[add] frame_finder.py 模块
- 用于从缓冲区中查找有效的帧消息
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frame_finder.py
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170
frame_finder.py
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from typing import Optional, Tuple
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import logging
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from frame import FrameFormat
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class FrameFinder:
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"""帧查找器 - 在数据缓冲区中查找符合帧格式的数据"""
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def __init__(self):
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"""初始化帧查找器"""
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self.frame_length = FrameFormat.FIXED_SIZE + FrameFormat.DATA_SIZE
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self.frame_header = FrameFormat.FRAME_HEADER
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self.logger = logging.getLogger(__name__)
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def find_frame_in_buffer(self, buffer: bytes, start_pos: int = 0) -> Tuple[Optional[bytes], int]:
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"""
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在给定的缓冲区数据中查找下一个有效帧
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Args:
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buffer: 要搜索的缓冲区数据
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start_pos: 开始搜索的位置
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Returns:
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Tuple[Optional[bytes], int]:
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- 找到的帧数据（如果没找到则为None）
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- 下一次搜索的起始位置（如果找到帧，则是帧后的位置；如果没找到，则是需要保留的数据起始位置）
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"""
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buffer_size = len(buffer)
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# 检查起始位置是否有效
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if start_pos >= buffer_size:
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self.logger.debug(f"起始位置无效: {start_pos} >= {buffer_size}，将移除所有数据")
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return None, buffer_size
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# 在缓冲区中查找帧头
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header_pos = self._find_header(buffer, start_pos)
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if header_pos is None:
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self.logger.debug(f"未找到帧头，将移除所有数据 ({buffer_size} 字节)")
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if buffer_size > 0:
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self.logger.debug(f"移除的数据: {buffer.hex()}")
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return None, buffer_size # 返回缓冲区末尾位置，表示当前数据都可以丢弃
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self.logger.debug(f"找到帧头位置: {header_pos}")
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if header_pos > start_pos:
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removed_data = buffer[start_pos:header_pos]
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self.logger.debug(f"将移除帧头前的无效数据: {removed_data.hex() if len(removed_data) > 0 else '无'} ({len(removed_data)} 字节)")
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# 检查是否有完整帧的数据
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if buffer_size - header_pos < self.frame_length:
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self.logger.debug(f"帧头后数据不足: {buffer_size - header_pos} < {self.frame_length}")
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self.logger.debug(f"保留从位置 {header_pos} 开始的数据: {buffer[header_pos:].hex()}")
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return None, header_pos # 返回帧头位置，表示需要保留从这个位置开始的数据
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# 提取并验证帧
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frame_data = buffer[header_pos:header_pos + self.frame_length]
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if self._verify_frame(frame_data):
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self.logger.debug(f"找到有效帧: {frame_data.hex()}")
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next_pos = header_pos + self.frame_length
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remaining_data = buffer[next_pos:] if next_pos < buffer_size else b''
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self.logger.debug(f"处理完帧后剩余数据: {remaining_data.hex() if remaining_data else '无'} ({len(remaining_data)} 字节)")
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return frame_data, next_pos
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else:
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self.logger.debug(f"帧验证失败，从下一个位置继续查找")
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# 防止在同一位置反复查找
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next_search_pos = header_pos + len(self.frame_header)
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if next_search_pos >= buffer_size:
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self.logger.debug(f"搜索位置已到达缓冲区末尾，将移除所有数据")
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return None, buffer_size
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removed_data = buffer[header_pos:next_search_pos]
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self.logger.debug(f"移除无效帧头数据: {removed_data.hex()} ({len(removed_data)} 字节)")
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return self.find_frame_in_buffer(buffer, next_search_pos)
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def _find_header(self, buffer: bytes, start_pos: int) -> Optional[int]:
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"""
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在缓冲区中查找帧头
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Args:
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buffer: 要搜索的缓冲区数据
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start_pos: 开始搜索的位置
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Returns:
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Optional[int]: 帧头位置，如果未找到则返回None
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"""
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header_len = len(self.frame_header)
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for i in range(start_pos, len(buffer) - header_len + 1):
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if buffer[i:i+header_len] == self.frame_header:
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return i
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return None
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def _verify_frame(self, frame_data: bytes) -> bool:
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"""
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验证帧的有效性
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Args:
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frame_data: 要验证的帧数据
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Returns:
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bool: 帧是否有效
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"""
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# 使用FrameFormat验证帧
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frame = FrameFormat.parse_frame(frame_data)
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return frame is not None
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if __name__ == "__main__":
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# 使用示例
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import logging
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# 配置日志
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logging.basicConfig(
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level=logging.DEBUG,
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format='%(asctime)s - %(levelname)s - %(message)s'
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)
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# 创建帧查找器实例
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finder = FrameFinder()
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# 测试数据：包含3个完整帧，中间夹杂一些无效数据
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test_data = bytes.fromhex(
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# 第一个有效帧
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"1CDFAAAAAAAA0200000049000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000F3"
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# 一些无效数据
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"FFFF1234"
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# 第二个有效帧
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"1CDFAAAAAAAA0300000049000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000F4"
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# 不完整的帧头
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"1CDF12"
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# 第三个有效帧
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"1CDFAAAAAAAA0400000049000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000F5"
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)
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print("初始测试数据:")
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print("总长度:", len(test_data))
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print("数据:", test_data.hex())
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print("\n开始查找帧:")
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# 模拟实际使用场景，从不同位置开始查找
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remaining_data = test_data
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frame_count = 0
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while len(remaining_data) > 0:
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frame, next_pos = finder.find_frame_in_buffer(remaining_data)
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if frame:
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frame_count += 1
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print(f"\n找到第 {frame_count} 个帧:")
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print(f"帧数据: {frame.hex()}")
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print(f"下一个搜索位置: {next_pos}")
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# 解析帧内容
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parsed_frame = FrameFormat.parse_frame(frame)
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if parsed_frame:
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print(f"命令码: 0x{parsed_frame.command:08X}")
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print(f"长度: {parsed_frame.length}")
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print(f"帧IDX: {parsed_frame.frame_idx}")
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print("通道数据:")
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for i, value in enumerate(parsed_frame.channels):
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print(f"通道 {i+1}: 0x{value:08X}")
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print(f"校验和: 0x{parsed_frame.checksum:02X}")
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# 更新剩余数据
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remaining_data = remaining_data[next_pos:]
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print(f"\n剩余数据: ({len(remaining_data)} 字节)")
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if remaining_data:
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print(f"数据: {remaining_data.hex()}")
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else:
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# 如果没有找到帧，next_pos 表示需要保留的数据起始位置
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if next_pos == len(remaining_data):
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print("\n没有更多帧了")
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break
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else:
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print(f"\n在当前位置未找到帧，移除 {next_pos} 字节无效数据")
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remaining_data = remaining_data[next_pos:]
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print(f"剩余数据: ({len(remaining_data)} 字节)")
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if remaining_data:
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print(f"数据: {remaining_data.hex()}")
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print(f"\n总共找到 {frame_count} 个帧")
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