Added buffer code

src/buffer/rollingbuffer.hpp

@@ -0,0 +1,137 @@
+#pragma once
+
+#include <stdexcept>
+#include <stdlib.h>
+#include <cstdint>
+#include <vector>
+
+
+/*
+This file defines a simple "RollingBuffer" class, based on the
+implementation of SampleBuffer in ncmpcpp.
+*/
+
+
+template<class T>
+struct RollingBuffer {
+	public:
+		typedef typename std::vector<T>::iterator Iterator;
+
+		RollingBuffer() : m_offset(0) { }
+
+		void put(Iterator begin, Iterator end);
+		size_t get(size_t elems, std::vector<T> &dest);
+
+		void resize(size_t n);
+		void clear();
+
+		size_t size() const;
+		const std::vector<T> &buffer() const;
+
+	private:
+		size_t m_offset;
+		std::vector<T> m_buffer;
+};
+
+
+
+template <class T>
+void RollingBuffer<T>::put(
+		RollingBuffer::Iterator begin,
+		RollingBuffer::Iterator end
+	) {
+
+	// How many elements to put
+	size_t elems = end - begin;
+	if (elems > m_buffer.size()) {
+		throw std::out_of_range("Size of the buffer is smaller than the amount of elements");
+	}
+
+	// How much space we have for new elements
+	size_t free_elems = m_buffer.size() - m_offset;
+
+	// If we don't have enough free space,
+	// make more by moving the buffer forwards.
+	if (elems > free_elems) {
+		size_t to_remove = elems - free_elems;
+		std::copy(
+			m_buffer.begin() + to_remove,
+			m_buffer.end() - free_elems,
+			m_buffer.begin()
+		);
+		m_offset -= to_remove;
+	}
+
+	// Add new elements to buffer
+	std::copy(begin, end, m_buffer.begin() + m_offset);
+	m_offset += elems;
+}
+
+
+
+template <class T>
+size_t RollingBuffer<T>::get(
+		size_t elems,
+		std::vector<T> &dest
+	) {
+	// elems: how many samples to get
+	// dest: where to put them
+
+
+	// (m_offset == 0) => we have no data
+	if (m_offset == 0) {
+		return 0;
+	}
+
+	// If too many elements are requested,
+	// give as much as we can.
+	if (elems > m_offset) {
+		elems = m_offset;
+	}
+
+	if (elems >= dest.size()) {
+		// If dest is smaller than request size,
+		// discard earlier elements to fit.
+		size_t elems_lost = elems - dest.size();
+		std::copy(m_buffer.begin() + elems_lost, m_buffer.begin() + elems, dest.begin());
+	} else {
+		// otherwise, copy samples to the destination buffer.
+		std::copy(dest.begin() + elems, dest.end(), dest.begin());
+		std::copy(m_buffer.begin(), m_buffer.begin() + elems, dest.end() - elems);
+	}
+
+	// Remove elements from the internal buffer.
+	std::copy(m_buffer.begin() + elems, m_buffer.begin() + m_offset, m_buffer.begin());
+	m_offset -= elems;
+
+	return elems;
+}
+
+
+
+template <class T>
+void RollingBuffer<T>::resize(size_t n) {
+	m_buffer.resize(n);
+	clear();
+}
+
+
+
+template <class T>
+void RollingBuffer<T>::clear() {
+	m_offset = 0;
+}
+
+
+
+template <class T>
+size_t RollingBuffer<T>::size() const {
+	return m_offset;
+}
+
+
+
+template <class T>
+const std::vector<T> &RollingBuffer<T>::buffer() const {
+	return m_buffer;
+}