1 // Copyright (c) 2011 The LevelDB Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. See the AUTHORS file for names of contributors. 4 5 #ifndef STORAGE_LEVELDB_INCLUDE_TABLE_H_ 6 #define STORAGE_LEVELDB_INCLUDE_TABLE_H_ 7 8 #include <cstdint> 9 10 #include "leveldb/export.h" 11 #include "leveldb/iterator.h" 12 13 namespace leveldb { 14 15 class Block; 16 class BlockHandle; 17 class Footer; 18 struct Options; 19 class RandomAccessFile; 20 struct ReadOptions; 21 class TableCache; 22 23 // A Table is a sorted map from strings to strings. Tables are 24 // immutable and persistent. A Table may be safely accessed from 25 // multiple threads without external synchronization. 26 class LEVELDB_EXPORT Table { 27 public: 28 // Attempt to open the table that is stored in bytes [0..file_size) 29 // of "file", and read the metadata entries necessary to allow 30 // retrieving data from the table. 31 // 32 // If successful, returns ok and sets "*table" to the newly opened 33 // table. The client should delete "*table" when no longer needed. 34 // If there was an error while initializing the table, sets "*table" 35 // to nullptr and returns a non-ok status. Does not take ownership of 36 // "*source", but the client must ensure that "source" remains live 37 // for the duration of the returned table's lifetime. 38 // 39 // *file must remain live while this Table is in use. 40 static Status Open(const Options& options, RandomAccessFile* file, 41 uint64_t file_size, Table** table); 42 43 Table(const Table&) = delete; 44 Table& operator=(const Table&) = delete; 45 46 ~Table(); 47 48 // Returns a new iterator over the table contents. 49 // The result of NewIterator() is initially invalid (caller must 50 // call one of the Seek methods on the iterator before using it). 51 Iterator* NewIterator(const ReadOptions&) const; 52 53 // Given a key, return an approximate byte offset in the file where 54 // the data for that key begins (or would begin if the key were 55 // present in the file). The returned value is in terms of file 56 // bytes, and so includes effects like compression of the underlying data. 57 // E.g., the approximate offset of the last key in the table will 58 // be close to the file length. 59 uint64_t ApproximateOffsetOf(const Slice& key) const; 60 61 private: 62 friend class TableCache; 63 struct Rep; 64 65 static Iterator* BlockReader(void*, const ReadOptions&, const Slice&); 66 Table(Rep * rep)67 explicit Table(Rep* rep) : rep_(rep) {} 68 69 // Calls (*handle_result)(arg, ...) with the entry found after a call 70 // to Seek(key). May not make such a call if filter policy says 71 // that key is not present. 72 Status InternalGet(const ReadOptions&, const Slice& key, void* arg, 73 void (*handle_result)(void* arg, const Slice& k, 74 const Slice& v)); 75 76 void ReadMeta(const Footer& footer); 77 void ReadFilter(const Slice& filter_handle_value); 78 79 Rep* const rep_; 80 }; 81 82 } // namespace leveldb 83 84 #endif // STORAGE_LEVELDB_INCLUDE_TABLE_H_ 85