atomicio.cc revision 11793 
1/*
2 * Copyright (c) 2008 The Hewlett-Packard Development Company
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Nathan Binkert
29 */
30
31#include "base/atomicio.hh"
32
33#include <cerrno>
34#include <cstdio>
35
36ssize_t
37atomic_read(int fd, void *s, size_t n)
38{
39    char *p = reinterpret_cast<char *>(s);
40    size_t pos = 0;
41
42    // Keep reading until we've gotten all of the data.
43    while (n > pos) {
44        ssize_t result = read(fd, p + pos, n - pos);
45
46        // We didn't get any more data, so we should probably punt,
47        // otherwise we'd just keep spinning
48        if (result == 0)
49            break;
50
51        // If there was an error, try again on EINTR/EAGAIN, pass the
52        // error up otherwise.
53        if (result == -1) {
54            if (errno == EINTR || errno == EAGAIN)
55                continue;
56            return result;
57        }
58
59        pos += result;
60    }
61
62    return pos;
63}
64
65ssize_t
66atomic_write(int fd, const void *s, size_t n)
67{
68    const char *p = reinterpret_cast<const char *>(s);
69    size_t pos = 0;
70
71    // Keep writing until we've written all of the data
72    while (n > pos) {
73        ssize_t result = write(fd, p + pos, n - pos);
74
75        // We didn't manage to write anything this time, so we should
76        // probably punt, otherwise we'd just keep spinning
77        if (result == 0)
78            break;
79
80        // If there was an error, try again on EINTR/EAGAIN, pass the
81        // error up otherwise.
82        if (result == -1) {
83            if (errno == EINTR || errno == EAGAIN)
84                continue;
85            return result;
86        }
87
88        pos += result;
89    }
90
91    return pos;
92}
93