CAB format
in [Visual Basic]
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From: mayayana on 25 Jan 2007 00:46 > > * There's cabinet.dll but the calls are all cdecl and > > I'm not experienced enough with C++ and typelibs > > to try Matthew Curland's cdecl-in-VB methods. > > My advice would be to study it for a while and see if you can > overcome that limitation. > > At least that way you'd be in control of the whole process. > That tip made me reconsider and look at the FDI functions in cabinet.dll, but they're monsters. It seems to require a number of functions, with numerous callbacks, in order to extract from a CAB. It's odd how many CAB options there are and how poor most of them are. A lot of the programs and code around date back to a time when only MSZIP compression was used. And the PDW VB6STKIT.dll actually has an extraction function, but I couldn't get it working. When I tried running Filemon to see what was going on it turned out that the DLL is hard-coded to look for the CAB in the %WIN% folder, despite one of the parameters being the CAB path! For some reason it seems that MS doesn't want CAB access to be easy.
From: mayayana on 26 Jan 2007 00:40 Problem: DOS window flashing with command-line EXE. I've managed to cobble together some C++ sample code and created a command-line EXE that works fine to extract files from CABs. It just takes a command line parameter of CAB file and path, unpacks the CAB, then quits. Just one catch: A DOS screen flashes by when it runs? What might cause that? I'm not writing any output.
From: Karl E. Peterson on 26 Jan 2007 14:39 mayayana <mayaXXyana1a(a)mindXXspring.com> wrote: > Problem: DOS window flashing with command-line EXE. > > I've managed to cobble together some C++ > sample code and created a command-line > EXE that works fine to extract files from CABs. > It just takes a command line parameter of > CAB file and path, unpacks the CAB, then > quits. Just one catch: A DOS screen flashes by > when it runs? What might cause that? I'm not > writing any output. You create a console application (in C++), and then ask (in a VB group!) why it creates a console??? -- ..NET: It's About Trust! http://vfred.mvps.org
From: mayayana on 26 Jan 2007 18:24 > You create a console application (in C++), and then ask (in a VB group!) why it > creates a console??? > -- :) Yes, I think I might have worked that out. I didn't realize there was a difference between a "Win32 Console Applcation" and a "Win32 Application". It's a VC++ issue but I've been working on a VB solution. I think I have it now. MS has a sample package called "cabview" that provides barebones C++ code for using cabinet.dll to extract from CABs. It was fairly simple to adapt that code. Ironically, though, I only came across it after 3 days of searching, and it was on a Chinese download site! It may be that no one else really needs this, but I'll be happy to share the code samples if anyone does. What I came up with was a small commandline EXE that extracts all of the CAB contents to curdir. (My C++ is not good enough to do much more than that.) It seems that the CDECL functions in cabinet.dll are really the only realistic way to extract. I had fairly good luck with parsing the actual binary structure of CABs, which turned out not to be so hard. But the trouble with that was that there are several variations on the compression method that can be used. So I could extract the compressed file streams but then I'd need several decompression routines (and their support files) to deal with the next step. With cabinet.dll the compression type can be ignored. For anyone who's interested, *don't waste your time with SetupIterateCabinet*. It works beautifully, but only on CABs compressed with MSZIP. On others the extraction callback returns error 13 on the first file.
From: Karl E. Peterson on 26 Jan 2007 19:10
mayayana <mayaXXyana1a(a)mindXXspring.com> wrote: >> You create a console application (in C++), and then ask (in a VB group!) why it >> creates a console??? > > :) Yes, I think I might have worked that out. I didn't > realize there was a difference between a "Win32 > Console Applcation" and a "Win32 Application". Ah yes, that _is_ a crucial distinction. <g> -- ..NET: It's About Trust! http://vfred.mvps.org |