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123 lines
3.5 KiB
Go
123 lines
3.5 KiB
Go
/*
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* MinIO Cloud Storage, (C) 2017 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 cmd
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import (
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"context"
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"github.com/klauspost/reedsolomon"
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"github.com/minio/minio/cmd/logger"
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)
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// Erasure - erasure encoding details.
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type Erasure struct {
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encoder reedsolomon.Encoder
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dataBlocks, parityBlocks int
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blockSize int64
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}
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// NewErasure creates a new ErasureStorage.
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func NewErasure(ctx context.Context, dataBlocks, parityBlocks int, blockSize int64) (e Erasure, err error) {
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e = Erasure{
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dataBlocks: dataBlocks,
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parityBlocks: parityBlocks,
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blockSize: blockSize,
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}
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e.encoder, err = reedsolomon.New(dataBlocks, parityBlocks, reedsolomon.WithAutoGoroutines(int(e.ShardSize())))
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if err != nil {
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logger.LogIf(ctx, err)
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return e, err
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}
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return
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}
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// EncodeData encodes the given data and returns the erasure-coded data.
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// It returns an error if the erasure coding failed.
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func (e *Erasure) EncodeData(ctx context.Context, data []byte) ([][]byte, error) {
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if len(data) == 0 {
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return make([][]byte, e.dataBlocks+e.parityBlocks), nil
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}
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encoded, err := e.encoder.Split(data)
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if err != nil {
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logger.LogIf(ctx, err)
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return nil, err
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}
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if err = e.encoder.Encode(encoded); err != nil {
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logger.LogIf(ctx, err)
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return nil, err
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}
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return encoded, nil
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}
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// DecodeDataBlocks decodes the given erasure-coded data.
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// It only decodes the data blocks but does not verify them.
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// It returns an error if the decoding failed.
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func (e *Erasure) DecodeDataBlocks(data [][]byte) error {
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needsReconstruction := false
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for _, b := range data[:e.dataBlocks] {
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if b == nil {
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needsReconstruction = true
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break
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}
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}
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if !needsReconstruction {
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return nil
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}
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return e.encoder.ReconstructData(data)
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}
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// DecodeDataAndParityBlocks decodes the given erasure-coded data and verifies it.
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// It returns an error if the decoding failed.
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func (e *Erasure) DecodeDataAndParityBlocks(ctx context.Context, data [][]byte) error {
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if err := e.encoder.Reconstruct(data); err != nil {
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logger.LogIf(ctx, err)
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return err
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}
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return nil
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}
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// ShardSize - returns actual shared size from erasure blockSize.
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func (e *Erasure) ShardSize() int64 {
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return ceilFrac(e.blockSize, int64(e.dataBlocks))
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}
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// ShardFileSize - returns final erasure size from original size.
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func (e *Erasure) ShardFileSize(totalLength int64) int64 {
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if totalLength == 0 {
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return 0
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}
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if totalLength == -1 {
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return -1
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}
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numShards := totalLength / e.blockSize
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lastBlockSize := totalLength % int64(e.blockSize)
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lastShardSize := ceilFrac(lastBlockSize, int64(e.dataBlocks))
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return numShards*e.ShardSize() + lastShardSize
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}
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// ShardFileTillOffset - returns the effectiv eoffset where erasure reading begins.
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func (e *Erasure) ShardFileTillOffset(startOffset, length, totalLength int64) int64 {
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shardSize := e.ShardSize()
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shardFileSize := e.ShardFileSize(totalLength)
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endShard := (startOffset + int64(length)) / e.blockSize
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tillOffset := endShard*shardSize + shardSize
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if tillOffset > shardFileSize {
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tillOffset = shardFileSize
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}
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return tillOffset
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}
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