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170 lines
4.7 KiB
170 lines
4.7 KiB
![]()
9 years ago
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/*
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* Minio Cloud Storage, (C) 2016 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package main
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import (
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"errors"
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"fmt"
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"io"
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slashpath "path"
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)
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// checkBlockSize return the size of a single block.
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// The first non-zero size is returned,
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// or 0 if all blocks are size 0.
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func checkBlockSize(blocks [][]byte) int {
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for _, block := range blocks {
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if len(block) != 0 {
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return len(block)
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}
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}
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return 0
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}
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// calculate the blockSize based on input length and total number of
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// data blocks.
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func getEncodedBlockLen(inputLen, dataBlocks int) (curBlockSize int) {
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curBlockSize = (inputLen + dataBlocks - 1) / dataBlocks
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return
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}
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// ReadFile - read file
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func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error) {
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// Input validation.
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if !isValidVolname(volume) {
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return nil, errInvalidArgument
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}
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if !isValidPath(path) {
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return nil, errInvalidArgument
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}
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// Initialize all readers.
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var readers = make([]io.ReadCloser, len(xl.storageDisks))
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// Extract metadata.
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metadata, err := xl.extractMetadata(volume, path)
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if err != nil {
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return nil, err
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}
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// Loop through and verify if all metadata files are in-tact.
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for index, disk := range xl.storageDisks {
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offset := int64(0)
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erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
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var erasuredPartReader io.ReadCloser
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erasuredPartReader, err = disk.ReadFile(volume, erasurePart, offset)
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if err != nil {
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// One of parts not found, we need to re-construct.
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if err == errFileNotFound {
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readers[index] = nil
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continue
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}
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// For all other errors return to the caller.
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return nil, err
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}
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readers[index] = erasuredPartReader
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}
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totalBlocks := xl.DataBlocks + xl.ParityBlocks // Total blocks.
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// Initialize pipe.
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pipeReader, pipeWriter := io.Pipe()
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go func() {
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var totalLeft = metadata.Size
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// Read until the totalLeft.
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for totalLeft > 0 {
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// Figure out the right blockSize as it was encoded before.
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var curBlockSize int
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if erasureBlockSize < totalLeft {
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curBlockSize = erasureBlockSize
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} else {
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curBlockSize = int(totalLeft)
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}
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// Calculate the current encoded block size.
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curEncBlockSize := getEncodedBlockLen(curBlockSize, xl.DataBlocks)
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enBlocks := make([][]byte, totalBlocks)
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// Loop through all readers and read.
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for index, reader := range readers {
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if reader == nil {
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// One of files missing, save it for reconstruction.
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enBlocks[index] = nil
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continue
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}
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// Initialize shard slice and fill the data from each parts.
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enBlocks[index] = make([]byte, curEncBlockSize)
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_, err = io.ReadFull(reader, enBlocks[index])
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if err != nil && err != io.ErrUnexpectedEOF {
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enBlocks[index] = nil
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}
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}
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// TODO need to verify block512Sum.
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// Check blocks if they are all zero in length.
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if checkBlockSize(enBlocks) == 0 {
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err = errors.New("Data likely corrupted, all blocks are zero in length.")
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pipeWriter.CloseWithError(err)
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return
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}
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// Verify the blocks.
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var ok bool
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ok, err = xl.ReedSolomon.Verify(enBlocks)
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if err != nil {
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pipeWriter.CloseWithError(err)
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return
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}
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// Verification failed, blocks require reconstruction.
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if !ok {
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err = xl.ReedSolomon.Reconstruct(enBlocks)
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if err != nil {
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pipeWriter.CloseWithError(err)
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return
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}
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// Verify reconstructed blocks again.
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ok, err = xl.ReedSolomon.Verify(enBlocks)
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if err != nil {
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pipeWriter.CloseWithError(err)
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return
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}
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if !ok {
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// Blocks cannot be reconstructed, corrupted data.
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err = errors.New("Verification failed after reconstruction, data likely corrupted.")
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pipeWriter.CloseWithError(err)
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return
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}
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}
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// Join the decoded blocks.
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err = xl.ReedSolomon.Join(pipeWriter, enBlocks, curBlockSize)
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if err != nil {
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pipeWriter.CloseWithError(err)
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return
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}
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// Save what's left after reading erasureBlockSize.
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totalLeft = totalLeft - erasureBlockSize
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}
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// Cleanly end the pipe after a successful decoding.
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pipeWriter.Close()
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// Cleanly close all the underlying data readers.
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for _, reader := range readers {
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reader.Close()
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}
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}()
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// Return the pipe for the top level caller to start reading.
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return pipeReader, nil
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}
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