remove writer from compressor

Author: methane

compress.go

@@ -87,15 +87,17 @@ func zCompress(src []byte, dst io.Writer) error {
 }
 
 type compressor struct {
-	mc         *mysqlConn
-	bytesBuf   []byte // read buffer (FIFO)
-	connWriter io.Writer
+	mc *mysqlConn
+	// read buffer (FIFO).
+	// We can not reuse already-read buffer until dropping Go 1.20 support.
+	// It is because of database/mysql's weired behavior.
+	// See https://github.com/go-sql-driver/mysql/issues/1435
+	bytesBuf []byte
 }
 
-func newCompressor(mc *mysqlConn, w io.Writer) *compressor {
+func newCompressor(mc *mysqlConn) *compressor {
 	return &compressor{
-		mc:         mc,
-		connWriter: w,
+		mc: mc,
 	}
 }
 
@@ -226,7 +228,7 @@ func (c *compressor) writeCompressedPacket(data []byte, uncompressedLen int) err
 	data[5] = byte(0xff & (uncompressedLen >> 8))
 	data[6] = byte(0xff & (uncompressedLen >> 16))
 
-	if _, err := c.connWriter.Write(data); err != nil {
+	if _, err := c.mc.netConn.Write(data); err != nil {
 		c.mc.cfg.Logger.Print(err)
 		return err
 	}

compress_test.go

@@ -13,6 +13,7 @@ import (
 	"crypto/rand"
 	"fmt"
 	"io"
+	"net"
 	"testing"
 )
 
@@ -34,14 +35,24 @@ func newMockBuf(data []byte) buffer {
 	}
 }
 
+type dummyConn struct {
+	buf bytes.Buffer
+	net.Conn
+}
+
+func (c *dummyConn) Write(data []byte) (int, error) {
+	return c.buf.Write(data)
+}
+
 // compressHelper compresses uncompressedPacket and checks state variables
 func compressHelper(t *testing.T, mc *mysqlConn, uncompressedPacket []byte) []byte {
 	// get status variables
 
 	cs := mc.compressSequence
 
-	var b bytes.Buffer
-	cw := newCompressor(mc, &b)
+	var b dummyConn
+	mc.netConn = &b
+	cw := newCompressor(mc)
 
 	n, err := cw.Write(uncompressedPacket)
 
@@ -64,7 +75,7 @@ func compressHelper(t *testing.T, mc *mysqlConn, uncompressedPacket []byte) []by
 		}
 	}
 
-	return b.Bytes()
+	return b.buf.Bytes()
 }
 
 // uncompressHelper uncompresses compressedPacket and checks state variables
@@ -74,7 +85,7 @@ func uncompressHelper(t *testing.T, mc *mysqlConn, compressedPacket []byte, expS
 
 	// mocking out buf variable
 	mc.buf = newMockBuf(compressedPacket)
-	cr := newCompressor(mc, nil)
+	cr := newCompressor(mc)
 
 	uncompressedPacket, err := cr.readNext(expSize)
 	if err != nil {

connector.go

@@ -169,7 +169,7 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
 	}
 
 	if mc.compress {
-		cmpr := newCompressor(mc, mc.packetWriter)
+		cmpr := newCompressor(mc)
 		mc.packetReader = cmpr
 		mc.packetWriter = cmpr
 	}