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// 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;
void 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:
struct Rep;
Rep* rep_;
explicit Table(Rep* rep) { rep_ = rep; }
static Iterator* BlockReader(void*, const ReadOptions&, const Slice&);
// 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.
friend class TableCache;
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);
};
} // namespace leveldb
#endif // STORAGE_LEVELDB_INCLUDE_TABLE_H_
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