chore: add comment

apache_adaptor/adaptor.go

@@ -24,49 +24,16 @@ import (
 	"github.com/cloudwego/gopkg/protocol/thrift"
 )
 
-type bufioxReaderWriter interface {
-	GetBufioxReader() bufiox.Reader
-	GetBufioxWriter() bufiox.Writer
-}
-
-type ByteBuffer interface {
-	// Next reads the next n bytes sequentially and returns the original buffer.
-	Next(n int) (p []byte, err error)
-
-	// ReadableLen returns the total length of readable buffer.
-	// Return: -1 means unreadable.
-	ReadableLen() (n int)
-}
-
-type nextReader struct {
-	nx ByteBuffer
-}
-
-func (nr nextReader) Read(p []byte) (n int, err error) {
-	readable := nr.nx.ReadableLen()
-	if readable == -1 {
-		return 0, err
-	}
-	if readable > len(p) {
-		readable = len(p)
-	}
-	data, err := nr.nx.Next(readable)
-	if err != nil {
-		return -1, err
-	}
-	copy(p, data)
-	return readable, nil
-}
-
-func next2Reader(n ByteBuffer) io.Reader {
-	return &nextReader{nx: n}
-}
-
+// AdaptRead receive a kitex binary protocol and read it by given function.
 func AdaptRead(iprot interface{}, readFunc func(buf []byte) (int, error)) error {
 	var br bufiox.Reader
+	// if iprot is from kitex v0.12.0+, use interface assert to get bufiox reader
 	if bp, ok := iprot.(bufioxReaderWriter); ok {
 		br = bp.GetBufioxReader()
 	} else {
+		// if iprot is from kitex version lower than v0.12.0, use reflection to get reader
+		// in kitex v0.10.0, reader is from the field 'br' which is a bufiox.Reader
+		// in kitex under v0.10.0, reader is from the field 'trans' which is kitex byteBuffer (mostly NetpollByteBuffer)
 		fieldNames := []string{"br", "trans"}
 		for _, fn := range fieldNames {
 			reader, exist, err := getUnexportField(iprot, fn)
@@ -77,7 +44,9 @@ func AdaptRead(iprot interface{}, readFunc func(buf []byte) (int, error)) error
 				switch r := reader.(type) {
 				case bufiox.Reader:
 					br = r
-				case ByteBuffer:
+				case byteBuffer:
+					// if reader is from byteBuffer, Read() function is not always available
+					// so use an adaptor to implement Read()  by Next() and ReadableLen()
 					rd := next2Reader(r)
 					br = bufiox.NewDefaultReader(rd)
 				default:
@@ -98,11 +67,16 @@ func AdaptRead(iprot interface{}, readFunc func(buf []byte) (int, error)) error
 	return err
 }
 
+// AdaptWrite receive a kitex binary protocol and write it by given function.
 func AdaptWrite(oprot interface{}, writeFunc func() []byte) error {
 	var bw bufiox.Writer
+	// if iprot is from kitex v0.12.0+, use interface assert to get bufiox writer
 	if bp, ok := oprot.(bufioxReaderWriter); ok {
 		bw = bp.GetBufioxWriter()
 	} else {
+		// if iprot is from kitex version lower than v0.12.0, use reflection to get writer
+		// in kitex v0.10.0, writer is from the field 'bw' which is a bufiox.Writer
+		// in kitex under v0.10.0, writer is from the field 'trans' which implements the interface io.Writer
 		fieldNames := []string{"bw", "trans"}
 		for _, fn := range fieldNames {
 			writer, exist, err := getUnexportField(oprot, fn)
@@ -133,6 +107,7 @@ func AdaptWrite(oprot interface{}, writeFunc func() []byte) error {
 	return bw.Flush()
 }
 
+// getUnexportField retrieves the value of an unexported struct field.
 func getUnexportField(p interface{}, fieldName string) (value interface{}, ok bool, error error) {
 	if reflect.TypeOf(p).Kind() != reflect.Ptr {
 		return nil, false, fmt.Errorf("%s is not a ptr", p)
@@ -143,3 +118,45 @@ func getUnexportField(p interface{}, fieldName string) (value interface{}, ok bo
 	}
 	return nil, false, nil
 }
+
+// bufioxReaderWriter
+type bufioxReaderWriter interface {
+	GetBufioxReader() bufiox.Reader
+	GetBufioxWriter() bufiox.Writer
+}
+
+// byteBuffer
+type byteBuffer interface {
+	// Next reads the next n bytes sequentially and returns the original buffer.
+	Next(n int) (p []byte, err error)
+
+	// ReadableLen returns the total length of readable buffer.
+	// Return: -1 means unreadable.
+	ReadableLen() (n int)
+}
+
+// nextReader is an adaptor that implement Read() by Next() and ReadableLen()
+type nextReader struct {
+	nx byteBuffer
+}
+
+// Read reads data from the nextReader's internal buffer into p.
+func (nr nextReader) Read(p []byte) (n int, err error) {
+	readable := nr.nx.ReadableLen()
+	if readable == -1 {
+		return 0, err
+	}
+	if readable > len(p) {
+		readable = len(p)
+	}
+	data, err := nr.nx.Next(readable)
+	if err != nil {
+		return -1, err
+	}
+	copy(p, data)
+	return readable, nil
+}
+
+func next2Reader(n byteBuffer) io.Reader {
+	return &nextReader{nx: n}
+}