Add Write/Read Range

reader.go

@@ -215,6 +215,22 @@ func (r *Reader) ReadBytes() (out []byte, err error) {
 
 // --------------------------- Other Types ---------------------------
 
+// ReadRange reads the length of the array from the underlying stream and
+// calls a callback function on each element of that array.
+func (r *Reader) ReadRange(fn func(i int, r *Reader) error) error {
+	length, err := r.ReadUvarint()
+	if err != nil {
+		return err
+	}
+
+	for i := 0; i < int(length); i++ {
+		if err := fn(i, r); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // ReadBool reads a single boolean value from the slice.
 func (r *Reader) ReadBool() (bool, error) {
 	b, err := r.src.ReadByte()

writer.go

@@ -223,6 +223,22 @@ func (w *Writer) WriteBytes(v []byte) error {
 
 // --------------------------- Other Types ---------------------------
 
+// WriteRange writes a specified length of an array and for each element of that
+// array calls the callback function with its index.
+func (w *Writer) WriteRange(length int, fn func(i int, w *Writer) error) error {
+	if err := w.WriteUvarint(uint64(length)); err != nil {
+		return err
+	}
+
+	for i := 0; i < length; i++ {
+		if err := fn(i, w); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // WriteBool writes a single boolean value into the buffer
 func (w *Writer) WriteBool(v bool) error {
 	w.scratch[0] = 0

writer_test.go

@@ -158,6 +158,29 @@ var Fixtures = map[string]struct {
 		Buffer: []byte{0x5, 0x52, 0x6f, 0x6d, 0x61, 0x6e},
 		Value:  person{Name: "Roman"},
 	},
+	"range": {
+		Encode: func(w *Writer) error {
+			v := []person{{Name: "Roman"}, {Name: "Florimond"}}
+			return w.WriteRange(len(v), func(i int, w *Writer) error {
+				return w.WriteSelf(&v[i])
+			})
+		},
+		Decode: func(r *Reader) (interface{}, error) {
+			var arr []person
+			err := r.ReadRange(func(i int, r *Reader) error {
+				var out person
+				if err := r.ReadSelf(&out); err != nil {
+					return err
+				}
+
+				arr = append(arr, out)
+				return nil
+			})
+			return arr, err
+		},
+		Buffer: []byte{0x2, 0x5, 0x52, 0x6f, 0x6d, 0x61, 0x6e, 0x9, 0x46, 0x6c, 0x6f, 0x72, 0x69, 0x6d, 0x6f, 0x6e, 0x64},
+		Value:  []person{{Name: "Roman"}, {Name: "Florimond"}},
+	},
 }
 
 func TestWrite(t *testing.T) {
@@ -176,6 +199,14 @@ func TestWriteFailuresString(t *testing.T) {
 	}, nil, 0)
 }
 
+func TestWriteFailures(t *testing.T) {
+	for n, tc := range Fixtures {
+		for x := 0; x < int(len(tc.Buffer))-1; x++ {
+			assertWriteN(t, n, tc.Encode, nil, x)
+		}
+	}
+}
+
 func TestWriteMethod(t *testing.T) {
 	w := NewWriter(bytes.NewBuffer(nil))
 	_, err := w.Write(nil)