Add a quick circular buffer class.

src/CircularBuffer.h

@@ -0,0 +1,90 @@
+ /*
+ * Copyright 2020, WindTerm.
+ *
+ * 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 CIRCULARBUFFER_H
+#define CIRCULARBUFFER_H
+
+#pragma once
+
+#include <QtAlgorithms>
+#include <QtGlobal>
+
+#define ROUND_UP_POW2(value)	{ (1 << (32 - qCountLeadingZeroBits(value))) }
+
+template <typename T>
+class CircularBuffer {
+public:
+	CircularBuffer(quint32 capacity)
+		: m_currentIndex(0) {
+		Q_ASSERT(capacity < (1 << 31));
+
+		m_capacity = ROUND_UP_POW2(capacity);
+		m_mask = m_capacity - 1;
+		m_buffer = static_cast<qint64 *>(calloc(m_capacity, sizeof(qint64)));
+
+		clear();
+	}
+
+	~CircularBuffer() {
+		free(m_buffer);
+		m_buffer = nullptr;
+	}
+
+	void append(const T &value) {
+		m_buffer[++m_currentIndex & m_mask] = value;
+	}
+
+	const T &at(qint64 index) const {
+		Q_ASSERT(index >= std::max<qint64>(0, m_currentIndex + 1 - m_capacity) && index <= m_currentIndex);
+		return m_buffer[index & m_mask];
+	}
+
+	int capacity() const { return m_capacity; }
+	void clear() {
+		m_currentIndex = -1;
+		memset(m_buffer, 0xFF, m_capacity * sizeof(qint64));
+
+#ifdef _DEBUG
+		for (int i = 0; i < m_capacity; i++) {
+			Q_ASSERT(m_buffer[i] == -1);
+		}
+#endif // _DEBUG
+	}
+
+	qint64 currentIndex() const { return m_currentIndex; }
+	qint64 minIndex() const { return std::max<qint64>(0, m_currentIndex + 1 - m_capacity); }
+
+	const T &operator [](qint64 index) const {
+		Q_ASSERT(index >= std::max<qint64>(0, m_currentIndex + 1 - m_capacity) && index <= m_currentIndex);
+		return m_buffer[index & m_mask];
+	}
+
+private:
+	T *m_buffer;
+	qint64 m_currentIndex;
+
+	int m_capacity;
+	int m_mask;
+};
+
+class Int64CircularBuffer : public CircularBuffer<qint64> {
+public:
+	Int64CircularBuffer(quint32 capacity)
+		: CircularBuffer<qint64>(capacity)
+	{}
+};
+
+#endif // CIRCULARBUFFER_H

src/README.md

@@ -4,6 +4,10 @@
 
 Below is a list of (some) WindTerm components in alphabetical order, along with a brief description of each.
 
+## CircularBuffer.h
+
+A quick circular buffer template class.
+
 ## Onigmo
 
 An improved version based on Onigmo 5.13.5. In particular, **the addition of iterator makes it possible to match gap buffer or nonadjacent memory blocks.** Please refer to the sample files for how to use.