remove_last_vpk.go

package main

import (
	"bufio"
	"bytes"
	"encoding/binary"
	"io"
	"os"
)

const (
	ExpectedSignature = 0x55aa1234
	ExpectedVersion   = 1
)

type VPKHeader struct {
	Signature uint32
	Version   uint32
	TreeSize  uint32
}

type VPKDirectoryEntry struct {
	CRC          uint32
	PreloadBytes uint16
	ArchiveIndex uint16
	EntryOffset  uint32
	EntryLength  uint32
	Terminator   int16
}

type VPKDirectoryEntryInfo struct {
	Ext     string
	Path    string
	Base    string
	Ent     VPKDirectoryEntry
	Preload []byte
}

func main() {
	f, err := os.Open("pak01_dir.vpk")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	var header VPKHeader
	err = binary.Read(f, binary.LittleEndian, &header)
	if err != nil {
		panic(err)
	}

	if header.Signature != ExpectedSignature {
		panic("Invalid signature")
	}

	if header.Version != ExpectedVersion {
		panic("Invalid version")
	}

	br := bufio.NewReader(io.LimitReader(f, int64(header.TreeSize)))

	var entries []VPKDirectoryEntryInfo

	nextString := func() string {
		s, err := br.ReadString(0)
		if err != nil {
			panic(err)
		}

		return s[:len(s)-1]
	}

	var maxArchive uint16

	for {
		ext := nextString()
		if ext == "" {
			break
		}

		for {
			path := nextString()
			if path == "" {
				break
			}

			for {
				base := nextString()
				if base == "" {
					break
				}

				var ent VPKDirectoryEntry
				err = binary.Read(br, binary.LittleEndian, &ent)
				if err != nil {
					panic(err)
				}

				preload := make([]byte, ent.PreloadBytes)
				_, err = io.ReadFull(br, preload)
				if err != nil {
					panic(err)
				}

				if ent.ArchiveIndex > maxArchive {
					maxArchive = ent.ArchiveIndex
				}

				entries = append(entries, VPKDirectoryEntryInfo{
					Ext:     ext,
					Path:    path,
					Base:    base,
					Ent:     ent,
					Preload: preload,
				})
			}
		}
	}

	var directory bytes.Buffer

	var lastExt, lastPath string
	for _, e := range entries {
		if e.Ent.ArchiveIndex == maxArchive {
			continue
		}

		if e.Ext != lastExt {
			if lastExt != "" {
				directory.WriteByte(0) // end path
				directory.WriteByte(0) // end ext
			}
			directory.WriteString(e.Ext)
			directory.WriteByte(0)
			directory.WriteString(e.Path)
			directory.WriteByte(0)
			lastExt = e.Ext
			lastPath = e.Path
		} else if e.Path != lastPath {
			directory.WriteByte(0)
			directory.WriteString(e.Path)
			directory.WriteByte(0)
			lastPath = e.Path
		}

		directory.WriteString(e.Base)
		directory.WriteByte(0)
		err = binary.Write(&directory, binary.LittleEndian, &e.Ent)
		if err != nil {
			panic(err)
		}
		directory.Write(e.Preload)
	}

	if lastExt != "" {
		directory.WriteByte(0)
		directory.WriteByte(0)
		directory.WriteByte(0)
	}

	header.TreeSize = uint32(directory.Len())
	f1, err := os.Create("pak01_dir2.vpk")
	if err != nil {
		panic(err)
	}
	defer f1.Close()

	err = binary.Write(f1, binary.LittleEndian, &header)
	if err != nil {
		panic(err)
	}

	_, err = f1.Write(directory.Bytes())
	if err != nil {
		panic(err)
	}
}