Recognizing IWAD/PWAD files with more accuracy (using CRC-32)
Doomsday's data file recognition code depends on a few quick-to-determine pieces of information, such as file size and the CRC-32 of the WAD directory lump listing.
However, some IWADs like Doom II v1.7 and v1.7a can only be recognized as unique files if one considers the full contents of the file and not just the metadata. CRC-32 is a pretty good choice for this as it is simple and fast to compute.
The data file recognizer should calculate the CRC-32 checksum of full WAD file contents (of all found WAD files) and use that as one of the criteria for detection.