Optimize rescan.

This change adds rescan fast paths for all current implementations of
the btcutil.Address interface.  Rather than encoding a payment address
string from a txout script, the minimum number of bytes (which depends
on the address type) are copied into a stack array and used as a
lookup key to a map exclusive for that address type.  This performs
better than the previous implementation due to avoiding the base58
encoding and generating less garbage (so each GC cycle completes
faster).

If the address type switch falls into the default (unhandled) case,
the encoded payment address is used as a fallback.  This keeps the
intended rescan behavior even when new implementations of
btcutil.Address are added without a rescan fast path.

Benchmarks indicate that when a fast path is followed, for 20 byte
RIPEMD-160 hashes (such as P2PKH and P2SH), skipping the payment
address encoding (and thus bypassing the base58 encoding code) can
result in map lookups up to 60x faster.

rpcwebsocket.go

@@ -6,6 +6,7 @@ package main
 
 import (
 	"bytes"
+	"code.google.com/p/go.crypto/ripemd160"
 	"code.google.com/p/go.net/websocket"
 	"container/list"
 	"crypto/sha256"
@@ -1431,10 +1432,24 @@ func handleNotifyNewTXs(wsc *wsClient, icmd btcjson.Cmd) (interface{}, *btcjson.
 	return nil, nil
 }
 
+type rescanKeys struct {
+	fallbacks           map[string]struct{}
+	pubKeyHashes        map[[ripemd160.Size]byte]struct{}
+	scriptHashes        map[[ripemd160.Size]byte]struct{}
+	compressedPubkeys   map[[33]byte]struct{}
+	uncompressedPubkeys map[[65]byte]struct{}
+	unspent             map[btcwire.OutPoint]struct{}
+}
+
 // rescanBlock rescans all transactions in a single block.  This is a helper
 // function for handleRescan.
-func rescanBlock(wsc *wsClient, cmd *btcws.RescanCmd, blk *btcutil.Block,
+func rescanBlock(wsc *wsClient, lookups *rescanKeys, blk *btcutil.Block) {
-	unspent map[btcwire.OutPoint]struct{}) {
+	// Vars used for map keys.  The item being checked is copied into
+	// these and then used as the lookup key.  Saves on GC.
+	var ripemd160Hash [ripemd160.Size]byte
+	var compressedPubkey [33]byte
+	var uncompressedPubkey [65]byte
+	var outpoint btcwire.OutPoint
 
 	for _, tx := range blk.Transactions() {
 		// Hexadecimal representation of this tx.  Only created if
@@ -1449,8 +1464,8 @@ func rescanBlock(wsc *wsClient, cmd *btcws.RescanCmd, blk *btcutil.Block,
 		recvNotified := false
 
 		for _, txin := range tx.MsgTx().TxIn {
-			if _, ok := unspent[txin.PreviousOutpoint]; ok {
+			if _, ok := lookups.unspent[txin.PreviousOutpoint]; ok {
-				delete(unspent, txin.PreviousOutpoint)
+				delete(lookups.unspent, txin.PreviousOutpoint)
 
 				if spentNotified {
 					continue
@@ -1480,12 +1495,53 @@ func rescanBlock(wsc *wsClient, cmd *btcws.RescanCmd, blk *btcutil.Block,
 				txout.PkScript, wsc.server.server.btcnet)
 
 			for _, addr := range addrs {
-				encodedAddr := addr.EncodeAddress()
+				switch a := addr.(type) {
-				if _, ok := cmd.Addresses[encodedAddr]; !ok {
+				case *btcutil.AddressPubKeyHash:
+					copy(ripemd160Hash[:], a.ScriptAddress())
+					if _, ok := lookups.pubKeyHashes[ripemd160Hash]; !ok {
 						continue
 					}
 
-				unspent[*btcwire.NewOutPoint(tx.Sha(), uint32(txOutIdx))] = struct{}{}
+				case *btcutil.AddressScriptHash:
+					copy(ripemd160Hash[:], a.ScriptAddress())
+					if _, ok := lookups.scriptHashes[ripemd160Hash]; !ok {
+						continue
+					}
+
+				case *btcutil.AddressPubKey:
+					pubkeyBytes := a.ScriptAddress()
+					switch len(pubkeyBytes) {
+					case 33: // Compressed
+						copy(compressedPubkey[:], pubkeyBytes)
+						_, ok := lookups.compressedPubkeys[compressedPubkey]
+						if !ok {
+							continue
+						}
+
+					case 65: // Uncompressed
+						copy(uncompressedPubkey[:], pubkeyBytes)
+						_, ok := lookups.uncompressedPubkeys[uncompressedPubkey]
+						if !ok {
+							continue
+						}
+
+					default: // wtf
+						continue
+					}
+
+				default:
+					// A new address type must have been added.  Encode as a
+					// payment address string and check the fallback map.
+					addrStr := addr.EncodeAddress()
+					_, ok := lookups.fallbacks[addrStr]
+					if !ok {
+						continue
+					}
+				}
+
+				copy(outpoint.Hash[:], tx.Sha()[:])
+				outpoint.Index = uint32(txOutIdx)
+				lookups.unspent[outpoint] = struct{}{}
 
 				if recvNotified {
 					continue
@@ -1529,9 +1585,65 @@ func handleRescan(wsc *wsClient, icmd btcjson.Cmd) (interface{}, *btcjson.Error)
 		rpcsLog.Infof("Beginning rescan for %d addresses", numAddrs)
 	}
 
+	// Build lookup maps.
+	lookups := rescanKeys{
+		fallbacks:           map[string]struct{}{},
+		pubKeyHashes:        map[[ripemd160.Size]byte]struct{}{},
+		scriptHashes:        map[[ripemd160.Size]byte]struct{}{},
+		compressedPubkeys:   map[[33]byte]struct{}{},
+		uncompressedPubkeys: map[[65]byte]struct{}{},
+		unspent:             map[btcwire.OutPoint]struct{}{},
+	}
+	var ripemd160Hash [ripemd160.Size]byte
+	var compressedPubkey [33]byte
+	var uncompressedPubkey [65]byte
+	for addrStr := range cmd.Addresses {
+		addr, err := btcutil.DecodeAddress(addrStr, activeNetParams.btcnet)
+		if err != nil {
+			jsonErr := btcjson.Error{
+				Code:    btcjson.ErrInvalidAddressOrKey.Code,
+				Message: "Rescan address " + addrStr + ": " + err.Error(),
+			}
+			return nil, &jsonErr
+		}
+		switch a := addr.(type) {
+		case *btcutil.AddressPubKeyHash:
+			copy(ripemd160Hash[:], a.ScriptAddress())
+			lookups.pubKeyHashes[ripemd160Hash] = struct{}{}
+
+		case *btcutil.AddressScriptHash:
+			copy(ripemd160Hash[:], a.ScriptAddress())
+			lookups.scriptHashes[ripemd160Hash] = struct{}{}
+
+		case *btcutil.AddressPubKey:
+			pubkeyBytes := a.ScriptAddress()
+			switch len(pubkeyBytes) {
+			case 33: // Compressed
+				copy(compressedPubkey[:], pubkeyBytes)
+				lookups.compressedPubkeys[compressedPubkey] = struct{}{}
+
+			case 65: // Uncompressed
+				copy(uncompressedPubkey[:], pubkeyBytes)
+				lookups.uncompressedPubkeys[uncompressedPubkey] = struct{}{}
+
+			default:
+				jsonErr := btcjson.Error{
+					Code:    btcjson.ErrInvalidAddressOrKey.Code,
+					Message: "Pubkey " + addrStr + " is of unknown length",
+				}
+				return nil, &jsonErr
+			}
+
+		default:
+			// A new address type must have been added.  Use encoded
+			// payment address string as a fallback until a fast path
+			// is added.
+			lookups.fallbacks[addrStr] = struct{}{}
+		}
+	}
+
 	minBlock := int64(cmd.BeginBlock)
 	maxBlock := int64(cmd.EndBlock)
-	unspent := make(map[btcwire.OutPoint]struct{})
 
 	// FetchHeightRange may not return a complete list of block shas for
 	// the given range, so fetch range as many times as necessary.
@@ -1561,7 +1673,7 @@ func handleRescan(wsc *wsClient, icmd btcjson.Cmd) (interface{}, *btcjson.Error)
 					blk.Height())
 				return nil, nil
 			default:
-				rescanBlock(wsc, cmd, blk, unspent)
+				rescanBlock(wsc, &lookups, blk)
 			}
 		}