View source for VPK (file format)/Vampire: The Masquerade – Bloodlines

'''VPK''' ("'''V'''ampire '''P'''ac'''K'''") is a package format used by {{Vtmb|4}}. It is a completely separate format from Valve's {{code|.vpk}} file format, added in {{Src|4}} ({{l4dbranch|1}}), now used in all modern {{Src|4}} and {{Src2|4}} games.

Vampire PacK files can be opened with {{vpkedit|1}} and PackFile Explorer (shipped with the Unofficial Patch's [[VTMB Unofficial Patch Setup|Bloodlines SDK]]).

From this point on they will be referred to as VPKs for ease of communication.

== Features ==
=== Self-contained ===

VPKs do not use any external archives like chunked Valve pack files. Instead, multiple standalone VPKs can be created, and the game will load them all as long as their filenames are formatted correctly. Their filenames must match <code>packXYY.vpk</code> where X and Y are both integers starting at 0.

=== Simple ===
VPKs are exceedingly easy to parse and modify compared to other pack file formats like Valve PacK files.

== File Format ==
=== Footer ===
VPK files have no header, but they do have a footer which acts in the same capacity as a header would, vaguely resembling a ZIP file in this regard. All VPKs should be at minimum 9 bytes long to contain the footer, and empty VPKs will be 9 null bytes. There are multiple empty VPKs shipped with {{Vtmb|1}} for unknown reasons.

<syntaxhighlight lang=cpp>struct VPKFooter
{
	unsigned int FileCount;
	unsigned int DirectoryOffset;	// Absolute from the start of the VPK
	unsigned char Version;			// Always 0
};</syntaxhighlight>

Since the version field is at the end of this struct, we can assume that the game is in fact reading each field sequentially in reverse. This would mean the version is being read before the other fields, which is sensible and follows the pattern of many other pack file formats. Your implementation may read the footer in any order however, because the version should always be zero.

=== File Entries ===
At the directory offset specified in the header, <code>FileCount</code> entries exist in a tightly packed array. The directory tree is usually written directly before the footer, but it can appear at any location in the VPK. Contrary to the footer's flow, the directory offset (and all offsets in the file entries) point to the beginning of the given data, and all reads from this point forward should add to the offset, not subtract from it.

<syntaxhighlight lang=cpp>struct VPKFileEntry
{
	unsigned int PathLength;
	char Path[PathLength];	// Is NOT null-terminated!
	unsigned int Offset;	// Absolute from the start of the VPK
	unsigned int Length;
};</syntaxhighlight>

=== File Contents ===
Seeking to the given <code>Offset</code> in the VPK and reading <code>Length</code> bytes will return the file data at the given <code>Path</code>. Each file entry maps to one file.

File contents are usually stored from the very start of the VPK to the file entry list, but just like the entry list, there is no rule requiring this to be the case.

==See also==
* {{vpkedit|1}} - Can browse, edit, and create Vampire PacK files
* [[VTMB Unofficial Patch Setup|Bloodlines SDK]] - Can browse and create Vampire PacK files
* [[VPK (file format)]] - Valve PacK file format, entirely separate from Vampire PacK file format

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[[Category:File formats|vpk]]