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annotate lib/safe-write.c @ 4052:9bc86ccaeda6

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safe-read.c, safe-write.c: Change variable names and comments, but not semantics, to minimize the differences between these two files.
author Jim Meyering <jim@meyering.net>
date Tue, 03 Dec 2002 10:55:51 +0000
parents 6a1238f585b1
children 02d9405a0354
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1 /* An interface to write that retries after interrupts.
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2 Copyright (C) 1993, 1994, 1998, 2002 Free Software Foundation, Inc.
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3
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4 This program is free software; you can redistribute it and/or modify
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5 it under the terms of the GNU General Public License as published by
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6 the Free Software Foundation; either version 2, or (at your option)
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7 any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program; if not, write to the Free Software Foundation,
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16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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17
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18 #if HAVE_CONFIG_H
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19 # include <config.h>
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20 #endif
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21
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22 /* Specification. */
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23 #include "safe-write.h"
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24
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25 /* Get ssize_t. */
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26 #include <sys/types.h>
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27 #if HAVE_UNISTD_H
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28 # include <unistd.h>
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29 #endif
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30
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31 #include <errno.h>
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32 #ifndef errno
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33 extern int errno;
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34 #endif
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35
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36 #ifdef EINTR
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37 # define IS_EINTR(x) ((x) == EINTR)
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38 #else
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39 # define IS_EINTR(x) 0
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40 #endif
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41
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42 #include <limits.h>
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43
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44 #ifndef CHAR_BIT
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45 # define CHAR_BIT 8
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46 #endif
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47
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48 /* The extra casts work around common compiler bugs. */
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49 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
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50 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
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51 It is necessary at least when t == time_t. */
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52 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
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53 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
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54 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
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55
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56 #ifndef INT_MAX
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57 # define INT_MAX TYPE_MAXIMUM (int)
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58 #endif
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59
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60 /* Write up to COUNT bytes at BUF to descriptor FD, retrying if interrupted.
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61 Return the actual number of bytes written, zero for EOF, or SAFE_RW_ERROR
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62 upon error. */
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63 size_t
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64 safe_write (int fd, const void *buf, size_t count)
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65 {
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66 ssize_t result;
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67
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68 /* POSIX limits COUNT to SSIZE_MAX, but we limit it further, requiring
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69 that COUNT <= INT_MAX, to avoid triggering a bug in Tru64 5.1.
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70 When decreasing COUNT, keep the file pointer block-aligned.
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71 Note that in any case, write may succeed, yet write fewer than COUNT
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72 bytes, so the caller must be prepared to handle partial results. */
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73 if (count > INT_MAX)
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74 count = INT_MAX & ~8191;
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75
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76 do
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77 {
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78 result = write (fd, buf, count);
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79 }
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80 while (result < 0 && IS_EINTR (errno));
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81
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82 return (size_t) result;
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83 }