From 9b7e3527b0a87c6b0d353ff45642cb560d2440d1 Mon Sep 17 00:00:00 2001
From: Dave Collins <davec@conformal.com>
Date: Wed, 6 Nov 2013 18:41:41 -0600
Subject: [PATCH] Optimize transaction Deserialize.

The benchmark results for the current commit:

Before: BenchmarkDeserializeTx    500000              4018 ns/op
After:  BenchmarkDeserializeTx    500000              3780 ns/op

The cumulative benchmark results since commit b7b700fd5aebb86addc93efecaa367a2f4976058:

Before: BenchmarkDeserializeTx    200000             10665 ns/op
After:  BenchmarkDeserializeTx    500000              3780 ns/op

This is part of the ongoing effort to optimize serialization as noted in
conformal/btcd#27.
---
 msgtx.go | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/msgtx.go b/msgtx.go
index 1c73b833..7e0ac38b 100644
--- a/msgtx.go
+++ b/msgtx.go
@@ -229,10 +229,12 @@ func (tx *MsgTx) Copy() *MsgTx {
 // See Deserialize for decoding transactions stored to disk, such as in a
 // database, as opposed to decoding transactions from the wire.
 func (msg *MsgTx) BtcDecode(r io.Reader, pver uint32) error {
-	err := readElement(r, &msg.Version)
+	buf := make([]byte, 4)
+	_, err := io.ReadFull(r, buf)
 	if err != nil {
 		return err
 	}
+	msg.Version = binary.LittleEndian.Uint32(buf)
 
 	count, err := readVarInt(r, pver)
 	if err != nil {
@@ -249,14 +251,14 @@ func (msg *MsgTx) BtcDecode(r io.Reader, pver uint32) error {
 		return messageError("MsgTx.BtcDecode", str)
 	}
 
-	msg.TxIn = make([]*TxIn, 0, count)
+	msg.TxIn = make([]*TxIn, count)
 	for i := uint64(0); i < count; i++ {
 		ti := TxIn{}
 		err = readTxIn(r, pver, msg.Version, &ti)
 		if err != nil {
 			return err
 		}
-		msg.TxIn = append(msg.TxIn, &ti)
+		msg.TxIn[i] = &ti
 	}
 
 	count, err = readVarInt(r, pver)
@@ -274,20 +276,21 @@ func (msg *MsgTx) BtcDecode(r io.Reader, pver uint32) error {
 		return messageError("MsgTx.BtcDecode", str)
 	}
 
-	msg.TxOut = make([]*TxOut, 0, count)
+	msg.TxOut = make([]*TxOut, count)
 	for i := uint64(0); i < count; i++ {
 		to := TxOut{}
 		err = readTxOut(r, pver, msg.Version, &to)
 		if err != nil {
 			return err
 		}
-		msg.TxOut = append(msg.TxOut, &to)
+		msg.TxOut[i] = &to
 	}
 
-	err = readElement(r, &msg.LockTime)
+	_, err = io.ReadFull(r, buf)
 	if err != nil {
 		return err
 	}
+	msg.LockTime = binary.LittleEndian.Uint32(buf)
 
 	return nil
 }