Compute the tarsum only when required. Newer versions of Docker only require the simple SHA256 checksum, so this should save us from writing to a temp file.

util/gzipstream.py

@@ -13,7 +13,8 @@ CHUNK_SIZE = 5 * 1024 * 1024
 
 class SizeInfo(object):
   def __init__(self):
-    self.size = 0
+    self.uncompressed_size = 0
+    self.compressed_size = 0
 
 def calculate_size_handler():
   """ Returns an object and a SocketReader handler. The handler will gunzip the data it receives,
@@ -28,8 +29,10 @@ def calculate_size_handler():
     # Note: We set a maximum CHUNK_SIZE to prevent the decompress from taking too much
     # memory. As a result, we have to loop until the unconsumed tail is empty.
     current_data = buf
+    size_info.compressed_size += len(current_data)
+    
     while len(current_data) > 0:
-      size_info.size += len(decompressor.decompress(current_data, CHUNK_SIZE))
+      size_info.uncompressed_size += len(decompressor.decompress(current_data, CHUNK_SIZE))
       current_data = decompressor.unconsumed_tail
 
   return size_info, fn