Initial commit

vendor/github.com/cockroachdb/pebble/internal/base/options.go

@@ -0,0 +1,76 @@
+// Copyright 2011 The LevelDB-Go and Pebble Authors. All rights reserved. Use
+// of this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+
+package base
+
+// SSTable block defaults.
+const (
+	DefaultBlockRestartInterval = 16
+	DefaultBlockSize            = 4096
+	DefaultBlockSizeThreshold   = 90
+)
+
+// FilterType is the level at which to apply a filter: block or table.
+type FilterType int
+
+// The available filter types.
+const (
+	TableFilter FilterType = iota
+)
+
+func (t FilterType) String() string {
+	switch t {
+	case TableFilter:
+		return "table"
+	}
+	return "unknown"
+}
+
+// FilterWriter provides an interface for creating filter blocks. See
+// FilterPolicy for more details about filters.
+type FilterWriter interface {
+	// AddKey adds a key to the current filter block.
+	AddKey(key []byte)
+
+	// Finish appends to dst an encoded filter tha holds the current set of
+	// keys. The writer state is reset after the call to Finish allowing the
+	// writer to be reused for the creation of additional filters.
+	Finish(dst []byte) []byte
+}
+
+// FilterPolicy is an algorithm for probabilistically encoding a set of keys.
+// The canonical implementation is a Bloom filter.
+//
+// Every FilterPolicy has a name. This names the algorithm itself, not any one
+// particular instance. Aspects specific to a particular instance, such as the
+// set of keys or any other parameters, will be encoded in the []byte filter
+// returned by NewWriter.
+//
+// The name may be written to files on disk, along with the filter data. To use
+// these filters, the FilterPolicy name at the time of writing must equal the
+// name at the time of reading. If they do not match, the filters will be
+// ignored, which will not affect correctness but may affect performance.
+type FilterPolicy interface {
+	// Name names the filter policy.
+	Name() string
+
+	// MayContain returns whether the encoded filter may contain given key.
+	// False positives are possible, where it returns true for keys not in the
+	// original set.
+	MayContain(ftype FilterType, filter, key []byte) bool
+
+	// NewWriter creates a new FilterWriter.
+	NewWriter(ftype FilterType) FilterWriter
+}
+
+// BlockPropertyFilter is used in an Iterator to filter sstables and blocks
+// within the sstable. It should not maintain any per-sstable state, and must
+// be thread-safe.
+type BlockPropertyFilter interface {
+	// Name returns the name of the block property collector.
+	Name() string
+	// Intersects returns true if the set represented by prop intersects with
+	// the set in the filter.
+	Intersects(prop []byte) (bool, error)
+}