120 lines
3 KiB
Go
120 lines
3 KiB
Go
/*
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* MinIO Cloud Storage, (C) 2016-2020 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 cmd
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import (
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"context"
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"io"
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"github.com/klauspost/reedsolomon"
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"github.com/minio/minio/cmd/logger"
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)
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// getDataBlockLen - get length of data blocks from encoded blocks.
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func getDataBlockLen(enBlocks [][]byte, dataBlocks int) int {
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size := 0
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// Figure out the data block length.
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for _, block := range enBlocks[:dataBlocks] {
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size += len(block)
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}
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return size
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}
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// Writes all the data blocks from encoded blocks until requested
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// outSize length. Provides a way to skip bytes until the offset.
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func writeDataBlocks(ctx context.Context, dst io.Writer, enBlocks [][]byte, dataBlocks int, offset int64, length int64) (int64, error) {
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// Offset and out size cannot be negative.
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if offset < 0 || length < 0 {
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logger.LogIf(ctx, errUnexpected)
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return 0, errUnexpected
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}
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// Do we have enough blocks?
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if len(enBlocks) < dataBlocks {
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logger.LogIf(ctx, reedsolomon.ErrTooFewShards)
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return 0, reedsolomon.ErrTooFewShards
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}
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// Do we have enough data?
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if int64(getDataBlockLen(enBlocks, dataBlocks)) < length {
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logger.LogIf(ctx, reedsolomon.ErrShortData)
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return 0, reedsolomon.ErrShortData
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}
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// Counter to decrement total left to write.
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write := length
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// Counter to increment total written.
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var totalWritten int64
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// Write all data blocks to dst.
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for _, block := range enBlocks[:dataBlocks] {
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// Skip blocks until we have reached our offset.
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if offset >= int64(len(block)) {
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// Decrement offset.
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offset -= int64(len(block))
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continue
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} else {
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// Skip until offset.
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block = block[offset:]
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// Reset the offset for next iteration to read everything
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// from subsequent blocks.
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offset = 0
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}
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// We have written all the blocks, write the last remaining block.
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if write < int64(len(block)) {
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n, err := dst.Write(block[:write])
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if err != nil {
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if err != io.ErrClosedPipe {
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logger.LogIf(ctx, err)
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}
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return 0, err
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}
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if int64(n) != write {
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return 0, io.ErrShortWrite
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}
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totalWritten += int64(n)
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break
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}
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// Copy the block.
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n, err := dst.Write(block)
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if err != nil {
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// The writer will be closed incase of range queries, which will emit ErrClosedPipe.
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if err != io.ErrClosedPipe {
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logger.LogIf(ctx, err)
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}
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return 0, err
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}
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if n != len(block) {
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return 0, io.ErrShortWrite
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}
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// Decrement output size.
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write -= int64(n)
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// Increment written.
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totalWritten += int64(n)
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}
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// Success.
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return totalWritten, nil
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}
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