Because Python's zip terminates once *any* of the input iterables
terminates, the previous code would not detect if the file was missing
resources or contained extra ones.
This is easier to debug (printing out a lambda doesn't show what values
it checks against) and makes it easier to check that the filter values
are valid.
With the new implementation, each filter is converted to a function,
then all resources are checked if they match any of the filter
functions. This is simpler than the old implementation, where the
resource lookup code was slightly different for some filter forms.
The _references map now stores Resource objects directly, instead of
constructing them only when they are looked up. Resource objects are
now lazy themselves, so the previous lazy resource creation mechanism
is redundant.
_LazyResourceMap is now a simple read-only wrapper around an existing
map. The custom class is now only used to provide a specialized repr.
The reading of resource name and data is now performed in the Resource
class (lazily, when the respective attributes are accessed) instead of
in ResourceFile._LazyResourceMap.
The new syntax supports the same operations as the old syntax, but is
clearer to understand and more extensible in the future. The old syntax
is still supported for now.
The old names ("system" and "application" compression) were not really
accurate in all cases, so the compression types are now referred to by
their number.
The non-stream-based APIs still exist as before and are not deprecated,
they just act as thin wrappers around the stream-based API.
The main rsrcfork module doesn't use the stream-based APIs yet, because
it reads each resource's data all at once and not incrementally.
