minio/erasure-readfile.go
Krishnan Parthasarathi 967c2b2940 Handled possible short writes to httpResponseWriter (#1804)
* XL: Handled possible short writes to httpResponseWriter

* Added tests for Range Header combinations
2016-05-30 11:27:15 -07:00

99 lines
2.9 KiB
Go

/*
* 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 "errors"
// ReadFile - decoded erasure coded file.
func (e erasure) ReadFile(volume, path string, startOffset int64, buffer []byte) (int64, error) {
// Calculate the current encoded block size.
curEncBlockSize := getEncodedBlockLen(int64(len(buffer)), e.DataBlocks)
offsetEncOffset := getEncodedBlockLen(startOffset, e.DataBlocks)
// Allocate encoded blocks up to storage disks.
enBlocks := make([][]byte, len(e.storageDisks))
// Counter to keep success data blocks.
var successDataBlocksCount = 0
var noReconstruct bool // Set for no reconstruction.
// Read from all the disks.
for index, disk := range e.storageDisks {
blockIndex := e.distribution[index] - 1
// Initialize shard slice and fill the data from each parts.
enBlocks[blockIndex] = make([]byte, curEncBlockSize)
if disk == nil {
enBlocks[blockIndex] = nil
continue
}
// Read the necessary blocks.
_, err := disk.ReadFile(volume, path, offsetEncOffset, enBlocks[blockIndex])
if err != nil {
enBlocks[blockIndex] = nil
}
// Verify if we have successfully read all the data blocks.
if blockIndex < e.DataBlocks && enBlocks[blockIndex] != nil {
successDataBlocksCount++
// Set when we have all the data blocks and no
// reconstruction is needed, so that we can avoid
// erasure reconstruction.
noReconstruct = successDataBlocksCount == e.DataBlocks
if noReconstruct {
// Break out we have read all the data blocks.
break
}
}
}
// Check blocks if they are all zero in length, we have corruption return error.
if checkBlockSize(enBlocks) == 0 {
return 0, errDataCorrupt
}
// Verify if reconstruction is needed, proceed with reconstruction.
if !noReconstruct {
err := e.ReedSolomon.Reconstruct(enBlocks)
if err != nil {
return 0, err
}
// Verify reconstructed blocks (parity).
ok, err := e.ReedSolomon.Verify(enBlocks)
if err != nil {
return 0, err
}
if !ok {
// Blocks cannot be reconstructed, corrupted data.
err = errors.New("Verification failed after reconstruction, data likely corrupted.")
return 0, err
}
}
// Get data blocks from encoded blocks.
dataBlocks, err := getDataBlocks(enBlocks, e.DataBlocks, len(buffer))
if err != nil {
return 0, err
}
// Copy data blocks.
copy(buffer, dataBlocks)
// Relenquish memory.
dataBlocks = nil
return int64(len(buffer)), nil
}