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

120 lines
2.8 KiB
Go

/*
* 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"
"strconv"
)
// Version - format version
const (
Version = uint32(1)
)
// 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
}
// Write 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, Version)
// 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
}
// ReadHeader - read an erasure block
func ReadHeader(reader io.Reader) (dataHeader DataHeader, err error) {
versionArray := make([]byte, 4)
if err := binary.Read(reader, binary.LittleEndian, versionArray); err != nil {
return dataHeader, err
}
version := binary.LittleEndian.Uint32(versionArray)
if version > Version || version == 0 {
return dataHeader, errors.New("Unknown version: " + strconv.FormatUint(uint64(version), 10))
}
decoder := gob.NewDecoder(reader)
err = decoder.Decode(&dataHeader)
return dataHeader, err
}