fix: build only recipes whose members match

scripts/romset_recipes.py

@@ -165,15 +165,38 @@ class AtomPool:
 def identify_archive(
     path: Path, recipes: dict[str, Recipe], pool: AtomPool
 ) -> str | None:
-    """Return the recipe label that reproduces *path* byte for byte."""
+    """Return the recipe label that reproduces *path* byte for byte.
+
+    Equal bytes need equal (name, crc32) members, which the archive's
+    central directory gives without inflating anything: building every
+    recipe at DEFLATE level 9 first took 94 s and 1 GB at pipeline step 1c.
+    """
+    held = _member_list(path)
+    if held is None:
+        return None
     original = path.read_bytes()
     for label, recipe in sorted(recipes.items()):
+        if sorted((name, crc.lower()) for name, crc in recipe) != held:
+            continue
         blob = pool.build(recipe)
         if blob is not None and blob == original:
             return label
     return None
 
 
+def _member_list(path: Path) -> list[tuple[str, str]] | None:
+    """Sorted (name, crc32) of an archive's members, from its directory."""
+    try:
+        with zipfile.ZipFile(path) as archive:
+            return sorted(
+                (info.filename, format(info.CRC, "08x"))
+                for info in archive.infolist() if not info.is_dir()
+            )
+    except (zipfile.BadZipFile, OSError) as exc:
+        print(f"  UNREADABLE: {path}: {exc}", file=sys.stderr)
+        return None
+
+
 def reconstruct(
     target_md5: str, recipes: dict[str, Recipe], pool: AtomPool
 ) -> tuple[str, bytes] | None:

tests/test_romset_recipes.py

@@ -8,6 +8,7 @@ import sys
 import tempfile
 import unittest
 import zipfile
+import zlib
 from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
@@ -557,5 +558,35 @@ class TheMissingReportNamesItsTargets(unittest.TestCase):
         self.assertIn("NO RECIPE: scummclassic.zip md5=dddddddd", text)
         self.assertLess(text.index("neogeo.zip"), text.index("aes.zip"))
 
+
+class IdentificationReadsTheDirectoryFirst(unittest.TestCase):
+    """identify_archive built every recipe at DEFLATE level 9 before
+    comparing bytes: 94 s and 1 GB at pipeline step 1c, mostly for recipes
+    whose members could never match."""
+
+    def test_a_recipe_with_other_members_is_never_built(self):
+        from torrentzip import build_torrentzip  # noqa: PLC0415
+
+        import romset_recipes  # noqa: PLC0415
+
+        rom = b"rom bytes"
+        crc = format(zlib.crc32(rom), "08x")
+        with tempfile.TemporaryDirectory(dir=ROOT / "tmp") as tmp:
+            archive = Path(tmp) / "set.zip"
+            archive.write_bytes(build_torrentzip([("a.rom", rom)]))
+
+            class Pool:
+                built: list = []
+
+                def build(self, recipe):
+                    self.built.append(recipe)
+                    return build_torrentzip([(name, rom) for name, _crc in recipe])
+
+            pool = Pool()
+            label = romset_recipes.identify_archive(
+                archive, {"other": [("b.rom", crc)], "match": [("a.rom", crc)]}, pool)
+        self.assertEqual(label, "match")
+        self.assertEqual(pool.built, [[("a.rom", crc)]])
+
 if __name__ == "__main__":
     unittest.main()