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include/fs/BufferedSource.h

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+#pragma once
+
+#include "fs/ISource.h"
+#include "tl/memory_buffer.h"
+
+namespace fs
+{
+/**
+ * ISource interface implementation where the access to the underneath source
+ * is done in buffered mode. This class must be used when there a lot of tiny
+ * random access to the source. For further information please check ISource.
+ */
+template<typename SourceType>
+class BufferedSource final : public ISource
+{
+public:
+	explicit BufferedSource(SourceType source, size_t bufferSize = 4096u);
+
+	BufferedSource(BufferedSource&& other) = default;
+	BufferedSource& operator=(BufferedSource&& other) = default;
+	BufferedSource(const BufferedSource& other) = delete;
+	BufferedSource& operator=(const BufferedSource& other) = delete;
+
+	tl::optional<Error> getLastError() const override;
+
+	size_t read(tl::span<uint8_t> data) override;
+
+	void seekBeg(uint64_t offset) override;
+	void seekRel(int64_t offset) override;
+
+	uint64_t tell() const override;
+
+	uint64_t getSize() const override;
+
+	bool isEOS() const override;
+
+	size_t getPreferredBufferSize() const override;
+private:
+	SourceType m_source;
+	uint64_t m_bufferStartOffset = 0;
+	uint64_t m_bufferOffset = 0;
+	bool m_endOfSource = false;
+	tl::memory_buffer m_buffer;
+	mutable tl::optional<Error> m_optLastError;
+};
+
+}