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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_DB_H_
+#define STORAGE_LEVELDB_INCLUDE_DB_H_
+
+#include <stdint.h>
+#include <stdio.h>
+#include "leveldb/iterator.h"
+#include "leveldb/options.h"
+
+namespace leveldb {
+
+// Update Makefile if you change these
+static const int kMajorVersion = 1;
+static const int kMinorVersion = 12;
+
+struct Options;
+struct ReadOptions;
+struct WriteOptions;
+class WriteBatch;
+
+// Abstract handle to particular state of a DB.
+// A Snapshot is an immutable object and can therefore be safely
+// accessed from multiple threads without any external synchronization.
+class Snapshot {
+ protected:
+ virtual ~Snapshot();
+};
+
+// A range of keys
+struct Range {
+ Slice start; // Included in the range
+ Slice limit; // Not included in the range
+
+ Range() { }
+ Range(const Slice& s, const Slice& l) : start(s), limit(l) { }
+};
+
+// A DB is a persistent ordered map from keys to values.
+// A DB is safe for concurrent access from multiple threads without
+// any external synchronization.
+class DB {
+ public:
+ // Open the database with the specified "name".
+ // Stores a pointer to a heap-allocated database in *dbptr and returns
+ // OK on success.
+ // Stores NULL in *dbptr and returns a non-OK status on error.
+ // Caller should delete *dbptr when it is no longer needed.
+ static Status Open(const Options& options,
+ const std::string& name,
+ DB** dbptr);
+
+ DB() { }
+ virtual ~DB();
+
+ // Set the database entry for "key" to "value". Returns OK on success,
+ // and a non-OK status on error.
+ // Note: consider setting options.sync = true.
+ virtual Status Put(const WriteOptions& options,
+ const Slice& key,
+ const Slice& value) = 0;
+
+ // Remove the database entry (if any) for "key". Returns OK on
+ // success, and a non-OK status on error. It is not an error if "key"
+ // did not exist in the database.
+ // Note: consider setting options.sync = true.
+ virtual Status Delete(const WriteOptions& options, const Slice& key) = 0;
+
+ // Apply the specified updates to the database.
+ // Returns OK on success, non-OK on failure.
+ // Note: consider setting options.sync = true.
+ virtual Status Write(const WriteOptions& options, WriteBatch* updates) = 0;
+
+ // If the database contains an entry for "key" store the
+ // corresponding value in *value and return OK.
+ //
+ // If there is no entry for "key" leave *value unchanged and return
+ // a status for which Status::IsNotFound() returns true.
+ //
+ // May return some other Status on an error.
+ virtual Status Get(const ReadOptions& options,
+ const Slice& key, std::string* value) = 0;
+
+ // Return a heap-allocated iterator over the contents of the database.
+ // The result of NewIterator() is initially invalid (caller must
+ // call one of the Seek methods on the iterator before using it).
+ //
+ // Caller should delete the iterator when it is no longer needed.
+ // The returned iterator should be deleted before this db is deleted.
+ virtual Iterator* NewIterator(const ReadOptions& options) = 0;
+
+ // Return a handle to the current DB state. Iterators created with
+ // this handle will all observe a stable snapshot of the current DB
+ // state. The caller must call ReleaseSnapshot(result) when the
+ // snapshot is no longer needed.
+ virtual const Snapshot* GetSnapshot() = 0;
+
+ // Release a previously acquired snapshot. The caller must not
+ // use "snapshot" after this call.
+ virtual void ReleaseSnapshot(const Snapshot* snapshot) = 0;
+
+ // DB implementations can export properties about their state
+ // via this method. If "property" is a valid property understood by this
+ // DB implementation, fills "*value" with its current value and returns
+ // true. Otherwise returns false.
+ //
+ //
+ // Valid property names include:
+ //
+ // "leveldb.num-files-at-level<N>" - return the number of files at level <N>,
+ // where <N> is an ASCII representation of a level number (e.g. "0").
+ // "leveldb.stats" - returns a multi-line string that describes statistics
+ // about the internal operation of the DB.
+ // "leveldb.sstables" - returns a multi-line string that describes all
+ // of the sstables that make up the db contents.
+ virtual bool GetProperty(const Slice& property, std::string* value) = 0;
+
+ // For each i in [0,n-1], store in "sizes[i]", the approximate
+ // file system space used by keys in "[range[i].start .. range[i].limit)".
+ //
+ // Note that the returned sizes measure file system space usage, so
+ // if the user data compresses by a factor of ten, the returned
+ // sizes will be one-tenth the size of the corresponding user data size.
+ //
+ // The results may not include the sizes of recently written data.
+ virtual void GetApproximateSizes(const Range* range, int n,
+ uint64_t* sizes) = 0;
+
+ // Compact the underlying storage for the key range [*begin,*end].
+ // In particular, deleted and overwritten versions are discarded,
+ // and the data is rearranged to reduce the cost of operations
+ // needed to access the data. This operation should typically only
+ // be invoked by users who understand the underlying implementation.
+ //
+ // begin==NULL is treated as a key before all keys in the database.
+ // end==NULL is treated as a key after all keys in the database.
+ // Therefore the following call will compact the entire database:
+ // db->CompactRange(NULL, NULL);
+ virtual void CompactRange(const Slice* begin, const Slice* end) = 0;
+
+ private:
+ // No copying allowed
+ DB(const DB&);
+ void operator=(const DB&);
+};
+
+// Destroy the contents of the specified database.
+// Be very careful using this method.
+Status DestroyDB(const std::string& name, const Options& options);
+
+// If a DB cannot be opened, you may attempt to call this method to
+// resurrect as much of the contents of the database as possible.
+// Some data may be lost, so be careful when calling this function
+// on a database that contains important information.
+Status RepairDB(const std::string& dbname, const Options& options);
+
+} // namespace leveldb
+
+#endif // STORAGE_LEVELDB_INCLUDE_DB_H_