minio/cmd/erasure-utils.go
2021-05-20 09:00:11 -07:00

119 lines
3.5 KiB
Go

// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package cmd
import (
"bytes"
"context"
"fmt"
"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, fmt.Errorf("diskBlocks(%d)/dataBlocks(%d) - %w", len(enBlocks), dataBlocks, reedsolomon.ErrTooFewShards))
return 0, reedsolomon.ErrTooFewShards
}
// Do we have enough data?
if int64(getDataBlockLen(enBlocks, dataBlocks)) < length {
logger.LogIf(ctx, fmt.Errorf("getDataBlockLen(enBlocks, dataBlocks)(%d)/length(%d) - %w", getDataBlockLen(enBlocks, dataBlocks), length, 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 {
// The writer will be closed incase of range queries, which will emit ErrClosedPipe.
// The reader pipe might be closed at ListObjects io.EOF ignore it.
if err != io.ErrClosedPipe && err != io.EOF {
logger.LogIf(ctx, err)
}
return 0, err
}
totalWritten += n
break
}
// Copy the block.
n, err := io.Copy(dst, bytes.NewReader(block))
if err != nil {
// The writer will be closed incase of range queries, which will emit ErrClosedPipe.
// The reader pipe might be closed at ListObjects io.EOF ignore it.
if err != io.ErrClosedPipe && err != io.EOF {
logger.LogIf(ctx, err)
}
return 0, err
}
// Decrement output size.
write -= n
// Increment written.
totalWritten += n
}
// Success.
return totalWritten, nil
}