Python 3 Windowsアニメーションカーソル（.ani）の情報を取得する

Windowsアニメーションカーソル（.ani）の情報を取得するサンプルコードです。

#rifffilereader.py
from __future__ import annotations

from io import FileIO
from os import SEEK_SET, SEEK_CUR
from typing import Tuple
from dataclasses import dataclass

@dataclass
class RIFFFileChunk:
    reader: RIFFFileReader
    signature: str
    data_size: int
    list_type: str
    data_position: int
    def read(self, size: int, offset: int = 0):
        if offset < 0:
            raise ValueError("オフセットが負です。")
        if size + offset > self.dataSize:
            raise ValueError("範囲外のデータを参照しました。")
        self.reader.file.seek(self.data_position + offset, SEEK_SET)
        return self.reader.file.read(size)
    def readinto(self, obj: bytes, offset: int=0) -> int | None:
        if offset < 0:
            raise ValueError("オフセットが負です。")
        if offset + len(bytes(obj)) > self.data_size:
            raise ValueError("範囲外のデータを参照しました。")
        f = self.reader.file
        f.seek(self.data_position + offset, SEEK_SET)
        return f.readinto(obj)

class RIFFFileReader:
    __path: str
    __f: FileIO
    __signature: str
    __data_size: int
    __form_type: str
    __chunks: Tuple[RIFFFileChunk]
    def __init__(self, path: str):
        self.__path = path
        f = open(path, "rb")
        # RIFFヘッダーの確認
        self.__signature = f.read(4).decode("ascii")
        if self.__signature != "RIFF":
            raise RuntimeError("ファイルはRIFFファイルではありません。")
        self.__data_size = int.from_bytes(f.read(4), byteorder="little", signed=False)
        self.__form_type = f.read(4).decode("ascii")
        self.__f = f

        chunks = []
        while True:
            signature = f.read(4).decode("ascii")
            if len(signature) == 0:
                break
            data_size = int.from_bytes(f.read(4), byteorder="little", signed=False)
            if signature == "LIST":
                list_type = f.read(4).decode("ascii")
                data_position = f.tell()
            else:
                list_type = None
                data_position = f.tell()
                f.seek(data_size, SEEK_CUR)
            chunks.append(RIFFFileChunk(self, signature, data_size, list_type, data_position))
        self.__chunks = tuple(chunks)
    def __enter__(self):
        return self
    def __exit__(self, exc_type, exc_value, traceback):
        self.close()
    def close(self):
        self.__f.close()
    @property
    def path(self) -> str:
        return self.__path
    @property
    def signature(self) -> str:
        return self.__signature
    @property
    def dataSize(self) -> int:
        return self.__data_size
    @property
    def formType(self) -> str:
        return self.__form_type
    @property
    def chunks(self) -> Tuple[RIFFFileChunk]:
        return self.__chunks
    @property
    def file(self) -> FileIO:
        return self.__f

#aniheader.py
from rifffilereader import RIFFFileReader
from ctypes import Structure, c_uint32

class ANIHeader(Structure):
    _fields_ = (
        ("size", c_uint32),      # cbSizeOf
        ("frames", c_uint32),    # cFrames
        ("steps", c_uint32),     # cSteps
        ("cx", c_uint32),
        ("cy", c_uint32),
        ("bit_count", c_uint32), # cBitCount
        ("planes", c_uint32),    # cPlanes
        ("jif_rate", c_uint32),  # JifRate
        ("flags", c_uint32),
    )
    @staticmethod
    def from_file(path: str):
        #from itertools document
        def first_true(iterable, default=False, pred=None):
            return next(filter(pred, iterable), default)
        with RIFFFileReader(path) as riff:
            anih_chunk = first_true(riff.chunks, lambda chunk: chunk.signature == "anih")
            aniHeader = ANIHeader()
            anih_chunk.readinto(aniHeader)
            return aniHeader

#main.py
from aniheader import ANIHeader
from ctypes import Structure

def structure_to_dict(struct: Structure):
    return dict((field, getattr(struct, field)) for field, _ in struct._fields_)

print(structure_to_dict(ANIHeader.from_file(r"C:\Windows\Cursors\aero_busy.ani")))
#{'size': 36, 'frames': 18, 'steps': 18, 'cx': 0, 'cy': 0, 'bit_count': 32, 'planes': 1, 'jif_rate': 3, 'flags': 1}

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Python 3 Windowsアニメーションカーソル（.ani）の情報を取得する

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