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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CC_DEBUG_RING_BUFFER_H_
#define CC_DEBUG_RING_BUFFER_H_
#include "base/logging.h"
namespace cc {
template<typename T, size_t kSize>
class RingBuffer {
public:
explicit RingBuffer()
: current_index_(0) {
}
size_t BufferSize() const {
return kSize;
}
size_t CurrentIndex() const {
return current_index_;
}
// tests if a value was saved to this index
bool IsFilledIndex(size_t n) const {
return BufferIndex(n) < current_index_;
}
// n = 0 returns the oldest value and
// n = bufferSize() - 1 returns the most recent value.
const T& ReadBuffer(size_t n) const {
DCHECK(IsFilledIndex(n));
return buffer_[BufferIndex(n)];
}
T* MutableReadBuffer(size_t n) {
DCHECK(IsFilledIndex(n));
return &buffer_[BufferIndex(n)];
}
void SaveToBuffer(const T& value) {
buffer_[BufferIndex(0)] = value;
current_index_++;
}
void Clear() {
current_index_ = 0;
}
// Iterator has const access to the RingBuffer it got retrieved from.
class Iterator {
public:
size_t index() const { return index_; }
const T* operator->() const { return &buffer_.ReadBuffer(index_); }
const T* operator*() const { return &buffer_.ReadBuffer(index_); }
Iterator& operator++() {
index_++;
if (index_ == kSize)
out_of_range_ = true;
return *this;
}
Iterator& operator--() {
if (index_ == 0)
out_of_range_ = true;
index_--;
return *this;
}
operator bool() const {
return buffer_.IsFilledIndex(index_) && !out_of_range_;
}
private:
Iterator(const RingBuffer<T, kSize>& buffer, size_t index)
: buffer_(buffer),
index_(index),
out_of_range_(false) {
}
const RingBuffer<T, kSize>& buffer_;
size_t index_;
bool out_of_range_;
friend class RingBuffer<T, kSize>;
};
// Returns an Iterator pointing to the oldest value in the buffer.
// Example usage (iterate from oldest to newest value):
// for (RingBuffer<T, kSize>::Iterator it = ring_buffer.Begin(); it; ++it) {}
Iterator Begin() const {
if (current_index_ < kSize)
return Iterator(*this, kSize - current_index_);
return Iterator(*this, 0);
}
// Returns an Iterator pointing to the newest value in the buffer.
// Example usage (iterate backwards from newest to oldest value):
// for (RingBuffer<T, kSize>::Iterator it = ring_buffer.End(); it; --it) {}
Iterator End() const {
return Iterator(*this, kSize - 1);
}
private:
inline size_t BufferIndex(size_t n) const {
return (current_index_ + n) % kSize;
}
T buffer_[kSize];
size_t current_index_;
};
} // namespace cc
#endif // CC_DEBUG_RING_BUFFER_H_
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