ByteStream consumer can write to interface{}

* fix(ByteStreamConsumer): may now write into an interface which
  underlying type is []byte or string.

* feat(ByteStreamConsumer): added support to io.ReaderFrom, preferred
  over io.Writer if available
* feat(ByteStreamProducer): added support to io.WriterTo, preferred
  over io.Reader if available

* refact(ByteStreamProducer): removed redundant case "string" and preferred
  the more general reflected case (supports aliased strings)

* test: refactored ByteStream tests
* test: added benchmark for bytestream.Consume

* fixes #167

Signed-off-by: Frederic BIDON <fredbi@yahoo.com>

bytestream.go

@@ -38,9 +38,16 @@ type byteStreamOpts struct {
 	Close bool
 }
 
-// ByteStreamConsumer creates a consumer for byte streams,
-// takes a Writer/BinaryUnmarshaler interface or binary slice by reference,
-// and reads from the provided reader
+// ByteStreamConsumer creates a consumer for byte streams.
+//
+// The consumer consumes from a provided reader into the data passed by reference.
+//
+// Supported output underlying types and interfaces, prioritized in this order:
+// - io.ReaderFrom (for maximum control)
+// - io.Writer (performs io.Copy)
+// - encoding.BinaryUnmarshaler
+// - *string
+// - *[]byte
 func ByteStreamConsumer(opts ...byteStreamOpt) Consumer {
 	var vals byteStreamOpts
 	for _, opt := range opts {
@@ -51,45 +58,70 @@ func ByteStreamConsumer(opts ...byteStreamOpt) Consumer {
 		if reader == nil {
 			return errors.New("ByteStreamConsumer requires a reader") // early exit
 		}
+		if data == nil {
+			return errors.New("nil destination for ByteStreamConsumer")
+		}
 
 		closer := defaultCloser
 		if vals.Close {
-			if cl, ok := reader.(io.Closer); ok {
+			if cl, isReaderCloser := reader.(io.Closer); isReaderCloser {
 				closer = cl.Close
 			}
 		}
 		defer func() {
 			_ = closer()
 		}()
 
-		if wrtr, ok := data.(io.Writer); ok {
-			_, err := io.Copy(wrtr, reader)
+		if readerFrom, isReaderFrom := data.(io.ReaderFrom); isReaderFrom {
+			_, err := readerFrom.ReadFrom(reader)
 			return err
 		}
 
-		buf := new(bytes.Buffer)
+		if writer, isDataWriter := data.(io.Writer); isDataWriter {
+			_, err := io.Copy(writer, reader)
+			return err
+		}
+
+		// buffers input before writing to data
+		var buf bytes.Buffer
 		_, err := buf.ReadFrom(reader)
 		if err != nil {
 			return err
 		}
 		b := buf.Bytes()
 
-		if bu, ok := data.(encoding.BinaryUnmarshaler); ok {
-			return bu.UnmarshalBinary(b)
-		}
+		switch destinationPointer := data.(type) {
+		case encoding.BinaryUnmarshaler:
+			return destinationPointer.UnmarshalBinary(b)
+		case *any:
+			switch (*destinationPointer).(type) {
+			case string:
+				*destinationPointer = string(b)
+
+				return nil
+
+			case []byte:
+				*destinationPointer = b
 
-		if data != nil {
-			if str, ok := data.(*string); ok {
-				*str = string(b)
 				return nil
 			}
-		}
+		default:
+			// check for the underlying type to be pointer to []byte or string,
+			if ptr := reflect.TypeOf(data); ptr.Kind() != reflect.Ptr {
+				return errors.New("destination must be a pointer")
+			}
 
-		if t := reflect.TypeOf(data); data != nil && t.Kind() == reflect.Ptr {
 			v := reflect.Indirect(reflect.ValueOf(data))
-			if t = v.Type(); t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Uint8 {
+			t := v.Type()
+
+			switch {
+			case t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Uint8:
 				v.SetBytes(b)
 				return nil
+
+			case t.Kind() == reflect.String:
+				v.SetString(string(b))
+				return nil
 			}
 		}
 
@@ -98,68 +130,87 @@ func ByteStreamConsumer(opts ...byteStreamOpt) Consumer {
 	})
 }
 
-// ByteStreamProducer creates a producer for byte streams,
-// takes a Reader/BinaryMarshaler interface or binary slice,
-// and writes to a writer (essentially a pipe)
+// ByteStreamProducer creates a producer for byte streams.
+//
+// The producer takes input data then writes to an output writer (essentially as a pipe).
+//
+// Supported input underlying types and interfaces, prioritized in this order:
+// - io.WriterTo (for maximum control)
+// - io.Reader (performs io.Copy). A ReadCloser is closed before exiting.
+// - encoding.BinaryMarshaler
+// - error (writes as a string)
+// - []byte
+// - string
+// - struct, other slices: writes as JSON
 func ByteStreamProducer(opts ...byteStreamOpt) Producer {
 	var vals byteStreamOpts
 	for _, opt := range opts {
 		opt(&vals)
 	}
+
 	return ProducerFunc(func(writer io.Writer, data interface{}) error {
 		if writer == nil {
 			return errors.New("ByteStreamProducer requires a writer") // early exit
 		}
+		if data == nil {
+			return errors.New("nil destination for ByteStreamProducer")
+		}
+
 		closer := defaultCloser
 		if vals.Close {
-			if cl, ok := writer.(io.Closer); ok {
+			if cl, isWriterCloser := writer.(io.Closer); isWriterCloser {
 				closer = cl.Close
 			}
 		}
 		defer func() {
 			_ = closer()
 		}()
 
-		if rc, ok := data.(io.ReadCloser); ok {
+		if rc, isDataCloser := data.(io.ReadCloser); isDataCloser {
 			defer rc.Close()
 		}
 
-		if rdr, ok := data.(io.Reader); ok {
-			_, err := io.Copy(writer, rdr)
+		switch origin := data.(type) {
+		case io.WriterTo:
+			_, err := origin.WriteTo(writer)
+			return err
+
+		case io.Reader:
+			_, err := io.Copy(writer, origin)
 			return err
-		}
 
-		if bm, ok := data.(encoding.BinaryMarshaler); ok {
-			bytes, err := bm.MarshalBinary()
+		case encoding.BinaryMarshaler:
+			bytes, err := origin.MarshalBinary()
 			if err != nil {
 				return err
 			}
 
 			_, err = writer.Write(bytes)
 			return err
-		}
-
-		if data != nil {
-			if str, ok := data.(string); ok {
-				_, err := writer.Write([]byte(str))
-				return err
-			}
 
-			if e, ok := data.(error); ok {
-				_, err := writer.Write([]byte(e.Error()))
-				return err
-			}
+		case error:
+			_, err := writer.Write([]byte(origin.Error()))
+			return err
 
+		default:
 			v := reflect.Indirect(reflect.ValueOf(data))
-			if t := v.Type(); t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Uint8 {
+			t := v.Type()
+
+			switch {
+			case t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Uint8:
 				_, err := writer.Write(v.Bytes())
 				return err
-			}
-			if t := v.Type(); t.Kind() == reflect.Struct || t.Kind() == reflect.Slice {
+
+			case t.Kind() == reflect.String:
+				_, err := writer.Write([]byte(v.String()))
+				return err
+
+			case t.Kind() == reflect.Struct || t.Kind() == reflect.Slice:
 				b, err := swag.WriteJSON(data)
 				if err != nil {
 					return err
 				}
+
 				_, err = writer.Write(b)
 				return err
 			}