implement a caching reader needed for crypto streams

utils/caching_reader.go

@@ -0,0 +1,35 @@
+package utils
+
+import "bytes"
+
+// CachingReader wraps a reader and saves all data it reads
+type CachingReader struct {
+	buf bytes.Buffer
+	r   ReadStream
+}
+
+// NewCachingReader returns a new CachingReader
+func NewCachingReader(r ReadStream) *CachingReader {
+	return &CachingReader{r: r}
+}
+
+// Read implements io.Reader
+func (r *CachingReader) Read(p []byte) (int, error) {
+	n, err := r.r.Read(p)
+	r.buf.Write(p[:n])
+	return n, err
+}
+
+// ReadByte implements io.ByteReader
+func (r *CachingReader) ReadByte() (byte, error) {
+	b, err := r.r.ReadByte()
+	if err == nil {
+		r.buf.WriteByte(b)
+	}
+	return b, err
+}
+
+// Get the data cached
+func (r *CachingReader) Get() []byte {
+	return r.buf.Bytes()
+}

utils/caching_reader_test.go

@@ -0,0 +1,36 @@
+package utils
+
+import (
+	"bytes"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Caching reader", func() {
+	It("caches Read()", func() {
+		r := bytes.NewReader([]byte("foobar"))
+		cr := NewCachingReader(r)
+		p := make([]byte, 3)
+		n, err := cr.Read(p)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(n).To(Equal(3))
+		Expect(p).To(Equal([]byte("foo")))
+		Expect(cr.Get()).To(Equal([]byte("foo")))
+	})
+
+	It("caches ReadByte()", func() {
+		r := bytes.NewReader([]byte("foobar"))
+		cr := NewCachingReader(r)
+		b, err := cr.ReadByte()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(b).To(Equal(byte('f')))
+		b, err = cr.ReadByte()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(b).To(Equal(byte('o')))
+		b, err = cr.ReadByte()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(b).To(Equal(byte('o')))
+		Expect(cr.Get()).To(Equal([]byte("foo")))
+	})
+})

utils/utils.go

@@ -6,6 +6,19 @@ import (
 	"io"
 )
 
+// ReadStream is the read part of a QUIC stream
+type ReadStream interface {
+	io.Reader
+	io.ByteReader
+}
+
+// Stream is the interface for QUIC streams
+type Stream interface {
+	io.Reader
+	io.ByteReader
+	io.Writer
+}
+
 // ReadUintN reads N bytes
 func ReadUintN(b io.ByteReader, length uint8) (uint64, error) {
 	var res uint64