STOR-519: Add db-connect, a SQL over HTTPS server

vendor/github.com/kshvakov/clickhouse/lib/binary/compress_writer.go

@@ -0,0 +1,79 @@
+// +build !clz4
+
+package binary
+
+import (
+	"encoding/binary"
+	"io"
+
+	"github.com/kshvakov/clickhouse/lib/cityhash102"
+	"github.com/kshvakov/clickhouse/lib/lz4"
+)
+
+type compressWriter struct {
+	writer io.Writer
+	// data uncompressed
+	data []byte
+	// data position
+	pos int
+	// data compressed
+	zdata []byte
+}
+
+// NewCompressWriter wrap the io.Writer
+func NewCompressWriter(w io.Writer) *compressWriter {
+	p := &compressWriter{writer: w}
+	p.data = make([]byte, BlockMaxSize, BlockMaxSize)
+
+	zlen := lz4.CompressBound(BlockMaxSize) + HeaderSize
+	p.zdata = make([]byte, zlen, zlen)
+	return p
+}
+
+func (cw *compressWriter) Write(buf []byte) (int, error) {
+	var n int
+	for len(buf) > 0 {
+		// Accumulate the data to be compressed.
+		m := copy(cw.data[cw.pos:], buf)
+		cw.pos += m
+		buf = buf[m:]
+
+		if cw.pos == len(cw.data) {
+			err := cw.Flush()
+			if err != nil {
+				return n, err
+			}
+		}
+		n += m
+	}
+	return n, nil
+}
+
+func (cw *compressWriter) Flush() (err error) {
+	if cw.pos == 0 {
+		return
+	}
+
+	// write the headers
+	compressedSize, err := lz4.Encode(cw.zdata[HeaderSize:], cw.data[:cw.pos])
+	if err != nil {
+		return err
+	}
+	compressedSize += CompressHeaderSize
+	// fill the header, compressed_size_32 + uncompressed_size_32
+	cw.zdata[16] = LZ4
+	binary.LittleEndian.PutUint32(cw.zdata[17:], uint32(compressedSize))
+	binary.LittleEndian.PutUint32(cw.zdata[21:], uint32(cw.pos))
+
+	// fill the checksum
+	checkSum := cityhash102.CityHash128(cw.zdata[16:], uint32(compressedSize))
+	binary.LittleEndian.PutUint64(cw.zdata[0:], checkSum.Lower64())
+	binary.LittleEndian.PutUint64(cw.zdata[8:], checkSum.Higher64())
+
+	cw.writer.Write(cw.zdata[:compressedSize+ChecksumSize])
+	if w, ok := cw.writer.(WriteFlusher); ok {
+		err = w.Flush()
+	}
+	cw.pos = 0
+	return
+}