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36a5f8ed7f
- Replace raw slice comparison with a call to user comparator.
Added test for custom comparators.
- Fix end of namespace comments.
- Fixed bug in picking inputs for a level-0 compaction.
When finding overlapping files, the covered range may expand
as files are added to the input set. We now correctly expand
the range when this happens instead of continuing to use the
old range. For example, suppose L0 contains files with the
following ranges:
F1: a .. d
F2: c .. g
F3: f .. j
and the initial compaction target is F3. We used to search
for range f..j which yielded {F2,F3}. However we now expand
the range as soon as another file is added. In this case,
when F2 is added, we expand the range to c..j and restart the
search. That picks up file F1 as well.
This change fixes a bug related to deleted keys showing up
incorrectly after a compaction as described in Issue 44.
(Sync with upstream @25072954)
100 lines
3.5 KiB
C++
100 lines
3.5 KiB
C++
// 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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//
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// A Cache is an interface that maps keys to values. It has internal
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// synchronization and may be safely accessed concurrently from
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// multiple threads. It may automatically evict entries to make room
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// for new entries. Values have a specified charge against the cache
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// capacity. For example, a cache where the values are variable
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// length strings, may use the length of the string as the charge for
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// the string.
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//
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// A builtin cache implementation with a least-recently-used eviction
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// policy is provided. Clients may use their own implementations if
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// they want something more sophisticated (like scan-resistance, a
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// custom eviction policy, variable cache sizing, etc.)
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#ifndef STORAGE_LEVELDB_INCLUDE_CACHE_H_
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#define STORAGE_LEVELDB_INCLUDE_CACHE_H_
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#include <stdint.h>
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#include "leveldb/slice.h"
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namespace leveldb {
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class Cache;
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// Create a new cache with a fixed size capacity. This implementation
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// of Cache uses a least-recently-used eviction policy.
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extern Cache* NewLRUCache(size_t capacity);
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class Cache {
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public:
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Cache() { }
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// Destroys all existing entries by calling the "deleter"
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// function that was passed to the constructor.
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virtual ~Cache();
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// Opaque handle to an entry stored in the cache.
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struct Handle { };
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// Insert a mapping from key->value into the cache and assign it
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// the specified charge against the total cache capacity.
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//
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// Returns a handle that corresponds to the mapping. The caller
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// must call this->Release(handle) when the returned mapping is no
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// longer needed.
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//
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// When the inserted entry is no longer needed, the key and
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// value will be passed to "deleter".
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virtual Handle* Insert(const Slice& key, void* value, size_t charge,
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void (*deleter)(const Slice& key, void* value)) = 0;
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// If the cache has no mapping for "key", returns NULL.
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//
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// Else return a handle that corresponds to the mapping. The caller
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// must call this->Release(handle) when the returned mapping is no
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// longer needed.
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virtual Handle* Lookup(const Slice& key) = 0;
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// Release a mapping returned by a previous Lookup().
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// REQUIRES: handle must not have been released yet.
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// REQUIRES: handle must have been returned by a method on *this.
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virtual void Release(Handle* handle) = 0;
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// Return the value encapsulated in a handle returned by a
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// successful Lookup().
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// REQUIRES: handle must not have been released yet.
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// REQUIRES: handle must have been returned by a method on *this.
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virtual void* Value(Handle* handle) = 0;
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// If the cache contains entry for key, erase it. Note that the
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// underlying entry will be kept around until all existing handles
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// to it have been released.
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virtual void Erase(const Slice& key) = 0;
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// Return a new numeric id. May be used by multiple clients who are
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// sharing the same cache to partition the key space. Typically the
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// client will allocate a new id at startup and prepend the id to
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// its cache keys.
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virtual uint64_t NewId() = 0;
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private:
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void LRU_Remove(Handle* e);
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void LRU_Append(Handle* e);
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void Unref(Handle* e);
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struct Rep;
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Rep* rep_;
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// No copying allowed
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Cache(const Cache&);
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void operator=(const Cache&);
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_UTIL_CACHE_H_
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