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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