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Diffstat (limited to 'Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/filter/filter.go')
-rw-r--r-- | Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/filter/filter.go | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/filter/filter.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/filter/filter.go new file mode 100644 index 000000000..7a925c5a8 --- /dev/null +++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/filter/filter.go @@ -0,0 +1,60 @@ +// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com> +// All rights reserved. +// +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +// Package filter provides interface and implementation of probabilistic +// data structure. +// +// The filter is resposible for creating small filter from a set of keys. +// These filter will then used to test whether a key is a member of the set. +// In many cases, a filter can cut down the number of disk seeks from a +// handful to a single disk seek per DB.Get call. +package filter + +// Buffer is the interface that wraps basic Alloc, Write and WriteByte methods. +type Buffer interface { + // Alloc allocs n bytes of slice from the buffer. This also advancing + // write offset. + Alloc(n int) []byte + + // Write appends the contents of p to the buffer. + Write(p []byte) (n int, err error) + + // WriteByte appends the byte c to the buffer. + WriteByte(c byte) error +} + +// Filter is the filter. +type Filter interface { + // Name returns the name of this policy. + // + // Note that if the filter encoding changes in an incompatible way, + // the name returned by this method must be changed. Otherwise, old + // incompatible filters may be passed to methods of this type. + Name() string + + // NewGenerator creates a new filter generator. + NewGenerator() FilterGenerator + + // Contains returns true if the filter contains the given key. + // + // The filter are filters generated by the filter generator. + Contains(filter, key []byte) bool +} + +// FilterGenerator is the filter generator. +type FilterGenerator interface { + // Add adds a key to the filter generator. + // + // The key may become invalid after call to this method end, therefor + // key must be copied if implementation require keeping key for later + // use. The key should not modified directly, doing so may cause + // undefined results. + Add(key []byte) + + // Generate generates filters based on keys passed so far. After call + // to Generate the filter generator maybe resetted, depends on implementation. + Generate(b Buffer) +} |