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118 lines
2.8 KiB
118 lines
2.8 KiB
/*
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* Mini Object Storage, (C) 2015 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package erasure1
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import (
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"bytes"
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"encoding/binary"
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"encoding/gob"
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"errors"
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"io"
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"strconv"
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)
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const (
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Version = uint32(1)
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)
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// DataHeader represents the structure serialized to gob.
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type DataHeader struct {
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// object + block stored
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Key string
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// chunk index of encoded block
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ChunkIndex uint8
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// Original Length of the block output
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OriginalLength uint32
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// Data Blocks
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EncoderK uint8
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// Parity Blocks
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EncoderM uint8
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// Matrix Technique
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EncoderTechnique EncoderTechnique
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}
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// EncoderTechnique specified the Matrix type used in encoding
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type EncoderTechnique int
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const (
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// Vandermonde matrix type
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Vandermonde EncoderTechnique = iota
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// Cauchy matrix type
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Cauchy
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)
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// validate populated header
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func validateHeader(header DataHeader) error {
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if header.Key == "" {
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return errors.New("Empty Key")
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}
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if header.EncoderTechnique > 1 {
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return errors.New("Invalid encoder technique")
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}
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return nil
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}
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// Write returns error upon any failure
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func Write(target io.Writer, key string, part uint8, length uint32, k, m uint8, technique EncoderTechnique, data io.Reader) error {
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header := DataHeader{
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Key: key,
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ChunkIndex: part,
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OriginalLength: length,
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EncoderK: k,
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EncoderM: m,
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EncoderTechnique: technique,
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}
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if err := validateHeader(header); err != nil {
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return err
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}
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var headerBuffer bytes.Buffer
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// encode header
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encoder := gob.NewEncoder(&headerBuffer)
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encoder.Encode(header)
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// write version
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binary.Write(target, binary.LittleEndian, Version)
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// write encoded header
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if _, err := io.Copy(target, &headerBuffer); err != nil {
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return err
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}
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// write data
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if _, err := io.Copy(target, data); err != nil {
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return err
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}
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return nil
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}
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// Read an erasure block
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func ReadHeader(reader io.Reader) (dataHeader DataHeader, err error) {
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versionArray := make([]byte, 4)
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if err := binary.Read(reader, binary.LittleEndian, versionArray); err != nil {
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return dataHeader, err
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}
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version := binary.LittleEndian.Uint32(versionArray)
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if version > Version || version == 0 {
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return dataHeader, errors.New("Unknown version: " + strconv.FormatUint(uint64(version), 10))
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}
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decoder := gob.NewDecoder(reader)
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err = decoder.Decode(&dataHeader)
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return dataHeader, err
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}
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