1 /*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "persistent_integer.h"
18
19 #include <fcntl.h>
20
21 #include <base/logging.h>
22 #include <base/posix/eintr_wrapper.h>
23
24 #include "constants.h"
25
26 namespace chromeos_metrics {
27
PersistentInteger(const std::string & name,const base::FilePath & directory)28 PersistentInteger::PersistentInteger(const std::string& name,
29 const base::FilePath& directory)
30 : value_(0),
31 version_(kVersion),
32 name_(name),
33 backing_file_path_(directory.Append(name_)),
34 synced_(false) {}
35
~PersistentInteger()36 PersistentInteger::~PersistentInteger() {}
37
Set(int64_t value)38 void PersistentInteger::Set(int64_t value) {
39 value_ = value;
40 Write();
41 }
42
Get()43 int64_t PersistentInteger::Get() {
44 // If not synced, then read. If the read fails, it's a good idea to write.
45 if (!synced_ && !Read())
46 Write();
47 return value_;
48 }
49
GetAndClear()50 int64_t PersistentInteger::GetAndClear() {
51 int64_t v = Get();
52 Set(0);
53 return v;
54 }
55
Add(int64_t x)56 void PersistentInteger::Add(int64_t x) {
57 Set(Get() + x);
58 }
59
Write()60 void PersistentInteger::Write() {
61 int fd = HANDLE_EINTR(open(backing_file_path_.value().c_str(),
62 O_WRONLY | O_CREAT | O_TRUNC,
63 S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH));
64 PCHECK(fd >= 0) << "cannot open " << backing_file_path_.value()
65 << " for writing";
66 PCHECK((HANDLE_EINTR(write(fd, &version_, sizeof(version_))) ==
67 sizeof(version_)) &&
68 (HANDLE_EINTR(write(fd, &value_, sizeof(value_))) ==
69 sizeof(value_)))
70 << "cannot write to " << backing_file_path_.value();
71 close(fd);
72 synced_ = true;
73 }
74
Read()75 bool PersistentInteger::Read() {
76 int fd = HANDLE_EINTR(open(backing_file_path_.value().c_str(), O_RDONLY));
77 if (fd < 0) {
78 PLOG(WARNING) << "cannot open " << backing_file_path_.value()
79 << " for reading";
80 return false;
81 }
82 int32_t version;
83 int64_t value;
84 bool read_succeeded = false;
85 if (HANDLE_EINTR(read(fd, &version, sizeof(version))) == sizeof(version) &&
86 version == version_ &&
87 HANDLE_EINTR(read(fd, &value, sizeof(value))) == sizeof(value)) {
88 value_ = value;
89 read_succeeded = true;
90 synced_ = true;
91 }
92 close(fd);
93 return read_succeeded;
94 }
95
96 } // namespace chromeos_metrics
97