Fix: race with the viewer and readiness of streams
[lttng-tools.git] / src / common / readwrite.c
CommitLineData
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1/*
2 * Copyright (C) 2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
3 *
4 * This library is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU Lesser General Public License, version 2.1 only,
6 * as published by the Free Software Foundation.
7 *
8 * This library is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
11 * for more details.
12 *
13 * You should have received a copy of the GNU Lesser General Public License
14 * along with this library; if not, write to the Free Software Foundation,
15 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
16 */
17
6cd525e8 18#include <assert.h>
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19#include <errno.h>
20#include <unistd.h>
21
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22#include "readwrite.h"
23
24/*
25 * lttng_read and lttng_write take care of EINTR and partial read/write.
26 * Upon success, they return the "count" received as parameter.
27 * They can return a negative value if an error occurs.
28 * If a value lower than the requested "count" is returned, it means an
29 * error occured.
30 * The error can be checked by querying errno.
31 */
32ssize_t lttng_read(int fd, void *buf, size_t count)
33{
34 size_t i = 0;
35 ssize_t ret;
36
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37 assert(buf);
38
33b14136 39 do {
6cd525e8 40 ret = read(fd, buf + i, count - i);
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41 if (ret < 0) {
42 if (errno == EINTR) {
43 continue; /* retry operation */
44 } else {
45 goto error;
46 }
47 }
48 i += ret;
49 assert(i <= count);
50 } while (count - i > 0 && ret > 0);
51 return i;
52
53error:
54 if (i == 0) {
55 return -1;
56 } else {
57 return i;
58 }
59}
60
61ssize_t lttng_write(int fd, const void *buf, size_t count)
62{
63 size_t i = 0;
64 ssize_t ret;
65
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66 assert(buf);
67
33b14136 68 do {
6cd525e8 69 ret = write(fd, buf + i, count - i);
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70 if (ret < 0) {
71 if (errno == EINTR) {
72 continue; /* retry operation */
73 } else {
74 goto error;
75 }
76 }
77 i += ret;
78 assert(i <= count);
79 } while (count - i > 0 && ret > 0);
80 return i;
81
82error:
83 if (i == 0) {
84 return -1;
85 } else {
86 return i;
87 }
88}
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