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 INCLUDE_PERFETTO_EXT_TRACING_CORE_SLICE_H_
18 #define INCLUDE_PERFETTO_EXT_TRACING_CORE_SLICE_H_
19 
20 #include <stddef.h>
21 #include <string.h>
22 
23 #include <memory>
24 #include <string>
25 #include <vector>
26 
27 #include "perfetto/base/logging.h"
28 
29 namespace perfetto {
30 
31 // A simple wrapper around a virtually contiguous memory range that contains a
32 // TracePacket, or just a portion of it.
33 struct Slice {
SliceSlice34   Slice() : start(nullptr), size(0) {}
SliceSlice35   Slice(const void* st, size_t sz) : start(st), size(sz) {}
36   Slice(Slice&& other) noexcept = default;
37 
38   // Create a Slice which owns |size| bytes of memory.
AllocateSlice39   static Slice Allocate(size_t size) {
40     Slice slice;
41     slice.own_data_.reset(new uint8_t[size]);
42     slice.start = &slice.own_data_[0];
43     slice.size = size;
44     return slice;
45   }
46 
TakeOwnershipSlice47   static Slice TakeOwnership(std::unique_ptr<uint8_t[]> buf, size_t size) {
48     Slice slice;
49     slice.own_data_ = std::move(buf);
50     slice.start = &slice.own_data_[0];
51     slice.size = size;
52     return slice;
53   }
54 
own_dataSlice55   uint8_t* own_data() {
56     PERFETTO_DCHECK(own_data_);
57     return own_data_.get();
58   }
59 
60   const void* start;
61   size_t size;
62 
63  private:
64   Slice(const Slice&) = delete;
65   void operator=(const Slice&) = delete;
66 
67   std::unique_ptr<uint8_t[]> own_data_;
68 };
69 
70 // TODO(primiano): most TracePacket(s) fit in a slice or two. We need something
71 // a bit more clever here that has inline capacity for 2 slices and then uses a
72 // std::forward_list or a std::vector for the less likely cases.
73 using Slices = std::vector<Slice>;
74 
75 }  // namespace perfetto
76 
77 #endif  // INCLUDE_PERFETTO_EXT_TRACING_CORE_SLICE_H_
78