Erasure layer now writes using new technique

pkg/storage/donut/erasure/erasure1/erasure.go

@@ -0,0 +1,98 @@
+/*
+ * Mini Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package erasure1
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/gob"
+	"errors"
+	"io"
+)
+
+// DataHeader represents the structure serialized to gob.
+type DataHeader struct {
+	// object + block stored
+	Key string
+	// chunk index of encoded block
+	ChunkIndex uint8
+	// Original Length of the block output
+	OriginalLength uint32
+	// Data Blocks
+	EncoderK uint8
+	// Parity Blocks
+	EncoderM uint8
+	// Matrix Technique
+	EncoderTechnique EncoderTechnique
+}
+
+// EncoderTechnique specified the Matrix type used in encoding
+type EncoderTechnique int
+
+const (
+	// Vandermonde matrix type
+	Vandermonde EncoderTechnique = iota
+	// Cauchy matrix type
+	Cauchy
+)
+
+// validate populated header
+func validateHeader(header DataHeader) error {
+	if header.Key == "" {
+		return errors.New("Empty Key")
+	}
+
+	if header.EncoderTechnique > 1 {
+		return errors.New("Invalid encoder technique")
+	}
+
+	return nil
+}
+
+// WriteData returns error upon any failure
+func Write(target io.Writer, key string, part uint8, length uint32, k, m uint8, technique EncoderTechnique, data io.Reader) error {
+	header := DataHeader{
+		Key:              key,
+		ChunkIndex:       part,
+		OriginalLength:   length,
+		EncoderK:         k,
+		EncoderM:         m,
+		EncoderTechnique: technique,
+	}
+
+	if err := validateHeader(header); err != nil {
+		return err
+	}
+
+	var headerBuffer bytes.Buffer
+	// encode header
+	encoder := gob.NewEncoder(&headerBuffer)
+	encoder.Encode(header)
+
+	// write version
+	binary.Write(target, binary.LittleEndian, uint32(1))
+
+	// write encoded header
+	if _, err := io.Copy(target, &headerBuffer); err != nil {
+		return err
+	}
+	// write data
+	if _, err := io.Copy(target, data); err != nil {
+		return err
+	}
+	return nil
+}

pkg/storage/donut/erasure/erasure1/erasure_test.go

@@ -0,0 +1,68 @@
+/*
+ * Mini Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package erasure1
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/gob"
+	"io"
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type MySuite struct{}
+
+var _ = Suite(&MySuite{})
+
+func (s *MySuite) TestSingleWrite(c *C) {
+	var testBuffer bytes.Buffer
+	testData := "Hello, World"
+	testHeader := DataHeader{
+		Key:              "testobj",
+		ChunkIndex:       1,
+		OriginalLength:   uint32(len(testData)),
+		EncoderK:         8,
+		EncoderM:         8,
+		EncoderTechnique: Cauchy,
+	}
+
+	err := Write(&testBuffer, testHeader.Key, testHeader.ChunkIndex, testHeader.OriginalLength, testHeader.EncoderK, testHeader.EncoderM, testHeader.EncoderTechnique, bytes.NewBufferString(testData))
+	c.Assert(err, IsNil)
+
+	actualVersion := make([]byte, 4)
+	_, err = testBuffer.Read(actualVersion)
+	c.Assert(err, IsNil)
+	c.Assert(binary.LittleEndian.Uint32(actualVersion), DeepEquals, uint32(1))
+
+	actualHeader := DataHeader{}
+
+	decoder := gob.NewDecoder(&testBuffer)
+	decoder.Decode(&actualHeader)
+
+	c.Assert(actualHeader, DeepEquals, testHeader)
+
+	var actualData bytes.Buffer
+
+	dataLength, err := io.Copy(&actualData, &testBuffer)
+	c.Assert(dataLength, Equals, int64(len(testData)))
+	c.Assert(actualData.Bytes(), DeepEquals, []byte(testData))
+	c.Assert(err, IsNil)
+}