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