ppsspp/Common/Data/Collections/FixedSizeQueue.h

// Copyright (C) 2003 Dolphin Project.

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 2.0 or later versions.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License 2.0 for more details.

// A copy of the GPL 2.0 should have been included with the program.
// If not, see http://www.gnu.org/licenses/

// Official SVN repository and contact information can be found at
// http://code.google.com/p/dolphin-emu/

#pragma once

#include <cstring>
#include "Common/MemoryUtil.h"
#include "Common/Serialize/Serializer.h"

// STL-look-a-like interface, but name is mixed case to distinguish it clearly from the
// real STL classes.

// Not fully featured, no safety checking yet. Add features as needed.

template <class T, int N>
class FixedSizeQueue {
public:
	FixedSizeQueue() {
		storage_ = new T[N];
		clear();
	}

	~FixedSizeQueue() {
		delete [] storage_;
	}

	// Disallow copies.
	FixedSizeQueue(FixedSizeQueue &other) = delete;
	FixedSizeQueue& operator=(const FixedSizeQueue &other) = delete;

	void clear() {
		head_ = 0;
		tail_ = 0;
		count_ = 0;
		// Not entirely necessary, but keeps things clean.
		memset(storage_, 0, sizeof(T) * N);
	}

	void push(T t) {
		storage_[tail_] = t;
		tail_++;
		if (tail_ == N)
			tail_ = 0;
		count_++;
	}

	// Gets pointers to write to directly.
	void pushPointers(size_t size, T **dest1, size_t *sz1, T **dest2, size_t *sz2) {
		if (tail_ + (int)size < N) {
			*dest1 = &storage_[tail_];
			*sz1 = size;
			tail_ += (int)size;
			if (tail_ == N) tail_ = 0;
			*dest2 = 0;
			*sz2 = 0;
		} else {
			*dest1 = &storage_[tail_];
			*sz1 = N - tail_;
			tail_ = (int)(size - *sz1);
			*dest2 = &storage_[0];
			*sz2 = tail_;
		}
		count_ += (int)size;
	}

	void popPointers(size_t size, const T **src1, size_t *sz1, const T **src2, size_t *sz2) {
		if ((int)size > count_) size = count_;

		if (head_ + size < N) {
			*src1 = &storage_[head_];
			*sz1 = size;
			head_ += (int)size;
			if (head_ == N) head_ = 0;
			*src2 = 0;
			*sz2 = 0;
		} else {
			*src1 = &storage_[head_];
			*sz1 = N - head_;
			head_ = (int)(size - *sz1);
			*src2 = &storage_[0];
			*sz2 = head_;
		}
		count_ -= (int)size;
	}

	void pop() {
		head_++;
		if (head_ == N)
			head_ = 0;
		count_--;
	}

	/*
	void push_array(const T *ptr, size_t num) {
		// TODO: memcpy
		for (size_t i = 0; i < num; i++) {
			push(ptr[i]);
		}
	}

	void pop_array(T *outptr, size_t num) {
		for (size_t i = 0; i < num; i++) {
			outptr[i] = front();
			pop();
		}
	}*/

	T pop_front() {
		const T &temp = storage_[head_];
		pop();
		return temp;
	}

	T &front() { return storage_[head_]; }

	const T &front() const { return storage_[head_]; }

	size_t size() const {
		return count_;
	}

	size_t capacity() const {
		return N;
	}

	int room() const {
		return N - count_;
	}

	bool empty() {
		return count_ == 0;
	}

	void DoState(PointerWrap &p) {
		int size = N;
		Do(p, size);
		if (size != N)
		{
			ERROR_LOG(Log::Common, "Savestate failure: Incompatible queue size.");
			return;
		}
		// TODO: This is quite wasteful, could just store the actual data. Would be slightly more complex though.
		DoArray<T>(p, storage_, N);
		Do(p, head_);
		Do(p, tail_);
		Do(p, count_);
		p.DoMarker("FixedSizeQueue");
	}

	// Compact serialization: stores only the live [head_, head_+count_) region
	// instead of the whole fixed storage. NOT format-compatible with DoState();
	// callers must gate on their own section version.
	void DoStateCompact(PointerWrap &p) {
		int size = N;
		Do(p, size);
		if (size != N) {
			ERROR_LOG(Log::Common, "Savestate failure: Incompatible queue size.");
			p.SetError(p.ERROR_FAILURE);
			return;
		}
		Do(p, count_);
		if (count_ < 0 || count_ > N) {
			ERROR_LOG(Log::Common, "Savestate failure: Bad compact queue count.");
			p.SetError(p.ERROR_FAILURE);
			return;
		}
		if (p.mode == PointerWrap::MODE_READ) {
			// Restore linearized: live data starts at the front of storage.
			head_ = 0;
			tail_ = count_ == N ? 0 : count_;
			DoArray<T>(p, storage_, count_);
		} else {
			if (head_ + count_ <= N) {
				DoArray<T>(p, storage_ + head_, count_);
			} else {
				// Live region wraps; write the two pieces in pop order. Raw
				// bytes only (POD DoArray has no per-call header), so the
				// single linear read above consumes them identically.
				const int firstPart = N - head_;
				DoArray<T>(p, storage_ + head_, firstPart);
				DoArray<T>(p, storage_, count_ - firstPart);
			}
		}
		p.DoMarker("FixedSizeQueue");
	}

private:
	T *storage_;
	int head_;
	int tail_;
	int count_;  // sacrifice 4 bytes for a simpler implementation. may optimize away in the future.
};