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 | <<setvbuf>>---specify file or stream buffering |
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21 | |
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22 | INDEX |
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23 | setvbuf |
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24 | |
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25 | SYNOPSIS |
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26 | #include <stdio.h> |
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27 | int setvbuf(FILE *<[fp]>, char *<[buf]>, |
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28 | int <[mode]>, size_t <[size]>); |
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29 | |
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30 | DESCRIPTION |
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31 | Use <<setvbuf>> to specify what kind of buffering you want for the |
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32 | file or stream identified by <[fp]>, by using one of the following |
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33 | values (from <<stdio.h>>) as the <[mode]> argument: |
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34 | |
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35 | o+ |
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36 | o _IONBF |
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37 | Do not use a buffer: send output directly to the host system for the |
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38 | file or stream identified by <[fp]>. |
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39 | |
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40 | o _IOFBF |
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41 | Use full output buffering: output will be passed on to the host system |
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42 | only when the buffer is full, or when an input operation intervenes. |
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43 | |
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44 | o _IOLBF |
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45 | Use line buffering: pass on output to the host system at every |
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46 | newline, as well as when the buffer is full, or when an input |
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47 | operation intervenes. |
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48 | o- |
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49 | |
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50 | Use the <[size]> argument to specify how large a buffer you wish. You |
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51 | can supply the buffer itself, if you wish, by passing a pointer to a |
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52 | suitable area of memory as <[buf]>. Otherwise, you may pass <<NULL>> |
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53 | as the <[buf]> argument, and <<setvbuf>> will allocate the buffer. |
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54 | |
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55 | WARNINGS |
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56 | You may only use <<setvbuf>> before performing any file operation other |
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57 | than opening the file. |
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58 | |
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59 | If you supply a non-null <[buf]>, you must ensure that the associated |
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60 | storage continues to be available until you close the stream |
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61 | identified by <[fp]>. |
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62 | |
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63 | RETURNS |
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64 | A <<0>> result indicates success, <<EOF>> failure (invalid <[mode]> or |
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65 | <[size]> can cause failure). |
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66 | |
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67 | PORTABILITY |
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68 | Both ANSI C and the System V Interface Definition (Issue 2) require |
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69 | <<setvbuf>>. However, they differ on the meaning of a <<NULL>> buffer |
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70 | pointer: the SVID issue 2 specification says that a <<NULL>> buffer |
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71 | pointer requests unbuffered output. For maximum portability, avoid |
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72 | <<NULL>> buffer pointers. |
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73 | |
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74 | Both specifications describe the result on failure only as a |
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75 | nonzero value. |
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76 | |
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77 | Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>, |
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78 | <<lseek>>, <<read>>, <<sbrk>>, <<write>>. |
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79 | */ |
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80 | |
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81 | #include <_ansi.h> |
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82 | #include <stdio.h> |
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83 | #include <stdlib.h> |
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84 | #include "local.h" |
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85 | |
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86 | /* |
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87 | * Set one of the three kinds of buffering, optionally including a buffer. |
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88 | */ |
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89 | |
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90 | int |
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91 | setvbuf (register FILE * fp, |
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92 | char *buf, |
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93 | register int mode, |
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94 | register size_t size) |
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95 | { |
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96 | int ret = 0; |
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97 | struct _reent *reent = _REENT; |
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98 | size_t iosize; |
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99 | int ttyflag; |
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100 | |
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101 | CHECK_INIT (reent, fp); |
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102 | |
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103 | /* |
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104 | * Verify arguments. The `int' limit on `size' is due to this |
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105 | * particular implementation. Note, buf and size are ignored |
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106 | * when setting _IONBF. |
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107 | */ |
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108 | if (mode != _IONBF) |
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109 | if ((mode != _IOFBF && mode != _IOLBF) || (int)(_POINTER_INT) size < 0) |
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110 | return (EOF); |
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111 | |
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112 | |
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113 | /* |
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114 | * Write current buffer, if any; drop read count, if any. |
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115 | * Make sure putc() will not think fp is line buffered. |
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116 | * Free old buffer if it was from malloc(). Clear line and |
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117 | * non buffer flags, and clear malloc flag. |
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118 | */ |
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119 | _newlib_flockfile_start (fp); |
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120 | _fflush_r (reent, fp); |
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121 | if (HASUB(fp)) |
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122 | FREEUB(reent, fp); |
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123 | fp->_r = fp->_lbfsize = 0; |
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124 | if (fp->_flags & __SMBF) |
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125 | _free_r (reent, (void *) fp->_bf._base); |
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126 | fp->_flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF); |
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127 | |
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128 | if (mode == _IONBF) |
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129 | goto nbf; |
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130 | |
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131 | /* |
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132 | * Find optimal I/O size for seek optimization. This also returns |
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133 | * a `tty flag' to suggest that we check isatty(fd), but we do not |
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134 | * care since our caller told us how to buffer. |
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135 | */ |
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136 | fp->_flags |= __swhatbuf_r (reent, fp, &iosize, &ttyflag); |
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137 | if (size == 0) |
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138 | { |
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139 | buf = NULL; |
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140 | size = iosize; |
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141 | } |
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142 | |
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143 | /* Allocate buffer if needed. */ |
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144 | if (buf == NULL) |
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145 | { |
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146 | if ((buf = malloc (size)) == NULL) |
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147 | { |
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148 | /* |
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149 | * Unable to honor user's request. We will return |
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150 | * failure, but try again with file system size. |
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151 | */ |
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152 | ret = EOF; |
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153 | if (size != iosize) |
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154 | { |
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155 | size = iosize; |
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156 | buf = malloc (size); |
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157 | } |
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158 | } |
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159 | if (buf == NULL) |
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160 | { |
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161 | /* No luck; switch to unbuffered I/O. */ |
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162 | nbf: |
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163 | fp->_flags |= __SNBF; |
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164 | fp->_w = 0; |
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165 | fp->_bf._base = fp->_p = fp->_nbuf; |
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166 | fp->_bf._size = 1; |
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167 | _newlib_flockfile_exit (fp); |
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168 | return (ret); |
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169 | } |
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170 | fp->_flags |= __SMBF; |
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171 | } |
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172 | |
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173 | /* |
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174 | * We're committed to buffering from here, so make sure we've |
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175 | * registered to flush buffers on exit. |
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176 | */ |
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177 | if (!reent->__sdidinit) |
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178 | __sinit(reent); |
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179 | |
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180 | #ifdef _FSEEK_OPTIMIZATION |
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181 | /* |
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182 | * Kill any seek optimization if the buffer is not the |
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183 | * right size. |
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184 | * |
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185 | * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)? |
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186 | */ |
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187 | if (size != iosize) |
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188 | fp->_flags |= __SNPT; |
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189 | #endif |
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190 | |
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191 | /* |
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192 | * Fix up the FILE fields, and set __cleanup for output flush on |
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193 | * exit (since we are buffered in some way). |
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194 | */ |
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195 | if (mode == _IOLBF) |
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196 | fp->_flags |= __SLBF; |
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197 | fp->_bf._base = fp->_p = (unsigned char *) buf; |
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198 | fp->_bf._size = size; |
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199 | /* fp->_lbfsize is still 0 */ |
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200 | if (fp->_flags & __SWR) |
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201 | { |
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202 | /* |
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203 | * Begin or continue writing: see __swsetup(). Note |
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204 | * that __SNBF is impossible (it was handled earlier). |
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205 | */ |
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206 | if (fp->_flags & __SLBF) |
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207 | { |
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208 | fp->_w = 0; |
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209 | fp->_lbfsize = -fp->_bf._size; |
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210 | } |
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211 | else |
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212 | fp->_w = size; |
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213 | } |
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214 | else |
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215 | { |
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216 | /* begin/continue reading, or stay in intermediate state */ |
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217 | fp->_w = 0; |
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218 | } |
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219 | |
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220 | _newlib_flockfile_end (fp); |
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221 | return 0; |
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222 | } |
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