You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
minio/cmd/erasure-utils.go

129 lines
3.7 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 cmd
import (
"bytes"
"context"
"io"
"github.com/klauspost/reedsolomon"
"github.com/minio/minio/cmd/logger"
)
// getDataBlockLen - get length of data blocks from encoded blocks.
func getDataBlockLen(enBlocks [][]byte, dataBlocks int) int {
size := 0
// Figure out the data block length.
for _, block := range enBlocks[:dataBlocks] {
size += len(block)
}
return size
}
// Writes all the data blocks from encoded blocks until requested
// outSize length. Provides a way to skip bytes until the offset.
func writeDataBlocks(ctx context.Context, dst io.Writer, enBlocks [][]byte, dataBlocks int, offset int64, length int64) (int64, error) {
// Offset and out size cannot be negative.
if offset < 0 || length < 0 {
logger.LogIf(ctx, errUnexpected)
return 0, errUnexpected
}
// Do we have enough blocks?
if len(enBlocks) < dataBlocks {
logger.LogIf(ctx, reedsolomon.ErrTooFewShards)
return 0, reedsolomon.ErrTooFewShards
}
// Do we have enough data?
if int64(getDataBlockLen(enBlocks, dataBlocks)) < length {
logger.LogIf(ctx, reedsolomon.ErrShortData)
return 0, reedsolomon.ErrShortData
}
// Counter to decrement total left to write.
write := length
// Counter to increment total written.
var totalWritten int64
// Write all data blocks to dst.
for _, block := range enBlocks[:dataBlocks] {
// Skip blocks until we have reached our offset.
if offset >= int64(len(block)) {
// Decrement offset.
offset -= int64(len(block))
continue
} else {
// Skip until offset.
block = block[offset:]
// Reset the offset for next iteration to read everything
// from subsequent blocks.
offset = 0
}
// We have written all the blocks, write the last remaining block.
if write < int64(len(block)) {
n, err := io.Copy(dst, bytes.NewReader(block[:write]))
if err != nil {
logger.LogIf(ctx, err)
return 0, err
}
totalWritten += n
break
}
// Copy the block.
n, err := io.Copy(dst, bytes.NewReader(block))
if err != nil {
logger.LogIf(ctx, err)
return 0, err
}
// Decrement output size.
write -= n
// Increment written.
totalWritten += n
}
// Success.
return totalWritten, nil
}
// Returns shard-file size.
func getErasureShardFileSize(blockSize int64, totalLength int64, dataBlocks int) int64 {
shardSize := ceilFrac(int64(blockSize), int64(dataBlocks))
numShards := totalLength / int64(blockSize)
lastBlockSize := totalLength % int64(blockSize)
lastShardSize := ceilFrac(lastBlockSize, int64(dataBlocks))
return shardSize*numShards + lastShardSize
}
// Returns the endOffset till which bitrotReader should read data using disk.ReadFile()
// partOffset, partLength and partSize are values of the object's part file.
func getErasureShardFileEndOffset(partOffset int64, partLength int64, partSize int64, erasureBlockSize int64, dataBlocks int) int64 {
shardSize := ceilFrac(erasureBlockSize, int64(dataBlocks))
shardFileSize := getErasureShardFileSize(erasureBlockSize, partSize, dataBlocks)
endShard := (partOffset + int64(partLength)) / erasureBlockSize
endOffset := endShard*shardSize + shardSize
if endOffset > shardFileSize {
endOffset = shardFileSize
}
return endOffset
}