server: Move all the top level files into cmd folder. (#2490)

This change brings a change which was done for the 'mc'
package to allow for clean repo and have a cleaner
github drop in experience.

cmd/erasure-healfile.go

@@ -0,0 +1,84 @@
+/*
+ * 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 cmd
+
+import "encoding/hex"
+
+// Heals the erasure coded file. reedsolomon.Reconstruct() is used to reconstruct the missing parts.
+func erasureHealFile(latestDisks []StorageAPI, outDatedDisks []StorageAPI, volume, path, healBucket, healPath string, size int64, blockSize int64, dataBlocks int, parityBlocks int, algo string) (checkSums []string, err error) {
+	var offset int64
+	remainingSize := size
+
+	// Hash for bitrot protection.
+	hashWriters := newHashWriters(len(outDatedDisks), bitRotAlgo)
+
+	for remainingSize > 0 {
+		curBlockSize := blockSize
+		if remainingSize < curBlockSize {
+			curBlockSize = remainingSize
+		}
+
+		// Calculate the block size that needs to be read from each disk.
+		curEncBlockSize := getChunkSize(curBlockSize, dataBlocks)
+
+		// Memory for reading data from disks and reconstructing missing data using erasure coding.
+		enBlocks := make([][]byte, len(latestDisks))
+
+		// Read data from the latest disks.
+		// FIXME: no need to read from all the disks. dataBlocks+1 is enough.
+		for index, disk := range latestDisks {
+			if disk == nil {
+				continue
+			}
+			enBlocks[index] = make([]byte, curEncBlockSize)
+			_, err := disk.ReadFile(volume, path, offset, enBlocks[index])
+			if err != nil {
+				enBlocks[index] = nil
+			}
+		}
+
+		// Reconstruct missing data.
+		err := decodeData(enBlocks, dataBlocks, parityBlocks)
+		if err != nil {
+			return nil, err
+		}
+
+		// Write to the healPath file.
+		for index, disk := range outDatedDisks {
+			if disk == nil {
+				continue
+			}
+			err := disk.AppendFile(healBucket, healPath, enBlocks[index])
+			if err != nil {
+				return nil, err
+			}
+			hashWriters[index].Write(enBlocks[index])
+		}
+		remainingSize -= curBlockSize
+		offset += curEncBlockSize
+	}
+
+	// Checksums for the bit rot.
+	checkSums = make([]string, len(outDatedDisks))
+	for index, disk := range outDatedDisks {
+		if disk == nil {
+			continue
+		}
+		checkSums[index] = hex.EncodeToString(hashWriters[index].Sum(nil))
+	}
+	return checkSums, nil
+}