Since becoming just another Chrome-based browser, Opera no longer uses files in this format. This was one of the worst-designed binary file formats I've ever seen, but, in fairness, it's the kind of binary format a lot of programmers would come up with. Part of the problem was the obvious attempt to design a format portable to different platforms, but the resulting complexity was crazy—and completely unnecessary. I would blame it on the increasing number of programmers divorced from programming down to the bare metal, but binary file formats in the "old days" weren't always much better as I remember.
dumps binary files used by the Opera web browser. The file format
is used for the cookies file ("
cookies4.dat"), the download
rescue file ("
download.dat"), and the visited links file
vlink4.dat"). The format is supposedly used for the disk cache
files, but I don't see any likely candidates in my Opera 9 cache directories.
The output of duop is currently Scheme-friendly S-expressions.
% duop [-debug] [-cache] [-cookies] [-download] [-index] [-visited] [file]
- writes debug information to standard output.
- specify the type of Opera file being dumped. By default, duop attempts to determine the file type based on the tag ID in the record following the header record.
- is the file to dump; if no file is specified, input is read from standard input.