Use buffered read while generating checksum for blob

Author: the-spectator

activestorage/app/models/active_storage/blob.rb

@@ -350,8 +350,9 @@ def compute_checksum_in_chunks(io)
       raise ArgumentError, "io must be rewindable" unless io.respond_to?(:rewind)
 
       OpenSSL::Digest::MD5.new.tap do |checksum|
-        while chunk = io.read(5.megabytes)
-          checksum << chunk
+        read_buffer = "".b
+        while io.read(5.megabytes, read_buffer)
+          checksum << read_buffer
         end
 
         io.rewind