From a5f702c41dd243a33e769b5211a2eda0a9d36124 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 29 Apr 2017 13:21:25 -0500
Subject: [PATCH] Reduce allocs and copies

---
 messages.go | 14 ++++++++++++++
 values.go   | 27 ++++++++++++---------------
 2 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/messages.go b/messages.go
index e229367a..0f17a6d2 100644
--- a/messages.go
+++ b/messages.go
@@ -118,6 +118,20 @@ func (wb *WriteBuf) closeMsg() {
 	binary.BigEndian.PutUint32(wb.buf[wb.sizeIdx:wb.sizeIdx+4], uint32(len(wb.buf)-wb.sizeIdx))
 }
 
+func (wb *WriteBuf) reserveSize() int {
+	sizePosition := len(wb.buf)
+	wb.buf = append(wb.buf, 0, 0, 0, 0)
+	return sizePosition
+}
+
+func (wb *WriteBuf) setComputedSize(sizePosition int) {
+	binary.BigEndian.PutUint32(wb.buf[sizePosition:], uint32(len(wb.buf)-sizePosition-4))
+}
+
+func (wb *WriteBuf) setSize(sizePosition int, size int32) {
+	binary.BigEndian.PutUint32(wb.buf[sizePosition:], uint32(size))
+}
+
 func (wb *WriteBuf) WriteByte(b byte) {
 	wb.buf = append(wb.buf, b)
 }
diff --git a/values.go b/values.go
index 3565df34..da12952a 100644
--- a/values.go
+++ b/values.go
@@ -106,29 +106,27 @@ func encodePreparedStatementArgument(wbuf *WriteBuf, oid pgtype.Oid, arg interfa
 
 	switch arg := arg.(type) {
 	case pgtype.BinaryEncoder:
-		buf := &bytes.Buffer{}
-		null, err := arg.EncodeBinary(wbuf.conn.ConnInfo, buf)
+		sp := wbuf.reserveSize()
+		null, err := arg.EncodeBinary(wbuf.conn.ConnInfo, wbuf)
 		if err != nil {
 			return err
 		}
 		if null {
-			wbuf.WriteInt32(-1)
+			wbuf.setSize(sp, -1)
 		} else {
-			wbuf.WriteInt32(int32(buf.Len()))
-			wbuf.WriteBytes(buf.Bytes())
+			wbuf.setComputedSize(sp)
 		}
 		return nil
 	case pgtype.TextEncoder:
-		buf := &bytes.Buffer{}
-		null, err := arg.EncodeText(wbuf.conn.ConnInfo, buf)
+		sp := wbuf.reserveSize()
+		null, err := arg.EncodeText(wbuf.conn.ConnInfo, wbuf)
 		if err != nil {
 			return err
 		}
 		if null {
-			wbuf.WriteInt32(-1)
+			wbuf.setSize(sp, -1)
 		} else {
-			wbuf.WriteInt32(int32(buf.Len()))
-			wbuf.WriteBytes(buf.Bytes())
+			wbuf.setComputedSize(sp)
 		}
 		return nil
 	case driver.Valuer:
@@ -161,16 +159,15 @@ func encodePreparedStatementArgument(wbuf *WriteBuf, oid pgtype.Oid, arg interfa
 			return err
 		}
 
-		buf := &bytes.Buffer{}
-		null, err := value.(pgtype.BinaryEncoder).EncodeBinary(wbuf.conn.ConnInfo, buf)
+		sp := wbuf.reserveSize()
+		null, err := value.(pgtype.BinaryEncoder).EncodeBinary(wbuf.conn.ConnInfo, wbuf)
 		if err != nil {
 			return err
 		}
 		if null {
-			wbuf.WriteInt32(-1)
+			wbuf.setSize(sp, -1)
 		} else {
-			wbuf.WriteInt32(int32(buf.Len()))
-			wbuf.WriteBytes(buf.Bytes())
+			wbuf.setComputedSize(sp)
 		}
 		return nil
 	}