Fix binary reading code performance.

This is not the Right fix ; the Right fix would be to read
the file in a buffered way. However this delivers tolerable
performance for a minimal amount of code changes.
We may want to skip submitting this patch, but keep it around
in case we need to use the functionality until we have a good
patch.

Change-Id: I1ba938f82acfd9436c3701d1078ff981afdbea60