103 lines
2.7 KiB
C
103 lines
2.7 KiB
C
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/**
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* Copyright 2012 Facebook
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* @author Tudor Bosman (tudorb@fb.com)
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*/
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#ifndef THRIFT_LIB_CPP_PROTOCOL_NEUTRONIUM_INTERNTABLE_H_
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#define THRIFT_LIB_CPP_PROTOCOL_NEUTRONIUM_INTERNTABLE_H_
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#include <memory>
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#include <unordered_map>
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#include <vector>
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#include "folly/Range.h"
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#include "folly/experimental/io/IOBuf.h"
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#include "folly/experimental/io/Cursor.h"
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namespace apache {
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namespace thrift {
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namespace protocol {
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namespace neutronium {
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/**
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* Interned string table.
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*
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* Strings are stored in a chain of IOBufs, so serializing and deserializing
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* the InternTable is fast and easy.
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*/
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class InternTable {
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public:
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InternTable();
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/**
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* Add a string to the table, returning the id.
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*/
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uint32_t add(folly::StringPiece str);
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/**
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* Get a string from the table, by id; throws std::out_of_range if the
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* id is invalid.
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*/
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folly::StringPiece get(uint32_t id) const {
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return strings_.at(id);
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}
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/**
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* Serialize the table to a IOBuf chain.
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* Note that part of the chain may be shared with the InternTable, so
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* you must call unshare() on the returned buffers if you want to
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* write to them.
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*/
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std::unique_ptr<folly::IOBuf> serialize();
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/**
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* Load the table from a IOBuf chain.
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* Takes ownership of the IOBuf chain.
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* InternTable will call unshare() appropriately before writing to
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* buffers from the provided chain.
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*/
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void deserialize(std::unique_ptr<folly::IOBuf>&& data);
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/**
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* Clear the table.
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*/
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void clear();
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private:
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// Performance optimization to reduce the number of calls to unshare() /
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// unshareOne(), which folly::io::Cursor benchmarks have shown to be
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// somewhat expensive. Given that we know that we only write to the tail
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// of the IOBuf chain, we can often tell with certainty that the tail
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// is private to us and so we don't need to check or call unshareOne().
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bool maybeShared_;
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std::unique_ptr<folly::IOBuf> head_;
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std::vector<folly::StringPiece> strings_;
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typedef
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std::unordered_map<folly::StringPiece, uint32_t, folly::StringPieceHash>
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StringMap;
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// Only allocate writer if needed (when actually add()ing)
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struct Writer {
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template <typename... Args>
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/* implicit */ Writer(Args... args) : appender(args...) { }
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folly::io::Appender appender;
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StringMap map;
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};
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std::unique_ptr<Writer> writer_;
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// Not copiable; not movable
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InternTable(const InternTable&) = delete;
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InternTable(InternTable&&) = delete;
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InternTable& operator=(const InternTable&) = delete;
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InternTable& operator=(InternTable&&) = delete;
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};
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} // namespace neutronium
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} // namespace protocol
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} // namespace thrift
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} // namespace apache
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#endif /* THRIFT_LIB_CPP_PROTOCOL_NEUTRONIUM_INTERNTABLE_H_ */
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