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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef SRC_TRACE_PROCESSOR_TRACE_BLOB_VIEW_H_
#define SRC_TRACE_PROCESSOR_TRACE_BLOB_VIEW_H_
#include <stddef.h>
#include <stdint.h>
#include <limits>
#include <memory>
#include "perfetto/base/logging.h"
namespace perfetto {
namespace trace_processor {
// This class is an equivalent of std::string_view for trace binary data.
// The main difference is that this class has also shared ownership of a portion
// of the raw trace.
// The underlying buffer will be freed once all the TraceBlobViews that refer
// to the same buffer have passed through the pipeline and been parsed.
class TraceBlobView {
public:
TraceBlobView(std::unique_ptr<uint8_t[]> buffer, size_t offset, size_t length)
: shbuf_(SharedBuf(std::move(buffer))),
offset_(static_cast<uint32_t>(offset)),
length_(static_cast<uint32_t>(length)) {
PERFETTO_DCHECK(offset <= std::numeric_limits<uint32_t>::max());
PERFETTO_DCHECK(length <= std::numeric_limits<uint32_t>::max());
}
// Allow std::move().
TraceBlobView(TraceBlobView&&) noexcept = default;
TraceBlobView& operator=(TraceBlobView&&) = default;
// Disable implicit copy.
TraceBlobView(const TraceBlobView&) = delete;
TraceBlobView& operator=(const TraceBlobView&) = delete;
TraceBlobView slice(size_t offset, size_t length) const {
PERFETTO_DCHECK(offset + length <= offset_ + length_);
return TraceBlobView(shbuf_, offset, length);
}
bool operator==(const TraceBlobView& rhs) const {
return (shbuf_ == rhs.shbuf_) && (offset_ == rhs.offset_) &&
(length_ == rhs.length_);
}
bool operator!=(const TraceBlobView& rhs) const { return !(*this == rhs); }
inline const uint8_t* data() const { return start() + offset_; }
size_t offset_of(const uint8_t* data) const {
// When a field is size 0, data can be equal to start() + offset_ + length_.
PERFETTO_DCHECK(data >= start() && data <= (start() + offset_ + length_));
return static_cast<size_t>(data - start());
}
size_t length() const { return length_; }
size_t offset() const { return offset_; }
private:
// An equivalent to std::shared_ptr<uint8_t>, with the differnce that:
// - Supports array types, available for shared_ptr only in C++17.
// - Is not thread safe, which is not needed for our purposes.
class SharedBuf {
public:
explicit SharedBuf(std::unique_ptr<uint8_t[]> mem) {
rcbuf_ = new RefCountedBuf(std::move(mem));
}
SharedBuf(const SharedBuf& copy) : rcbuf_(copy.rcbuf_) {
PERFETTO_DCHECK(rcbuf_->refcount > 0);
rcbuf_->refcount++;
}
~SharedBuf() {
if (!rcbuf_)
return;
PERFETTO_DCHECK(rcbuf_->refcount > 0);
if (--rcbuf_->refcount == 0) {
RefCountedBuf* rcbuf = rcbuf_;
rcbuf_ = nullptr;
delete rcbuf;
}
}
SharedBuf(SharedBuf&& other) noexcept {
rcbuf_ = other.rcbuf_;
other.rcbuf_ = nullptr;
}
SharedBuf& operator=(SharedBuf&& other) {
if (this != &other) {
// A bit of a ugly but pragmatic pattern to implement move assignment.
// First invoke the distructor and then invoke the move constructor
// inline via placement-new.
this->~SharedBuf();
new (this) SharedBuf(std::move(other));
}
return *this;
}
bool operator==(const SharedBuf& x) const { return x.rcbuf_ == rcbuf_; }
bool operator!=(const SharedBuf& x) const { return !(x == *this); }
const uint8_t* data() const { return rcbuf_->mem.get(); }
private:
struct RefCountedBuf {
explicit RefCountedBuf(std::unique_ptr<uint8_t[]> buf)
: refcount(1), mem(std::move(buf)) {}
int refcount;
std::unique_ptr<uint8_t[]> mem;
};
RefCountedBuf* rcbuf_ = nullptr;
};
inline const uint8_t* start() const { return shbuf_.data(); }
TraceBlobView(SharedBuf b, size_t o, size_t l)
: shbuf_(b),
offset_(static_cast<uint32_t>(o)),
length_(static_cast<uint32_t>(l)) {}
SharedBuf shbuf_;
uint32_t offset_;
uint32_t length_; // Measured from |offset_|, not from |data()|.
};
} // namespace trace_processor
} // namespace perfetto
#endif // SRC_TRACE_PROCESSOR_TRACE_BLOB_VIEW_H_