Implements zero fill behaviour for large offset in WriteStream

This requires a very intricate WriteStream test, which will be in the next commit.

storagedriver/s3/s3.go

@@ -192,6 +192,7 @@ func (d *Driver) WriteStream(path string, offset int64, reader io.Reader) (total
 	}
 
 	partNumber := 1
+	bytesRead := 0
 	parts := []s3.Part{}
 	var part s3.Part
 
@@ -201,6 +202,7 @@ func (d *Driver) WriteStream(path string, offset int64, reader io.Reader) (total
 	}
 
 	buf := make([]byte, chunkSize)
+	zeroBuf := make([]byte, chunkSize)
 
 	// We never want to leave a dangling multipart upload, our only consistent state is
 	// when there is a whole object at path. This is in order to remain consistent with
@@ -211,54 +213,86 @@ func (d *Driver) WriteStream(path string, offset int64, reader io.Reader) (total
 	// made prior to the machine crashing.
 	defer func() {
 		if len(parts) > 0 {
-			err = multi.Complete(parts)
+			if multi == nil {
-			if err != nil {
+				// Parts should be empty if the multi is not initialized
+				panic("Unreachable")
+			} else {
+				if multi.Complete(parts) != nil {
 					multi.Abort()
 				}
 			}
+		}
 	}()
 
+	// Fills from 0 to total from current
+	fromSmallCurrent := func(total int64) error {
+		current, err := d.ReadStream(path, 0)
+		if err != nil {
+			return err
+		}
+
+		bytesRead = 0
+		for int64(bytesRead) < total {
+			//The loop should very rarely enter a second iteration
+			nn, err := io.ReadFull(current, buf[bytesRead:total])
+			if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
+				return err
+			}
+
+			bytesRead += nn
+		}
+		return nil
+	}
+
+	// Fills from parameter to chunkSize from reader
+	fromReader := func(from int64) error {
+		bytesRead = 0
+		for int64(bytesRead) < chunkSize {
+			nn, err := io.ReadFull(reader, buf[from+int64(bytesRead):])
+			totalRead += int64(nn)
+			bytesRead += nn
+
+			if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
+				return err
+			}
+		}
+
+		part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf[0:int64(bytesRead)+from]))
+		if err != nil {
+			return err
+		}
+
+		return nil
+	}
+
 	if offset > 0 {
 		resp, err := d.Bucket.Head(d.s3Path(path), nil)
 		if err != nil {
+			if s3Err, ok := err.(*s3.Error); !ok || s3Err.Code != "NoSuchKey" {
 				return 0, err
 			}
-		if resp.ContentLength < offset {
-			return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
 		}
 
-		if resp.ContentLength < chunkSize {
+		currentLength := int64(0)
-			// If everything written so far is less than the minimum part size of 5MB, we need
+		if err == nil {
-			// to fill out the first part up to that minimum.
+			currentLength = resp.ContentLength
-			current, err := d.ReadStream(path, 0)
-			if err != nil {
-				return 0, err
 		}
 
-			bytesRead, err := io.ReadFull(current, buf[0:offset])
+		if currentLength >= offset {
-			if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
+			if offset < chunkSize {
-				return 0, err
+				// chunkSize > currentLength >= offset
-			} else if int64(bytesRead) != offset {
+				if err = fromSmallCurrent(offset); err != nil {
-				//TODO Maybe a different error? I don't even think this case is reachable...
-				return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
-			}
-
-			bytesRead, err = io.ReadFull(reader, buf[offset:])
-			totalRead += int64(bytesRead)
-
-			if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
 					return totalRead, err
 				}
 
-			part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf[0:int64(bytesRead)+offset]))
+				if err = fromReader(offset); err != nil {
-			if err != nil {
 					return totalRead, err
 				}
 			} else {
-			fmt.Println("About to PutPartCopy")
+				// currentLength >= offset >= chunkSize
-			// If the file that we already have is larger than 5MB, then we make it the first part
+				_, part, err = multi.PutPartCopy(partNumber,
-			// of the new multipart upload.
+					s3.CopyOptions{CopySourceOptions: "bytes=0-" + strconv.FormatInt(offset-1, 10)},
-			_, part, err = multi.PutPartCopy(partNumber, s3.CopyOptions{}, d.Bucket.Name+"/"+d.s3Path(path))
+					d.Bucket.Name+"/"+d.s3Path(path))
 				if err != nil {
 					return 0, err
 				}
@@ -270,6 +304,150 @@ func (d *Driver) WriteStream(path string, offset int64, reader io.Reader) (total
 			if totalRead+offset < chunkSize {
 				return totalRead, nil
 			}
+		} else {
+			// Fills between parameters with 0s but only when to - from <= chunkSize
+			fromZeroFillSmall := func(from, to int64) error {
+				bytesRead = 0
+				for from+int64(bytesRead) < to {
+					nn, err := io.ReadFull(bytes.NewReader(zeroBuf), buf[from+int64(bytesRead):to])
+					bytesRead += nn
+
+					if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
+						return err
+					}
+				}
+
+				return nil
+			}
+
+			// Fills between parameters with 0s, making new parts
+			fromZeroFillLarge := func(from, to int64) error {
+				bytesRead64 := int64(0)
+				for to-(from+bytesRead64) >= chunkSize {
+					part, err := multi.PutPart(int(partNumber), bytes.NewReader(zeroBuf))
+					if err != nil {
+						return err
+					}
+					bytesRead64 += chunkSize
+
+					parts = append(parts, part)
+					partNumber++
+				}
+
+				bytesRead = 0
+				for from+bytesRead64+int64(bytesRead) < to {
+					nn, err := io.ReadFull(bytes.NewReader(zeroBuf), buf[0+bytesRead:(to-from)%chunkSize])
+					bytesRead64 += int64(nn)
+
+					if err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
+						return err
+					}
+				}
+
+				return nil
+			}
+
+			// currentLength < offset
+			if currentLength < chunkSize {
+				if offset < chunkSize {
+					// chunkSize > offset > currentLength
+					if err = fromSmallCurrent(currentLength); err != nil {
+						return totalRead, err
+					}
+
+					if err = fromZeroFillSmall(currentLength, offset); err != nil {
+						return totalRead, err
+					}
+
+					if err = fromReader(offset); err != nil {
+						return totalRead, err
+					}
+
+					part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf))
+					if err != nil {
+						return totalRead, err
+					}
+
+					parts = append(parts, part)
+					partNumber++
+
+					if totalRead+offset < chunkSize {
+						return totalRead, nil
+					}
+				} else {
+					// offset >= chunkSize > currentLength
+					if err = fromSmallCurrent(currentLength); err != nil {
+						return totalRead, err
+					}
+
+					if err = fromZeroFillSmall(currentLength, chunkSize); err != nil {
+						return totalRead, err
+					}
+
+					part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf))
+					if err != nil {
+						return totalRead, err
+					}
+
+					parts = append(parts, part)
+					partNumber++
+
+					//Zero fill from chunkSize up to offset, then some reader
+					if err = fromZeroFillLarge(chunkSize, offset); err != nil {
+						return totalRead, err
+					}
+
+					if err = fromReader(offset % chunkSize); err != nil {
+						return totalRead, err
+					}
+
+					part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf))
+					if err != nil {
+						return totalRead, err
+					}
+
+					parts = append(parts, part)
+					partNumber++
+
+					if totalRead+(offset%chunkSize) < chunkSize {
+						return totalRead, nil
+					}
+				}
+			} else {
+				// offset > currentLength >= chunkSize
+				_, part, err = multi.PutPartCopy(partNumber,
+					s3.CopyOptions{CopySourceOptions: "bytes=0-" + strconv.FormatInt(currentLength-1, 10)},
+					d.Bucket.Name+"/"+d.s3Path(path))
+				if err != nil {
+					return 0, err
+				}
+
+				parts = append(parts, part)
+				partNumber++
+
+				//Zero fill from currentLength up to offset, then some reader
+				if err = fromZeroFillLarge(currentLength, offset); err != nil {
+					return totalRead, err
+				}
+
+				if err = fromReader((offset - currentLength) % chunkSize); err != nil {
+					return totalRead, err
+				}
+
+				part, err = multi.PutPart(int(partNumber), bytes.NewReader(buf))
+				if err != nil {
+					return totalRead, err
+				}
+
+				parts = append(parts, part)
+				partNumber++
+
+				if totalRead+((offset-currentLength)%chunkSize) < chunkSize {
+					return totalRead, nil
+				}
+			}
+
+		}
 	}
 
 	for {

storagedriver/testsuites/testsuites.go

@@ -916,9 +916,13 @@ func (suite *DriverSuite) testFileStreams(c *check.C, size int64) {
 	tf.Sync()
 	tf.Seek(0, os.SEEK_SET)
 
+	totalRead := int64(0)
+	for totalRead < size {
 		nn, err := suite.StorageDriver.WriteStream(filename, 0, tf)
 		c.Assert(err, check.IsNil)
-	c.Assert(nn, check.Equals, size)
+		totalRead += nn
+	}
+	c.Assert(totalRead, check.Equals, size)
 
 	reader, err := suite.StorageDriver.ReadStream(filename, 0)
 	c.Assert(err, check.IsNil)