Checkpoint implementing PATCH according to Docker

storage/basestorage.py

@@ -1,7 +1,7 @@
 import tempfile
 
 from digest.digest_tools import content_path
-
+from util.registry.filelike import READ_UNTIL_END
 
 class StoragePaths(object):
   shared_images = 'sharedimages'
@@ -90,12 +90,12 @@ class BaseStorage(StoragePaths):
   def get_checksum(self, path):
     raise NotImplementedError
 
-  def stream_write_to_fp(self, in_fp, out_fp, num_bytes=-1):
+  def stream_write_to_fp(self, in_fp, out_fp, num_bytes=READ_UNTIL_END):
     """ Copy the specified number of bytes from the input file stream to the output stream. If
         num_bytes < 0 copy until the stream ends.
     """
     bytes_copied = 0
-    while bytes_copied < num_bytes or num_bytes == -1:
+    while bytes_copied < num_bytes or num_bytes == READ_UNTIL_END:
       size_to_read = min(num_bytes - bytes_copied, self.buffer_size)
       if size_to_read < 0:
         size_to_read = self.buffer_size
@@ -126,7 +126,7 @@ class BaseStorageV2(BaseStorage):
     """ Upload the specified amount of data from the given file pointer to the chunked destination
         specified, starting at the given offset. Returns the number of bytes uploaded, and a new
         version of the storage_metadata. Raises InvalidChunkException if the offset or length can
-        not be accepted.
+        not be accepted. Pass length as -1 to upload as much data from the in_fp as possible.
     """
     raise NotImplementedError