1 /*
2  * Copyright (C) 2017 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 ART_RUNTIME_BACKTRACE_HELPER_H_
18 #define ART_RUNTIME_BACKTRACE_HELPER_H_
19 
20 #include <stddef.h>
21 #include <stdint.h>
22 
23 namespace art {
24 
25 // Using libbacktrace
26 class BacktraceCollector {
27  public:
BacktraceCollector(uintptr_t * out_frames,size_t max_depth,size_t skip_count)28   BacktraceCollector(uintptr_t* out_frames, size_t max_depth, size_t skip_count)
29       : out_frames_(out_frames), max_depth_(max_depth), skip_count_(skip_count) {}
30 
NumFrames()31   size_t NumFrames() const {
32     return num_frames_;
33   }
34 
35   // Collect the backtrace, do not call more than once.
36   void Collect();
37 
38  private:
39   uintptr_t* const out_frames_ = nullptr;
40   size_t num_frames_ = 0u;
41   const size_t max_depth_ = 0u;
42   size_t skip_count_ = 0u;
43 };
44 
45 // A bounded sized backtrace.
46 template <size_t kMaxFrames>
47 class FixedSizeBacktrace {
48  public:
Collect(size_t skip_count)49   void Collect(size_t skip_count) {
50     BacktraceCollector collector(frames_, kMaxFrames, skip_count);
51     collector.Collect();
52     num_frames_ = collector.NumFrames();
53   }
54 
Hash()55   uint64_t Hash() const {
56     uint64_t hash = 9314237;
57     for (size_t i = 0; i < num_frames_; ++i) {
58       hash = hash * 2654435761 + frames_[i];
59       hash += (hash >> 13) ^ (hash << 6);
60     }
61     return hash;
62   }
63 
64  private:
65   uintptr_t frames_[kMaxFrames];
66   size_t num_frames_;
67 };
68 
69 }  // namespace art
70 
71 #endif  // ART_RUNTIME_BACKTRACE_HELPER_H_
72