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 #include <cinttypes>
18 #include <cstring>
19
20 #include "android-base/logging.h"
21
22 #include "wifilogd/message_buffer.h"
23
24 namespace android {
25 namespace wifilogd {
26
27 using local_utils::CopyFromBufferOrDie;
28
MessageBuffer(size_t size)29 MessageBuffer::MessageBuffer(size_t size)
30 : data_(new uint8_t[size]), capacity_(size), read_pos_(0), write_pos_(0) {
31 CHECK(size > GetHeaderSize());
32 }
33
Append(const uint8_t * message,uint16_t message_len)34 bool MessageBuffer::Append(const uint8_t* message, uint16_t message_len) {
35 CHECK(message_len);
36
37 if (!CanFitNow(message_len)) {
38 return false;
39 }
40
41 AppendHeader(message_len);
42 AppendRawBytes(message, message_len);
43 return true;
44 }
45
CanFitEver(uint16_t length) const46 bool MessageBuffer::CanFitEver(uint16_t length) const {
47 // This unusual formulation is intended to avoid overflow.
48 return capacity_ - GetHeaderSize() >= length;
49 }
50
CanFitNow(uint16_t length) const51 bool MessageBuffer::CanFitNow(uint16_t length) const {
52 // This unusual formulation is intended to avoid overflow/underflow.
53 return GetFreeSize() >= GetHeaderSize() &&
54 GetFreeSize() - GetHeaderSize() >= length;
55 }
56
Clear()57 void MessageBuffer::Clear() {
58 read_pos_ = 0;
59 write_pos_ = 0;
60 }
61
ConsumeNextMessage()62 std::tuple<const uint8_t*, size_t> MessageBuffer::ConsumeNextMessage() {
63 if (read_pos_ == write_pos_) {
64 return {nullptr, 0};
65 }
66
67 const auto& header = CopyFromBufferOrDie<LengthHeader>(
68 data_.get() + read_pos_, GetReadableSize());
69 read_pos_ += sizeof(header);
70
71 const uint8_t* payload_start = data_.get() + read_pos_;
72 read_pos_ += header.payload_len;
73 CHECK(read_pos_ <= write_pos_);
74
75 return {payload_start, header.payload_len};
76 }
77
Rewind()78 void MessageBuffer::Rewind() { read_pos_ = 0; }
79
80 // Private methods below.
81
AppendHeader(uint16_t message_len)82 void MessageBuffer::AppendHeader(uint16_t message_len) {
83 LengthHeader header;
84 header.payload_len = message_len;
85 AppendRawBytes(&header, sizeof(header));
86 }
87
AppendRawBytes(const void * data_start,size_t data_len)88 void MessageBuffer::AppendRawBytes(const void* data_start, size_t data_len) {
89 std::memcpy(data_.get() + write_pos_, data_start, data_len);
90 write_pos_ += data_len;
91 CHECK(write_pos_ <= capacity_);
92 }
93
94 } // namespace wifilogd
95 } // namespace android
96