From ddf24e642795181d818ff0e452aa72ae4aa13e0f Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Tue, 22 Oct 2013 10:54:55 +0200
Subject: [PATCH 1/9] use the connection buffer for writing

---
 benchmark_test.go |   7 +-
 buffer.go         |  51 +++++-
 packets.go        | 390 +++++++++++++++++++++++++++-------------------
 3 files changed, 281 insertions(+), 167 deletions(-)

diff --git a/benchmark_test.go b/benchmark_test.go
index 2fb3f6b2b..67ce9c547 100644
--- a/benchmark_test.go
+++ b/benchmark_test.go
@@ -69,23 +69,26 @@ func BenchmarkQuery(b *testing.B) {
 
 	stmt := tb.checkStmt(db.Prepare("SELECT val FROM foo WHERE id=?"))
 	defer stmt.Close()
-	b.StartTimer()
 
 	remain := int64(b.N)
 	var wg sync.WaitGroup
 	wg.Add(concurrencyLevel)
 	defer wg.Wait()
+	b.StartTimer()
+
 	for i := 0; i < concurrencyLevel; i++ {
 		go func() {
-			defer wg.Done()
 			for {
 				if atomic.AddInt64(&remain, -1) < 0 {
+					wg.Done()
 					return
 				}
+
 				var got string
 				tb.check(stmt.QueryRow(1).Scan(&got))
 				if got != "one" {
 					b.Errorf("query = %q; want one", got)
+					wg.Done()
 					return
 				}
 			}
diff --git a/buffer.go b/buffer.go
index d6c8b72e4..e47cdf455 100644
--- a/buffer.go
+++ b/buffer.go
@@ -12,7 +12,10 @@ import "io"
 
 const defaultBufSize = 4096
 
-// A read buffer similar to bufio.Reader but zero-copy-ish
+// A buffer which is used for both reading and writing.
+// This is possible since communication on each connection is synchronous.
+// In other words, we can't write and read simultaneously on the same connection.
+// The buffer is similar to bufio.Reader / Writer but zero-copy-ish
 // Also highly optimized for this particular use case.
 type buffer struct {
 	buf    []byte
@@ -37,8 +40,11 @@ func (b *buffer) fill(need int) (err error) {
 	}
 
 	// grow buffer if necessary
+	// TODO: let the buffer shrink again at some point
+	//       Maybe keep the org buf slice and swap back?
 	if need > len(b.buf) {
-		newBuf := make([]byte, need)
+		// Round up to the next multiple of the default size
+		newBuf := make([]byte, ((need/defaultBufSize)+1)*defaultBufSize)
 		copy(newBuf, b.buf)
 		b.buf = newBuf
 	}
@@ -74,3 +80,44 @@ func (b *buffer) readNext(need int) (p []byte, err error) {
 	b.length -= need
 	return
 }
+
+// returns a buffer with the requested size.
+// If possible, a slice from the existing buffer is returned.
+// Otherwise a bigger buffer is made.
+// Only one buffer (total) can be used at a time.
+func (b *buffer) writeBuffer(length int) []byte {
+	if b.length > 0 {
+		return nil
+	}
+
+	// test (cheap) general case first
+	if length <= defaultBufSize || length <= cap(b.buf) {
+		return b.buf[:length]
+	}
+
+	if length < maxPacketSize {
+		b.buf = make([]byte, length)
+		return b.buf
+	}
+	return make([]byte, length)
+}
+
+// shortcut which can be used if the requested buffer is guaranteed to be
+// smaller than defaultBufSize
+// Only one buffer (total) can be used at a time.
+func (b *buffer) smallWriteBuffer(length int) []byte {
+	if b.length == 0 {
+		return b.buf[:length]
+	}
+	return nil
+}
+
+// takeCompleteBuffer returns the complete existing buffer.
+// This can be used if the necessary buffer size is unknown.
+// Only one buffer (total) can be used at a time.
+func (b *buffer) takeCompleteBuffer() []byte {
+	if b.length == 0 {
+		return b.buf
+	}
+	return nil
+}
diff --git a/packets.go b/packets.go
index 9b4c99e8e..d30f644e6 100644
--- a/packets.go
+++ b/packets.go
@@ -239,8 +239,13 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 		pktLen += n + 1
 	}
 
-	// Calculate packet length and make buffer with that size
-	data := make([]byte, pktLen+4)
+	// Calculate packet length and get buffer with that size
+	data := mc.buf.smallWriteBuffer(pktLen + 4)
+	if data == nil {
+		// can not take the buffer. Something must be wrong with the connection
+		errLog.Print("Busy buffer")
+		return driver.ErrBadConn
+	}
 
 	// ClientFlags [32 bit]
 	data[4] = byte(clientFlags)
@@ -249,10 +254,10 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	data[7] = byte(clientFlags >> 24)
 
 	// MaxPacketSize [32 bit] (none)
-	//data[8] = 0x00
-	//data[9] = 0x00
-	//data[10] = 0x00
-	//data[11] = 0x00
+	data[8] = 0x00
+	data[9] = 0x00
+	data[10] = 0x00
+	data[11] = 0x00
 
 	// Charset [1 byte]
 	data[12] = collation_utf8_general_ci
@@ -293,7 +298,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	if len(mc.cfg.user) > 0 {
 		pos += copy(data[pos:], mc.cfg.user)
 	}
-	//data[pos] = 0x00
+	data[pos] = 0x00
 	pos++
 
 	// ScrambleBuffer [length encoded integer]
@@ -303,7 +308,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	// Databasename [null terminated string]
 	if len(mc.cfg.dbname) > 0 {
 		pos += copy(data[pos:], mc.cfg.dbname)
-		//data[pos] = 0x00
+		data[pos] = 0x00
 	}
 
 	// Send Auth packet
@@ -318,7 +323,12 @@ func (mc *mysqlConn) writeOldAuthPacket(cipher []byte) error {
 
 	// Calculate the packet lenght and add a tailing 0
 	pktLen := len(scrambleBuff) + 1
-	data := make([]byte, pktLen+4)
+	data := mc.buf.smallWriteBuffer(pktLen + 4)
+	if data == nil {
+		// can not take the buffer. Something must be wrong with the connection
+		errLog.Print("Busy buffer")
+		return driver.ErrBadConn
+	}
 
 	// Add the packet header  [24bit length + 1 byte sequence]
 	data[0] = byte(pktLen)
@@ -340,17 +350,24 @@ func (mc *mysqlConn) writeCommandPacket(command byte) error {
 	// Reset Packet Sequence
 	mc.sequence = 0
 
+	data := mc.buf.smallWriteBuffer(4 + 1)
+	if data == nil {
+		// can not take the buffer. Something must be wrong with the connection
+		errLog.Print("Busy buffer")
+		return driver.ErrBadConn
+	}
+
+	// Add the packet header [24bit length + 1 byte sequence]
+	data[0] = 0x01 // 1 byte long
+	data[1] = 0x00
+	data[2] = 0x00
+	data[3] = 0x00 // sequence is always 0
+
+	// Add command byte
+	data[4] = command
+
 	// Send CMD packet
-	return mc.writePacket([]byte{
-		// Add the packet header [24bit length + 1 byte sequence]
-		0x01, // 1 byte long
-		0x00,
-		0x00,
-		0x00, // mc.sequence
-
-		// Add command byte
-		command,
-	})
+	return mc.writePacket(data)
 }
 
 func (mc *mysqlConn) writeCommandPacketStr(command byte, arg string) error {
@@ -358,13 +375,18 @@ func (mc *mysqlConn) writeCommandPacketStr(command byte, arg string) error {
 	mc.sequence = 0
 
 	pktLen := 1 + len(arg)
-	data := make([]byte, pktLen+4)
+	data := mc.buf.writeBuffer(pktLen + 4)
+	if data == nil {
+		// can not take the buffer. Something must be wrong with the connection
+		errLog.Print("Busy buffer")
+		return driver.ErrBadConn
+	}
 
 	// Add the packet header [24bit length + 1 byte sequence]
 	data[0] = byte(pktLen)
 	data[1] = byte(pktLen >> 8)
 	data[2] = byte(pktLen >> 16)
-	//data[3] = mc.sequence
+	data[3] = 0x00 // sequence is always 0
 
 	// Add command byte
 	data[4] = command
@@ -380,23 +402,30 @@ func (mc *mysqlConn) writeCommandPacketUint32(command byte, arg uint32) error {
 	// Reset Packet Sequence
 	mc.sequence = 0
 
+	data := mc.buf.smallWriteBuffer(4 + 1 + 4)
+	if data == nil {
+		// can not take the buffer. Something must be wrong with the connection
+		errLog.Print("Busy buffer")
+		return driver.ErrBadConn
+	}
+
+	// Add the packet header [24bit length + 1 byte sequence]
+	data[0] = 0x05 // 1 bytes long
+	data[1] = 0x00
+	data[2] = 0x00
+	data[3] = 0x00 // sequence is always 0
+
+	// Add command byte
+	data[4] = command
+
+	// Add arg [32 bit]
+	data[5] = byte(arg)
+	data[6] = byte(arg >> 8)
+	data[7] = byte(arg >> 16)
+	data[8] = byte(arg >> 24)
+
 	// Send CMD packet
-	return mc.writePacket([]byte{
-		// Add the packet header [24bit length + 1 byte sequence]
-		0x05, // 5 bytes long
-		0x00,
-		0x00,
-		0x00, // mc.sequence
-
-		// Add command byte
-		command,
-
-		// Add arg [32 bit]
-		byte(arg),
-		byte(arg >> 8),
-		byte(arg >> 16),
-		byte(arg >> 24),
-	})
+	return mc.writePacket(data)
 }
 
 /******************************************************************************
@@ -599,10 +628,10 @@ func (mc *mysqlConn) readColumns(count int) (columns []mysqlField, err error) {
 
 // Read Packets as Field Packets until EOF-Packet or an Error appears
 // http://dev.mysql.com/doc/internals/en/text-protocol.html#packet-ProtocolText::ResultsetRow
-func (rows *mysqlRows) readRow(dest []driver.Value) (err error) {
+func (rows *mysqlRows) readRow(dest []driver.Value) error {
 	data, err := rows.mc.readPacket()
 	if err != nil {
-		return
+		return err
 	}
 
 	// EOF Packet
@@ -641,24 +670,22 @@ func (rows *mysqlRows) readRow(dest []driver.Value) (err error) {
 				continue
 			}
 		}
-		return // err
+		return err // err != nil
 	}
 
-	return
+	return nil
 }
 
 // Reads Packets until EOF-Packet or an Error appears. Returns count of Packets read
-func (mc *mysqlConn) readUntilEOF() (err error) {
-	var data []byte
-
+func (mc *mysqlConn) readUntilEOF() error {
 	for {
-		data, err = mc.readPacket()
+		data, err := mc.readPacket()
 
 		// No Err and no EOF Packet
 		if err == nil && data[0] != iEOF {
 			continue
 		}
-		return // Err or EOF
+		return err // Err or EOF
 	}
 }
 
@@ -710,11 +737,16 @@ func (stmt *mysqlStmt) readPrepareResultPacket() (columnCount uint16, err error)
 }
 
 // http://dev.mysql.com/doc/internals/en/prepared-statements.html#com-stmt-send-long-data
-func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) (err error) {
+func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 	maxLen := stmt.mc.maxPacketAllowed - 1
 	pktLen := maxLen
 	argLen := len(arg)
+
+	// Can not use the write buffer since
+	// a) the buffer is too small
+	// b) it is in use
 	data := make([]byte, 4+1+4+2+argLen)
+
 	copy(data[4+1+4+2:], arg)
 
 	for argLen > 0 {
@@ -742,7 +774,7 @@ func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) (err error)
 		data[10] = byte(paramID >> 8)
 
 		// Send CMD packet
-		err = stmt.mc.writePacket(data[:4+pktLen])
+		err := stmt.mc.writePacket(data[:4+pktLen])
 		if err == nil {
 			argLen -= pktLen - (1 + 4 + 2)
 			data = data[pktLen-(1+4+2):]
@@ -758,7 +790,7 @@ func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) (err error)
 }
 
 // Execute Prepared Statement
-// http://dev.mysql.com/doc/internals/en/prepared-statements.html#com-stmt-execute
+// http://dev.mysql.com/doc/internals/en/com-stmt-execute.html
 func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 	if len(args) != stmt.paramCount {
 		return fmt.Errorf(
@@ -770,107 +802,32 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 	// Reset packet-sequence
 	stmt.mc.sequence = 0
 
-	pktLen := 1 + 4 + 1 + 4 + ((stmt.paramCount + 7) >> 3) + 1 + (stmt.paramCount << 1)
-	paramValues := make([][]byte, stmt.paramCount)
-	paramTypes := make([]byte, (stmt.paramCount << 1))
-	bitMask := uint64(0)
-	var i int
-
-	for i = range args {
-		// build NULL-bitmap
-		if args[i] == nil {
-			bitMask += 1 << uint(i)
-			paramTypes[i<<1] = fieldTypeNULL
-			continue
-		}
-
-		// cache types and values
-		switch v := args[i].(type) {
-		case int64:
-			paramTypes[i<<1] = fieldTypeLongLong
-			paramValues[i] = uint64ToBytes(uint64(v))
-			pktLen += 8
-			continue
-
-		case float64:
-			paramTypes[i<<1] = fieldTypeDouble
-			paramValues[i] = uint64ToBytes(math.Float64bits(v))
-			pktLen += 8
-			continue
-
-		case bool:
-			paramTypes[i<<1] = fieldTypeTiny
-			pktLen++
-			if v {
-				paramValues[i] = []byte{0x01}
-			} else {
-				paramValues[i] = []byte{0x00}
-			}
-			continue
-
-		case []byte:
-			paramTypes[i<<1] = fieldTypeString
-			if len(v) < stmt.mc.maxPacketAllowed-pktLen-(stmt.paramCount-(i+1))*64 {
-				paramValues[i] = append(
-					lengthEncodedIntegerToBytes(uint64(len(v))),
-					v...,
-				)
-				pktLen += len(paramValues[i])
-				continue
-			} else {
-				err := stmt.writeCommandLongData(i, v)
-				if err == nil {
-					continue
-				}
-				return err
-			}
-
-		case string:
-			paramTypes[i<<1] = fieldTypeString
-			if len(v) < stmt.mc.maxPacketAllowed-pktLen-(stmt.paramCount-(i+1))*64 {
-				paramValues[i] = append(
-					lengthEncodedIntegerToBytes(uint64(len(v))),
-					[]byte(v)...,
-				)
-				pktLen += len(paramValues[i])
-				continue
-			} else {
-				err := stmt.writeCommandLongData(i, []byte(v))
-				if err == nil {
-					continue
-				}
-				return err
-			}
-
-		case time.Time:
-			paramTypes[i<<1] = fieldTypeString
-
-			var val []byte
-			if v.IsZero() {
-				val = []byte("0000-00-00")
-			} else {
-				val = []byte(v.In(stmt.mc.cfg.loc).Format(timeFormat))
-			}
-
-			paramValues[i] = append(
-				lengthEncodedIntegerToBytes(uint64(len(val))),
-				val...,
-			)
-			pktLen += len(paramValues[i])
-			continue
+	var data []byte
 
-		default:
-			return fmt.Errorf("Can't convert type: %T", args[i])
+	if len(args) == 0 {
+		const pktLen = 1 + 4 + 1 + 4
+		data = stmt.mc.buf.writeBuffer(4 + pktLen)
+		if data == nil {
+			// can not take the buffer. Something must be wrong with the connection
+			errLog.Print("Busy buffer")
+			return driver.ErrBadConn
 		}
-	}
 
-	data := make([]byte, pktLen+4)
+		// packet header [4 bytes]
+		data[0] = byte(pktLen)
+		data[1] = byte(pktLen >> 8)
+		data[2] = byte(pktLen >> 16)
+		data[3] = 0x00 // sequence is always 0
+	} else {
+		data = stmt.mc.buf.takeCompleteBuffer()
+		if data == nil {
+			// can not take the buffer. Something must be wrong with the connection
+			errLog.Print("Busy buffer")
+			return driver.ErrBadConn
+		}
 
-	// packet header [4 bytes]
-	data[0] = byte(pktLen)
-	data[1] = byte(pktLen >> 8)
-	data[2] = byte(pktLen >> 16)
-	data[3] = stmt.mc.sequence
+		// header (bytes 0-3) is added after we know the packet size
+	}
 
 	// command [1 byte]
 	data[4] = comStmtExecute
@@ -882,32 +839,139 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 	data[8] = byte(stmt.id >> 24)
 
 	// flags (0: CURSOR_TYPE_NO_CURSOR) [1 byte]
-	//data[9] = 0x00
+	data[9] = 0x00
 
 	// iteration_count (uint32(1)) [4 bytes]
 	data[10] = 0x01
-	//data[11] = 0x00
-	//data[12] = 0x00
-	//data[13] = 0x00
-
-	if stmt.paramCount > 0 {
-		// NULL-bitmap [(param_count+7)/8 bytes]
-		pos := 14 + ((stmt.paramCount + 7) >> 3)
-		// Convert bitMask to bytes
-		for i = 14; i < pos; i++ {
-			data[i] = byte(bitMask >> uint((i-14)<<3))
-		}
+	data[11] = 0x00
+	data[12] = 0x00
+	data[13] = 0x00
+
+	if len(args) > 0 {
+		// NULL-bitmap [(len(args)+7)/8 bytes]
+		nullMask := uint64(0)
+
+		pos := 4 + 1 + 4 + 1 + 4 + ((len(args) + 7) >> 3)
 
 		// newParameterBoundFlag 1 [1 byte]
 		data[pos] = 0x01
 		pos++
 
-		// type of parameters [param_count*2 bytes]
-		pos += copy(data[pos:], paramTypes)
+		// type of each parameter [len(args)*2 bytes]
+		paramTypes := data[pos:]
+		pos += (len(args) << 1)
+
+		// value of each parameter [n bytes]
+		paramValues := data[pos:pos]
+		valuesCap := cap(paramValues)
+
+		for i := range args {
+			// build NULL-bitmap
+			if args[i] == nil {
+				nullMask += 1 << uint(i)
+				paramTypes[i+i] = fieldTypeNULL
+				continue
+			}
+
+			// cache types and values
+			switch v := args[i].(type) {
+			case int64:
+				paramTypes[i+i] = fieldTypeLongLong
+				if cap(paramValues) <= len(paramValues)+8 {
+					paramValues = paramValues[:len(paramValues)+8]
+					binary.LittleEndian.PutUint64(paramValues, uint64(v))
+				} else {
+					paramValues = append(paramValues,
+						uint64ToBytes(uint64(v))...,
+					)
+				}
+
+			case float64:
+				paramTypes[i+i] = fieldTypeDouble
+				if cap(paramValues) <= len(paramValues)+8 {
+					paramValues = paramValues[:len(paramValues)+8]
+					binary.LittleEndian.PutUint64(paramValues, math.Float64bits(v))
+				} else {
+					paramValues = append(paramValues,
+						uint64ToBytes(math.Float64bits(v))...,
+					)
+				}
+
+			case bool:
+				paramTypes[i+i] = fieldTypeTiny
+				if v {
+					paramValues = append(paramValues, 0x01)
+				} else {
+					paramValues = append(paramValues, 0x00)
+				}
+
+			case []byte:
+				paramTypes[i+i] = fieldTypeString
+				if len(v) < stmt.mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
+					paramValues = append(paramValues,
+						lengthEncodedIntegerToBytes(uint64(len(v)))...,
+					)
+					paramValues = append(paramValues, v...)
+				} else {
+					if err := stmt.writeCommandLongData(i, v); err != nil {
+						return err
+					}
+				}
+
+			case string:
+				paramTypes[i+i] = fieldTypeString
+				if len(v) < stmt.mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
+					paramValues = append(paramValues,
+						lengthEncodedIntegerToBytes(uint64(len(v)))...,
+					)
+					paramValues = append(paramValues, v...)
+				} else {
+					if err := stmt.writeCommandLongData(i, []byte(v)); err != nil {
+						return err
+					}
+				}
+
+			case time.Time:
+				paramTypes[i+i] = fieldTypeString
+
+				var val []byte
+				if v.IsZero() {
+					val = []byte("0000-00-00")
+				} else {
+					val = []byte(v.In(stmt.mc.cfg.loc).Format(timeFormat))
+				}
+
+				paramValues = append(paramValues,
+					lengthEncodedIntegerToBytes(uint64(len(val)))...,
+				)
+				paramValues = append(paramValues, val...)
+
+			default:
+				return fmt.Errorf("Can't convert type: %T", args[i])
+			}
+		}
+
+		// Check if param values exceeded the available buffer
+		// In that case we must build the data packet with the new values buffer
+		if valuesCap != cap(paramValues) {
+			data = append(data[:pos], paramValues...)
+			stmt.mc.buf.buf = data
+		}
+
+		pos += len(paramValues)
+		data = data[:pos]
+
+		pktLen := pos - 4
+
+		// packet header [4 bytes]
+		data[0] = byte(pktLen)
+		data[1] = byte(pktLen >> 8)
+		data[2] = byte(pktLen >> 16)
+		data[3] = stmt.mc.sequence
 
-		// values for the parameters [n bytes]
-		for i = range paramValues {
-			pos += copy(data[pos:], paramValues[i])
+		// Convert nullMask to bytes
+		for i, max := 14, 14+((stmt.paramCount+7)>>3); i < max; i++ {
+			data[i] = byte(nullMask >> uint((i-14)<<3))
 		}
 	}
 

From 656614d3b2d1e3a93885e6cee65dfdf532e34885 Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Tue, 22 Oct 2013 11:43:53 +0200
Subject: [PATCH 2/9] writeExecutePacket: fix capacity check

---
 packets.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packets.go b/packets.go
index d30f644e6..471ee9815 100644
--- a/packets.go
+++ b/packets.go
@@ -877,7 +877,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 			switch v := args[i].(type) {
 			case int64:
 				paramTypes[i+i] = fieldTypeLongLong
-				if cap(paramValues) <= len(paramValues)+8 {
+				if cap(paramValues)-len(paramValues)-8 >= 0 {
 					paramValues = paramValues[:len(paramValues)+8]
 					binary.LittleEndian.PutUint64(paramValues, uint64(v))
 				} else {
@@ -888,7 +888,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 			case float64:
 				paramTypes[i+i] = fieldTypeDouble
-				if cap(paramValues) <= len(paramValues)+8 {
+				if cap(paramValues)-len(paramValues)-8 >= 0 {
 					paramValues = paramValues[:len(paramValues)+8]
 					binary.LittleEndian.PutUint64(paramValues, math.Float64bits(v))
 				} else {

From 3d95bd01faee84ee252a5ff19407cda98fb1beb3 Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Tue, 22 Oct 2013 18:58:58 +0200
Subject: [PATCH 3/9] writeExecutePacket: fix packing

---
 packets.go | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/packets.go b/packets.go
index 471ee9815..da6395da5 100644
--- a/packets.go
+++ b/packets.go
@@ -868,8 +868,9 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		for i := range args {
 			// build NULL-bitmap
 			if args[i] == nil {
-				nullMask += 1 << uint(i)
+				nullMask |= 1 << uint(i)
 				paramTypes[i+i] = fieldTypeNULL
+				paramTypes[i+i+1] = 0x00
 				continue
 			}
 
@@ -877,9 +878,11 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 			switch v := args[i].(type) {
 			case int64:
 				paramTypes[i+i] = fieldTypeLongLong
+				paramTypes[i+i+1] = 0x00
+
 				if cap(paramValues)-len(paramValues)-8 >= 0 {
 					paramValues = paramValues[:len(paramValues)+8]
-					binary.LittleEndian.PutUint64(paramValues, uint64(v))
+					binary.LittleEndian.PutUint64(paramValues[len(paramValues)-8:], uint64(v))
 				} else {
 					paramValues = append(paramValues,
 						uint64ToBytes(uint64(v))...,
@@ -888,9 +891,11 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 			case float64:
 				paramTypes[i+i] = fieldTypeDouble
+				paramTypes[i+i+1] = 0x00
+
 				if cap(paramValues)-len(paramValues)-8 >= 0 {
 					paramValues = paramValues[:len(paramValues)+8]
-					binary.LittleEndian.PutUint64(paramValues, math.Float64bits(v))
+					binary.LittleEndian.PutUint64(paramValues[len(paramValues)-8:], math.Float64bits(v))
 				} else {
 					paramValues = append(paramValues,
 						uint64ToBytes(math.Float64bits(v))...,
@@ -899,6 +904,8 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 			case bool:
 				paramTypes[i+i] = fieldTypeTiny
+				paramTypes[i+i+1] = 0x00
+
 				if v {
 					paramValues = append(paramValues, 0x01)
 				} else {
@@ -907,6 +914,8 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 			case []byte:
 				paramTypes[i+i] = fieldTypeString
+				paramTypes[i+i+1] = 0x00
+
 				if len(v) < stmt.mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
 					paramValues = append(paramValues,
 						lengthEncodedIntegerToBytes(uint64(len(v)))...,
@@ -920,6 +929,8 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 			case string:
 				paramTypes[i+i] = fieldTypeString
+				paramTypes[i+i+1] = 0x00
+
 				if len(v) < stmt.mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
 					paramValues = append(paramValues,
 						lengthEncodedIntegerToBytes(uint64(len(v)))...,
@@ -933,6 +944,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 			case time.Time:
 				paramTypes[i+i] = fieldTypeString
+				paramTypes[i+i+1] = 0x00
 
 				var val []byte
 				if v.IsZero() {

From 33d6df2bf4e7bdb45cccbf05ddc650e78c2bffef Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Tue, 22 Oct 2013 23:58:37 +0200
Subject: [PATCH 4/9] various refactoring

---
 packets.go | 157 ++++++++++++++++++++++-------------------------------
 1 file changed, 65 insertions(+), 92 deletions(-)

diff --git a/packets.go b/packets.go
index da6395da5..84913b6af 100644
--- a/packets.go
+++ b/packets.go
@@ -23,9 +23,9 @@ import (
 // http://dev.mysql.com/doc/internals/en/client-server-protocol.html
 
 // Read packet to buffer 'data'
-func (mc *mysqlConn) readPacket() (data []byte, err error) {
+func (mc *mysqlConn) readPacket() ([]byte, error) {
 	// Read packet header
-	data, err = mc.buf.readNext(4)
+	data, err := mc.buf.readNext(4)
 	if err != nil {
 		errLog.Print(err.Error())
 		mc.Close()
@@ -97,7 +97,7 @@ func (mc *mysqlConn) writePacket(data []byte) error {
 	return mc.splitPacket(data)
 }
 
-func (mc *mysqlConn) splitPacket(data []byte) (err error) {
+func (mc *mysqlConn) splitPacket(data []byte) error {
 	pktLen := len(data) - 4
 
 	if pktLen > mc.maxPacketAllowed {
@@ -141,10 +141,10 @@ func (mc *mysqlConn) splitPacket(data []byte) (err error) {
 
 // Handshake Initialization Packet
 // http://dev.mysql.com/doc/internals/en/connection-phase.html#packet-Protocol::Handshake
-func (mc *mysqlConn) readInitPacket() (cipher []byte, err error) {
+func (mc *mysqlConn) readInitPacket() ([]byte, error) {
 	data, err := mc.readPacket()
 	if err != nil {
-		return
+		return nil, err
 	}
 
 	if data[0] == iERR {
@@ -153,11 +153,11 @@ func (mc *mysqlConn) readInitPacket() (cipher []byte, err error) {
 
 	// protocol version [1 byte]
 	if data[0] < minProtocolVersion {
-		err = fmt.Errorf(
+		return nil, fmt.Errorf(
 			"Unsupported MySQL Protocol Version %d. Protocol Version %d or higher is required",
 			data[0],
-			minProtocolVersion)
-		return
+			minProtocolVersion,
+		)
 	}
 
 	// server version [null terminated string]
@@ -165,7 +165,7 @@ func (mc *mysqlConn) readInitPacket() (cipher []byte, err error) {
 	pos := 1 + bytes.IndexByte(data[1:], 0x00) + 1 + 4
 
 	// first part of the password cipher [8 bytes]
-	cipher = data[pos : pos+8]
+	cipher := data[pos : pos+8]
 
 	// (filler) always 0x00 [1 byte]
 	pos += 8 + 1
@@ -205,7 +205,7 @@ func (mc *mysqlConn) readInitPacket() (cipher []byte, err error) {
 		//return errMalformPkt
 	}
 
-	return
+	return cipher, nil
 }
 
 // Client Authentication Packet
@@ -497,7 +497,7 @@ func (mc *mysqlConn) handleErrorPacket(data []byte) error {
 
 	// SQL State [optional: # + 5bytes string]
 	//sqlstate := string(data[pos : pos+6])
-	if data[pos] == 0x23 {
+	if data[3] == 0x23 {
 		pos = 9
 	}
 
@@ -510,7 +510,7 @@ func (mc *mysqlConn) handleErrorPacket(data []byte) error {
 
 // Ok Packet
 // http://dev.mysql.com/doc/internals/en/overview.html#packet-OK_Packet
-func (mc *mysqlConn) handleOkPacket(data []byte) (err error) {
+func (mc *mysqlConn) handleOkPacket(data []byte) error {
 	var n, m int
 
 	// 0x00 [1 byte]
@@ -525,72 +525,66 @@ func (mc *mysqlConn) handleOkPacket(data []byte) (err error) {
 
 	// warning count [2 bytes]
 	if !mc.strict {
-		return
+		return nil
 	} else {
 		pos := 1 + n + m + 2
 		if binary.LittleEndian.Uint16(data[pos:pos+2]) > 0 {
-			err = mc.getWarnings()
+			return mc.getWarnings()
 		}
+		return nil
 	}
-
-	// message [until end of packet]
-	return
 }
 
 // Read Packets as Field Packets until EOF-Packet or an Error appears
 // http://dev.mysql.com/doc/internals/en/text-protocol.html#packet-Protocol::ColumnDefinition41
-func (mc *mysqlConn) readColumns(count int) (columns []mysqlField, err error) {
-	var data []byte
-	var i, pos, n int
-	var name []byte
-
-	columns = make([]mysqlField, count)
+func (mc *mysqlConn) readColumns(count int) ([]mysqlField, error) {
+	columns := make([]mysqlField, count)
 
-	for {
-		data, err = mc.readPacket()
+	for i := 0; ; i++ {
+		data, err := mc.readPacket()
 		if err != nil {
-			return
+			return nil, err
 		}
 
 		// EOF Packet
 		if data[0] == iEOF && (len(data) == 5 || len(data) == 1) {
-			if i != count {
-				err = fmt.Errorf("ColumnsCount mismatch n:%d len:%d", count, len(columns))
+			if i == count {
+				return columns, nil
 			}
-			return
+			return nil, fmt.Errorf("ColumnsCount mismatch n:%d len:%d", count, len(columns))
 		}
 
 		// Catalog
-		pos, err = skipLengthEnodedString(data)
+		pos, err := skipLengthEnodedString(data)
 		if err != nil {
-			return
+			return nil, err
 		}
 
 		// Database [len coded string]
-		n, err = skipLengthEnodedString(data[pos:])
+		n, err := skipLengthEnodedString(data[pos:])
 		if err != nil {
-			return
+			return nil, err
 		}
 		pos += n
 
 		// Table [len coded string]
 		n, err = skipLengthEnodedString(data[pos:])
 		if err != nil {
-			return
+			return nil, err
 		}
 		pos += n
 
 		// Original table [len coded string]
 		n, err = skipLengthEnodedString(data[pos:])
 		if err != nil {
-			return
+			return nil, err
 		}
 		pos += n
 
 		// Name [len coded string]
-		name, _, n, err = readLengthEnodedString(data[pos:])
+		name, _, n, err := readLengthEnodedString(data[pos:])
 		if err != nil {
-			return
+			return nil, err
 		}
 		columns[i].name = string(name)
 		pos += n
@@ -598,7 +592,7 @@ func (mc *mysqlConn) readColumns(count int) (columns []mysqlField, err error) {
 		// Original name [len coded string]
 		n, err = skipLengthEnodedString(data[pos:])
 		if err != nil {
-			return
+			return nil, err
 		}
 
 		// Filler [1 byte]
@@ -621,8 +615,6 @@ func (mc *mysqlConn) readColumns(count int) (columns []mysqlField, err error) {
 		//if pos < len(data) {
 		//	defaultVal, _, err = bytesToLengthCodedBinary(data[pos:])
 		//}
-
-		i++
 	}
 }
 
@@ -656,7 +648,10 @@ func (rows *mysqlRows) readRow(dest []driver.Value) error {
 					switch rows.columns[i].fieldType {
 					case fieldTypeTimestamp, fieldTypeDateTime,
 						fieldTypeDate, fieldTypeNewDate:
-						dest[i], err = parseDateTime(string(dest[i].([]byte)), rows.mc.cfg.loc)
+						dest[i], err = parseDateTime(
+							string(dest[i].([]byte)),
+							rows.mc.cfg.loc,
+						)
 						if err == nil {
 							continue
 						}
@@ -695,61 +690,52 @@ func (mc *mysqlConn) readUntilEOF() error {
 
 // Prepare Result Packets
 // http://dev.mysql.com/doc/internals/en/prepared-statements.html#com-stmt-prepare-response
-func (stmt *mysqlStmt) readPrepareResultPacket() (columnCount uint16, err error) {
+func (stmt *mysqlStmt) readPrepareResultPacket() (uint16, error) {
 	data, err := stmt.mc.readPacket()
 	if err == nil {
-		// Position
-		pos := 0
-
 		// packet indicator [1 byte]
-		if data[pos] != iOK {
-			err = stmt.mc.handleErrorPacket(data)
-			return
+		if data[0] != iOK {
+			return 0, stmt.mc.handleErrorPacket(data)
 		}
-		pos++
 
 		// statement id [4 bytes]
-		stmt.id = binary.LittleEndian.Uint32(data[pos : pos+4])
-		pos += 4
+		stmt.id = binary.LittleEndian.Uint32(data[1 : 1+4])
 
 		// Column count [16 bit uint]
-		columnCount = binary.LittleEndian.Uint16(data[pos : pos+2])
-		pos += 2
+		columnCount := binary.LittleEndian.Uint16(data[1+4 : 1+4+2])
 
 		// Param count [16 bit uint]
-		stmt.paramCount = int(binary.LittleEndian.Uint16(data[pos : pos+2]))
-		pos += 2
+		stmt.paramCount = int(binary.LittleEndian.Uint16(data[1+4+2 : 1+4+2+2]))
 
 		// Reserved [8 bit]
-		pos++
 
 		// Warning count [16 bit uint]
 		if !stmt.mc.strict {
-			return
+			return columnCount, nil
 		} else {
 			// Check for warnings count > 0, only available in MySQL > 4.1
-			if len(data) >= 12 && binary.LittleEndian.Uint16(data[pos:pos+2]) > 0 {
-				err = stmt.mc.getWarnings()
+			if len(data) >= 12 && binary.LittleEndian.Uint16(data[1+4+2+2+1:1+4+2+2+1+2]) > 0 {
+				return columnCount, stmt.mc.getWarnings()
 			}
+			return columnCount, nil
 		}
 	}
-	return
+	return 0, err
 }
 
 // http://dev.mysql.com/doc/internals/en/prepared-statements.html#com-stmt-send-long-data
 func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 	maxLen := stmt.mc.maxPacketAllowed - 1
 	pktLen := maxLen
-	argLen := len(arg)
 
 	// Can not use the write buffer since
 	// a) the buffer is too small
 	// b) it is in use
-	data := make([]byte, 4+1+4+2+argLen)
+	data := make([]byte, 4+1+4+2+len(arg))
 
 	copy(data[4+1+4+2:], arg)
 
-	for argLen > 0 {
+	for argLen := len(arg); argLen > 0; argLen -= pktLen - (1 + 4 + 2) {
 		if 1+4+2+argLen < maxLen {
 			pktLen = 1 + 4 + 2 + argLen
 		}
@@ -776,7 +762,6 @@ func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 		// Send CMD packet
 		err := stmt.mc.writePacket(data[:4+pktLen])
 		if err == nil {
-			argLen -= pktLen - (1 + 4 + 2)
 			data = data[pktLen-(1+4+2):]
 			continue
 		}
@@ -796,7 +781,8 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		return fmt.Errorf(
 			"Arguments count mismatch (Got: %d Has: %d)",
 			len(args),
-			stmt.paramCount)
+			stmt.paramCount,
+		)
 	}
 
 	// Reset packet-sequence
@@ -991,10 +977,10 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 }
 
 // http://dev.mysql.com/doc/internals/en/prepared-statements.html#packet-ProtocolBinary::ResultsetRow
-func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
+func (rows *mysqlRows) readBinaryRow(dest []driver.Value) error {
 	data, err := rows.mc.readPacket()
 	if err != nil {
-		return
+		return err
 	}
 
 	// packet indicator [1 byte]
@@ -1010,22 +996,16 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 
 	// NULL-bitmap,  [(column-count + 7 + 2) / 8 bytes]
 	pos := 1 + (len(dest)+7+2)>>3
-	nullBitMap := data[1:pos]
-
-	// values [rest]
-	var n int
-	var unsigned bool
+	nullMask := data[1:pos]
 
 	for i := range dest {
 		// Field is NULL
 		// (byte >> bit-pos) % 2 == 1
-		if ((nullBitMap[(i+2)>>3] >> uint((i+2)&7)) & 1) == 1 {
+		if ((nullMask[(i+2)>>3] >> uint((i+2)&7)) & 1) == 1 {
 			dest[i] = nil
 			continue
 		}
 
-		unsigned = rows.columns[i].flags&flagUnsigned != 0
-
 		// Convert to byte-coded string
 		switch rows.columns[i].fieldType {
 		case fieldTypeNULL:
@@ -1034,7 +1014,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 
 		// Numeric Types
 		case fieldTypeTiny:
-			if unsigned {
+			if rows.columns[i].flags&flagUnsigned != 0 {
 				dest[i] = int64(data[pos])
 			} else {
 				dest[i] = int64(int8(data[pos]))
@@ -1043,7 +1023,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 			continue
 
 		case fieldTypeShort, fieldTypeYear:
-			if unsigned {
+			if rows.columns[i].flags&flagUnsigned != 0 {
 				dest[i] = int64(binary.LittleEndian.Uint16(data[pos : pos+2]))
 			} else {
 				dest[i] = int64(int16(binary.LittleEndian.Uint16(data[pos : pos+2])))
@@ -1052,7 +1032,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 			continue
 
 		case fieldTypeInt24, fieldTypeLong:
-			if unsigned {
+			if rows.columns[i].flags&flagUnsigned != 0 {
 				dest[i] = int64(binary.LittleEndian.Uint32(data[pos : pos+4]))
 			} else {
 				dest[i] = int64(int32(binary.LittleEndian.Uint32(data[pos : pos+4])))
@@ -1061,7 +1041,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 			continue
 
 		case fieldTypeLongLong:
-			if unsigned {
+			if rows.columns[i].flags&flagUnsigned != 0 {
 				val := binary.LittleEndian.Uint64(data[pos : pos+8])
 				if val > math.MaxInt64 {
 					dest[i] = uint64ToString(val)
@@ -1090,6 +1070,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 			fieldTypeMediumBLOB, fieldTypeLongBLOB, fieldTypeBLOB,
 			fieldTypeVarString, fieldTypeString, fieldTypeGeometry:
 			var isNull bool
+			var n int
 			dest[i], isNull, n, err = readLengthEnodedString(data[pos:])
 			pos += n
 			if err == nil {
@@ -1100,14 +1081,11 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 					continue
 				}
 			}
-			return // err
+			return err
 
 		// Date YYYY-MM-DD
 		case fieldTypeDate, fieldTypeNewDate:
-			var num uint64
-			var isNull bool
-			num, isNull, n = readLengthEncodedInteger(data[pos:])
-
+			num, isNull, n := readLengthEncodedInteger(data[pos:])
 			pos += n
 
 			if isNull {
@@ -1130,10 +1108,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 
 		// Time [-][H]HH:MM:SS[.fractal]
 		case fieldTypeTime:
-			var num uint64
-			var isNull bool
-			num, isNull, n = readLengthEncodedInteger(data[pos:])
-
+			num, isNull, n := readLengthEncodedInteger(data[pos:])
 			pos += n
 
 			if num == 0 {
@@ -1179,9 +1154,7 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 
 		// Timestamp YYYY-MM-DD HH:MM:SS[.fractal]
 		case fieldTypeTimestamp, fieldTypeDateTime:
-			var num uint64
-			var isNull bool
-			num, isNull, n = readLengthEncodedInteger(data[pos:])
+			num, isNull, n := readLengthEncodedInteger(data[pos:])
 
 			pos += n
 
@@ -1209,5 +1182,5 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) (err error) {
 		}
 	}
 
-	return
+	return nil
 }

From 5975ca92129ebc024aa295759dc9e8ad19687a6f Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Wed, 23 Oct 2013 13:17:59 +0200
Subject: [PATCH 5/9] more refactoring

Try to remove unnecessary indirections and initialisations with zero.
Also update links to the MySQL doc
---
 connection.go | 57 ++++++++++++++++++++++++---------------------------
 packets.go    | 57 +++++++++++++++++++++++++++------------------------
 rows.go       |  6 +++---
 statement.go  | 37 ++++++++++++++++-----------------
 4 files changed, 78 insertions(+), 79 deletions(-)

diff --git a/connection.go b/connection.go
index 36a27b572..f769f7869 100644
--- a/connection.go
+++ b/connection.go
@@ -136,14 +136,14 @@ func (mc *mysqlConn) Prepare(query string) (driver.Stmt, error) {
 	columnCount, err := stmt.readPrepareResultPacket()
 	if err == nil {
 		if stmt.paramCount > 0 {
-			stmt.params, err = stmt.mc.readColumns(stmt.paramCount)
+			stmt.params, err = mc.readColumns(stmt.paramCount)
 			if err != nil {
 				return nil, err
 			}
 		}
 
 		if columnCount > 0 {
-			err = stmt.mc.readUntilEOF()
+			err = mc.readUntilEOF()
 		}
 	}
 
@@ -171,26 +171,24 @@ func (mc *mysqlConn) Exec(query string, args []driver.Value) (driver.Result, err
 }
 
 // Internal function to execute commands
-func (mc *mysqlConn) exec(query string) (err error) {
+func (mc *mysqlConn) exec(query string) error {
 	// Send command
-	err = mc.writeCommandPacketStr(comQuery, query)
+	err := mc.writeCommandPacketStr(comQuery, query)
 	if err != nil {
-		return
+		return err
 	}
 
 	// Read Result
-	var resLen int
-	resLen, err = mc.readResultSetHeaderPacket()
+	resLen, err := mc.readResultSetHeaderPacket()
 	if err == nil && resLen > 0 {
-		err = mc.readUntilEOF()
-		if err != nil {
-			return
+		if err = mc.readUntilEOF(); err != nil {
+			return err
 		}
 
 		err = mc.readUntilEOF()
 	}
 
-	return
+	return err
 }
 
 func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, error) {
@@ -211,7 +209,6 @@ func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, erro
 				return rows, err
 			}
 		}
-
 		return nil, err
 	}
 
@@ -221,29 +218,29 @@ func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, erro
 
 // Gets the value of the given MySQL System Variable
 // The returned byte slice is only valid until the next read
-func (mc *mysqlConn) getSystemVar(name string) (val []byte, err error) {
+func (mc *mysqlConn) getSystemVar(name string) ([]byte, error) {
 	// Send command
-	err = mc.writeCommandPacketStr(comQuery, "SELECT @@"+name)
+	if err := mc.writeCommandPacketStr(comQuery, "SELECT @@"+name); err != nil {
+		return nil, err
+	}
+
+	// Read Result
+	resLen, err := mc.readResultSetHeaderPacket()
 	if err == nil {
-		// Read Result
-		var resLen int
-		resLen, err = mc.readResultSetHeaderPacket()
-		if err == nil {
-			rows := &mysqlRows{mc, false, nil, false}
+		rows := &mysqlRows{mc, false, nil, false}
 
-			if resLen > 0 {
-				// Columns
-				rows.columns, err = mc.readColumns(resLen)
+		if resLen > 0 {
+			// Columns
+			rows.columns, err = mc.readColumns(resLen)
+			if err != nil {
+				return nil, err
 			}
+		}
 
-			dest := make([]driver.Value, resLen)
-			err = rows.readRow(dest)
-			if err == nil {
-				val = dest[0].([]byte)
-				err = mc.readUntilEOF()
-			}
+		dest := make([]driver.Value, resLen)
+		if err = rows.readRow(dest); err == nil {
+			return dest[0].([]byte), mc.readUntilEOF()
 		}
 	}
-
-	return
+	return nil, err
 }
diff --git a/packets.go b/packets.go
index 84913b6af..a14b7761e 100644
--- a/packets.go
+++ b/packets.go
@@ -140,7 +140,7 @@ func (mc *mysqlConn) splitPacket(data []byte) error {
 ******************************************************************************/
 
 // Handshake Initialization Packet
-// http://dev.mysql.com/doc/internals/en/connection-phase.html#packet-Protocol::Handshake
+// http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::Handshake
 func (mc *mysqlConn) readInitPacket() ([]byte, error) {
 	data, err := mc.readPacket()
 	if err != nil {
@@ -197,7 +197,6 @@ func (mc *mysqlConn) readInitPacket() ([]byte, error) {
 		// TODO: Verify string termination
 		// EOF if version (>= 5.5.7 and < 5.5.10) or (>= 5.6.0 and < 5.6.2)
 		// \NUL otherwise
-		// http://dev.mysql.com/doc/internals/en/connection-phase.html#packet-Protocol::Handshake
 		//
 		//if data[len(data)-1] == 0 {
 		//	return
@@ -209,7 +208,7 @@ func (mc *mysqlConn) readInitPacket() ([]byte, error) {
 }
 
 // Client Authentication Packet
-// http://dev.mysql.com/doc/internals/en/connection-phase.html#packet-Protocol::HandshakeResponse
+// http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::HandshakeResponse
 func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	// Adjust client flags based on server support
 	clientFlags := clientProtocol41 |
@@ -263,7 +262,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	data[12] = collation_utf8_general_ci
 
 	// SSL Connection Request Packet
-	// http://dev.mysql.com/doc/internals/en/connection-phase.html#packet-Protocol::SSLRequest
+	// http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::SSLRequest
 	if mc.cfg.tls != nil {
 		// Packet header  [24bit length + 1 byte sequence]
 		data[0] = byte((4 + 4 + 1 + 23))
@@ -316,7 +315,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 }
 
 //  Client old authentication packet
-// http://dev.mysql.com/doc/internals/en/connection-phase.html#packet-Protocol::AuthSwitchResponse
+// http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::AuthSwitchResponse
 func (mc *mysqlConn) writeOldAuthPacket(cipher []byte) error {
 	// User password
 	scrambleBuff := scrambleOldPassword(cipher, []byte(mc.cfg.passwd))
@@ -454,7 +453,7 @@ func (mc *mysqlConn) readResultOK() error {
 }
 
 // Result Set Header Packet
-// http://dev.mysql.com/doc/internals/en/text-protocol.html#packet-ProtocolText::Resultset
+// http://dev.mysql.com/doc/internals/en/com-query-response.html#packet-ProtocolText::Resultset
 func (mc *mysqlConn) readResultSetHeaderPacket() (int, error) {
 	data, err := mc.readPacket()
 	if err == nil {
@@ -482,7 +481,7 @@ func (mc *mysqlConn) readResultSetHeaderPacket() (int, error) {
 }
 
 // Error Packet
-// http://dev.mysql.com/doc/internals/en/overview.html#packet-ERR_Packet
+// http://dev.mysql.com/doc/internals/en/generic-response-packets.html#packet-ERR_Packet
 func (mc *mysqlConn) handleErrorPacket(data []byte) error {
 	if data[0] != iERR {
 		return errMalformPkt
@@ -509,7 +508,7 @@ func (mc *mysqlConn) handleErrorPacket(data []byte) error {
 }
 
 // Ok Packet
-// http://dev.mysql.com/doc/internals/en/overview.html#packet-OK_Packet
+// http://dev.mysql.com/doc/internals/en/generic-response-packets.html#packet-OK_Packet
 func (mc *mysqlConn) handleOkPacket(data []byte) error {
 	var n, m int
 
@@ -536,7 +535,7 @@ func (mc *mysqlConn) handleOkPacket(data []byte) error {
 }
 
 // Read Packets as Field Packets until EOF-Packet or an Error appears
-// http://dev.mysql.com/doc/internals/en/text-protocol.html#packet-Protocol::ColumnDefinition41
+// http://dev.mysql.com/doc/internals/en/com-query-response.html#packet-Protocol::ColumnDefinition41
 func (mc *mysqlConn) readColumns(count int) ([]mysqlField, error) {
 	columns := make([]mysqlField, count)
 
@@ -619,9 +618,11 @@ func (mc *mysqlConn) readColumns(count int) ([]mysqlField, error) {
 }
 
 // Read Packets as Field Packets until EOF-Packet or an Error appears
-// http://dev.mysql.com/doc/internals/en/text-protocol.html#packet-ProtocolText::ResultsetRow
+// http://dev.mysql.com/doc/internals/en/com-query-response.html#packet-ProtocolText::ResultsetRow
 func (rows *mysqlRows) readRow(dest []driver.Value) error {
-	data, err := rows.mc.readPacket()
+	mc := rows.mc
+
+	data, err := mc.readPacket()
 	if err != nil {
 		return err
 	}
@@ -642,7 +643,7 @@ func (rows *mysqlRows) readRow(dest []driver.Value) error {
 		pos += n
 		if err == nil {
 			if !isNull {
-				if !rows.mc.parseTime {
+				if !mc.parseTime {
 					continue
 				} else {
 					switch rows.columns[i].fieldType {
@@ -650,7 +651,7 @@ func (rows *mysqlRows) readRow(dest []driver.Value) error {
 						fieldTypeDate, fieldTypeNewDate:
 						dest[i], err = parseDateTime(
 							string(dest[i].([]byte)),
-							rows.mc.cfg.loc,
+							mc.cfg.loc,
 						)
 						if err == nil {
 							continue
@@ -689,7 +690,7 @@ func (mc *mysqlConn) readUntilEOF() error {
 ******************************************************************************/
 
 // Prepare Result Packets
-// http://dev.mysql.com/doc/internals/en/prepared-statements.html#com-stmt-prepare-response
+// http://dev.mysql.com/doc/internals/en/com-stmt-prepare-response.html
 func (stmt *mysqlStmt) readPrepareResultPacket() (uint16, error) {
 	data, err := stmt.mc.readPacket()
 	if err == nil {
@@ -723,7 +724,7 @@ func (stmt *mysqlStmt) readPrepareResultPacket() (uint16, error) {
 	return 0, err
 }
 
-// http://dev.mysql.com/doc/internals/en/prepared-statements.html#com-stmt-send-long-data
+// http://dev.mysql.com/doc/internals/en/com-stmt-send-long-data.html
 func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 	maxLen := stmt.mc.maxPacketAllowed - 1
 	pktLen := maxLen
@@ -785,14 +786,16 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		)
 	}
 
+	mc := stmt.mc
+
 	// Reset packet-sequence
-	stmt.mc.sequence = 0
+	mc.sequence = 0
 
 	var data []byte
 
 	if len(args) == 0 {
 		const pktLen = 1 + 4 + 1 + 4
-		data = stmt.mc.buf.writeBuffer(4 + pktLen)
+		data = mc.buf.writeBuffer(4 + pktLen)
 		if data == nil {
 			// can not take the buffer. Something must be wrong with the connection
 			errLog.Print("Busy buffer")
@@ -805,7 +808,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		data[2] = byte(pktLen >> 16)
 		data[3] = 0x00 // sequence is always 0
 	} else {
-		data = stmt.mc.buf.takeCompleteBuffer()
+		data = mc.buf.takeCompleteBuffer()
 		if data == nil {
 			// can not take the buffer. Something must be wrong with the connection
 			errLog.Print("Busy buffer")
@@ -902,7 +905,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 				paramTypes[i+i] = fieldTypeString
 				paramTypes[i+i+1] = 0x00
 
-				if len(v) < stmt.mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
+				if len(v) < mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
 					paramValues = append(paramValues,
 						lengthEncodedIntegerToBytes(uint64(len(v)))...,
 					)
@@ -917,7 +920,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 				paramTypes[i+i] = fieldTypeString
 				paramTypes[i+i+1] = 0x00
 
-				if len(v) < stmt.mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
+				if len(v) < mc.maxPacketAllowed-pos-len(paramValues)-(len(args)-(i+1))*64 {
 					paramValues = append(paramValues,
 						lengthEncodedIntegerToBytes(uint64(len(v)))...,
 					)
@@ -936,7 +939,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 				if v.IsZero() {
 					val = []byte("0000-00-00")
 				} else {
-					val = []byte(v.In(stmt.mc.cfg.loc).Format(timeFormat))
+					val = []byte(v.In(mc.cfg.loc).Format(timeFormat))
 				}
 
 				paramValues = append(paramValues,
@@ -953,7 +956,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		// In that case we must build the data packet with the new values buffer
 		if valuesCap != cap(paramValues) {
 			data = append(data[:pos], paramValues...)
-			stmt.mc.buf.buf = data
+			mc.buf.buf = data
 		}
 
 		pos += len(paramValues)
@@ -965,18 +968,18 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		data[0] = byte(pktLen)
 		data[1] = byte(pktLen >> 8)
 		data[2] = byte(pktLen >> 16)
-		data[3] = stmt.mc.sequence
+		data[3] = mc.sequence
 
 		// Convert nullMask to bytes
-		for i, max := 14, 14+((stmt.paramCount+7)>>3); i < max; i++ {
-			data[i] = byte(nullMask >> uint((i-14)<<3))
+		for i, max := 0, (stmt.paramCount+7)>>3; i < max; i++ {
+			data[i+14] = byte(nullMask >> uint(i<<3))
 		}
 	}
 
-	return stmt.mc.writePacket(data)
+	return mc.writePacket(data)
 }
 
-// http://dev.mysql.com/doc/internals/en/prepared-statements.html#packet-ProtocolBinary::ResultsetRow
+// http://dev.mysql.com/doc/internals/en/binary-protocol-resultset-row.html
 func (rows *mysqlRows) readBinaryRow(dest []driver.Value) error {
 	data, err := rows.mc.readPacket()
 	if err != nil {
diff --git a/rows.go b/rows.go
index 726f02ac0..71dcfb1a7 100644
--- a/rows.go
+++ b/rows.go
@@ -26,12 +26,12 @@ type mysqlRows struct {
 	eof     bool
 }
 
-func (rows *mysqlRows) Columns() (columns []string) {
-	columns = make([]string, len(rows.columns))
+func (rows *mysqlRows) Columns() []string {
+	columns := make([]string, len(rows.columns))
 	for i := range columns {
 		columns[i] = rows.columns[i].name
 	}
-	return
+	return columns
 }
 
 func (rows *mysqlRows) Close() (err error) {
diff --git a/statement.go b/statement.go
index 56b12533f..025f2ecf5 100644
--- a/statement.go
+++ b/statement.go
@@ -19,14 +19,14 @@ type mysqlStmt struct {
 	params     []mysqlField
 }
 
-func (stmt *mysqlStmt) Close() (err error) {
+func (stmt *mysqlStmt) Close() error {
 	if stmt.mc == nil || stmt.mc.netConn == nil {
 		return errInvalidConn
 	}
 
-	err = stmt.mc.writeCommandPacketUint32(comStmtClose, stmt.id)
+	err := stmt.mc.writeCommandPacketUint32(comStmtClose, stmt.id)
 	stmt.mc = nil
-	return
+	return err
 }
 
 func (stmt *mysqlStmt) NumInput() int {
@@ -34,33 +34,34 @@ func (stmt *mysqlStmt) NumInput() int {
 }
 
 func (stmt *mysqlStmt) Exec(args []driver.Value) (driver.Result, error) {
-	stmt.mc.affectedRows = 0
-	stmt.mc.insertId = 0
-
 	// Send command
 	err := stmt.writeExecutePacket(args)
 	if err != nil {
 		return nil, err
 	}
 
+	mc := stmt.mc
+
+	mc.affectedRows = 0
+	mc.insertId = 0
+
 	// Read Result
-	var resLen int
-	resLen, err = stmt.mc.readResultSetHeaderPacket()
+	resLen, err := mc.readResultSetHeaderPacket()
 	if err == nil {
 		if resLen > 0 {
 			// Columns
-			err = stmt.mc.readUntilEOF()
+			err = mc.readUntilEOF()
 			if err != nil {
 				return nil, err
 			}
 
 			// Rows
-			err = stmt.mc.readUntilEOF()
+			err = mc.readUntilEOF()
 		}
 		if err == nil {
 			return &mysqlResult{
-				affectedRows: int64(stmt.mc.affectedRows),
-				insertId:     int64(stmt.mc.insertId),
+				affectedRows: int64(mc.affectedRows),
+				insertId:     int64(mc.insertId),
 			}, nil
 		}
 	}
@@ -75,21 +76,19 @@ func (stmt *mysqlStmt) Query(args []driver.Value) (driver.Rows, error) {
 		return nil, err
 	}
 
+	mc := stmt.mc
+
 	// Read Result
-	var resLen int
-	resLen, err = stmt.mc.readResultSetHeaderPacket()
+	resLen, err := mc.readResultSetHeaderPacket()
 	if err != nil {
 		return nil, err
 	}
 
-	rows := &mysqlRows{stmt.mc, true, nil, false}
+	rows := &mysqlRows{mc, true, nil, false}
 
 	if resLen > 0 {
 		// Columns
-		rows.columns, err = stmt.mc.readColumns(resLen)
-		if err != nil {
-			return nil, err
-		}
+		rows.columns, err = mc.readColumns(resLen)
 	}
 
 	return rows, err

From 8751b72867eb0d06af3c5f8a2a61e29d475760b6 Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Wed, 23 Oct 2013 17:32:44 +0200
Subject: [PATCH 6/9] buffer: rename take buffer funcs

---
 buffer.go  |  4 ++--
 packets.go | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/buffer.go b/buffer.go
index e47cdf455..ed13fa283 100644
--- a/buffer.go
+++ b/buffer.go
@@ -85,7 +85,7 @@ func (b *buffer) readNext(need int) (p []byte, err error) {
 // If possible, a slice from the existing buffer is returned.
 // Otherwise a bigger buffer is made.
 // Only one buffer (total) can be used at a time.
-func (b *buffer) writeBuffer(length int) []byte {
+func (b *buffer) takeBuffer(length int) []byte {
 	if b.length > 0 {
 		return nil
 	}
@@ -105,7 +105,7 @@ func (b *buffer) writeBuffer(length int) []byte {
 // shortcut which can be used if the requested buffer is guaranteed to be
 // smaller than defaultBufSize
 // Only one buffer (total) can be used at a time.
-func (b *buffer) smallWriteBuffer(length int) []byte {
+func (b *buffer) takeSmallBuffer(length int) []byte {
 	if b.length == 0 {
 		return b.buf[:length]
 	}
diff --git a/packets.go b/packets.go
index a14b7761e..6db9e5d06 100644
--- a/packets.go
+++ b/packets.go
@@ -239,7 +239,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	}
 
 	// Calculate packet length and get buffer with that size
-	data := mc.buf.smallWriteBuffer(pktLen + 4)
+	data := mc.buf.takeSmallBuffer(pktLen + 4)
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print("Busy buffer")
@@ -322,7 +322,7 @@ func (mc *mysqlConn) writeOldAuthPacket(cipher []byte) error {
 
 	// Calculate the packet lenght and add a tailing 0
 	pktLen := len(scrambleBuff) + 1
-	data := mc.buf.smallWriteBuffer(pktLen + 4)
+	data := mc.buf.takeSmallBuffer(pktLen + 4)
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print("Busy buffer")
@@ -349,7 +349,7 @@ func (mc *mysqlConn) writeCommandPacket(command byte) error {
 	// Reset Packet Sequence
 	mc.sequence = 0
 
-	data := mc.buf.smallWriteBuffer(4 + 1)
+	data := mc.buf.takeSmallBuffer(4 + 1)
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print("Busy buffer")
@@ -374,7 +374,7 @@ func (mc *mysqlConn) writeCommandPacketStr(command byte, arg string) error {
 	mc.sequence = 0
 
 	pktLen := 1 + len(arg)
-	data := mc.buf.writeBuffer(pktLen + 4)
+	data := mc.buf.takeBuffer(pktLen + 4)
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print("Busy buffer")
@@ -401,7 +401,7 @@ func (mc *mysqlConn) writeCommandPacketUint32(command byte, arg uint32) error {
 	// Reset Packet Sequence
 	mc.sequence = 0
 
-	data := mc.buf.smallWriteBuffer(4 + 1 + 4)
+	data := mc.buf.takeSmallBuffer(4 + 1 + 4)
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print("Busy buffer")
@@ -795,7 +795,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 	if len(args) == 0 {
 		const pktLen = 1 + 4 + 1 + 4
-		data = mc.buf.writeBuffer(4 + pktLen)
+		data = mc.buf.takeBuffer(4 + pktLen)
 		if data == nil {
 			// can not take the buffer. Something must be wrong with the connection
 			errLog.Print("Busy buffer")

From 605647ed915515f124b755441a68205274ac67d3 Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Wed, 23 Oct 2013 17:34:47 +0200
Subject: [PATCH 7/9] changelog: Add write buffer

---
 CHANGELOG.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 72c71d429..764b1c3ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,7 +7,8 @@ Changes:
   - Made closing rows and connections error tolerant. This allows for example deferring rows.Close() without checking for errors
   - New Logo
   - Changed the copyright header to include all contributors
-  - Optimized the read buffer
+  - Optimized the buffer for reading
+  - Use the buffer also for writing. This results in zero allocations (by the driver) for most queries
   - Improved the LOAD INFILE documentation
   - The driver struct is now exported to make the driver directly accessible
   - Refactored the driver tests

From d8e6c384d4d4e681abd0a4e09bf86150b3a2345d Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Wed, 23 Oct 2013 18:42:11 +0200
Subject: [PATCH 8/9] writeCommandPacketUint32: fix packet length comment

---
 packets.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packets.go b/packets.go
index 6db9e5d06..129e6ac33 100644
--- a/packets.go
+++ b/packets.go
@@ -409,7 +409,7 @@ func (mc *mysqlConn) writeCommandPacketUint32(command byte, arg uint32) error {
 	}
 
 	// Add the packet header [24bit length + 1 byte sequence]
-	data[0] = 0x05 // 1 bytes long
+	data[0] = 0x05 // 5 bytes long
 	data[1] = 0x00
 	data[2] = 0x00
 	data[3] = 0x00 // sequence is always 0

From 228ba3461b36875338ec7967f4a0f38cc4f130a1 Mon Sep 17 00:00:00 2001
From: Julien Schmidt <github@julienschmidt.com>
Date: Thu, 24 Oct 2013 02:56:56 +0200
Subject: [PATCH 9/9] packets: YAR (yet another refactoring)

---
 packets.go | 50 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/packets.go b/packets.go
index 129e6ac33..731749cd2 100644
--- a/packets.go
+++ b/packets.go
@@ -360,7 +360,7 @@ func (mc *mysqlConn) writeCommandPacket(command byte) error {
 	data[0] = 0x01 // 1 byte long
 	data[1] = 0x00
 	data[2] = 0x00
-	data[3] = 0x00 // sequence is always 0
+	data[3] = 0x00 // new command, sequence id is always 0
 
 	// Add command byte
 	data[4] = command
@@ -385,7 +385,7 @@ func (mc *mysqlConn) writeCommandPacketStr(command byte, arg string) error {
 	data[0] = byte(pktLen)
 	data[1] = byte(pktLen >> 8)
 	data[2] = byte(pktLen >> 16)
-	data[3] = 0x00 // sequence is always 0
+	data[3] = 0x00 // new command, sequence id is always 0
 
 	// Add command byte
 	data[4] = command
@@ -412,7 +412,7 @@ func (mc *mysqlConn) writeCommandPacketUint32(command byte, arg uint32) error {
 	data[0] = 0x05 // 5 bytes long
 	data[1] = 0x00
 	data[2] = 0x00
-	data[3] = 0x00 // sequence is always 0
+	data[3] = 0x00 // new command, sequence id is always 0
 
 	// Add command byte
 	data[4] = command
@@ -495,8 +495,8 @@ func (mc *mysqlConn) handleErrorPacket(data []byte) error {
 	pos := 3
 
 	// SQL State [optional: # + 5bytes string]
-	//sqlstate := string(data[pos : pos+6])
 	if data[3] == 0x23 {
+		//sqlstate := string(data[4 : 4+5])
 		pos = 9
 	}
 
@@ -700,13 +700,13 @@ func (stmt *mysqlStmt) readPrepareResultPacket() (uint16, error) {
 		}
 
 		// statement id [4 bytes]
-		stmt.id = binary.LittleEndian.Uint32(data[1 : 1+4])
+		stmt.id = binary.LittleEndian.Uint32(data[1:5])
 
 		// Column count [16 bit uint]
-		columnCount := binary.LittleEndian.Uint16(data[1+4 : 1+4+2])
+		columnCount := binary.LittleEndian.Uint16(data[5:7])
 
 		// Param count [16 bit uint]
-		stmt.paramCount = int(binary.LittleEndian.Uint16(data[1+4+2 : 1+4+2+2]))
+		stmt.paramCount = int(binary.LittleEndian.Uint16(data[7:9]))
 
 		// Reserved [8 bit]
 
@@ -715,7 +715,7 @@ func (stmt *mysqlStmt) readPrepareResultPacket() (uint16, error) {
 			return columnCount, nil
 		} else {
 			// Check for warnings count > 0, only available in MySQL > 4.1
-			if len(data) >= 12 && binary.LittleEndian.Uint16(data[1+4+2+2+1:1+4+2+2+1+2]) > 0 {
+			if len(data) >= 12 && binary.LittleEndian.Uint16(data[10:12]) > 0 {
 				return columnCount, stmt.mc.getWarnings()
 			}
 			return columnCount, nil
@@ -729,16 +729,22 @@ func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 	maxLen := stmt.mc.maxPacketAllowed - 1
 	pktLen := maxLen
 
+	// After the header (bytes 0-3) follows before the data:
+	// 1 byte command
+	// 4 bytes stmtID
+	// 2 bytes paramID
+	const dataOffset = 1 + 4 + 2
+
 	// Can not use the write buffer since
 	// a) the buffer is too small
 	// b) it is in use
 	data := make([]byte, 4+1+4+2+len(arg))
 
-	copy(data[4+1+4+2:], arg)
+	copy(data[4+dataOffset:], arg)
 
-	for argLen := len(arg); argLen > 0; argLen -= pktLen - (1 + 4 + 2) {
-		if 1+4+2+argLen < maxLen {
-			pktLen = 1 + 4 + 2 + argLen
+	for argLen := len(arg); argLen > 0; argLen -= pktLen - dataOffset {
+		if dataOffset+argLen < maxLen {
+			pktLen = dataOffset + argLen
 		}
 
 		// Add the packet header [24bit length + 1 byte sequence]
@@ -763,7 +769,7 @@ func (stmt *mysqlStmt) writeCommandLongData(paramID int, arg []byte) error {
 		// Send CMD packet
 		err := stmt.mc.writePacket(data[:4+pktLen])
 		if err == nil {
-			data = data[pktLen-(1+4+2):]
+			data = data[pktLen-dataOffset:]
 			continue
 		}
 		return err
@@ -806,7 +812,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 		data[0] = byte(pktLen)
 		data[1] = byte(pktLen >> 8)
 		data[2] = byte(pktLen >> 16)
-		data[3] = 0x00 // sequence is always 0
+		data[3] = 0x00 // new command, sequence id is always 0
 	} else {
 		data = mc.buf.takeCompleteBuffer()
 		if data == nil {
@@ -871,7 +877,10 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 				if cap(paramValues)-len(paramValues)-8 >= 0 {
 					paramValues = paramValues[:len(paramValues)+8]
-					binary.LittleEndian.PutUint64(paramValues[len(paramValues)-8:], uint64(v))
+					binary.LittleEndian.PutUint64(
+						paramValues[len(paramValues)-8:],
+						uint64(v),
+					)
 				} else {
 					paramValues = append(paramValues,
 						uint64ToBytes(uint64(v))...,
@@ -884,7 +893,10 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 
 				if cap(paramValues)-len(paramValues)-8 >= 0 {
 					paramValues = paramValues[:len(paramValues)+8]
-					binary.LittleEndian.PutUint64(paramValues[len(paramValues)-8:], math.Float64bits(v))
+					binary.LittleEndian.PutUint64(
+						paramValues[len(paramValues)-8:],
+						math.Float64bits(v),
+					)
 				} else {
 					paramValues = append(paramValues,
 						uint64ToBytes(math.Float64bits(v))...,
@@ -991,10 +1003,10 @@ func (rows *mysqlRows) readBinaryRow(dest []driver.Value) error {
 		// EOF Packet
 		if data[0] == iEOF && len(data) == 5 {
 			return io.EOF
-		} else {
-			// Error otherwise
-			return rows.mc.handleErrorPacket(data)
 		}
+
+		// Error otherwise
+		return rows.mc.handleErrorPacket(data)
 	}
 
 	// NULL-bitmap,  [(column-count + 7 + 2) / 8 bytes]