commit c54facf66be1c4e137121f36b300543f6673ea7c
Author: Alexander Neumann <alexander@bumpern.de>
Date:   Sun Apr 6 12:22:58 2014 +0200

    Add hashing package

diff --git a/hashing/hashing_suite_test.go b/hashing/hashing_suite_test.go
new file mode 100644
index 000000000..880599f83
--- /dev/null
+++ b/hashing/hashing_suite_test.go
@@ -0,0 +1,12 @@
+package hashing_test
+
+import (
+	"testing"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+func TestHashing(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Hashing Suite")
+}
diff --git a/hashing/hashing_test.go b/hashing/hashing_test.go
new file mode 100644
index 000000000..67a8e8676
--- /dev/null
+++ b/hashing/hashing_test.go
@@ -0,0 +1,77 @@
+package hashing_test
+
+import (
+	"bytes"
+	"crypto/md5"
+	"crypto/sha1"
+	"encoding/hex"
+	"hash"
+
+	"github.com/fd0/khepri/hashing"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Hashing", func() {
+	var static_tests = []struct {
+		hash   func() hash.Hash
+		text   string
+		digest string
+	}{
+		{md5.New, "foobar\n", "14758f1afd44c09b7992073ccf00b43d"},
+		// test data from http://www.nsrl.nist.gov/testdata/
+		{sha1.New, "abc", "a9993e364706816aba3e25717850c26c9cd0d89d"},
+		{sha1.New, "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq", "84983e441c3bd26ebaae4aa1f95129e5e54670f1"},
+	}
+
+	var _ = Describe("Reader", func() {
+		Context("Static Strings", func() {
+			It("Should compute digest", func() {
+				for _, t := range static_tests {
+					r := hashing.NewReader(bytes.NewBuffer([]byte(t.text)), t.hash)
+
+					n, err := r.Read(make([]byte, len(t.text)+1))
+
+					if n != len(t.text) {
+						Fail("not enough bytes read")
+					}
+
+					if err != nil {
+						panic(err)
+					}
+
+					digest := r.Hash()
+
+					h := hex.EncodeToString(digest)
+					Expect(h).Should(Equal(t.digest))
+				}
+			})
+		})
+	})
+
+	var _ = Describe("Writer", func() {
+		Context("Static Strings", func() {
+			It("Should compute digest", func() {
+				for _, t := range static_tests {
+					var buf bytes.Buffer
+					w := hashing.NewWriter(&buf, t.hash)
+
+					n, err := w.Write([]byte(t.text))
+
+					if n != len(t.text) {
+						Fail("not enough bytes read")
+					}
+
+					if err != nil {
+						panic(err)
+					}
+
+					digest := w.Hash()
+
+					h := hex.EncodeToString(digest)
+					Expect(h).Should(Equal(t.digest))
+				}
+			})
+		})
+	})
+})
diff --git a/hashing/implementation.go b/hashing/implementation.go
new file mode 100644
index 000000000..b83f24cb0
--- /dev/null
+++ b/hashing/implementation.go
@@ -0,0 +1,109 @@
+// Copyright (c) 2014, Alexander Neumann <alexander@bumpern.de>
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+// list of conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+// this list of conditions and the following disclaimer in the documentation
+// and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Packgae hashing provides hashing readers and writers.
+package hashing
+
+import (
+	"hash"
+	"io"
+)
+
+// Reader is the interfaces that wraps a normal reader. When Hash() is called,
+// it returns the hash for all data that has been read so far.
+type Reader interface {
+	io.Reader
+	Hash() []byte
+}
+
+// Writer is the interfaces that wraps a normal writer. When Hash() is called,
+// it returns the hash for all data that has been written so far.
+type Writer interface {
+	io.Writer
+	Hash() []byte
+}
+
+type reader struct {
+	reader io.Reader
+	hash   hash.Hash
+}
+
+// NewReader wraps an io.Reader and in addition feeds all data read through the
+// given hash.
+func NewReader(r io.Reader, h func() hash.Hash) *reader {
+	return &reader{
+		reader: r,
+		hash:   h(),
+	}
+}
+
+func (h *reader) Read(p []byte) (int, error) {
+	// call original reader
+	n, err := h.reader.Read(p)
+
+	// hash bytes
+	if n > 0 {
+		// hash
+		h.hash.Write(p[0:n])
+	}
+
+	// return result
+	return n, err
+}
+
+func (h *reader) Hash() []byte {
+	return h.hash.Sum([]byte{})
+}
+
+type writer struct {
+	writer io.Writer
+	hash   hash.Hash
+}
+
+// NewWriter wraps an io.Reader and in addition feeds all data written through
+// the given hash.
+func NewWriter(w io.Writer, h func() hash.Hash) *writer {
+	return &writer{
+		writer: w,
+		hash:   h(),
+	}
+}
+
+func (h *writer) Write(p []byte) (int, error) {
+	// call original writer
+	n, err := h.writer.Write(p)
+
+	// hash bytes
+	if n > 0 {
+		// hash
+		h.hash.Write(p[0:n])
+	}
+
+	// return result
+	return n, err
+}
+
+func (h *writer) Hash() []byte {
+	return h.hash.Sum([]byte{})
+}