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minio/cmd/erasure.go

115 lines
3.7 KiB

/*
* Minio Cloud Storage, (C) 2017 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 cmd
import (
"crypto/subtle"
"hash"
"github.com/klauspost/reedsolomon"
)
// OfflineDisk represents an unavailable disk.
var OfflineDisk StorageAPI // zero value is nil
// ErasureFileInfo contains information about an erasure file operation (create, read, heal).
type ErasureFileInfo struct {
Size int64
Algorithm BitrotAlgorithm
Checksums [][]byte
}
// ErasureStorage represents an array of disks.
// The disks contain erasure coded and bitrot-protected data.
type ErasureStorage struct {
disks []StorageAPI
erasure reedsolomon.Encoder
dataBlocks, parityBlocks int
}
// NewErasureStorage creates a new ErasureStorage. The storage erasure codes and protects all data written to
// the disks.
func NewErasureStorage(disks []StorageAPI, dataBlocks, parityBlocks int) (s ErasureStorage, err error) {
erasure, err := reedsolomon.New(dataBlocks, parityBlocks)
if err != nil {
return s, traceErrorf("failed to create erasure coding: %v", err)
}
s = ErasureStorage{
disks: make([]StorageAPI, len(disks)),
erasure: erasure,
dataBlocks: dataBlocks,
parityBlocks: parityBlocks,
}
copy(s.disks, disks)
return
}
// ErasureEncode encodes the given data and returns the erasure-coded data.
// It returns an error if the erasure coding failed.
func (s *ErasureStorage) ErasureEncode(data []byte) ([][]byte, error) {
encoded, err := s.erasure.Split(data)
if err != nil {
return nil, traceErrorf("failed to split data: %v", err)
}
if err = s.erasure.Encode(encoded); err != nil {
return nil, traceErrorf("failed to encode data: %v", err)
}
return encoded, nil
}
// ErasureDecodeDataBlocks decodes the given erasure-coded data.
// It only decodes the data blocks but does not verify them.
// It returns an error if the decoding failed.
func (s *ErasureStorage) ErasureDecodeDataBlocks(data [][]byte) error {
if err := s.erasure.ReconstructData(data); err != nil {
return traceErrorf("failed to reconstruct data: %v", err)
}
return nil
}
// ErasureDecodeDataAndParityBlocks decodes the given erasure-coded data and verifies it.
// It returns an error if the decoding failed.
func (s *ErasureStorage) ErasureDecodeDataAndParityBlocks(data [][]byte) error {
if err := s.erasure.Reconstruct(data); err != nil {
return traceErrorf("failed to reconstruct data: %v", err)
}
return nil
}
// NewBitrotVerifier returns a new BitrotVerifier implementing the given algorithm.
func NewBitrotVerifier(algorithm BitrotAlgorithm, checksum []byte) *BitrotVerifier {
return &BitrotVerifier{algorithm.New(), algorithm, checksum, false}
}
// BitrotVerifier can be used to verify protected data.
type BitrotVerifier struct {
hash.Hash
algorithm BitrotAlgorithm
sum []byte
verified bool
}
// Verify returns true iff the computed checksum of the verifier matches the the checksum provided when the verifier
// was created.
func (v *BitrotVerifier) Verify() bool {
v.verified = true
return subtle.ConstantTimeCompare(v.Sum(nil), v.sum) == 1
}
// IsVerified returns true iff Verify was called at least once.
func (v *BitrotVerifier) IsVerified() bool { return v.verified }