |
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| 11 | * University may not be used to endorse or promote products derived |
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| 12 | * from this software without specific prior written permission. |
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| 13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR |
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| 14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED |
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| 15 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. |
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| 16 | */ |
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| 17 | |
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| 18 | /* |
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| 19 | FUNCTION |
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| 20 | <<fseeko64>>---set file position for large file |
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| 21 | |
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| 22 | INDEX |
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| 23 | fseeko64 |
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| 24 | INDEX |
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| 25 | _fseeko64_r |
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| 26 | |
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| 27 | SYNOPSIS |
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| 28 | #include <stdio.h> |
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| 29 | int fseeko64(FILE *<[fp]>, _off64_t <[offset]>, int <[whence]>); |
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| 30 | int _fseeko64_r (struct _reent *<[ptr]>, FILE *<[fp]>, |
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| 31 | _off64_t <[offset]>, int <[whence]>); |
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| 32 | |
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| 33 | DESCRIPTION |
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| 34 | Objects of type <<FILE>> can have a ``position'' that records how much |
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| 35 | of the file your program has already read. Many of the <<stdio>> functions |
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| 36 | depend on this position, and many change it as a side effect. |
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| 37 | |
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| 38 | You can use <<fseeko64>> to set the position for the file identified by |
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| 39 | <[fp]> that was opened via <<fopen64>>. The value of <[offset]> determines |
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| 40 | the new position, in one of three ways selected by the value of <[whence]> |
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| 41 | (defined as macros in `<<stdio.h>>'): |
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| 42 | |
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| 43 | <<SEEK_SET>>---<[offset]> is the absolute file position (an offset |
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| 44 | from the beginning of the file) desired. <[offset]> must be positive. |
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| 45 | |
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| 46 | <<SEEK_CUR>>---<[offset]> is relative to the current file position. |
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| 47 | <[offset]> can meaningfully be either positive or negative. |
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| 48 | |
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| 49 | <<SEEK_END>>---<[offset]> is relative to the current end of file. |
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| 50 | <[offset]> can meaningfully be either positive (to increase the size |
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| 51 | of the file) or negative. |
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| 52 | |
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| 53 | See <<ftello64>> to determine the current file position. |
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| 54 | |
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| 55 | RETURNS |
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| 56 | <<fseeko64>> returns <<0>> when successful. On failure, the |
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| 57 | result is <<EOF>>. The reason for failure is indicated in <<errno>>: |
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| 58 | either <<ESPIPE>> (the stream identified by <[fp]> doesn't support |
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| 59 | repositioning or wasn't opened via <<fopen64>>) or <<EINVAL>> |
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| 60 | (invalid file position). |
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| 61 | |
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| 62 | PORTABILITY |
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| 63 | <<fseeko64>> is a glibc extension. |
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| 64 | |
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| 65 | Supporting OS subroutines required: <<close>>, <<fstat64>>, <<isatty>>, |
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| 66 | <<lseek64>>, <<read>>, <<sbrk>>, <<write>>. |
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| 67 | */ |
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| 68 | |
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| 69 | #include <stdio.h> |
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| 70 | #include <time.h> |
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| 71 | #include <fcntl.h> |
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| 72 | #include <stdlib.h> |
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| 73 | #include <errno.h> |
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| 74 | #include <sys/types.h> |
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| 75 | #include <sys/stat.h> |
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| 76 | #include "local.h" |
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| 77 | |
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| 78 | #define POS_ERR (-(_fpos64_t)1) |
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| 79 | |
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| 80 | #ifdef __LARGE64_FILES |
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| 81 | |
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| 82 | /* |
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| 83 | * Seek the given file to the given offset. |
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| 84 | * `Whence' must be one of the three SEEK_* macros. |
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| 85 | */ |
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| 86 | |
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| 87 | _off64_t |
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| 88 | _fseeko64_r (struct _reent *ptr, |
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| 89 | register FILE *fp, |
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| 90 | _off64_t offset, |
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| 91 | int whence) |
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| 92 | { |
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| 93 | _fpos64_t (*seekfn) (struct _reent *, void *, _fpos64_t, int); |
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| 94 | _fpos64_t target, curoff; |
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| 95 | size_t n; |
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| 96 | |
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| 97 | struct stat64 st; |
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| 98 | int havepos; |
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| 99 | |
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| 100 | /* Only do 64-bit seek on large file. */ |
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| 101 | if (!(fp->_flags & __SL64)) |
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| 102 | { |
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| 103 | if ((_off_t) offset != offset) |
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| 104 | { |
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| 105 | ptr->_errno = EOVERFLOW; |
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| 106 | return EOF; |
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| 107 | } |
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| 108 | return (_off64_t) _fseeko_r (ptr, fp, offset, whence); |
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| 109 | } |
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| 110 | |
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| 111 | /* Make sure stdio is set up. */ |
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| 112 | |
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| 113 | CHECK_INIT (ptr, fp); |
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| 114 | |
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| 115 | _newlib_flockfile_start (fp); |
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| 116 | |
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| 117 | curoff = fp->_offset; |
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| 118 | |
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| 119 | /* If we've been doing some writing, and we're in append mode |
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| 120 | then we don't really know where the filepos is. */ |
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| 121 | |
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| 122 | if (fp->_flags & __SAPP && fp->_flags & __SWR) |
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| 123 | { |
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| 124 | /* So flush the buffer and seek to the end. */ |
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| 125 | _fflush_r (ptr, fp); |
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| 126 | } |
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| 127 | |
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| 128 | /* Have to be able to seek. */ |
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| 129 | |
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| 130 | if ((seekfn = fp->_seek64) == NULL) |
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| 131 | { |
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| 132 | ptr->_errno = ESPIPE; /* ??? */ |
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| 133 | _newlib_flockfile_exit(fp); |
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| 134 | return EOF; |
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| 135 | } |
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| 136 | |
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| 137 | /* |
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| 138 | * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. |
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| 139 | * After this, whence is either SEEK_SET or SEEK_END. |
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| 140 | */ |
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| 141 | |
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| 142 | switch (whence) |
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| 143 | { |
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| 144 | case SEEK_CUR: |
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| 145 | /* |
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| 146 | * In order to seek relative to the current stream offset, |
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| 147 | * we have to first find the current stream offset a la |
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| 148 | * ftell (see ftell for details). |
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| 149 | */ |
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| 150 | _fflush_r (ptr, fp); /* may adjust seek offset on append stream */ |
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| 151 | if (fp->_flags & __SOFF) |
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| 152 | curoff = fp->_offset; |
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| 153 | else |
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| 154 | { |
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| 155 | curoff = seekfn (ptr, fp->_cookie, (_fpos64_t) 0, SEEK_CUR); |
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| 156 | if (curoff == -1L) |
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| 157 | { |
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| 158 | _newlib_flockfile_exit(fp); |
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| 159 | return EOF; |
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| 160 | } |
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| 161 | } |
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| 162 | if (fp->_flags & __SRD) |
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| 163 | { |
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| 164 | curoff -= fp->_r; |
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| 165 | if (HASUB (fp)) |
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| 166 | curoff -= fp->_ur; |
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| 167 | } |
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| 168 | else if (fp->_flags & __SWR && fp->_p != NULL) |
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| 169 | curoff += fp->_p - fp->_bf._base; |
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| 170 | |
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| 171 | offset += curoff; |
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| 172 | whence = SEEK_SET; |
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| 173 | havepos = 1; |
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| 174 | break; |
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| 175 | |
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| 176 | case SEEK_SET: |
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| 177 | case SEEK_END: |
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| 178 | havepos = 0; |
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| 179 | break; |
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| 180 | |
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| 181 | default: |
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| 182 | ptr->_errno = EINVAL; |
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| 183 | _newlib_flockfile_exit(fp); |
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| 184 | return (EOF); |
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| 185 | } |
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| 186 | |
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| 187 | /* |
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| 188 | * Can only optimise if: |
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| 189 | * reading (and not reading-and-writing); |
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| 190 | * not unbuffered; and |
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| 191 | * this is a `regular' Unix file (and hence seekfn==__sseek). |
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| 192 | * We must check __NBF first, because it is possible to have __NBF |
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| 193 | * and __SOPT both set. |
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| 194 | */ |
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| 195 | |
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| 196 | if (fp->_bf._base == NULL) |
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| 197 | __smakebuf_r (ptr, fp); |
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| 198 | |
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| 199 | #if _FSEEK_OPTIMIZATION |
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| 200 | if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT)) |
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| 201 | goto dumb; |
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| 202 | if ((fp->_flags & __SOPT) == 0) |
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| 203 | { |
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| 204 | if (seekfn != __sseek64 |
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| 205 | || fp->_file < 0 |
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| 206 | || _fstat64_r (ptr, fp->_file, &st) |
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| 207 | || (st.st_mode & S_IFMT) != S_IFREG) |
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| 208 | { |
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| 209 | fp->_flags |= __SNPT; |
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| 210 | goto dumb; |
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| 211 | } |
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| 212 | #ifdef HAVE_BLKSIZE |
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| 213 | fp->_blksize = st.st_blksize; |
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| 214 | #else |
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| 215 | fp->_blksize = 1024; |
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| 216 | #endif |
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| 217 | fp->_flags |= __SOPT; |
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| 218 | } |
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| 219 | |
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| 220 | /* |
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| 221 | * We are reading; we can try to optimise. |
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| 222 | * Figure out where we are going and where we are now. |
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| 223 | */ |
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| 224 | |
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| 225 | if (whence == SEEK_SET) |
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| 226 | target = offset; |
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| 227 | else |
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| 228 | { |
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| 229 | if (_fstat64_r (ptr, fp->_file, &st)) |
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| 230 | goto dumb; |
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| 231 | target = st.st_size + offset; |
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| 232 | } |
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| 233 | |
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| 234 | if (!havepos) |
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| 235 | { |
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| 236 | if (fp->_flags & __SOFF) |
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| 237 | curoff = fp->_offset; |
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| 238 | else |
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| 239 | { |
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| 240 | curoff = seekfn (ptr, fp->_cookie, (_fpos64_t)0, SEEK_CUR); |
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| 241 | if (curoff == POS_ERR) |
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| 242 | goto dumb; |
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| 243 | } |
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| 244 | curoff -= fp->_r; |
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| 245 | if (HASUB (fp)) |
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| 246 | curoff -= fp->_ur; |
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| 247 | } |
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| 248 | |
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| 249 | /* |
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| 250 | * Compute the number of bytes in the input buffer (pretending |
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| 251 | * that any ungetc() input has been discarded). Adjust current |
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| 252 | * offset backwards by this count so that it represents the |
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| 253 | * file offset for the first byte in the current input buffer. |
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| 254 | */ |
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| 255 | |
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| 256 | if (HASUB (fp)) |
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| 257 | { |
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| 258 | curoff += fp->_r; /* kill off ungetc */ |
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| 259 | n = fp->_up - fp->_bf._base; |
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| 260 | curoff -= n; |
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| 261 | n += fp->_ur; |
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| 262 | } |
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| 263 | else |
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| 264 | { |
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| 265 | n = fp->_p - fp->_bf._base; |
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| 266 | curoff -= n; |
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| 267 | n += fp->_r; |
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| 268 | } |
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| 269 | |
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| 270 | /* |
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| 271 | * If the target offset is within the current buffer, |
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| 272 | * simply adjust the pointers, clear EOF, undo ungetc(), |
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| 273 | * and return. |
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| 274 | */ |
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| 275 | |
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| 276 | if (target >= curoff && target < curoff + n) |
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| 277 | { |
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| 278 | register int o = target - curoff; |
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| 279 | |
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| 280 | fp->_p = fp->_bf._base + o; |
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| 281 | fp->_r = n - o; |
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| 282 | if (HASUB (fp)) |
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| 283 | FREEUB (ptr, fp); |
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| 284 | fp->_flags &= ~__SEOF; |
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| 285 | _newlib_flockfile_exit(fp); |
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| 286 | return 0; |
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| 287 | } |
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| 288 | |
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| 289 | /* |
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| 290 | * The place we want to get to is not within the current buffer, |
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| 291 | * but we can still be kind to the kernel copyout mechanism. |
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| 292 | * By aligning the file offset to a block boundary, we can let |
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| 293 | * the kernel use the VM hardware to map pages instead of |
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| 294 | * copying bytes laboriously. Using a block boundary also |
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| 295 | * ensures that we only read one block, rather than two. |
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| 296 | */ |
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| 297 | |
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| 298 | curoff = target & ~((_fpos64_t)(fp->_blksize - 1)); |
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| 299 | if (seekfn (ptr, fp->_cookie, curoff, SEEK_SET) == POS_ERR) |
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| 300 | goto dumb; |
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| 301 | fp->_r = 0; |
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| 302 | fp->_p = fp->_bf._base; |
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| 303 | if (HASUB (fp)) |
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| 304 | FREEUB (ptr, fp); |
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| 305 | fp->_flags &= ~__SEOF; |
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| 306 | n = target - curoff; |
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| 307 | if (n) |
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| 308 | { |
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| 309 | if (__srefill_r (ptr, fp) || fp->_r < n) |
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| 310 | goto dumb; |
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| 311 | fp->_p += n; |
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| 312 | fp->_r -= n; |
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| 313 | } |
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| 314 | _newlib_flockfile_end(fp); |
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| 315 | return 0; |
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| 316 | |
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| 317 | /* |
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| 318 | * We get here if we cannot optimise the seek ... just |
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| 319 | * do it. Allow the seek function to change fp->_bf._base. |
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| 320 | */ |
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| 321 | #endif |
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| 322 | |
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| 323 | dumb: |
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| 324 | if (_fflush_r (ptr, fp) |
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| 325 | || seekfn (ptr, fp->_cookie, offset, whence) == POS_ERR) |
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| 326 | { |
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| 327 | _funlockfile(fp); |
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| 328 | return EOF; |
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| 329 | } |
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| 330 | /* success: clear EOF indicator and discard ungetc() data */ |
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| 331 | if (HASUB (fp)) |
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| 332 | FREEUB (ptr, fp); |
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| 333 | fp->_p = fp->_bf._base; |
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| 334 | fp->_r = 0; |
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| 335 | /* fp->_w = 0; *//* unnecessary (I think...) */ |
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| 336 | fp->_flags &= ~__SEOF; |
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| 337 | _funlockfile(fp); |
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| 338 | return 0; |
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| 339 | } |
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| 340 | |
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| 341 | #ifndef _REENT_ONLY |
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| 342 | |
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| 343 | _off64_t |
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| 344 | fseeko64 (register FILE *fp, |
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| 345 | _off64_t offset, |
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| 346 | int whence) |
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| 347 | { |
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| 348 | return _fseeko64_r (_REENT, fp, offset, whence); |
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| 349 | } |
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| 350 | |
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| 351 | #endif /* !_REENT_ONLY */ |
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| 352 | |
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| 353 | #endif /* __LARGE64_FILES */ |
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