XL: Cleanup, comments and all the updated functions. (#1830)

erasure-readfile.go

@@ -19,36 +19,86 @@ package main
 import (
 	"encoding/hex"
 	"errors"
+
+	"github.com/klauspost/reedsolomon"
 )
 
-// isValidBlock - calculates the checksum hash for the block and
-// validates if its correct returns true for valid cases, false otherwise.
-func (e erasureConfig) isValidBlock(volume, path string, blockIdx int) bool {
-	diskIndex := -1
+// PartObjectChecksum - returns the checksum for the part name from the checksum slice.
+func (e erasureInfo) PartObjectChecksum(partName string) checkSumInfo {
+	for _, checksum := range e.Checksum {
+		if checksum.Name == partName {
+			return checksum
+		}
+	}
+	return checkSumInfo{}
+}
+
+// xlMetaPartBlockChecksums - get block checksums for a given part.
+func metaPartBlockChecksums(disks []StorageAPI, eInfos []erasureInfo, partName string) (blockCheckSums []checkSumInfo) {
+	for index := range disks {
+		// Save the read checksums for a given part.
+		blockCheckSums = append(blockCheckSums, eInfos[index].PartObjectChecksum(partName))
+	}
+	return blockCheckSums
+}
+
+// Takes block index and block distribution to get the disk index.
+func toDiskIndex(blockIdx int, distribution []int) (diskIndex int) {
+	diskIndex = -1
 	// Find out the right disk index for the input block index.
-	for index, blockIndex := range e.distribution {
+	for index, blockIndex := range distribution {
 		if blockIndex == blockIdx {
 			diskIndex = index
 		}
 	}
+	return diskIndex
+}
+
+// isValidBlock - calculates the checksum hash for the block and
+// validates if its correct returns true for valid cases, false otherwise.
+func isValidBlock(disks []StorageAPI, volume, path string, diskIndex int, blockCheckSums []checkSumInfo) bool {
 	// Unknown block index requested, treat it as error.
 	if diskIndex == -1 {
 		return false
 	}
 	// Disk is not present, treat entire block to be non existent.
-	if e.storageDisks[diskIndex] == nil {
+	if disks[diskIndex] == nil {
 		return false
 	}
 	// Read everything for a given block and calculate hash.
-	hashBytes, err := hashSum(e.storageDisks[diskIndex], volume, path, newHash(e.checkSumAlgo))
+	hashWriter := newHash(blockCheckSums[diskIndex].Algorithm)
+	hashBytes, err := hashSum(disks[diskIndex], volume, path, hashWriter)
 	if err != nil {
 		return false
 	}
-	return hex.EncodeToString(hashBytes) == e.hashChecksums[diskIndex]
+	return hex.EncodeToString(hashBytes) == blockCheckSums[diskIndex].Hash
+}
+
+// decodeData - decode encoded blocks.
+func decodeData(enBlocks [][]byte, dataBlocks, parityBlocks int) error {
+	rs, err := reedsolomon.New(dataBlocks, parityBlocks)
+	if err != nil {
+		return err
+	}
+	err = rs.Reconstruct(enBlocks)
+	if err != nil {
+		return err
+	}
+	// Verify reconstructed blocks (parity).
+	ok, err := rs.Verify(enBlocks)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		// Blocks cannot be reconstructed, corrupted data.
+		err = errors.New("Verification failed after reconstruction, data likely corrupted.")
+		return err
+	}
+	return nil
 }
 
 // ReadFile - decoded erasure coded file.
-func (e erasureConfig) ReadFile(volume, path string, size int64, blockSize int64) ([]byte, error) {
+func erasureReadFile(disks []StorageAPI, volume string, path string, partName string, size int64, eInfos []erasureInfo) ([]byte, error) {
 	// Return data buffer.
 	var buffer []byte
 
@@ -58,31 +108,37 @@ func (e erasureConfig) ReadFile(volume, path string, size int64, blockSize int64
 	// Starting offset for reading.
 	startOffset := int64(0)
 
+	// Gather previously calculated block checksums.
+	blockCheckSums := metaPartBlockChecksums(disks, eInfos, partName)
+
+	// Pick one erasure info.
+	eInfo := eInfos[0]
+
 	// Write until each parts are read and exhausted.
 	for totalSizeLeft > 0 {
 		// Calculate the proper block size.
 		var curBlockSize int64
-		if blockSize < totalSizeLeft {
-			curBlockSize = blockSize
+		if eInfo.BlockSize < totalSizeLeft {
+			curBlockSize = eInfo.BlockSize
 		} else {
 			curBlockSize = totalSizeLeft
 		}
 
 		// Calculate the current encoded block size.
-		curEncBlockSize := getEncodedBlockLen(curBlockSize, e.dataBlocks)
-		offsetEncOffset := getEncodedBlockLen(startOffset, e.dataBlocks)
+		curEncBlockSize := getEncodedBlockLen(curBlockSize, eInfo.DataBlocks)
+		offsetEncOffset := getEncodedBlockLen(startOffset, eInfo.DataBlocks)
 
 		// Allocate encoded blocks up to storage disks.
-		enBlocks := make([][]byte, len(e.storageDisks))
+		enBlocks := make([][]byte, len(disks))
 
 		// 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
-			if !e.isValidBlock(volume, path, blockIndex) {
+		for index, disk := range disks {
+			blockIndex := eInfo.Distribution[index] - 1
+			if !isValidBlock(disks, volume, path, toDiskIndex(blockIndex, eInfo.Distribution), blockCheckSums) {
 				continue
 			}
 			// Initialize shard slice and fill the data from each parts.
@@ -93,12 +149,12 @@ func (e erasureConfig) ReadFile(volume, path string, size int64, blockSize int64
 				enBlocks[blockIndex] = nil
 			}
 			// Verify if we have successfully read all the data blocks.
-			if blockIndex < e.dataBlocks && enBlocks[blockIndex] != nil {
+			if blockIndex < eInfo.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
+				noReconstruct = successDataBlocksCount == eInfo.DataBlocks
 				if noReconstruct {
 					// Break out we have read all the data blocks.
 					break
@@ -113,24 +169,14 @@ func (e erasureConfig) ReadFile(volume, path string, size int64, blockSize int64
 
 		// Verify if reconstruction is needed, proceed with reconstruction.
 		if !noReconstruct {
-			err := e.reedSolomon.Reconstruct(enBlocks)
+			err := decodeData(enBlocks, eInfo.DataBlocks, eInfo.ParityBlocks)
 			if err != nil {
 				return nil, err
 			}
-			// Verify reconstructed blocks (parity).
-			ok, err := e.reedSolomon.Verify(enBlocks)
-			if err != nil {
-				return nil, err
-			}
-			if !ok {
-				// Blocks cannot be reconstructed, corrupted data.
-				err = errors.New("Verification failed after reconstruction, data likely corrupted.")
-				return nil, err
-			}
 		}
 
 		// Get data blocks from encoded blocks.
-		dataBlocks, err := getDataBlocks(enBlocks, e.dataBlocks, int(curBlockSize))
+		dataBlocks, err := getDataBlocks(enBlocks, eInfo.DataBlocks, int(curBlockSize))
 		if err != nil {
 			return nil, err
 		}