PyPianoCatSongDataExtractor
感谢@whc2001提供的C#版本源代码
用于解压某电子琴学习机的数据包文件
闲着没事移植去了Python，方便使用
import os
import struct
from typing import List, Tuple
Encoding = 'gbk'
key = None
def getKey(file_data: bytes) -> bytes:
key_a = file_data[1024:1024+32]
key_b = file_data[1056:1056+32]
ret = bytearray(32)
for i in range(32):
ret[i] = (key_b[i] - key_a[i]) % 256
return ret
def getDir(file_data: bytes) -> List[Tuple[str, int, int]]:
ret = []
dir_num = struct.unpack('I', file_data[252:256])[0]
for i in range(dir_num):
offset = 1280 + i * 128
item = bytearray(file_data[offset:offset+128])
for j in range(len(item)):
item[j] = (item[j] - key[j % 32]) % 256
dir_name = item[:120].decode(Encoding).rstrip('\x00')
dir_data_length = struct.unpack('I', item[120:124])[0] << 7
dir_data_offset = struct.unpack('I', item[124:128])[0]
ret.append((dir_name, dir_data_length, dir_data_offset))
return ret
def getFile(file_data: bytes, dir_data_offset: int, dir_data_length: int) -> List[Tuple[str, int, int]]:
ret = []
for i in range(dir_data_length // 128):
offset = dir_data_offset + i * 128
item = bytearray(file_data[offset:offset+128])
for j in range(len(item)):
item[j] = (item[j] - key[j % 32]) % 256
file_name = item[:64].decode(Encoding).rstrip('\x00')
song_data_offset = struct.unpack('I', item[64:68])[0]
song_data_length = struct.unpack('I', item[68:72])[0]
ret.append((file_name, song_data_offset, song_data_length))
return ret
def getSong(file_data: bytes, song_data_offset: int, song_data_length: int) -> bytes:
return file_data[song_data_offset:song_data_offset+song_data_length]
def main(input_path: str, output_path: str):
global key
if not os.path.exists(input_path):
print(f"File Not Found in {input_path}")
exit(1)
if not os.path.exists(output_path):
os.makedirs(output_path)
with open(input_path, 'rb') as f:
data = f.read()
key = getKey(data)
dirs = getDir(data)
for dir_name, dir_data_length, dir_data_offset in dirs:
dir_path = os.path.join(output_path, dir_name)
os.makedirs(dir_path, exist_ok=True)
songs = getFile(data, dir_data_offset, dir_data_length)
for file_name, song_data_offset, song_data_length in songs:
print(f"{dir_name} -> {file_name}")
song_data = getSong(data, song_data_offset, song_data_length)
with open(os.path.join(dir_path, f"{file_name}.mid"), 'wb') as f:
f.write(song_data)
if __name__ == "__main__":
import sys
if len(sys.argv) != 3:
print("Usage: PianoCatSongDataExtractor.py <INPUT_FILE> <OUTPUT_FOLDER>")
exit(1)
main(sys.argv[1], sys.argv[2])
