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Add hashing package

This commit is contained in:
Alexander Neumann 2014-04-06 12:22:58 +02:00
commit c54facf66b
3 changed files with 198 additions and 0 deletions

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package hashing_test
import (
"testing"
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
)
func TestHashing(t *testing.T) {
RegisterFailHandler(Fail)
RunSpecs(t, "Hashing Suite")
}

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hashing/hashing_test.go Normal file
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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))
}
})
})
})
})

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hashing/implementation.go Normal file
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// 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{})
}