1 /*
2  * Copyright (C) 2016 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 #ifndef OS_H_
18 #define OS_H_
19 
20 #include <time.h>
21 
22 #include <cstdint>
23 #include <memory>
24 #include <string>
25 #include <tuple>
26 #include <utility>
27 
28 #include "android-base/macros.h"
29 
30 #include "wifilogd/local_utils.h"
31 #include "wifilogd/raw_os.h"
32 
33 namespace android {
34 namespace wifilogd {
35 
36 // Abstracts operating system calls.
37 //
38 // There are three reasons we want to abstract OS calls:
39 // 1. Allow tests to run hermetically.
40 // 2. Verify that the application logic invokes the OS calls as expected.
41 // 3. Provide interfaces that as easier to use, than the underlying OS calls.
42 class Os {
43  public:
44   using Errno = int;
45 
46   struct Timestamp {
47     uint32_t secs;  // Sufficient through 2100.
48     uint32_t nsecs;
49   };
50 
51   static constexpr int kInvalidFd = -1;
52   static constexpr auto kMaxNanos = 999'999'999;
53 
54   // Constructs an Os instance.
55   Os();
56 
57   // Constructs an Os instance, with the caller-provided RawOs. This method
58   // allows tests to provide a MockRawOs.
59   explicit Os(std::unique_ptr<RawOs> raw_os);
60 
61   virtual ~Os();
62 
63   // Returns the Android control socket with name |socket_name|. If no such
64   // socket exists, or the init daemon has not provided this process with
65   // access to said socket, returns {kInvalidFd, errno}.
66   virtual std::tuple<int, Errno> GetControlSocket(
67       const std::string& socket_name);
68 
69   // Returns the current time, as reported by the clock with |clock_id|.
70   virtual Timestamp GetTimestamp(clockid_t clock_id) const;
71 
72   // Suspends execution of this process, for |sleep_time_nsec|. The passed
73   // value must not exceed kMaxNanos.
74   virtual void Nanosleep(uint32_t sleep_time_nsec);
75 
76   // Receives a datagram of up to |buflen| from |fd|, writing the data to |buf|.
77   // Returns the size of the datagram, and the result of the operation (0 for
78   // success, |errno| otherwise).
79   //
80   // Notes:
81   // - |buflen| may not exceed the maximal value for ssize_t.
82   // - The call blocks until a datagram is available.
83   // - If the datagram is larger than |buflen|, only |buflen| bytes will
84   //   be received. The returned size_t will, however, reflect the full
85   //   length of the datagram.
86   virtual std::tuple<size_t, Errno> ReceiveDatagram(int fd, NONNULL void* buf,
87                                                     size_t buflen);
88 
89   // Writes |buflen| bytes from |buf| to |fd|. Returns the number of bytes
90   // written, and the result of the operation (0 for success, |errno|
91   // otherwise).
92   //
93   // Notes:
94   // - |buflen| may not exceed the maximal value for ssize_t.
95   // - The returned size_t will not exceed |buflen|.
96   virtual std::tuple<size_t, Errno> Write(int fd, NONNULL const void* buf,
97                                           size_t buflen);
98 
99  private:
100   const std::unique_ptr<RawOs> raw_os_;
101 
102   DISALLOW_COPY_AND_ASSIGN(Os);
103 };
104 
105 }  // namespace wifilogd
106 }  // namespace android
107 
108 #endif  // OS_H_
109