quicvarint: add Reader and Writer interfaces (#3233)

quicvarint/io_test.go

@@ -0,0 +1,72 @@
+package quicvarint
+
+import (
+	"bytes"
+	"io"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+type nopReader struct{}
+
+func (r *nopReader) Read(_ []byte) (int, error) {
+	return 0, io.ErrUnexpectedEOF
+}
+
+var _ io.Reader = &nopReader{}
+
+type nopWriter struct{}
+
+func (r *nopWriter) Write(_ []byte) (int, error) {
+	return 0, io.ErrShortBuffer
+}
+
+var _ io.Writer = &nopWriter{}
+
+var _ = Describe("Varint I/O", func() {
+	Context("Reader", func() {
+		Context("NewReader", func() {
+			It("passes through a Reader unchanged", func() {
+				b := bytes.NewReader([]byte{0})
+				r := NewReader(b)
+				Expect(r).To(Equal(b))
+			})
+
+			It("wraps an io.Reader", func() {
+				n := &nopReader{}
+				r := NewReader(n)
+				Expect(r).ToNot(Equal(n))
+			})
+		})
+
+		It("returns an error when reading from an underlying io.Reader fails", func() {
+			r := NewReader(&nopReader{})
+			val, err := r.ReadByte()
+			Expect(err).To(Equal(io.ErrUnexpectedEOF))
+			Expect(val).To(Equal(byte(0)))
+		})
+	})
+
+	Context("Writer", func() {
+		Context("NewWriter", func() {
+			It("passes through a Writer unchanged", func() {
+				b := &bytes.Buffer{}
+				w := NewWriter(b)
+				Expect(w).To(Equal(b))
+			})
+
+			It("wraps an io.Writer", func() {
+				n := &nopWriter{}
+				w := NewWriter(n)
+				Expect(w).ToNot(Equal(n))
+			})
+		})
+
+		It("returns an error when writing to an underlying io.Writer fails", func() {
+			w := NewWriter(&nopWriter{})
+			err := w.WriteByte(0)
+			Expect(err).To(Equal(io.ErrShortBuffer))
+		})
+	})
+})