Optimise reader and writing (#12)

codec.go

@@ -130,7 +130,7 @@ type onePtrEncoder struct {
 }
 
 func (e *onePtrEncoder) Encode(ptr unsafe.Pointer, w *Writer) {
-	e.enc.Encode(unsafe.Pointer(&ptr), w)
+	e.enc.Encode(noescape(unsafe.Pointer(&ptr)), w)
 }
 
 func encoderOfType(cfg *frozenConfig, schema Schema, typ reflect2.Type) ValEncoder {

noescape.go

@@ -0,0 +1,8 @@
+package avro
+
+import (
+	"unsafe"
+)
+
+//go:linkname noescape runtime.noescape
+func noescape(p unsafe.Pointer) unsafe.Pointer

reader.go

@@ -185,8 +185,8 @@ func (r *Reader) ReadLong() int64 {
 
 // ReadFloat reads a Float from the Reader.
 func (r *Reader) ReadFloat() float32 {
-	buf := make([]byte, 4)
-	r.Read(buf)
+	var buf [4]byte
+	r.Read(buf[:])
 
 	float := *(*float32)(unsafe.Pointer(&buf[0]))
 
@@ -195,8 +195,8 @@ func (r *Reader) ReadFloat() float32 {
 
 // ReadDouble reads a Double from the Reader.
 func (r *Reader) ReadDouble() float64 {
-	buf := make([]byte, 8)
-	r.Read(buf)
+	var buf [8]byte
+	r.Read(buf[:])
 
 	float := *(*float64)(unsafe.Pointer(&buf[0]))
 
@@ -220,12 +220,19 @@ func (r *Reader) ReadBytes() []byte {
 
 // ReadString reads a String from the Reader.
 func (r *Reader) ReadString() string {
-	size := r.ReadLong()
+	size := int(r.ReadLong())
 	if size < 0 {
 		r.ReportError("ReadString", "invalid string length")
 		return ""
 	}
 
+	// The string is entirely in the current buffer, fast path.
+	if r.head+size < r.tail {
+		ret := string(r.buf[r.head : r.head+size])
+		r.head += size
+		return ret
+	}
+
 	buf := make([]byte, size)
 	r.Read(buf)
 

writer.go

@@ -172,16 +172,26 @@ func (w *Writer) WriteBlockHeader(l int64, s int64) {
 
 // WriteBlockCB writes a block using the callback.
 func (w *Writer) WriteBlockCB(callback func(w *Writer) int64) int64 {
-	capturedAt := len(w.buf)
+	var dummyHeader [18]byte
+	headerStart := len(w.buf)
+
+	// Write dummy header
+	w.Write(dummyHeader[:])
 
+	// Write block data
+	capturedAt := len(w.buf)
 	length := callback(w)
+	size := int64(len(w.buf) - capturedAt)
+
+	// Take a reference to the block data
+	captured := w.buf[capturedAt:len(w.buf)]
 
-	captured := make([]byte, len(w.buf)-capturedAt)
-	copy(captured, w.buf[capturedAt:])
-	w.buf = w.buf[:capturedAt]
+	// Rewrite the header
+	w.buf = w.buf[:headerStart]
+	w.WriteBlockHeader(length, size)
 
-	w.WriteBlockHeader(length, int64(len(captured)))
-	w.Write(captured)
+	// Copy the block data back to its position
+	w.buf = append(w.buf, captured...)
 
 	return length
 }