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 #include "perfetto/protozero/scattered_stream_writer.h"
18
19 #include <algorithm>
20
21 #include "perfetto/base/logging.h"
22
23 namespace protozero {
24
~Delegate()25 ScatteredStreamWriter::Delegate::~Delegate() {}
26
ScatteredStreamWriter(Delegate * delegate)27 ScatteredStreamWriter::ScatteredStreamWriter(Delegate* delegate)
28 : delegate_(delegate),
29 cur_range_({nullptr, nullptr}),
30 write_ptr_(nullptr) {}
31
~ScatteredStreamWriter()32 ScatteredStreamWriter::~ScatteredStreamWriter() {}
33
Reset(ContiguousMemoryRange range)34 void ScatteredStreamWriter::Reset(ContiguousMemoryRange range) {
35 written_previously_ += static_cast<uint64_t>(write_ptr_ - cur_range_.begin);
36 cur_range_ = range;
37 write_ptr_ = range.begin;
38 PERFETTO_DCHECK(!write_ptr_ || write_ptr_ < cur_range_.end);
39 }
40
Extend()41 void ScatteredStreamWriter::Extend() {
42 Reset(delegate_->GetNewBuffer());
43 }
44
WriteBytesSlowPath(const uint8_t * src,size_t size)45 void ScatteredStreamWriter::WriteBytesSlowPath(const uint8_t* src,
46 size_t size) {
47 size_t bytes_left = size;
48 while (bytes_left > 0) {
49 if (write_ptr_ >= cur_range_.end)
50 Extend();
51 const size_t burst_size = std::min(bytes_available(), bytes_left);
52 WriteBytesUnsafe(src, burst_size);
53 bytes_left -= burst_size;
54 src += burst_size;
55 }
56 }
57
58 // TODO(primiano): perf optimization: I suspect that at the end this will always
59 // be called with |size| == 4, in which case we might just hardcode it.
ReserveBytes(size_t size)60 uint8_t* ScatteredStreamWriter::ReserveBytes(size_t size) {
61 if (write_ptr_ + size > cur_range_.end) {
62 // Assume the reservations are always < Delegate::GetNewBuffer().size(),
63 // so that one single call to Extend() will definitely give enough headroom.
64 Extend();
65 PERFETTO_DCHECK(write_ptr_ + size <= cur_range_.end);
66 }
67 uint8_t* begin = write_ptr_;
68 write_ptr_ += size;
69 #if PERFETTO_DCHECK_IS_ON()
70 memset(begin, 0, size);
71 #endif
72 return begin;
73 }
74
75 } // namespace protozero
76