add more methods to the protocol.ConnectionID

This will make it easier to change the underlying type of the connection
ID (potentially an array is faster than a byte slice).

internal/protocol/connection_id.go

@@ -3,6 +3,8 @@ package protocol
 import (
 	"bytes"
 	"crypto/rand"
+	"fmt"
+	"io"
 )
 
 // A ConnectionID in QUIC
@@ -17,7 +19,38 @@ func GenerateConnectionID() (ConnectionID, error) {
 	return ConnectionID(b), nil
 }
 
+// ReadConnectionID reads a connection ID of length len from the given io.Reader.
+// It returns io.EOF if there are not enough bytes to read.
+func ReadConnectionID(r io.Reader, len int) (ConnectionID, error) {
+	if len == 0 {
+		return nil, nil
+	}
+	c := make(ConnectionID, len)
+	_, err := io.ReadFull(r, c)
+	if err == io.ErrUnexpectedEOF {
+		return nil, io.EOF
+	}
+	return c, err
+}
+
 // Equal says if two connection IDs are equal
 func (c ConnectionID) Equal(other ConnectionID) bool {
 	return bytes.Equal(c, other)
 }
+
+// Len returns the length of the connection ID in bytes
+func (c ConnectionID) Len() int {
+	return len(c)
+}
+
+// Bytes returns the byte representation
+func (c ConnectionID) Bytes() []byte {
+	return []byte(c)
+}
+
+func (c ConnectionID) String() string {
+	if c.Len() == 0 {
+		return "(empty)"
+	}
+	return fmt.Sprintf("%#x", c.Bytes())
+}

internal/protocol/connection_id_test.go

@@ -1,6 +1,9 @@
 package protocol
 
 import (
+	"bytes"
+	"io"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )
@@ -23,4 +26,59 @@ var _ = Describe("Connection ID generation", func() {
 		Expect(c1.Equal(c2)).To(BeFalse())
 		Expect(c2.Equal(c1)).To(BeFalse())
 	})
+
+	It("reads the connection ID", func() {
+		buf := bytes.NewBuffer([]byte{1, 2, 3, 4, 5, 6, 7, 8, 9})
+		c, err := ReadConnectionID(buf, 9)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(c.Bytes()).To(Equal([]byte{1, 2, 3, 4, 5, 6, 7, 8, 9}))
+	})
+
+	It("returns io.EOF if there's not enough data to read", func() {
+		buf := bytes.NewBuffer([]byte{1, 2, 3, 4})
+		_, err := ReadConnectionID(buf, 5)
+		Expect(err).To(MatchError(io.EOF))
+	})
+
+	It("returns nil for a 0 length connection ID", func() {
+		buf := bytes.NewBuffer([]byte{1, 2, 3, 4})
+		c, err := ReadConnectionID(buf, 0)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(c).To(BeNil())
+	})
+
+	It("returns the length", func() {
+		c := ConnectionID{1, 2, 3, 4, 5, 6, 7}
+		Expect(c.Len()).To(Equal(7))
+	})
+
+	It("has 0 length for the default value", func() {
+		var c ConnectionID
+		Expect(c.Len()).To(BeZero())
+	})
+
+	It("returns the bytes", func() {
+		c := ConnectionID([]byte{1, 2, 3, 4, 5, 6, 7})
+		Expect(c.Bytes()).To(Equal([]byte{1, 2, 3, 4, 5, 6, 7}))
+	})
+
+	It("returns a nil byte slice for the default value", func() {
+		var c ConnectionID
+		Expect(c.Bytes()).To(BeNil())
+	})
+
+	It("has a string representation", func() {
+		c := ConnectionID([]byte{0xde, 0xad, 0xbe, 0xef, 0x42})
+		Expect(c.String()).To(Equal("0xdeadbeef42"))
+	})
+
+	It("has a long string representation", func() {
+		c := ConnectionID{0x13, 0x37, 0, 0, 0xde, 0xca, 0xfb, 0xad}
+		Expect(c.String()).To(Equal("0x13370000decafbad"))
+	})
+
+	It("has a string representation for the default value", func() {
+		var c ConnectionID
+		Expect(c.String()).To(Equal("(empty)"))
+	})
 })