update mssql drive to last working version 20180314172330-6a30f4e59a44 (#7306)

vendor/github.com/denisenkom/go-mssqldb/buf.go

@@ -2,12 +2,14 @@ package mssql
 
 import (
 	"encoding/binary"
-	"io"
 	"errors"
+	"io"
 )
 
+type packetType uint8
+
 type header struct {
-	PacketType uint8
+	PacketType packetType
 	Status     uint8
 	Size       uint16
 	Spid       uint16
@@ -15,55 +17,84 @@ type header struct {
 	Pad        uint8
 }
 
+// tdsBuffer reads and writes TDS packets of data to the transport.
+// The write and read buffers are separate to make sending attn signals
+// possible without locks. Currently attn signals are only sent during
+// reads, not writes.
 type tdsBuffer struct {
-	buf         []byte
-	pos         uint16
-	transport   io.ReadWriteCloser
-	size        uint16
+	transport io.ReadWriteCloser
+
+	packetSize int
+
+	// Write fields.
+	wbuf        []byte
+	wpos        int
+	wPacketSeq  byte
+	wPacketType packetType
+
+	// Read fields.
+	rbuf        []byte
+	rpos        int
+	rsize       int
 	final       bool
-	packet_type uint8
-	afterFirst  func()
+	rPacketType packetType
+
+	// afterFirst is assigned to right after tdsBuffer is created and
+	// before the first use. It is executed after the first packet is
+	// written and then removed.
+	afterFirst func()
 }
 
-func newTdsBuffer(bufsize int, transport io.ReadWriteCloser) *tdsBuffer {
-	buf := make([]byte, bufsize)
-	w := new(tdsBuffer)
-	w.buf = buf
-	w.pos = 8
-	w.transport = transport
-	w.size = 0
-	return w
+func newTdsBuffer(bufsize uint16, transport io.ReadWriteCloser) *tdsBuffer {
+	return &tdsBuffer{
+		packetSize: int(bufsize),
+		wbuf:       make([]byte, 1<<16),
+		rbuf:       make([]byte, 1<<16),
+		rpos:       8,
+		transport:  transport,
+	}
+}
+
+func (rw *tdsBuffer) ResizeBuffer(packetSize int) {
+	rw.packetSize = packetSize
+}
+
+func (w *tdsBuffer) PackageSize() int {
+	return w.packetSize
 }
 
 func (w *tdsBuffer) flush() (err error) {
-	// writing packet size
-	binary.BigEndian.PutUint16(w.buf[2:], w.pos)
+	// Write packet size.
+	w.wbuf[0] = byte(w.wPacketType)
+	binary.BigEndian.PutUint16(w.wbuf[2:], uint16(w.wpos))
+	w.wbuf[6] = w.wPacketSeq
 
-	// writing packet into underlying transport
-	if _, err = w.transport.Write(w.buf[:w.pos]); err != nil {
+	// Write packet into underlying transport.
+	if _, err = w.transport.Write(w.wbuf[:w.wpos]); err != nil {
 		return err
 	}
+	// It is possible to create a whole new buffer after a flush.
+	// Useful for debugging. Normally reuse the buffer.
+	// w.wbuf = make([]byte, 1<<16)
 
-	// execute afterFirst hook if it is set
+	// Execute afterFirst hook if it is set.
 	if w.afterFirst != nil {
 		w.afterFirst()
 		w.afterFirst = nil
 	}
 
-	w.pos = 8
-	// packet number
-	w.buf[6] += 1
+	w.wpos = 8
+	w.wPacketSeq++
 	return nil
 }
 
 func (w *tdsBuffer) Write(p []byte) (total int, err error) {
-	total = 0
 	for {
-		copied := copy(w.buf[w.pos:], p)
-		w.pos += uint16(copied)
+		copied := copy(w.wbuf[w.wpos:w.packetSize], p)
+		w.wpos += copied
 		total += copied
 		if copied == len(p) {
-			break
+			return
 		}
 		if err = w.flush(); err != nil {
 			return
@@ -74,66 +105,64 @@ func (w *tdsBuffer) Write(p []byte) (total int, err error) {
 }
 
 func (w *tdsBuffer) WriteByte(b byte) error {
-	if int(w.pos) == len(w.buf) {
+	if int(w.wpos) == len(w.wbuf) {
 		if err := w.flush(); err != nil {
 			return err
 		}
 	}
-	w.buf[w.pos] = b
-	w.pos += 1
+	w.wbuf[w.wpos] = b
+	w.wpos += 1
 	return nil
 }
 
-func (w *tdsBuffer) BeginPacket(packet_type byte) {
-	w.buf[0] = packet_type
-	w.buf[1] = 0 // packet is incomplete
-	w.buf[4] = 0 // spid
-	w.buf[5] = 0
-	w.buf[6] = 1 // packet id
-	w.buf[7] = 0 // window
-	w.pos = 8
+func (w *tdsBuffer) BeginPacket(packetType packetType) {
+	w.wbuf[1] = 0 // Packet is incomplete. This byte is set again in FinishPacket.
+	w.wpos = 8
+	w.wPacketSeq = 1
+	w.wPacketType = packetType
 }
 
 func (w *tdsBuffer) FinishPacket() error {
-	w.buf[1] = 1 // this is last packet
+	w.wbuf[1] = 1 // Mark this as the last packet in the message.
 	return w.flush()
 }
 
+var headerSize = binary.Size(header{})
+
 func (r *tdsBuffer) readNextPacket() error {
-	header := header{}
+	h := header{}
 	var err error
-	err = binary.Read(r.transport, binary.BigEndian, &header)
+	err = binary.Read(r.transport, binary.BigEndian, &h)
 	if err != nil {
 		return err
 	}
-	offset := uint16(binary.Size(header))
-	if int(header.Size) > len(r.buf) {
+	if int(h.Size) > len(r.rbuf) {
 		return errors.New("Invalid packet size, it is longer than buffer size")
 	}
-	if int(offset) > int(header.Size) {
+	if headerSize > int(h.Size) {
 		return errors.New("Invalid packet size, it is shorter than header size")
 	}
-	_, err = io.ReadFull(r.transport, r.buf[offset:header.Size])
+	_, err = io.ReadFull(r.transport, r.rbuf[headerSize:h.Size])
 	if err != nil {
 		return err
 	}
-	r.pos = offset
-	r.size = header.Size
-	r.final = header.Status != 0
-	r.packet_type = header.PacketType
+	r.rpos = headerSize
+	r.rsize = int(h.Size)
+	r.final = h.Status != 0
+	r.rPacketType = h.PacketType
 	return nil
 }
 
-func (r *tdsBuffer) BeginRead() (uint8, error) {
+func (r *tdsBuffer) BeginRead() (packetType, error) {
 	err := r.readNextPacket()
 	if err != nil {
 		return 0, err
 	}
-	return r.packet_type, nil
+	return r.rPacketType, nil
 }
 
 func (r *tdsBuffer) ReadByte() (res byte, err error) {
-	if r.pos == r.size {
+	if r.rpos == r.rsize {
 		if r.final {
 			return 0, io.EOF
 		}
@@ -142,8 +171,8 @@ func (r *tdsBuffer) ReadByte() (res byte, err error) {
 			return 0, err
 		}
 	}
-	res = r.buf[r.pos]
-	r.pos++
+	res = r.rbuf[r.rpos]
+	r.rpos++
 	return res, nil
 }
 
@@ -207,7 +236,7 @@ func (r *tdsBuffer) readUcs2(numchars int) string {
 func (r *tdsBuffer) Read(buf []byte) (copied int, err error) {
 	copied = 0
 	err = nil
-	if r.pos == r.size {
+	if r.rpos == r.rsize {
 		if r.final {
 			return 0, io.EOF
 		}
@@ -216,7 +245,7 @@ func (r *tdsBuffer) Read(buf []byte) (copied int, err error) {
 			return
 		}
 	}
-	copied = copy(buf, r.buf[r.pos:r.size])
-	r.pos += uint16(copied)
+	copied = copy(buf, r.rbuf[r.rpos:r.rsize])
+	r.rpos += copied
 	return
 }