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4709
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1 /* Detect write error on a stream. |
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2 Copyright (C) 2003 Free Software Foundation, Inc. |
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3 Written by Bruno Haible <bruno@clisp.org>, 2003. |
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4 |
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5 This program is free software; you can redistribute it and/or modify |
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6 it under the terms of the GNU General Public License as published by |
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7 the Free Software Foundation; either version 2, or (at your option) |
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8 any later version. |
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9 |
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10 This program is distributed in the hope that it will be useful, |
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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13 GNU General Public License for more details. |
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14 |
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15 You should have received a copy of the GNU General Public License |
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16 along with this program; if not, write to the Free Software Foundation, |
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17 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ |
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18 |
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19 #if HAVE_CONFIG_H |
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20 # include <config.h> |
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21 #endif |
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22 |
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23 /* Specification. */ |
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24 #include "fwriteerror.h" |
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25 |
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26 #include <errno.h> |
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27 |
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28 int |
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29 fwriteerror (FILE *fp) |
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30 { |
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31 /* Need to |
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32 1. test the error indicator of the stream, |
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33 2. flush the buffers (what fclose() would do), testing for error again. |
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34 We can equally well swap these steps; this leads to smaller code. */ |
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35 |
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36 /* Clear errno, so that on non-POSIX systems the caller doesn't see a |
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37 wrong value of errno when we return -1. */ |
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38 errno = 0; |
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39 |
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40 if (fflush (fp)) |
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41 return -1; /* errno is set here */ |
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42 |
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43 if (ferror (fp)) |
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44 { |
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45 /* The stream had an error earlier, but its errno was lost. If the |
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46 error was not temporary, we can get the same errno by writing and |
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47 flushing one more byte. We can do so because at this point the |
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48 stream's contents is garbage anyway. */ |
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49 if (fputc ('\0', fp) == EOF) |
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50 return -1; /* errno is set here */ |
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51 if (fflush (fp)) |
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52 return -1; /* errno is set here */ |
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53 /* Give up on errno. */ |
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54 errno = 0; |
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55 return -1; |
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56 } |
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57 |
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58 return 0; |
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59 } |
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60 |
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61 |
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62 #if TEST |
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63 |
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64 /* Name of a file on which writing fails. On systems without /dev/full, |
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65 you can choose a filename on a full filesystem. */ |
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66 #define UNWRITABLE_FILE "/dev/full" |
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67 |
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68 int |
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69 main () |
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70 { |
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71 static int sizes[] = |
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72 { |
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73 511, 512, 513, |
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74 1023, 1024, 1025, |
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75 2047, 2048, 2049, |
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76 4095, 4096, 4097, |
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77 8191, 8192, 8193 |
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78 }; |
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79 static char dummy[8193]; |
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80 unsigned int i, j; |
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81 |
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82 for (i = 0; i < sizeof (sizes) / sizeof (sizes[0]); i++) |
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83 { |
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84 size_t size = sizes[i]; |
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85 |
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86 for (j = 0; j < 2; j++) |
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87 { |
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88 /* Run a test depending on i and j: |
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89 Write size bytes and then calls fflush if j==1. */ |
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90 FILE *stream = fopen (UNWRITABLE_FILE, "w"); |
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91 |
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92 if (stream == NULL) |
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93 { |
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94 fprintf (stderr, "Test %u:%u: could not open file\n", i, j); |
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95 continue; |
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96 } |
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97 |
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98 fwrite (dummy, 347, 1, stream); |
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99 fwrite (dummy, size - 347, 1, stream); |
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100 if (j) |
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101 fflush (stream); |
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102 |
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103 if (fwriteerror (stream) == -1) |
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104 { |
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105 if (errno != ENOSPC) |
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106 fprintf (stderr, "Test %u:%u: fwriteerror ok, errno = %d\n", |
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107 i, j, errno); |
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108 } |
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109 else |
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110 fprintf (stderr, "Test %u:%u: fwriteerror found no error!\n", |
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111 i, j); |
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112 |
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113 if (fclose (stream)) |
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114 fprintf (stderr, "Test %u:%u: fclose failed, errno = %d\n", |
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115 i, j, errno); |
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116 } |
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117 } |
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118 |
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119 return 0; |
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120 } |
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121 |
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122 #endif |
