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minio/erasure-utils.go

101 lines
2.6 KiB

/*
* Minio Cloud Storage, (C) 2016 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 main
import (
"crypto/sha512"
"hash"
"io"
"github.com/klauspost/reedsolomon"
)
// newHashWriters - inititialize a slice of hashes for the disk count.
func newHashWriters(diskCount int) []hash.Hash {
hashWriters := make([]hash.Hash, diskCount)
for index := range hashWriters {
hashWriters[index] = newHash("sha512")
}
return hashWriters
}
// newHash - gives you a newly allocated hash depending on the input algorithm.
func newHash(algo string) hash.Hash {
switch algo {
case "sha512":
return sha512.New()
// Add new hashes here.
default:
return sha512.New()
}
}
func hashSum(disk StorageAPI, volume, path string, writer hash.Hash) ([]byte, error) {
startOffset := int64(0)
// Read until io.EOF.
for {
buf := make([]byte, blockSizeV1)
n, err := disk.ReadFile(volume, path, startOffset, buf)
if err == io.EOF {
break
}
if err != nil {
return nil, err
}
writer.Write(buf[:n])
startOffset += n
}
return writer.Sum(nil), nil
}
// getDataBlocks - fetches the data block only part of the input encoded blocks.
func getDataBlocks(enBlocks [][]byte, dataBlocks int, curBlockSize int) (data []byte, err error) {
if len(enBlocks) < dataBlocks {
return nil, reedsolomon.ErrTooFewShards
}
size := 0
blocks := enBlocks[:dataBlocks]
for _, block := range blocks {
size += len(block)
}
if size < curBlockSize {
return nil, reedsolomon.ErrShortData
}
write := curBlockSize
for _, block := range blocks {
if write < len(block) {
data = append(data, block[:write]...)
return data, nil
}
data = append(data, block...)
write -= len(block)
}
return data, nil
}
// getBlockInfo - find start/end block and bytes to skip for given offset, length and block size.
func getBlockInfo(offset, length, blockSize int64) (startBlock, bytesToSkip, endBlock int64) {
// Calculate start block for given offset and how many bytes to skip to get the offset.
startBlock = offset / blockSize
bytesToSkip = offset % blockSize
// Calculate end block for given size to read
endBlock = (offset + length) / blockSize
return
}