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