From 59bc5dfa4286f32bc2feba30157ba360becf2057 Mon Sep 17 00:00:00 2001
From: Alex Bates <hi@imalex.xyz>
Date: Sun, 18 Oct 2020 15:04:49 +0100
Subject: [PATCH] match fs.bin

---
 tools/build_assets_fs.py | 73 +++++++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 27 deletions(-)

diff --git a/tools/build_assets_fs.py b/tools/build_assets_fs.py
index 607866bee9..39a8e329f7 100755
--- a/tools/build_assets_fs.py
+++ b/tools/build_assets_fs.py
@@ -9,60 +9,79 @@ import shutil
 
 tools_dir = Path(__file__).parent.absolute()
 
-with open("assets/fs.json", "r") as f:
-    config = json.loads(f.read())
+def next_multiple(pos, multiple):
+    return pos + pos % multiple
 
 def build_mapfs(src_dir, build_dir, out_bin):
+    with open(src_dir + ".json", "r") as f:
+        config = json.loads(f.read())
+
+    # every TOC entry's name field has data after the null terminator made up from all the previous name fields.
+    # we probably don't have to do this for the game to read the data properly (it doesn't read past the null terminator
+    # of `string`), but the original devs' equivalent to build_assets_fs.py had this bug so we need to replicate it to match.
+    written_names = []
+
     with open(out_bin, "wb") as f:
         f.write(config["title"].encode("ascii"))
 
-        next_data_pos = 0x20 + (len(config["assets"]) + 1) * 0x1C
+        next_data_pos = (len(config["assets"]) + 1) * 0x1C
 
         asset_idx = 0
         for asset in config["assets"]:
-            offset = 0x20 + asset_idx * 0x1C
-
+            toc_entry_pos = 0x20 + asset_idx * 0x1C
 
             src_path = Path(src_dir, asset["path"])
             build_path = Path(build_dir, asset["path"])
 
-            name = asset["name"]
-            src_size = src_path.stat().st_size
-            compressed_size = build_path.stat().st_size + 1
+            # data for TOC entry
+            name = asset["name"] + "\0"
+            offset = next_data_pos
+            size = next_multiple(build_path.stat().st_size, 2)
+            decompressed_size = src_path.stat().st_size
 
-            print({
-                "name": name,
-                "offset": (next_data_pos + 0x20),
-                "size": compressed_size,
-                "decompressed_size": src_size,
-            })
+            print(f"{name} {offset:08X} {size:08X} {decompressed_size:08X}")
 
-            # write TOC row
-            f.seek(offset)
-            f.write(name.encode('ascii'))
-            f.seek(offset + 0x10)
-            f.write((next_data_pos - 0x20).to_bytes(4, byteorder="big"))
-            f.write(compressed_size.to_bytes(4, byteorder="big"))
-            f.write(src_size.to_bytes(4, byteorder="big"))
+            written_names.append(name)
+            # write all previously-written names; required to match
+            for prev_name in written_names:
+                f.seek(toc_entry_pos)
+                f.write(prev_name.encode('ascii'))
 
-            # write data
-            f.seek(next_data_pos)
+            # write TOC entry.
+            f.seek(toc_entry_pos + 0x10)
+            f.write(offset.to_bytes(4, byteorder="big"))
+            f.write(size.to_bytes(4, byteorder="big"))
+            f.write(decompressed_size.to_bytes(4, byteorder="big"))
+
+            # write data.
+            f.seek(0x20 + next_data_pos)
             f.write(build_path.read_bytes())
-            next_data_pos += compressed_size
+            next_data_pos += size
 
             asset_idx += 1
 
-        f.seek(0x20 + asset_idx * 0x1C)
-        f.write(b"end_data")
+        # end_data
+        toc_entry_pos = 0x20 + asset_idx * 0x1C
+
+        written_names.append("end_data\0")
+        for prev_name in written_names:
+            f.seek(toc_entry_pos)
+            f.write(prev_name.encode('ascii'))
+
+        f.seek(toc_entry_pos + 0x18)
+        f.write((0x903F0000).to_bytes(4, byteorder="big")) # TODO: figure out purpose
 
 def build_file(src_dir, out_dir, filename):
+    with open(src_dir + ".json", "r") as f:
+        config = json.loads(f.read())
+
     asset = None
     for a in config["assets"]:
         if (a["path"] == filename):
             asset = a
 
     if not asset:
-        print("asset not configured in json file")
+        print("asset not configured in {}.json".format(src_dir))
         exit(1)
 
     src_path = Path(src_dir, filename)