"""
2026/4/5
TMY
比特位打包器
"""
class BitPacker:
    def __init__(self, total_bytes):
        self.buf = bytearray(total_bytes)

    def set_bits(self, start_byte, start_bit, bit_len, value):
        """
        start_byte: 起始字节
        start_bit:  起始比特位（0~7）
        bit_len:    比特长度
        value:      无符号整数值
        """
        value = int(value) & ((1 << bit_len) - 1)
        bit_pos = start_byte * 8 + start_bit

        for i in range(bit_len):
            bit = (value >> (bit_len - 1 - i)) & 1
            byte_idx = bit_pos // 8
            bit_idx = 7 - (bit_pos % 8)
            if bit:
                self.buf[byte_idx] |= (1 << bit_idx)
            else:
                self.buf[byte_idx] &= ~(1 << bit_idx)
            bit_pos += 1

    def get_bytes(self):
        return bytes(self.buf)