Tools: Add a small Python tool to print FSTs

Tools/print-fs-fst.py

@@ -0,0 +1,58 @@
+import argparse
+import struct
+
+def read_entry(f) -> dict:
+    name = struct.unpack_from("12s", f.read(12))[0]
+    uid = struct.unpack_from(">I", f.read(4))[0]
+    gid = struct.unpack_from(">H", f.read(2))[0]
+    is_file = struct.unpack_from("?", f.read(1))[0]
+    modes = struct.unpack_from("BBB", f.read(3))
+    attr = struct.unpack_from("B", f.read(2))[0]
+    x3 = struct.unpack_from(">I", f.read(4))[0]
+    num_children = struct.unpack_from(">I", f.read(4))[0]
+
+    children = []
+    for i in range(num_children):
+        children.append(read_entry(f))
+
+    return {
+        "name": name,
+        "uid": uid,
+        "gid": gid,
+        "is_file": is_file,
+        "modes": modes,
+        "attr": attr,
+        "x3": x3,
+        "children": children,
+    }
+
+COLOR_RESET = "\x1b[0;00m"
+BOLD = "\x1b[0;37m"
+COLOR_BLUE = "\x1b[1;34m"
+COLOR_GREEN = "\x1b[0;32m"
+
+def print_entry(entry, indent) -> None:
+    mode_str = {0: "--", 1: "r-", 2: "-w", 3: "rw"}
+
+    sp = ' ' * indent
+    color = BOLD if entry["is_file"] else COLOR_BLUE
+
+    owner = f"{COLOR_GREEN}{entry['uid']:04x}{COLOR_RESET}:{entry['gid']:04x}"
+    attrs = f"{''.join(mode_str[mode] for mode in entry['modes'])}"
+    other_attrs = f"{entry['attr']} {entry['x3']}"
+
+    print(f"{sp}{color}{entry['name'].decode()}{COLOR_RESET} [{owner} {attrs} {other_attrs}]")
+    for child in entry["children"]:
+        print_entry(child, indent + 2)
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Prints a FST in a tree-like format.")
+    parser.add_argument("file")
+    args = parser.parse_args()
+
+    with open(args.file, "rb") as f:
+        root = read_entry(f)
+
+    print_entry(root, 0)
+
+main()