multi: preallocate memory.

blockchain/chainio.go

@@ -728,7 +728,7 @@ func serializeSpendJournalEntry(stxos []spentTxOut) ([]byte, error) {
 
 	// Calculate the size needed to serialize the entire journal entry.
 	var size int
-	var sizes []int
+	sizes := make([]int, 0, len(stxos))
 	for i := range stxos {
 		sz := spentTxOutSerializeSize(&stxos[i])
 		sizes = append(sizes, sz)
@@ -762,9 +762,12 @@ func dbFetchSpendJournalEntry(dbTx database.Tx, block *dcrutil.Block) ([]spentTx
 	// Exclude the coinbase transaction since it can't spend anything.
 	spendBucket := dbTx.Metadata().Bucket(dbnamespace.SpendJournalBucketName)
 	serialized := spendBucket.Get(block.Hash()[:])
-	var blockTxns []*wire.MsgTx
-	blockTxns = append(blockTxns, block.MsgBlock().STransactions...)
-	blockTxns = append(blockTxns, block.MsgBlock().Transactions[1:]...)
+	msgBlock := block.MsgBlock()
+
+	blockTxns := make([]*wire.MsgTx, 0, len(msgBlock.STransactions)+
+		len(msgBlock.Transactions[1:]))
+	blockTxns = append(blockTxns, msgBlock.STransactions...)
+	blockTxns = append(blockTxns, msgBlock.Transactions[1:]...)
 	if len(blockTxns) > 0 && len(serialized) == 0 {
 		panicf("missing spend journal data for %s", block.Hash())
 	}

blockchain/merkle.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013-2016 The btcsuite developers
-// Copyright (c) 2015-2016 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 

blockchain/stake/internal/ticketdb/chainio.go

@@ -244,13 +244,21 @@ type BestChainState struct {
 }
 
 // serializeBestChainState returns the serialization of the passed block best
-// chain state.  This is data to be stored in the chain state bucket. This
-// function will panic if the number of tickets per block is less than the
+// chain state.  This is data to be stored in the chain state bucket.
+// This function will panic if the number of tickets per block is less than the
 // size of next winners, which should never happen unless there is memory
 // corruption.
 func serializeBestChainState(state BestChainState) []byte {
+	if int(state.PerBlock) < len(state.NextWinners) {
+		errStr := fmt.Sprintf("PerBlock:%d < NextWinners:%d",
+			state.PerBlock, len(state.NextWinners))
+		panic(errStr)
+	}
+
+	serializedDataLen := minimumBestChainStateSize +
+		(chainhash.HashSize * int(state.PerBlock))
 	// Serialize the chain state.
-	serializedData := make([]byte, minimumBestChainStateSize)
+	serializedData := make([]byte, serializedDataLen)
 
 	offset := 0
 	copy(serializedData[offset:offset+chainhash.HashSize], state.Hash[:])
@@ -267,8 +275,6 @@ func serializeBestChainState(state BestChainState) []byte {
 	offset += 2
 
 	// Serialize the next winners.
-	ticketBuffer := make([]byte, chainhash.HashSize*int(state.PerBlock))
-	serializedData = append(serializedData, ticketBuffer...)
 	for i := range state.NextWinners {
 		copy(serializedData[offset:offset+chainhash.HashSize],
 			state.NextWinners[i][:])

blockmanager.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013-2016 The btcsuite developers
-// Copyright (c) 2015-2018 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -688,13 +688,6 @@ func (b *blockManager) current() bool {
 // access through the block mananger. All template access must also be routed
 // through the block manager.
 func (b *blockManager) checkBlockForHiddenVotes(block *dcrutil.Block) {
-	var votesFromBlock []*dcrutil.Tx
-	for _, stx := range block.STransactions() {
-		if stake.IsSSGen(stx.MsgTx()) {
-			votesFromBlock = append(votesFromBlock, stx)
-		}
-	}
-
 	// Identify the cached parent template; it's possible that
 	// the parent template hasn't yet been updated, so we may
 	// need to use the current template.
@@ -728,6 +721,14 @@ func (b *blockManager) checkBlockForHiddenVotes(block *dcrutil.Block) {
 		return
 	}
 
+	votesFromBlock := make([]*dcrutil.Tx, 0,
+		activeNetParams.TicketsPerBlock)
+	for _, stx := range block.STransactions() {
+		if stake.IsSSGen(stx.MsgTx()) {
+			votesFromBlock = append(votesFromBlock, stx)
+		}
+	}
+
 	// Now that we have the template, grab the votes and compare
 	// them with those found in the newly added block. If we don't
 	// the votes, they will need to be added to our block template.
@@ -791,7 +792,7 @@ func (b *blockManager) checkBlockForHiddenVotes(block *dcrutil.Block) {
 	// calculated.
 	template.Block.ClearSTransactions()
 	updatedTxTreeStake := make([]*dcrutil.Tx, 0,
-		votesTotal+len(oldTickets)+len(oldRevocations))
+		len(newVotes)+len(oldTickets)+len(oldRevocations))
 	for _, vote := range newVotes {
 		updatedTxTreeStake = append(updatedTxTreeStake, vote)
 		template.Block.AddSTransaction(vote.MsgTx())
@@ -837,7 +838,8 @@ func (b *blockManager) checkBlockForHiddenVotes(block *dcrutil.Block) {
 
 	// Patch the header. First, reconstruct the merkle trees, then
 	// correct the number of voters, and finally recalculate the size.
-	var updatedTxTreeRegular []*dcrutil.Tx
+	updatedTxTreeRegular := make([]*dcrutil.Tx, 0,
+		len(template.Block.Transactions))
 	updatedTxTreeRegular = append(updatedTxTreeRegular, coinbase)
 	for i, mtx := range template.Block.Transactions {
 		// Coinbase

dcrec/edwards/curve_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2015-2016 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -196,7 +196,7 @@ type ScalarMultVector struct {
 
 func testVectorsScalarMult() []ScalarMultVector {
 	tvsmh := testVectorsScalarMultHex()
-	var tvsms []ScalarMultVector
+	tvsms := make([]ScalarMultVector, 0, len(tvsmh))
 	for _, v := range tvsmh {
 		bIn, _ := hex.DecodeString(v.bIn)
 		s, _ := hex.DecodeString(v.s)

dcrec/secp256k1/schnorr/ecdsa_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2015-2016 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -93,7 +93,7 @@ type SchorrSigningTestVector struct {
 }
 
 func GetSigningTestVectors() []*SchorrSigningTestVector {
-	var tvs []*SchorrSigningTestVector
+	tvs := make([]*SchorrSigningTestVector, 0, len(schnorrSigningTestVectors))
 	for _, v := range schnorrSigningTestVectors {
 		msg, _ := hex.DecodeString(v.msg)
 		nonce, _ := hex.DecodeString(v.nonce)

dcrec/secp256k1/schnorr/threshold_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2015-2016 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -177,7 +177,7 @@ type ThresholdTestVector struct {
 }
 
 func GetThresholdTestVectors() []*ThresholdTestVector {
-	var tvs []*ThresholdTestVector
+	tvs := make([]*ThresholdTestVector, 0, len(thresholdTestVectorsHex))
 	for _, v := range thresholdTestVectorsHex {
 		msg, _ := hex.DecodeString(v.msg)
 		combSig, _ := hex.DecodeString(v.combinedSignature)

dcrjson/parse_test.go

@@ -60,7 +60,7 @@ func TestDecodeConcatenatedHashes(t *testing.T) {
 		decodeHash("000000000000437482b6d47f82f374cde539440ddb108b0a76886f0d87d126b9"),
 		decodeHash("000000000000c41019872ff7db8fd2e9bfa05f42d3f8fee8e895e8c1e5b8dcba"),
 	}
-	var concatenatedHashBytes []byte
+	concatenatedHashBytes := make([]byte, 0, len(testHashes))
 	for _, h := range testHashes {
 		concatenatedHashBytes = append(concatenatedHashBytes, h[:]...)
 	}

dcrutil/address.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013, 2014 The btcsuite developers
-// Copyright (c) 2015-2018 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 

rpcwebsocket.go

@@ -921,7 +921,7 @@ func (m *wsNotificationManager) UnregisterStakeDifficulty(wsc *wsClient) {
 // maturing ticket updates.
 func (*wsNotificationManager) notifyNewTickets(clients map[chan struct{}]*wsClient, tnd *blockchain.TicketNotificationsData) {
 	// Create a ticket map to export as JSON.
-	var tickets []string
+	tickets := make([]string, 0, len(tnd.TicketsNew))
 	for _, h := range tnd.TicketsNew {
 		tickets = append(tickets, h.String())
 	}