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Copy patherasure-utils.go
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100 lines (86 loc) · 2.6 KB
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/*
* 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"
"io"
"github.com/klauspost/reedsolomon"
"github.com/minio/minio/pkg/errors"
)
// 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(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 {
return 0, errors.Trace(errUnexpected)
}
// Do we have enough blocks?
if len(enBlocks) < dataBlocks {
return 0, errors.Trace(reedsolomon.ErrTooFewShards)
}
// Do we have enough data?
if int64(getDataBlockLen(enBlocks, dataBlocks)) < length {
return 0, errors.Trace(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 {
return 0, errors.Trace(err)
}
totalWritten += n
break
}
// Copy the block.
n, err := io.Copy(dst, bytes.NewReader(block))
if err != nil {
return 0, errors.Trace(err)
}
// Decrement output size.
write -= n
// Increment written.
totalWritten += n
}
// Success.
return totalWritten, nil
}