Add the skeleton of a CBF indexer

blockchain/indexers/cbfindex.go

@@ -0,0 +1,111 @@
+// Copyright (c) 2017 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package indexers
+
+import (
+	"errors"
+
+	"github.com/btcsuite/btcd/blockchain"
+	"github.com/btcsuite/btcd/database"
+	"github.com/btcsuite/btcutil"
+)
+
+const (
+	// cbfIndexName is the human-readable name for the index.
+	cbfIndexName = "committed bloom filter index"
+)
+
+var (
+	// cbfIndexKey is the name of the db bucket used to house the
+	// block hash -> CBF index.
+	cbfIndexKey = []byte("cbfbyhashidx")
+
+	// errNoCBFEntry is an error that indicates a requested entry does
+	// not exist in the CBF index.
+	errCBFEntry = errors.New("no entry in the block ID index")
+)
+
+// The serialized format for keys and values in the block hash to CBF bucket is:
+//   <hash> = <CBF>
+//
+//   Field           Type              Size
+//   hash            chainhash.Hash    32 bytes
+//   CBF             []byte            variable
+//   -----
+//   Total: > 32 bytes
+
+// CBFIndex implements a CBF by hash index.
+type CBFIndex struct {
+	db database.DB
+}
+
+// Ensure the CBFIndex type implements the Indexer interface.
+var _ Indexer = (*CBFIndex)(nil)
+
+// Init initializes the hash-based CBF index.
+//
+// This is part of the Indexer interface.
+func (idx *CBFIndex) Init() error {
+	return nil
+}
+
+// Key returns the database key to use for the index as a byte slice.
+//
+// This is part of the Indexer interface.
+func (idx *CBFIndex) Key() []byte {
+	return cbfIndexKey
+}
+
+// Name returns the human-readable name of the index.
+//
+// This is part of the Indexer interface.
+func (idx *CBFIndex) Name() string {
+	return cbfIndexName
+}
+
+// Create is invoked when the indexer manager determines the index needs
+// to be created for the first time.  It creates the buckets for the hash-based
+// CBF index.
+//
+// This is part of the Indexer interface.
+func (idx *CBFIndex) Create(dbTx database.Tx) error {
+	meta := dbTx.Metadata()
+	_, err := meta.CreateBucket(cbfIndexKey)
+	return err
+}
+
+// ConnectBlock is invoked by the index manager when a new block has been
+// connected to the main chain.  This indexer adds a hash-to-CBF mapping for
+// every passed block.
+//
+// This is part of the Indexer interface.
+func (idx *CBFIndex) ConnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
+	return nil
+}
+
+// DisconnectBlock is invoked by the index manager when a block has been
+// disconnected from the main chain.  This indexer removes the hash-to-CBF
+// mapping for every passed block.
+//
+// This is part of the Indexer interface.
+func (idx *CBFIndex) DisconnectBlock(dbTx database.Tx, block *btcutil.Block, view *blockchain.UtxoViewpoint) error {
+	return nil
+}
+
+// NewCBFIndex returns a new instance of an indexer that is used to create a
+// mapping of the hashes of all blocks in the blockchain to their respective
+// committed bloom filters.
+//
+// It implements the Indexer interface which plugs into the IndexManager that in
+// turn is used by the blockchain package.  This allows the index to be
+// seamlessly maintained along with the chain.
+func NewCBFIndex(db database.DB) *CBFIndex {
+	return &CBFIndex{db: db}
+}
+
+// DropCBFIndex drops the CBF index from the provided database if exists.
+func DropCBFIndex(db database.DB) error {
+	return dropIndex(db, cbfIndexKey, cbfIndexName)
+}