Jason Molenda f77a812941 [lldb] Add a GetSubsetExtractorSP method to DataExtractor (#177309) ...

We have many places where an ObjectFile subclass will take the
DataExtractor representing the entire binary, create a subsection of
that in a new DataExtractor for processing. For instance, an object file
might have symbol table entries with offsets into the string table. A
common code pattern is to create a DataExtractor representing the string
table, and then pulling out the c-strings based on those offsets from
the string table DataExtractor.

When code does this, it creates a new DataExtractor, copies the
Endianness and Wordsize from the original, copies the DataBufferSP from
the original, and specifies a new start and offset into the DataBuffer.

However, if the binary is actaully stored in a VirtualDataExtractor,
this code pattern loses the correct virtual-to-physical table
translation and will not work correctly. This new method simplifies this
common pattern, and correctly takes a subset of a VirtualDataExtractor.

The current implementation only allows a subset of a
VirtualDataExtractor that is contained within a single virtual entry
(LookupTable entry) and returns a DataExtractor with the corret offsets
calculated from the LookupTable. If we need to a VirtualDataExtractor to
create a Subset DataExtractor representing multiple separate virtual
ranges of data, we'll need to copy over the LookupTable entries that
cover all the bytes, and update them to be relative to the new
VirtualDataExtractor. It's a bit of work, and it's not needed right now,
so I'm not tackling that.

I am working on a larger PR which needs this new method. This PR
contains a unit test that uses it.

rdar://148939795

2026-01-23 14:06:32 -08:00

36 KiB

Raw Blame History

View Raw