Add Map as new primitive type

Author: oxzi

README.md

@@ -6,12 +6,13 @@ developed to be used in [`dtn7-go`][dtn7-go], an implementation of the
 `cboring` is both boring to use and bored about the amount of data to handle.
 
 
-## Non-Features
+## Features
 
-- Supports the subset of [CBOR's][cbor] features necessary for [BPv7][bpbis]:
+- Supports a selected subset of [CBOR's][cbor] features:
     - Unsigned Integer
     - Byte and Text String
     - Arrays, both of definite and indefinite length
+    - Maps of definite length
     - Booleans
 - Small and clear codebase:
     - Only works on streams, Go's `io.Reader` or `io.Writer`

major.go

@@ -13,6 +13,7 @@ const (
 	ByteString MajorType = 0x40
 	TextString MajorType = 0x60
 	Array      MajorType = 0x80
+	Map        MajorType = 0xA0
 	SimpleData MajorType = 0xE0
 )
 

primitives.go

@@ -55,3 +55,17 @@ func ReadArrayLength(r io.Reader) (n uint64, err error) {
 func WriteArrayLength(n uint64, w io.Writer) error {
 	return WriteMajors(Array, n, w)
 }
+
+/*** Map ***/
+
+// ReadMapPairLength expects a map at the Reader's position and returns the
+// amount of pairs stored.
+func ReadMapPairLength(r io.Reader) (n uint64, err error) {
+	return ReadExpectMajors(Map, r)
+}
+
+// WriteMapPairLength writes the type definition for a map with the given
+// amount of pairs into the Writer.
+func WriteMapPairLength(n uint64, w io.Writer) error {
+	return WriteMajors(Map, n, w)
+}

primitives_test.go

@@ -167,3 +167,36 @@ func TestArrayLen(t *testing.T) {
 		}
 	}
 }
+
+/*** Map ***/
+
+func TestMapPairLen(t *testing.T) {
+	tests := []struct {
+		data []byte
+		len  uint64
+	}{
+		{[]byte{0xA0}, 0},
+		{[]byte{0xA1}, 1},
+		{[]byte{0xB8, 0x19}, 25},
+	}
+
+	for _, test := range tests {
+		// Read
+		buff := bytes.NewBuffer(test.data)
+		if n, err := ReadMapPairLength(buff); err != nil {
+			t.Fatal(err)
+		} else if n != test.len {
+			t.Fatalf("Resulting length %d is not %d", n, test.len)
+		}
+
+		// Write
+		buff.Reset()
+		if err := WriteMapPairLength(test.len, buff); err != nil {
+			t.Fatal(err)
+		}
+
+		if bb := buff.Bytes(); !reflect.DeepEqual(bb, test.data) {
+			t.Fatalf("Serialized data mismatches: %x != %x", bb, test.data)
+		}
+	}
+}