implement a caching reader needed for crypto streams

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")))
+	})
+})