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package mssql
import (
"encoding/binary"
"errors"
"io"
)
type packetType uint8
type header struct {
PacketType packetType
Status uint8
Size uint16
Spid uint16
PacketNo uint8
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 {
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
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 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) {
// Write packet size.
w.wbuf[0] = byte(w.wPacketType)
binary.BigEndian.PutUint16(w.wbuf[2:], uint16(w.wpos))
w.wbuf[6] = w.wPacketSeq
// 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.
if w.afterFirst != nil {
w.afterFirst()
w.afterFirst = nil
}
w.wpos = 8
w.wPacketSeq++
return nil
}
func (w *tdsBuffer) Write(p []byte) (total int, err error) {
for {
copied := copy(w.wbuf[w.wpos:w.packetSize], p)
w.wpos += copied
total += copied
if copied == len(p) {
return
}
if err = w.flush(); err != nil {
return
}
p = p[copied:]
}
}
func (w *tdsBuffer) WriteByte(b byte) error {
if int(w.wpos) == len(w.wbuf) || w.wpos == w.packetSize {
if err := w.flush(); err != nil {
return err
}
}
w.wbuf[w.wpos] = b
w.wpos += 1
return nil
}
func (w *tdsBuffer) BeginPacket(packetType packetType, resetSession bool) {
status := byte(0)
if resetSession {
switch packetType {
// Reset session can only be set on the following packet types.
case packSQLBatch, packRPCRequest, packTransMgrReq:
status = 0x8
}
}
w.wbuf[1] = status // 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.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 {
h := header{}
var err error
err = binary.Read(r.transport, binary.BigEndian, &h)
if err != nil {
return err
}
if int(h.Size) > r.packetSize {
return errors.New("Invalid packet size, it is longer than buffer size")
}
if headerSize > int(h.Size) {
return errors.New("Invalid packet size, it is shorter than header size")
}
_, err = io.ReadFull(r.transport, r.rbuf[headerSize:h.Size])
if err != nil {
return err
}
r.rpos = headerSize
r.rsize = int(h.Size)
r.final = h.Status != 0
r.rPacketType = h.PacketType
return nil
}
func (r *tdsBuffer) BeginRead() (packetType, error) {
err := r.readNextPacket()
if err != nil {
return 0, err
}
return r.rPacketType, nil
}
func (r *tdsBuffer) ReadByte() (res byte, err error) {
if r.rpos == r.rsize {
if r.final {
return 0, io.EOF
}
err = r.readNextPacket()
if err != nil {
return 0, err
}
}
res = r.rbuf[r.rpos]
r.rpos++
return res, nil
}
func (r *tdsBuffer) byte() byte {
b, err := r.ReadByte()
if err != nil {
badStreamPanic(err)
}
return b
}
func (r *tdsBuffer) ReadFull(buf []byte) {
_, err := io.ReadFull(r, buf[:])
if err != nil {
badStreamPanic(err)
}
}
func (r *tdsBuffer) uint64() uint64 {
var buf [8]byte
r.ReadFull(buf[:])
return binary.LittleEndian.Uint64(buf[:])
}
func (r *tdsBuffer) int32() int32 {
return int32(r.uint32())
}
func (r *tdsBuffer) uint32() uint32 {
var buf [4]byte
r.ReadFull(buf[:])
return binary.LittleEndian.Uint32(buf[:])
}
func (r *tdsBuffer) uint16() uint16 {
var buf [2]byte
r.ReadFull(buf[:])
return binary.LittleEndian.Uint16(buf[:])
}
func (r *tdsBuffer) BVarChar() string {
l := int(r.byte())
return r.readUcs2(l)
}
func (r *tdsBuffer) UsVarChar() string {
l := int(r.uint16())
return r.readUcs2(l)
}
func (r *tdsBuffer) readUcs2(numchars int) string {
b := make([]byte, numchars*2)
r.ReadFull(b)
res, err := ucs22str(b)
if err != nil {
badStreamPanic(err)
}
return res
}
func (r *tdsBuffer) Read(buf []byte) (copied int, err error) {
copied = 0
err = nil
if r.rpos == r.rsize {
if r.final {
return 0, io.EOF
}
err = r.readNextPacket()
if err != nil {
return
}
}
copied = copy(buf, r.rbuf[r.rpos:r.rsize])
r.rpos += copied
return
}
|
