XL/erasure: fix for skipping 0 padding. (#1737)

Fixes #1736

erasure-readfile.go

@@ -23,7 +23,7 @@ import (
 )
 
 // ReadFile - decoded erasure coded file.
-func (e erasure) ReadFile(volume, path string, startOffset int64) (io.ReadCloser, error) {
+func (e erasure) ReadFile(volume, path string, startOffset int64, totalSize int64) (io.ReadCloser, error) {
 	// Input validation.
 	if !isValidVolname(volume) {
 		return nil, errInvalidArgument
@@ -32,13 +32,13 @@ func (e erasure) ReadFile(volume, path string, startOffset int64) (io.ReadCloser
 		return nil, errInvalidArgument
 	}
 
-	var wg = &sync.WaitGroup{}
+	var rwg = &sync.WaitGroup{}
 
 	readers := make([]io.ReadCloser, len(e.storageDisks))
 	for index, disk := range e.storageDisks {
-		wg.Add(1)
+		rwg.Add(1)
 		go func(index int, disk StorageAPI) {
-			defer wg.Done()
+			defer rwg.Done()
 			// If disk.ReadFile returns error and we don't have read
 			// quorum it will be taken care as ReedSolomon.Reconstruct()
 			// will fail later.
@@ -49,18 +49,28 @@ func (e erasure) ReadFile(volume, path string, startOffset int64) (io.ReadCloser
 		}(index, disk)
 	}
 
-	wg.Wait()
+	// Wait for all readers.
+	rwg.Wait()
 
 	// Initialize pipe.
 	pipeReader, pipeWriter := io.Pipe()
 
 	go func() {
+		var totalLeft = totalSize
 		// Read until EOF.
-		for {
+		for totalLeft > 0 {
+			// Figure out the right blockSize as it was encoded
+			// before.
+			var curBlockSize int64
+			if erasureBlockSize < totalLeft {
+				curBlockSize = erasureBlockSize
+			} else {
+				curBlockSize = totalLeft
+			}
 			// Calculate the current encoded block size.
-			curEncBlockSize := getEncodedBlockLen(erasureBlockSize, e.DataBlocks)
+			curEncBlockSize := getEncodedBlockLen(curBlockSize, e.DataBlocks)
 			enBlocks := make([][]byte, len(e.storageDisks))
-			// Loop through all readers and read.
+			// Read all the readers.
 			for index, reader := range readers {
 				// Initialize shard slice and fill the data from each parts.
 				enBlocks[index] = make([]byte, curEncBlockSize)
@@ -68,26 +78,11 @@ func (e erasure) ReadFile(volume, path string, startOffset int64) (io.ReadCloser
 					continue
 				}
 				// Read the necessary blocks.
-				n, rErr := io.ReadFull(reader, enBlocks[index])
-				if rErr == io.EOF {
-					// Close the pipe.
-					pipeWriter.Close()
-
-					// Cleanly close all the underlying data readers.
-					for _, reader := range readers {
-						if reader == nil {
-							continue
-						}
-						reader.Close()
-					}
-					return
-				}
+				_, rErr := io.ReadFull(reader, enBlocks[index])
 				if rErr != nil && rErr != io.ErrUnexpectedEOF {
 					readers[index].Close()
 					readers[index] = nil
-					continue
 				}
-				enBlocks[index] = enBlocks[index][:n]
 			}
 
 			// Check blocks if they are all zero in length.
@@ -131,17 +126,18 @@ func (e erasure) ReadFile(volume, path string, startOffset int64) (io.ReadCloser
 			}
 
 			// Get all the data blocks.
-			dataBlocks := getDataBlocks(enBlocks, e.DataBlocks)
+			dataBlocks := getDataBlocks(enBlocks, e.DataBlocks, int(curBlockSize))
 
-			// Verify if the offset is right for the block, if not move to
-			// the next block.
+			// Verify if the offset is right for the block, if not move to the next block.
 			if startOffset > 0 {
 				startOffset = startOffset - int64(len(dataBlocks))
 				// Start offset is greater than or equal to zero, skip the dataBlocks.
 				if startOffset >= 0 {
+					totalLeft = totalLeft - erasureBlockSize
 					continue
 				}
-				// Now get back the remaining offset if startOffset is negative.
+				// Now get back the remaining offset if startOffset is
+				// negative.
 				startOffset = startOffset + int64(len(dataBlocks))
 			}
 
@@ -154,6 +150,20 @@ func (e erasure) ReadFile(volume, path string, startOffset int64) (io.ReadCloser
 
 			// Reset offset to '0' to read rest of the blocks.
 			startOffset = int64(0)
+
+			// Save what's left after reading erasureBlockSize.
+			totalLeft = totalLeft - erasureBlockSize
+		}
+
+		// Cleanly end the pipe after a successful decoding.
+		pipeWriter.Close()
+
+		// Cleanly close all the underlying data readers.
+		for _, reader := range readers {
+			if reader == nil {
+				continue
+			}
+			reader.Close()
 		}
 	}()