newResettableInputStream(file, fileNotFoundMsg)
.disableClose(), // requires explicit release
currentPosition, length, true);
String checksum = TreeHashGenerator.calculateTreeHash(inputSubStream);
byte[] binaryChecksum = BinaryUtils.fromHex(checksum);
inputSubStream.reset();
UploadMultipartPartRequest req = new UploadMultipartPartRequest()
.withAccountId(accountId)
.withChecksum(checksum)
.withBody(inputSubStream)
.withRange("bytes " + currentPosition + "-" + (currentPosition + length - 1) + "/*")