The new system will make it easier to port the deobfuscator to different
revisions.
There are two main changes:
- The addition of a Profile class, which contains a list of excluded
classes, methods and fields, and the maximum obfuscated name length.
It is passed to Transformers that require it with dependency
injection.
- New ClassFilter and MemberFilter infrastructure. The MemberFilter
class adds support for filtering fields and methods based on the
owner and descriptor, in addition to the name. This makes the filters
more precise than the previous system. It also supports globs, which
makes it easy to filter whole groups of classes, fields and methods
in one go.
The Profile class uses a ClassFilter and MemberFilters to
represent the list of excluded classes, methods and fields.
A separate benefit is the addition of a separate entry points filter
to the Profile class. Prior to this commit, many Transformers re-used
the excluded method filter to find entry points, which is less precise
(many of the excluded methods in 550 are not entry points).
Support for filtering methods by owner and descriptor in addition to
name allows the DEFAULT_PUBLIC_CTOR_CLASSES Set in VisibilityTransformer to
be combined with the entry points filter.
In the future it might be desirable to split the excluded method set
into three separate sets:
- One to represent methods that can't be renamed.
- One to represent methods whose signature can't be changed.
- One to represent methods that can't be removed.
Signed-off-by: Graham <gpe@openrs2.dev>
The new transformer uses a different approach to the old one. It starts
exploring the call graph from the entry points, recursively analysing
method calls. Methods are only re-analysed if their possible argument
values change, with the Unknown value being used if we can't identify a
single integer constant at a call site. This prevents us from recursing
infinitely if the client code does.
While this first pass does simplify branches in order to ignore dummy
method calls that are never evaluated at runtime, it operates on a copy
of the method (as we initially ignore more calls while the argument
value sets are smaller, ignoring fewer calls as they build up).
A separate second pass simplifies branches on the original method and
inlines singleton constants, paving the way for the UnusedArgTransformer
to actually remove the newly unused arguments.
This new approach has several benefits:
- It is much faster than the old approach, as we only re-analyse methods
as required by argument value changes, rather than re-analysing every
method during every pass.
- It doesn't require special cases for dealing with mutually recursive
dummy calls. The old approach hard-coded special cases for mutually
recursive calls involving groups of 1 and 2 methods. The code for this
wasn't clean. Furthermore, while it was just about good enough for the
HD client, the SD client contains a mutually recursive group of 3
methods. The new approach is capable of dealing with mutually
recursive groups of any size.
Finally, the new transformer has a much cleaner implementation.
Signed-off-by: Graham <gpe@openrs2.dev>
Graham