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 "event_log_list_builder.h"
18 
19 #include <cinttypes>
20 #include <memory>
21 #include <string>
22 #include <android-base/logging.h>
23 #include <log/log.h>
24 
25 namespace {
26 
27 const size_t MAX_EVENT_PAYLOAD_SIZE = 512 - 1;  // Leave room for final '\n'.
28 const size_t EVENT_TYPE_SIZE = 1;  // Size in bytes of the event type marker.
29 
30 }  // namespace
31 
EventLogListBuilder()32 EventLogListBuilder::EventLogListBuilder()
33     : payload_count_(0),
34       payload_size_(0),
35       payload_(std::make_unique<uint8_t[]>(MAX_EVENT_PAYLOAD_SIZE)) {
36   memset(payload_.get(), 0, MAX_EVENT_PAYLOAD_SIZE);
37 
38   // Set up the top-level EventLog data type.
39   AppendByte(EVENT_TYPE_LIST);
40 
41   // Skip over the byte prepresenting the number of items in the list. This
42   // value is set in Release().
43   payload_size_++;
44 }
45 
Append(int value)46 bool EventLogListBuilder::Append(int value) {
47   DCHECK_NE(static_cast<uint8_t*>(nullptr), payload_.get());
48 
49   if (!IsSpaceAvailable(sizeof(value) + EVENT_TYPE_SIZE)) {
50     return false;
51   }
52 
53   AppendByte(EVENT_TYPE_INT);
54   AppendData(&value, sizeof(value));
55 
56   payload_count_++;
57   return true;
58 }
59 
Append(const std::string & value)60 bool EventLogListBuilder::Append(const std::string& value) {
61   DCHECK_NE(static_cast<uint8_t*>(nullptr), payload_.get());
62 
63   int len = value.length();
64   if (!IsSpaceAvailable(sizeof(len) + len)) {
65     return false;
66   }
67 
68   AppendByte(EVENT_TYPE_STRING);
69   AppendData(&len, sizeof(len));
70   AppendData(value.c_str(), len);
71 
72   payload_count_++;
73   return true;
74 }
75 
Release(std::unique_ptr<uint8_t[]> * log,size_t * size)76 void EventLogListBuilder::Release(std::unique_ptr<uint8_t[]>* log,
77                                   size_t* size) {
78   // Finalize the log payload.
79   payload_[1] = payload_count_;
80 
81   // Return the log payload.
82   *size = payload_size_;
83   *log = std::move(payload_);
84 }
85 
AppendData(const void * data,size_t size)86 void EventLogListBuilder::AppendData(const void* data, size_t size) {
87   DCHECK_LT(payload_size_ + size, MAX_EVENT_PAYLOAD_SIZE);
88   memcpy(&payload_[payload_size_], data, size);
89   payload_size_ += size;
90 }
91 
AppendByte(uint8_t byte)92 void EventLogListBuilder::AppendByte(uint8_t byte) {
93   DCHECK_LT(payload_size_ + sizeof(byte), MAX_EVENT_PAYLOAD_SIZE);
94   payload_[payload_size_++] = byte;
95 }
96 
IsSpaceAvailable(size_t value_size)97 bool EventLogListBuilder::IsSpaceAvailable(size_t value_size) {
98   size_t space_needed = value_size + EVENT_TYPE_SIZE;
99   if (payload_size_ + space_needed > MAX_EVENT_PAYLOAD_SIZE) {
100     size_t remaining = MAX_EVENT_PAYLOAD_SIZE - payload_size_;
101     LOG(WARNING) << "Not enough space for value. remain=" <<
102         remaining << "; needed=" << space_needed;
103     return false;
104   }
105 
106   return true;
107 }
108