// Copyright (c) 2011 The LevelDB Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. See the AUTHORS file for names of contributors. #ifndef STORAGE_LEVELDB_INCLUDE_TABLE_H_ #define STORAGE_LEVELDB_INCLUDE_TABLE_H_ #include <stdint.h> #include "leveldb/export.h" #include "leveldb/iterator.h" namespace leveldb { class Block; class BlockHandle; class Footer; struct Options; class RandomAccessFile; struct ReadOptions; class TableCache; // A Table is a sorted map from strings to strings. Tables are // immutable and persistent. A Table may be safely accessed from // multiple threads without external synchronization. class LEVELDB_EXPORT Table { public: // Attempt to open the table that is stored in bytes [0..file_size) // of "file", and read the metadata entries necessary to allow // retrieving data from the table. // // If successful, returns ok and sets "*table" to the newly opened // table. The client should delete "*table" when no longer needed. // If there was an error while initializing the table, sets "*table" // to nullptr and returns a non-ok status. Does not take ownership of // "*source", but the client must ensure that "source" remains live // for the duration of the returned table's lifetime. // // *file must remain live while this Table is in use. static Status Open(const Options& options, RandomAccessFile* file, uint64_t file_size, Table** table); Table(const Table&) = delete; Table& operator=(const Table&) = delete; ~Table(); // Returns a new iterator over the table contents. // The result of NewIterator() is initially invalid (caller must // call one of the Seek methods on the iterator before using it). Iterator* NewIterator(const ReadOptions&) const; // Given a key, return an approximate byte offset in the file where // the data for that key begins (or would begin if the key were // present in the file). The returned value is in terms of file // bytes, and so includes effects like compression of the underlying data. // E.g., the approximate offset of the last key in the table will // be close to the file length. uint64_t ApproximateOffsetOf(const Slice& key) const; private: friend class TableCache; struct Rep; static Iterator* BlockReader(void*, const ReadOptions&, const Slice&); explicit Table(Rep* rep) : rep_(rep) {} // Calls (*handle_result)(arg, ...) with the entry found after a call // to Seek(key). May not make such a call if filter policy says // that key is not present. Status InternalGet(const ReadOptions&, const Slice& key, void* arg, void (*handle_result)(void* arg, const Slice& k, const Slice& v)); void ReadMeta(const Footer& footer); void ReadFilter(const Slice& filter_handle_value); Rep* const rep_; }; } // namespace leveldb #endif // STORAGE_LEVELDB_INCLUDE_TABLE_H_