[thin_show_dups] variable_chunk_stream

base/rolling_hash.h

@@ -0,0 +1,61 @@
+#ifndef BASE_ROLLING_HASH_H
+#define BASE_ROLLING_HASH_H
+
+#include <list>
+#include <stdint.h>
+#include <boost/optional.hpp>
+
+//----------------------------------------------------------------
+
+namespace base {
+	class rolling_hash {
+	public:
+		rolling_hash(unsigned window_size);
+
+		void reset();
+
+		// Returns the current hash
+		uint32_t step(uint8_t byte);
+
+		uint32_t get_hash() const;
+
+	private:
+		void update_hash(uint8_t byte);
+
+		uint32_t a_;
+		uint32_t a_to_k_minus_1_;
+
+		// FIXME: use a ring buffer
+		std::list<uint8_t> chars_;
+
+		uint32_t hash_;
+		uint32_t window_size_;
+	};
+
+	class content_based_hash {
+	public:
+		content_based_hash(unsigned window_size);
+		void reset();
+
+		// Returns a break point relative to the last reset/break.
+		boost::optional<unsigned> step(uint8_t byte);
+
+	private:
+		bool hit_break(uint32_t div) const;
+
+		rolling_hash rhash_;
+
+		uint32_t backup_div_;
+		uint32_t div_;
+
+		unsigned min_len_;
+		unsigned max_len_;
+
+		unsigned len_;
+		boost::optional<unsigned> backup_break_;
+	};
+}
+
+//----------------------------------------------------------------
+
+#endif