Sessiond: Implement cmd_clear_session
[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
6c1c0768 18#define _LGPL_SOURCE
6cd525e8 19#include <assert.h>
aeb16260 20#include <errno.h>
636ae5db 21#include <limits.h>
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22#include <unistd.h>
23
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24#include "readwrite.h"
25
26/*
27 * lttng_read and lttng_write take care of EINTR and partial read/write.
28 * Upon success, they return the "count" received as parameter.
29 * They can return a negative value if an error occurs.
30 * If a value lower than the requested "count" is returned, it means an
83f4233d 31 * error occurred.
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32 * The error can be checked by querying errno.
33 */
73ec1cf9 34LTTNG_HIDDEN
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35ssize_t lttng_read(int fd, void *buf, size_t count)
36{
37 size_t i = 0;
38 ssize_t ret;
39
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40 assert(buf);
41
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42 /*
43 * Deny a read count that can be bigger then the returned value max size.
44 * This makes the function to never return an overflow value.
45 */
46 if (count > SSIZE_MAX) {
47 return -EINVAL;
48 }
49
33b14136 50 do {
6cd525e8 51 ret = read(fd, buf + i, count - i);
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52 if (ret < 0) {
53 if (errno == EINTR) {
54 continue; /* retry operation */
55 } else {
56 goto error;
57 }
58 }
59 i += ret;
60 assert(i <= count);
61 } while (count - i > 0 && ret > 0);
62 return i;
63
64error:
65 if (i == 0) {
66 return -1;
67 } else {
68 return i;
69 }
70}
71
73ec1cf9 72LTTNG_HIDDEN
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73ssize_t lttng_write(int fd, const void *buf, size_t count)
74{
75 size_t i = 0;
76 ssize_t ret;
77
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78 assert(buf);
79
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80 /*
81 * Deny a write count that can be bigger then the returned value max size.
82 * This makes the function to never return an overflow value.
83 */
84 if (count > SSIZE_MAX) {
85 return -EINVAL;
86 }
87
33b14136 88 do {
6cd525e8 89 ret = write(fd, buf + i, count - i);
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90 if (ret < 0) {
91 if (errno == EINTR) {
92 continue; /* retry operation */
93 } else {
94 goto error;
95 }
96 }
97 i += ret;
98 assert(i <= count);
99 } while (count - i > 0 && ret > 0);
100 return i;
101
102error:
103 if (i == 0) {
104 return -1;
105 } else {
106 return i;
107 }
108}
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