VP (Volition Package) files are a packaging file format, used to package multiple files into a single file, while maintaining directory structure. They do not use any sort of compression.
On Win32, the most popular VP viewer is VPView32. However, almost all the editors can also be used to extract files from VPs.
wxVPView is modeled on VPView32, but with cross platform support (Win/OSX/Linux)
As of this writing, there are a few different editors.
Features an explorer-like interface, and is fairly easy to use to create or modify VPs.
Features a Winzip-like interface, is very easy to use to create, modify, and extract files and directories to/from VPs.
Somewhat more difficult to use than VPCS or QuickVP, but also adds the ability to merge VP files, update files already in a VP, and edit files already in a VP.
The latest VP editor, with the ability to both read and edit VPs. It is possible to place a batch of files anywhere in a VP directory, in contrast to VPMage, which requires you to import either a "Data" folder or another VP.
Based on .NET 4.5 VPGUI is a new editor with nifty features like drag-and-drop & a browser like history.
VP files are made up of three main components; the header, followed by the individual files, and finally the index for the entries.
char header; //Always "VPVP" int version; //As of this version, still 2. int diroffset; //Offset to the file index int direntries; //Number of entries
Files are simply stored in the VP, one right after the other. No spacing or null termination is necessary.
The index is a series of "direntries"; each directory has the structure, as seen below.
int offset; //Offset of the file data for this entry. int size; //Size of the file data for this entry char name; //Null-terminated filename, directory name, or ".." for backdir int timestamp; //Time the file was last modified, in unix time.
Each direntry may be a directory, a file, or a backdir. A directory entry signifies the start of a directory, and has the name entry set to the name of the directory; a backdir has the name of "..", and represents the end of a directory.
Because there is no type descriptor inherent to the format, directories are identified by the "size" being set to 0. See cfilesystem.cpp.
Timestamps are not used in identifying directories.
VP files cannot contain empty files. See cfilearchiver.cpp.
All valid VP files should start with the "data" directory as the toplevel.
VP files can contain empty directory entries. For example, "sparky_hi_fs2.vp" has an empty "data/fonts/" directory entry.
Note that it isn't necessary at all to add backdirs at the end of a VP file.
FreeSpace 2 directory structure
FS2 Data Structure
To Descent Network (archival link), for getting file structure information before anyone else.