lib/prompb: remove superflouos bytes copying in ReadSnappy

lib/bytesutil/bytebuffer.go

@@ -13,6 +13,7 @@ var (
 	// Verify ByteBuffer implements the given interfaces.
 	_ io.Writer       = &ByteBuffer{}
 	_ fs.ReadAtCloser = &ByteBuffer{}
+	_ io.ReaderFrom   = &ByteBuffer{}
 
 	// Verify reader implement filestream.ReadCloser interface.
 	_ filestream.ReadCloser = &reader{}
@@ -48,6 +49,30 @@ func (bb *ByteBuffer) ReadAt(p []byte, offset int64) {
 	}
 }
 
+// ReadFrom reads all the data from r to bb until EOF.
+func (bb *ByteBuffer) ReadFrom(r io.Reader) (int64, error) {
+	b := bb.B
+	bLen := len(b)
+	b = Resize(b, 4*1024)
+	b = b[:cap(b)]
+	offset := bLen
+	for {
+		if free := len(b) - offset; free < offset {
+			n := len(b)
+			b = append(b, make([]byte, n)...)
+		}
+		n, err := r.Read(b[offset:])
+		offset += n
+		if err != nil {
+			bb.B = b[:offset]
+			if err == io.EOF {
+				err = nil
+			}
+			return int64(offset - bLen), err
+		}
+	}
+}
+
 // MustClose closes bb for subsequent re-use.
 func (bb *ByteBuffer) MustClose() {
 	// Do nothing, since certain code rely on bb reading after MustClose call.

lib/bytesutil/bytebuffer_test.go

@@ -1,6 +1,7 @@
 package bytesutil
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"testing"
@@ -66,6 +67,92 @@ func TestByteBuffer(t *testing.T) {
 	}
 }
 
+func TestByteBufferReadFrom(t *testing.T) {
+	var bbPool ByteBufferPool
+
+	t.Run("zero_bytes", func(t *testing.T) {
+		t.Parallel()
+		bb := bbPool.Get()
+		defer bbPool.Put(bb)
+		src := bytes.NewBufferString("")
+		n, err := bb.ReadFrom(src)
+		if err != nil {
+			t.Fatalf("error when reading empty string: %s", err)
+		}
+		if n != 0 {
+			t.Fatalf("unexpected number of bytes read; got %d; want %d", n, 0)
+		}
+		if len(bb.B) != 0 {
+			t.Fatalf("unexpejcted len(bb.B); got %d; want %d", len(bb.B), 0)
+		}
+	})
+
+	t.Run("non_zero_bytes", func(t *testing.T) {
+		t.Parallel()
+		bb := bbPool.Get()
+		defer bbPool.Put(bb)
+		s := "foobarbaz"
+		src := bytes.NewBufferString(s)
+		n, err := bb.ReadFrom(src)
+		if err != nil {
+			t.Fatalf("error when reading non-empty string: %s", err)
+		}
+		if n != int64(len(s)) {
+			t.Fatalf("unexpected number of bytes read; got %d; want %d", n, len(s))
+		}
+		if string(bb.B) != s {
+			t.Fatalf("unexpected value read; got %q; want %q", bb.B, s)
+		}
+	})
+
+	t.Run("big_number_of_bytes", func(t *testing.T) {
+		t.Parallel()
+		bb := bbPool.Get()
+		defer bbPool.Put(bb)
+		b := make([]byte, 1024*1024+234)
+		for i := range b {
+			b[i] = byte(i)
+		}
+		src := bytes.NewBuffer(b)
+		n, err := bb.ReadFrom(src)
+		if err != nil {
+			t.Fatalf("cannot read big value: %s", err)
+		}
+		if n != int64(len(b)) {
+			t.Fatalf("unexpected number of bytes read; got %d; want %d", n, len(b))
+		}
+		if string(bb.B) != string(b) {
+			t.Fatalf("unexpected value read; got %q; want %q", bb.B, b)
+		}
+	})
+
+	t.Run("non_empty_bb", func(t *testing.T) {
+		t.Parallel()
+		bb := bbPool.Get()
+		defer bbPool.Put(bb)
+		prefix := []byte("prefix")
+		bb.B = append(bb.B[:0], prefix...)
+		s := "aosdfdsafdjsf"
+		src := bytes.NewBufferString(s)
+		n, err := bb.ReadFrom(src)
+		if err != nil {
+			t.Fatalf("cannot read to non-empty bb: %s", err)
+		}
+		if n != int64(len(s)) {
+			t.Fatalf("unexpected number of bytes read; got %d; want %d", n, len(s))
+		}
+		if len(bb.B) != len(prefix)+len(s) {
+			t.Fatalf("unexpected bb.B len; got %d; want %d", len(bb.B), len(prefix)+len(s))
+		}
+		if string(bb.B[:len(prefix)]) != string(prefix) {
+			t.Fatalf("unexpected prefix; got %q; want %q", bb.B[:len(prefix)], prefix)
+		}
+		if string(bb.B[len(prefix):]) != s {
+			t.Fatalf("unexpected data read; got %q; want %q", bb.B[len(prefix):], s)
+		}
+	})
+}
+
 func TestByteBufferRead(t *testing.T) {
 	var bb ByteBuffer
 

lib/prompb/util.go

@@ -11,13 +11,9 @@ import (
 // ReadSnappy reads r, unpacks it using snappy, appends it to dst
 // and returns the result.
 func ReadSnappy(dst []byte, r io.Reader, maxSize int64) ([]byte, error) {
-	bb := bodyBufferPool.Get()
-	bb.B = bb.B[:0]
-	cb := copyBufferPool.Get()
-	cb.B = bytesutil.Resize(cb.B, 16*1024)
 	lr := io.LimitReader(r, maxSize+1)
-	reqLen, err := io.CopyBuffer(bb, lr, cb.B)
-	copyBufferPool.Put(cb)
+	bb := bodyBufferPool.Get()
+	reqLen, err := bb.ReadFrom(lr)
 	if err != nil {
 		bodyBufferPool.Put(bb)
 		return dst, fmt.Errorf("cannot read compressed request: %s", err)
@@ -45,7 +41,6 @@ func ReadSnappy(dst []byte, r io.Reader, maxSize int64) ([]byte, error) {
 }
 
 var bodyBufferPool bytesutil.ByteBufferPool
-var copyBufferPool bytesutil.ByteBufferPool
 
 // Reset resets wr.
 func (wr *WriteRequest) Reset() {