Implement String for OutPoint.

msgtx.go

@@ -9,6 +9,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"strconv"
 )
 
 const (
@@ -75,6 +76,21 @@ func NewOutPoint(hash *ShaHash, index uint32) *OutPoint {
 	}
 }
 
+// String returns the OutPoint in the human-readable form "hash:index".
+func (o OutPoint) String() string {
+	// Allocate enough for hash string, colon, and 10 digits.  Although
+	// at the time of writing, the number of digits can be no greater than
+	// the length of the decimal representation of maxTxOutPerMessage, the
+	// maximum message payload may increase in the future and this
+	// optimization may go unnoticed, so allocate space for 10 decimal
+	// digits, which will fit any uint32.
+	buf := make([]byte, 2*HashSize+1, 2*HashSize+1+10)
+	copy(buf, o.Hash.String())
+	buf[2*HashSize] = ':'
+	buf = strconv.AppendUint(buf, uint64(o.Index), 10)
+	return string(buf)
+}
+
 // TxIn defines a bitcoin transaction input.
 type TxIn struct {
 	PreviousOutPoint OutPoint

msgtx_test.go

@@ -6,6 +6,7 @@ package btcwire_test
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"reflect"
 	"testing"
@@ -44,6 +45,8 @@ func TestTx(t *testing.T) {
 	}
 
 	// Ensure we get the same transaction output point data back out.
+	// NOTE: This is a block hash and made up index, but we're only
+	// testing package functionality.
 	prevOutIndex := uint32(1)
 	prevOut := btcwire.NewOutPoint(hash, prevOutIndex)
 	if !prevOut.Hash.IsEqual(hash) {
@@ -54,6 +57,11 @@ func TestTx(t *testing.T) {
 		t.Errorf("NewOutPoint: wrong index - got %v, want %v",
 			prevOut.Index, prevOutIndex)
 	}
+	prevOutStr := fmt.Sprintf("%s:%d", hash.String(), prevOutIndex)
+	if s := prevOut.String(); s != prevOutStr {
+		t.Errorf("OutPoint.String: unexpected result - got %v, "+
+			"want %v", s, prevOutStr)
+	}
 
 	// Ensure we get the same transaction input back out.
 	sigScript := []byte{0x04, 0x31, 0xdc, 0x00, 0x1b, 0x01, 0x62}