Stephen J Day b6270d9c14 Handle empty blob files more appropriately ... Several API tests were added to ensure correct acceptance of zero-size and empty tar files. This led to several changes in the storage backend around the guarantees of remote file reading, which backs the layer and layer upload type. In support of these changes, zero-length and empty checks have been added to the digest package. These provide a sanity check against upstream tarsum changes. The fileReader has been modified to be more robust when reading and seeking on zero-length or non-existent files. The file no longer needs to exist for the reader to be created. Seeks can now move beyond the end of the file, causing reads to issue an io.EOF. This eliminates errors during certain race conditions for reading files which should be detected by stat calls. As a part of this, a few error types were factored out and the read buffer size was increased to something more reasonable. Signed-off-by: Stephen J Day <stephen.day@docker.com>		2015-02-02 13:01:49 -08:00
docs	Handle empty blob files more appropriately	2015-02-02 13:01:49 -08:00