[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 | <<fflush>>, <<fflush_unlocked>>---flush buffered file output |
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| 21 | |
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| 22 | INDEX |
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| 23 | fflush |
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| 24 | INDEX |
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| 25 | fflush_unlocked |
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| 26 | INDEX |
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| 27 | _fflush_r |
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| 28 | INDEX |
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| 29 | _fflush_unlocked_r |
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| 30 | |
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| 31 | SYNOPSIS |
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| 32 | #include <stdio.h> |
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| 33 | int fflush(FILE *<[fp]>); |
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| 34 | |
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| 35 | #define _BSD_SOURCE |
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| 36 | #include <stdio.h> |
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| 37 | int fflush_unlocked(FILE *<[fp]>); |
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| 38 | |
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| 39 | #include <stdio.h> |
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| 40 | int _fflush_r(struct _reent *<[reent]>, FILE *<[fp]>); |
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| 41 | |
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| 42 | #define _BSD_SOURCE |
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| 43 | #include <stdio.h> |
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| 44 | int _fflush_unlocked_r(struct _reent *<[reent]>, FILE *<[fp]>); |
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| 45 | |
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| 46 | DESCRIPTION |
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| 47 | The <<stdio>> output functions can buffer output before delivering it |
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| 48 | to the host system, in order to minimize the overhead of system calls. |
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| 49 | |
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| 50 | Use <<fflush>> to deliver any such pending output (for the file |
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| 51 | or stream identified by <[fp]>) to the host system. |
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| 52 | |
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| 53 | If <[fp]> is <<NULL>>, <<fflush>> delivers pending output from all |
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| 54 | open files. |
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| 55 | |
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| 56 | Additionally, if <[fp]> is a seekable input stream visiting a file |
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| 57 | descriptor, set the position of the file descriptor to match next |
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| 58 | unread byte, useful for obeying POSIX semantics when ending a process |
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| 59 | without consuming all input from the stream. |
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| 60 | |
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| 61 | <<fflush_unlocked>> is a non-thread-safe version of <<fflush>>. |
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| 62 | <<fflush_unlocked>> may only safely be used within a scope |
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| 63 | protected by flockfile() (or ftrylockfile()) and funlockfile(). This |
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| 64 | function may safely be used in a multi-threaded program if and only |
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| 65 | if they are called while the invoking thread owns the (FILE *) |
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| 66 | object, as is the case after a successful call to the flockfile() or |
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| 67 | ftrylockfile() functions. If threads are disabled, then |
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| 68 | <<fflush_unlocked>> is equivalent to <<fflush>>. |
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| 69 | |
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| 70 | The alternate functions <<_fflush_r>> and <<_fflush_unlocked_r>> are |
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| 71 | reentrant versions, where the extra argument <[reent]> is a pointer to |
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| 72 | a reentrancy structure, and <[fp]> must not be NULL. |
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| 73 | |
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| 74 | RETURNS |
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| 75 | <<fflush>> returns <<0>> unless it encounters a write error; in that |
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| 76 | situation, it returns <<EOF>>. |
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| 77 | |
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| 78 | PORTABILITY |
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| 79 | ANSI C requires <<fflush>>. The behavior on input streams is only |
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| 80 | specified by POSIX, and not all implementations follow POSIX rules. |
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| 81 | |
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| 82 | <<fflush_unlocked>> is a BSD extension also provided by GNU libc. |
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| 83 | |
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| 84 | No supporting OS subroutines are required. |
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| 85 | */ |
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| 86 | |
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| 87 | #include <_ansi.h> |
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| 88 | #include <stdio.h> |
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| 89 | #include <errno.h> |
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| 90 | #include "local.h" |
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| 91 | |
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| 92 | #ifdef __IMPL_UNLOCKED__ |
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| 93 | #define _fflush_r _fflush_unlocked_r |
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| 94 | #define fflush fflush_unlocked |
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| 95 | #endif |
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| 96 | |
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| 97 | #ifndef __IMPL_UNLOCKED__ |
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| 98 | /* Flush a single file, or (if fp is NULL) all files. */ |
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| 99 | |
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| 100 | /* Core function which does not lock file pointer. This gets called |
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| 101 | directly from __srefill. */ |
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| 102 | int |
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| 103 | __sflush_r (struct _reent *ptr, |
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| 104 | register FILE * fp) |
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| 105 | { |
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| 106 | register unsigned char *p; |
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| 107 | register _READ_WRITE_BUFSIZE_TYPE n; |
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| 108 | register _READ_WRITE_RETURN_TYPE t; |
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| 109 | short flags; |
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| 110 | |
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| 111 | flags = fp->_flags; |
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| 112 | if ((flags & __SWR) == 0) |
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| 113 | { |
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| 114 | #ifdef _FSEEK_OPTIMIZATION |
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| 115 | /* For a read stream, an fflush causes the next seek to be |
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| 116 | unoptimized (i.e. forces a system-level seek). This conforms |
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| 117 | to the POSIX and SUSv3 standards. */ |
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| 118 | fp->_flags |= __SNPT; |
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| 119 | #endif |
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| 120 | |
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| 121 | /* For a seekable stream with buffered read characters, we will attempt |
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| 122 | a seek to the current position now. A subsequent read will then get |
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| 123 | the next byte from the file rather than the buffer. This conforms |
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| 124 | to the POSIX and SUSv3 standards. Note that the standards allow |
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| 125 | this seek to be deferred until necessary, but we choose to do it here |
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| 126 | to make the change simpler, more contained, and less likely |
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| 127 | to miss a code scenario. */ |
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| 128 | if ((fp->_r > 0 || fp->_ur > 0) && fp->_seek != NULL) |
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| 129 | { |
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| 130 | int tmp_errno; |
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| 131 | #ifdef __LARGE64_FILES |
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| 132 | _fpos64_t curoff; |
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| 133 | #else |
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| 134 | _fpos_t curoff; |
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| 135 | #endif |
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| 136 | |
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| 137 | /* Save last errno and set errno to 0, so we can check if a device |
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| 138 | returns with a valid position -1. We restore the last errno if |
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| 139 | no other error condition has been encountered. */ |
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| 140 | tmp_errno = ptr->_errno; |
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| 141 | ptr->_errno = 0; |
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| 142 | /* Get the physical position we are at in the file. */ |
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| 143 | if (fp->_flags & __SOFF) |
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| 144 | curoff = fp->_offset; |
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| 145 | else |
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| 146 | { |
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| 147 | /* We don't know current physical offset, so ask for it. |
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| 148 | Only ESPIPE and EINVAL are ignorable. */ |
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| 149 | #ifdef __LARGE64_FILES |
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| 150 | if (fp->_flags & __SL64) |
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| 151 | curoff = fp->_seek64 (ptr, fp->_cookie, 0, SEEK_CUR); |
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| 152 | else |
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| 153 | #endif |
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| 154 | curoff = fp->_seek (ptr, fp->_cookie, 0, SEEK_CUR); |
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| 155 | if (curoff == -1L && ptr->_errno != 0) |
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| 156 | { |
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| 157 | int result = EOF; |
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| 158 | if (ptr->_errno == ESPIPE || ptr->_errno == EINVAL) |
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| 159 | { |
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| 160 | result = 0; |
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| 161 | ptr->_errno = tmp_errno; |
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| 162 | } |
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| 163 | else |
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| 164 | fp->_flags |= __SERR; |
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| 165 | return result; |
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| 166 | } |
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| 167 | } |
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| 168 | if (fp->_flags & __SRD) |
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| 169 | { |
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| 170 | /* Current offset is at end of buffer. Compensate for |
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| 171 | characters not yet read. */ |
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| 172 | curoff -= fp->_r; |
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| 173 | if (HASUB (fp)) |
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| 174 | curoff -= fp->_ur; |
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| 175 | } |
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| 176 | /* Now physically seek to after byte last read. */ |
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| 177 | #ifdef __LARGE64_FILES |
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| 178 | if (fp->_flags & __SL64) |
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| 179 | curoff = fp->_seek64 (ptr, fp->_cookie, curoff, SEEK_SET); |
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| 180 | else |
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| 181 | #endif |
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| 182 | curoff = fp->_seek (ptr, fp->_cookie, curoff, SEEK_SET); |
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| 183 | if (curoff != -1 || ptr->_errno == 0 |
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| 184 | || ptr->_errno == ESPIPE || ptr->_errno == EINVAL) |
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| 185 | { |
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| 186 | /* Seek successful or ignorable error condition. |
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| 187 | We can clear read buffer now. */ |
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| 188 | #ifdef _FSEEK_OPTIMIZATION |
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| 189 | fp->_flags &= ~__SNPT; |
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| 190 | #endif |
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| 191 | fp->_r = 0; |
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| 192 | fp->_p = fp->_bf._base; |
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| 193 | if ((fp->_flags & __SOFF) && (curoff != -1 || ptr->_errno == 0)) |
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| 194 | fp->_offset = curoff; |
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| 195 | ptr->_errno = tmp_errno; |
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| 196 | if (HASUB (fp)) |
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| 197 | FREEUB (ptr, fp); |
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| 198 | } |
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| 199 | else |
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| 200 | { |
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| 201 | fp->_flags |= __SERR; |
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| 202 | return EOF; |
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| 203 | } |
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| 204 | } |
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| 205 | return 0; |
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| 206 | } |
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| 207 | if ((p = fp->_bf._base) == NULL) |
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| 208 | { |
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| 209 | /* Nothing to flush. */ |
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| 210 | return 0; |
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| 211 | } |
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| 212 | n = fp->_p - p; /* write this much */ |
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| 213 | |
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| 214 | /* |
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| 215 | * Set these immediately to avoid problems with longjmp |
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| 216 | * and to allow exchange buffering (via setvbuf) in user |
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| 217 | * write function. |
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| 218 | */ |
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| 219 | fp->_p = p; |
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| 220 | fp->_w = flags & (__SLBF | __SNBF) ? 0 : fp->_bf._size; |
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| 221 | |
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| 222 | while (n > 0) |
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| 223 | { |
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| 224 | t = fp->_write (ptr, fp->_cookie, (char *) p, n); |
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| 225 | if (t <= 0) |
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| 226 | { |
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| 227 | fp->_flags |= __SERR; |
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| 228 | return EOF; |
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| 229 | } |
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| 230 | p += t; |
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| 231 | n -= t; |
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| 232 | } |
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| 233 | return 0; |
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| 234 | } |
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| 235 | |
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| 236 | #ifdef _STDIO_BSD_SEMANTICS |
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| 237 | /* Called from _cleanup_r. At exit time, we don't need file locking, |
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| 238 | and we don't want to move the underlying file pointer unless we're |
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| 239 | writing. */ |
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| 240 | int |
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| 241 | __sflushw_r (struct _reent *ptr, |
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| 242 | register FILE *fp) |
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| 243 | { |
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| 244 | return (fp->_flags & __SWR) ? __sflush_r (ptr, fp) : 0; |
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| 245 | } |
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| 246 | #endif |
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| 247 | |
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| 248 | #endif /* __IMPL_UNLOCKED__ */ |
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| 249 | |
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| 250 | int |
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| 251 | _fflush_r (struct _reent *ptr, |
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| 252 | register FILE * fp) |
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| 253 | { |
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| 254 | int ret; |
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| 255 | |
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| 256 | #ifdef _REENT_SMALL |
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| 257 | /* For REENT_SMALL platforms, it is possible we are being |
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| 258 | called for the first time on a std stream. This std |
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| 259 | stream can belong to a reentrant struct that is not |
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| 260 | _REENT. If CHECK_INIT gets called below based on _REENT, |
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| 261 | we will end up changing said file pointers to the equivalent |
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| 262 | std stream off of _REENT. This causes unexpected behavior if |
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| 263 | there is any data to flush on the _REENT std stream. There |
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| 264 | are two alternatives to fix this: 1) make a reentrant fflush |
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| 265 | or 2) simply recognize that this file has nothing to flush |
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| 266 | and return immediately before performing a CHECK_INIT. Choice |
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| 267 | 2 is implemented here due to its simplicity. */ |
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| 268 | if (fp->_bf._base == NULL) |
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| 269 | return 0; |
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| 270 | #endif /* _REENT_SMALL */ |
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| 271 | |
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| 272 | CHECK_INIT (ptr, fp); |
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| 273 | |
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| 274 | if (!fp->_flags) |
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| 275 | return 0; |
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| 276 | |
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| 277 | _newlib_flockfile_start (fp); |
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| 278 | ret = __sflush_r (ptr, fp); |
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| 279 | _newlib_flockfile_end (fp); |
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| 280 | return ret; |
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| 281 | } |
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| 282 | |
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| 283 | #ifndef _REENT_ONLY |
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| 284 | |
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| 285 | int |
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| 286 | fflush (register FILE * fp) |
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| 287 | { |
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| 288 | if (fp == NULL) |
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| 289 | return _fwalk_reent (_GLOBAL_REENT, _fflush_r); |
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| 290 | |
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| 291 | return _fflush_r (_REENT, fp); |
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| 292 | } |
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| 293 | |
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| 294 | #endif /* _REENT_ONLY */ |
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