unpack.py

import os,struct,binascii

def get_int4():
        return int( struct.unpack("I",index.read(4))[0] )
def get_int2():
        return int( struct.unpack("H",index.read(2))[0] )

def get_sz():
        out = ""
        while True:
                cur = index.read(1)
                if cur == b'\x00': break
                out += struct.unpack("c",cur)[0].decode("ASCII")
        return out

index = open("cstrike_pak_dir.vpk",'rb')

print( "Signature:",binascii.b2a_hex(index.read(4)) )
print( "Version:",get_int4() )
print( "Directory length:", get_int4() )
print( "Unknown1:", get_int4() )
unknown2 = get_int4() # footer length?
print( "Unknown2:", unknown2 )
unknown3 = get_int4()
print( "Unknown3:", unknown3 )
print( "Unknown4:", get_int4() )

class VpkFile():
        path = ""
        CRC = -1
        archive_index = -1
        offset = -1
        length = -1
        preload = bytes()

vpk_files = []

while True:
        extension = get_sz()
        if not extension: break

        while True:
                folder = get_sz()
                if not folder: break

                while True:
                        filename = get_sz()
                        if not filename: break

                        cur_file = VpkFile()
                        vpk_files.append(cur_file)
                        cur_file.path = "{}/{}.{}".format(folder,filename,extension)

                        cur_file.CRC = get_int4()
                        preload_bytes = get_int2()
                        cur_file.archive_index = get_int2()
                        if cur_file.archive_index == b'\x7fff':
                                print("EMBED")
                        cur_file.offset = get_int4()
                        cur_file.length = get_int4()
                        get_int2() # terminator

                        if preload_bytes:
                                cur_file.preload = index.read(preload_bytes)

index.close()

print("Extracting...")
for vf in vpk_files:
        print(vf.path,"({} bytes)".format(len(vf.preload)+vf.length))
        ending = vf.path.replace("/","\\")
        if ending[0] == " ":
            ending = ending[:0]
            if len(ending) == 0:
                ending = "xyz"
        full_path = os.path.join(os.getcwd(),"vpk_extracted",ending)

        dir = os.path.dirname(full_path)
        if not os.path.isdir(dir):
                os.makedirs(dir)
        out_data = open(full_path,'wb')
        out_data.write(vf.preload)
        if vf.length:
                vpk = open("cstrike_pak_{}.vpk".format(str(vf.archive_index).zfill(3)),'rb')
                vpk.seek(vf.offset)
                out_data.write(vpk.read(vf.length))
                vpk.close()
        out_data.close()