(PHP 5 >= 5.1.2, PECL hash >= 1.1)
hash_update_file — Pump data into an active hashing context from a file
$context
   , string $filename
   [, resource $context = NULL
  ] )
context
     Hashing context returned by hash_init().
filename
     URL describing location of file to be hashed; Supports fopen wrappers.
context
     Stream context as returned by stream_context_create().
   成功时返回 TRUE, 或者在失败时返回 FALSE.