(extensions.archives) adding id_software.Pak support

bsp_tool/extensions/archives/id_software.py

@@ -1,14 +1,66 @@
+from __future__ import annotations
+import io
+import struct
+from typing import Dict, List
 import zipfile
 
 from . import base
 
 
+class PakFileEntry:
+    def __init__(self, filepath: str, offset: int, size: int):
+        self.filepath = filepath
+        self.offset = offset
+        self.size = size
+
+    def __repr__(self) -> str:
+        return f"PakFileEntry(filepath={self.filepath}, offset={self.offset}, size={self.size})"
+
+    @classmethod
+    def from_stream(cls, stream: io.BytesIO) -> PakFileEntry:
+        return cls(*struct.unpack("56s2I", stream.read(64)))
+
+
 class Pak(base.Archive):
     # https://quakewiki.org/wiki/.pak
     ext = "*.pak"
+    files: Dict[str, PakFileEntry]
+
+    def __init__(self, filepath: str = None):
+        self.files = dict()
+        if filepath is not None:
+            self._from_file(filepath)
+
+    def __repr__(self) -> str:
+        return f"<{self.__class__.__name__} {len(self.files)} files @ 0x{id(self):016X}>"
+
+    def __del__(self):
+        self.file.close()
+
+    def __exit__(self):
+        self.file.close()
+
+    def _from_file(self, filepath: str):
+        self.file = open(filepath, "rb")
+        assert self.file.read(4) == b"PACK", "not a .pak file"
+        # file table
+        offset, size = struct.unpack("2I", self.file.read(8))
+        assert size % 64 == 0, "unexpected file table size"
+        self.file.seek(offset)
+        self.files = {
+            e.filepath.split(b"\0")[0].decode(): e
+            for e in [
+                PakFileEntry.from_stream(self.file)
+                for i in range(size // 64)]}
+
+    def read(self, filepath: str) -> bytes:
+        assert filepath in self.files
+        entry = self.files[filepath]
+        self.file.seek(entry.offset)
+        return self.file.read(entry.size)
 
-    def __init__(self):
-        raise NotImplementedError()
+    def namelist(self) -> List[str]:
+        return sorted(self.files.keys())
 
 
 class Pk3(zipfile.ZipFile, base.Archive):