chronaxis.sources.asc
源码基线：8904c2f744951857659abd40aaa3535d57faf53c
1"""逐行读取标准ASC及显式Sclicer布局，返回带物理行号的真实CAN记录。23支持标准经典CAN及统计尾、远程/错误帧和CAN FD数据行；header的absolute是段内累计时间，4relative是相邻事件时间差。relative输出以首段为零，epoch输出使用显式时区的日期。5日期/进制/通道/载荷长度严格检查；时间顺序默认全检，实际计算可限定所需帧。6未知行拒绝，不从头回退或修复输入文件。7只拥有一个有界文本行和当前记录；向调用方交出的记录若长期保留，须由调用方计费。8模块导入及ASCSpec构造无文件操作；ASCRead显式创建时预约预算并只读打开文件。9"""1011from dataclasses import dataclass12from datetime import datetime, timedelta, timezone13from decimal import Decimal, localcontext14import codecs15from pathlib import Path16import re1718from ..legacy.records import LegacyRawFrame19from ..results.budget import ResourceBudget, _reserve_owned_ram, _release_owned_ram, _cleanup_owner20from ..timebase.conversion import checked_add_ns, convert_time, require_int64_ns21from .raw_can import CANTextError, RawCANRecord2223# 16Ki字符足以容纳64字节帧及标准附加字段；过长行显式失败而不无限读取。24MAX_ASC_LINE_CHARS = 1638425DLC_LENGTHS = (0, 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 20, 24, 32, 48, 64)26MONTHS = dict(zip(('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep',27 'Oct', 'Nov', 'Dec'), range(1, 13)))282930@dataclass(frozen=True)31class ASCSpec:32 """固定一次ASC读取的格式、编码、时间参考；不猜测本地时区。"""3334 path: Path # 单文件，连续多文件的时序合并由外层负责。35 parser_version: str = 'vector-asc-v1' # 标准布局含统计尾；statistics保留显式入口，sclicer须显式选择。36 encoding: str = 'utf-8-sig' # 严格解码，兼容UTF-8 BOM，不自动换编码。37 time_reference: str = 'relative' # relative为首段原点，epoch为显式日期/时区。38 timezone_offset_minutes: int | None = None # epoch必填，避免依赖宿主时区。39 offset_ns: int = 0 # 一次明确的int64平移，不更改原始时间文本。4041 def __post_init__(self):42 """校验静态契约。参数: 无。返回: None。异常: 类型或不支持的选项。43 """44 # 路径只校验类型；是否存在、是否可读在ASCRead创建时验证。45 if not isinstance(self.path, Path) or type(self.encoding) is not str or not self.encoding:46 raise TypeError('ASC需要Path和明确编码')47 # 单行字节定位只接受换行由单字节LF表示的编码；UTF-16/32另需专门读取协议。48 if codecs.lookup(self.encoding).name not in ('utf-8', 'utf-8-sig', 'ascii', 'gbk', 'cp1252', 'iso8859-1'):49 raise ValueError('ASC当前只支持UTF-8/ASCII/GBK/CP1252/Latin-1逐行编码')50 if (self.parser_version not in ('vector-asc-v1', 'vector-asc-statistics-v1', 'sclicer-asc-v1')51 or self.time_reference not in ('relative', 'epoch')):52 raise ValueError('不支持的ASC解析版本或时间参考')53 zone = self.timezone_offset_minutes54 if zone is not None and (type(zone) is not int or not -1439 <= zone <= 1439):55 raise ValueError('ASC时区偏移需-1439到1439整数分钟')56 if self.time_reference == 'epoch' and zone is None:57 raise ValueError('ASC日历时间需要显式时区偏移')58 require_int64_ns(self.offset_ns)596061def _date(text):62 """解析ASC英文日期，不调用宿主时区。参数: text为去掉星期后的日期。6364 返回: 无时区datetime。异常: ValueError为月份或日期格式不支持。65 """66 # 月份用固定表，避免Windows语言环境影响；12/24小时及毫秒/微秒分别接受。67 parts = text.split()68 if len(parts) not in (4, 5) or parts[0] not in MONTHS:69 raise ValueError('ASC日期需要英文月份和明确年月日')70 parts[0] = str(MONTHS[parts[0]])71 for pattern in ('%m %d %I:%M:%S.%f %p %Y', '%m %d %I:%M:%S %p %Y',72 '%m %d %H:%M:%S.%f %Y', '%m %d %H:%M:%S %Y'):73 try:74 return datetime.strptime(' '.join(parts), pattern)75 except ValueError:76 # 这里只尝试已声明日期布局，绝不重新打开数据或回退报文格式。77 continue78 raise ValueError('ASC日期格式或取值无效')798081def _unsigned(text, base, maximum, label):82 """严格解析无符号字段。参数: text原文、base进制、maximum上限、label诊断名。8384 返回: int。异常: ValueError为符号、非法字符、空值或越界；拒绝下划线和隐式前缀。85 """86 # int本身会接受正号/下划线；协议数值先限定字符，避免宽松解析隐藏坏行。87 alphabet = r'[0-9a-fA-F]+' if base == 16 else r'[0-9]+'88 if not re.fullmatch(alphabet, text):89 raise ValueError(label + '字符或进制错误')90 value = int(text, base)91 if value > maximum:92 raise ValueError(label + '越界')93 return value949596def _status_event(tokens: list[str]) -> bool:97 """识别已知CAN控制器状态事件，验证格式后告知调用方不产生数据帧。9899 参数: tokens为去掉时间的有界字段列表；时间累加必须由调用方预先完成。100 返回: bool；普通帧为False，完整的chip status事件为True，无文件或状态副作用。101 异常: ValueError为CAN事件的未知状态、通道、计数或残缺布局；不跳过未知事件。102 """103 # 仅接受明确的状态事件，避免把损坏帧和其他协议行当作可忽略的元数据。104 if not tokens or tokens[0] != 'CAN':105 return False106 match = re.fullmatch(107 r'CAN ([0-9]+) Status:\s*chip status '108 r'(?:error active|error passive|warning level|busoff|bus off)'109 r'(?: - TxErr: ([0-9]+) RxErr: ([0-9]+))?', ' '.join(tokens), re.IGNORECASE)110 if match is None:111 raise ValueError('不支持或损坏的ASC总线状态事件，需要chip status及完整的可选TxErr/RxErr计数')112 channel = _unsigned(match[1], 10, 65536, 'ASC状态事件通道')113 if channel == 0:114 raise ValueError('ASC状态事件通道从1开始')115 # 诊断计数仅验证为有界非负整数，不把状态行转换成信号样本或保存额外结果。116 if match[2] is not None:117 _unsigned(match[2], 10, 0xffffffffffffffff, 'ASC发送错误计数')118 _unsigned(match[3], 10, 0xffffffffffffffff, 'ASC接收错误计数')119 return True120121122def _fd_error_diagnostics(tokens: list[str]) -> int:123 """检查Vector CAN FD错误帧的结构，返回描述实际帧类型的扩展标志。124125 参数: tokens为ErrorFrame后的错误文字、诊断字段、部分载荷和完整计时尾。126 返回: extFlags整数；不保留错误文字、部分载荷或诊断ID供正常信号解码。127 异常: ValueError为未知阶段、缺字段、无效数值、载荷数量不符或保留位非零。128 已损坏帧的DLC与已取得的DataLength可能不一致，不套用正常帧的长度关系。129 """130 # 错误描述含空格；Arb./Data.之后的位置字段结构固定，不能按描述的词数切割。131 phases = [index for index, token in enumerate(tokens) if token in ('Arb.', 'Data.')]132 if len(phases) != 1 or phases[0] < 4:133 raise ValueError('ASC CAN FD错误帧需要错误描述、flags/code/codeExt及Arb.或Data.阶段')134 phase = phases[0]135 for name, value in zip(('flags', 'code', 'codeExt'), tokens[phase - 3:phase]):136 _unsigned(value, 16, 0xffffffffffffffff, 'ASC CAN FD错误帧' + name)137 fields = tokens[phase + 1:]138 if len(fields) < 13:139 raise ValueError('ASC CAN FD错误帧诊断字段或计时尾不完整')140 position, identifier, brs, esi, dlc, length = fields[:6]141 _unsigned(position, 10, 0xffffffffffffffff, 'ASC CAN FD错误位置')142 numeric_id = identifier[:-1] if identifier[-1:].lower() == 'x' else identifier143 _unsigned(numeric_id, 16, 0xffffffff, 'ASC CAN FD诊断ID')144 if brs not in ('0', '1') or esi not in ('0', '1'):145 raise ValueError('ASC CAN FD错误帧BRS/ESI需要0或1')146 _unsigned(dlc, 16, 15, 'ASC CAN FD诊断DLC')147 size = _unsigned(length, 10, 64, 'ASC CAN FD诊断载荷长度')148 if len(fields) != 6 + size + 7:149 raise ValueError('ASC CAN FD错误帧载荷数量或七项计时尾不符')150 # 诊断字段固定为十六进制，Position、DataLength和MessageDuration使用十进制。151 for token in fields[6:6 + size]:152 _unsigned(token, 16, 255, 'ASC CAN FD诊断载荷字节')153 duration, extended, *timing = fields[6 + size:]154 _unsigned(duration, 10, 0xffffffffffffffff, 'ASC CAN FD错误帧持续时间')155 flags = _unsigned(extended, 16, 31, 'ASC CAN FD扩展错误标志')156 for token in timing:157 _unsigned(token, 16, 0xffffffffffffffff, 'ASC CAN FD错误帧CRC或位时序')158 return flags159160161def _error_diagnostics(tokens: list[str], *, fd: bool) -> int | None:162 """验证错误帧的已知诊断尾，不将可能受损的诊断ID或DLC当成正常帧字段。163164 参数: tokens为ErrorFrame之后的字段；fd表明是否为CAN FD布局。165 返回: 完整FD诊断的extFlags，其他已知形式返回None；无副作用。166 异常: ValueError为未知/残缺诊断或无效数值。167 """168 # 裸错误帧继续可用；FD附诊断按自身完整布局核验，不套用经典ECC尾。169 if not tokens:170 return171 if fd:172 return _fd_error_diagnostics(tokens)173 text = ' '.join(tokens)174 if re.fullmatch(r'ECC:\s*[01]{8}', text):175 return176 names = ['Flags', 'CodeExt', 'Code', 'ID', 'DLC', 'Position', 'Length']177 if len(tokens) != 21 or tokens[0::3] != names or tokens[1::3] != ['='] * 7:178 raise ValueError('ASC错误帧诊断需8位ECC或完整Flags/CodeExt/Code/ID/DLC/Position/Length字段')179 # 此诊断格式明确使用0x前缀或十进制数，不跟随数据载荷的base头部。180 for name, value in zip(names, tokens[2::3]):181 hexadecimal = value.startswith(('0x', '0X'))182 _unsigned(value[2:] if hexadecimal else value, 16 if hexadecimal else 10,183 0xffffffffffffffff, 'ASC错误帧' + name)184185186def _frame(tokens, base, seconds):187 """解析标准数据部分，精确检查长度。参数: tokens不含时间；base为10/16；seconds为兼容秒。188189 返回: (LegacyRawFrame, DLC编码或None)。异常: ValueError为未知布局、身份或载荷错误。190 """191 # CAN FD标准顺序是CANFD 通道 方向 ID；经典CAN是通道 ID 方向 类型。192 if not tokens:193 raise ValueError('ASC行缺少帧或事件内容')194 fd = tokens[0] == 'CANFD'195 if fd:196 tokens = tokens[1:]197 channel = _unsigned(tokens[0], 10, 65536, 'ASC通道')198 if channel == 0:199 raise ValueError('ASC通道从1开始')200 fields = dict(timestamp=seconds, channel=channel - 1, is_fd=fd, is_rx=True,201 is_extended_id=False, is_remote_frame=False, is_error_frame=False,202 bitrate_switch=False, error_state_indicator=False, arbitration_id=0, dlc=0, data=b'')203 rest = tokens[1:]204 if fd:205 direction, rest = rest[0], rest[1:]206 elif rest and rest[0].lower() == 'errorframe':207 # 经典错误帧没有独立方向字段；后面可能是ECC或CAN-Core诊断，不能当作方向。208 direction = 'Rx'209 else:210 direction = rest[1] if len(rest) > 1 else 'Rx'211 # 错误帧没有载荷，但FD格式仍明确给出方向，必须在提前返回前保存。212 if direction not in ('Rx', 'Tx'):213 raise ValueError('ASC方向需要Rx或Tx')214 fields['is_rx'] = direction == 'Rx'215 if rest[0].lower() == 'errorframe':216 error_flags = _error_diagnostics(rest[1:], fd=fd)217 fields['is_error_frame'] = True218 if error_flags is not None:219 # CANFD通道也可能接收经典错误帧；使用扩展标志，不把部分诊断数据伪装成有效载荷。220 fields.update(is_fd=bool(error_flags & 1), bitrate_switch=bool(error_flags & 2),221 error_state_indicator=bool(error_flags & 4))222 return LegacyRawFrame(**fields), None223 identifier = rest[0]224 extended = identifier[-1:].lower() == 'x'225 fields['is_extended_id'] = extended226 fields['arbitration_id'] = _unsigned(identifier[:-1] if extended else identifier,227 base, 0x1fffffff if extended else 0x7ff, 'ASC报文ID')228 if fd:229 rest = rest[1:]230 # 标准ASC可在ID后有一个符号名称；它不是载荷，也不从名称推断信号。231 if rest[0] not in ('0', '1'):232 rest = rest[1:]233 brs, esi, dlc_text, length_text, *payload = rest234 if brs not in ('0', '1') or esi not in ('0', '1'):235 raise ValueError('CAN FD BRS/ESI需要0或1')236 code = _unsigned(dlc_text, base, 15, 'CAN FD DLC编码')237 length = _unsigned(length_text, 10, 64, 'CAN FD载荷长度')238 if DLC_LENGTHS[code] != length:239 raise ValueError('CAN FD DLC编码与实际长度不一致')240 fields.update(bitrate_switch=brs == '1', error_state_indicator=esi == '1')241 # 可省略控制器计时尾；存在时必须是标准8个数值，不吞掉多余payload。242 tail = payload[length:]243 if len(tail) not in (0, 8):244 raise ValueError('CAN FD载荷或标准附加字段数量错误')245 for index, token in enumerate(tail):246 _unsigned(token, 16 if index >= 2 else 10, 0xffffffffffffffff, 'CAN FD附加字段')247 payload = payload[:length]248 else:249 if len(rest) < 3:250 raise ValueError('经典CAN行缺少ID、方向或d/r类型')251 _, _, frame_type, *tail = rest252 if frame_type not in ('d', 'r'):253 raise ValueError('经典CAN类型需要d或r')254 # 远程帧可省略DLC；None保留未知含义。兼容帧的0仅是内存占位，导出须看dlc_code。255 if frame_type == 'r' and not tail:256 fields['is_remote_frame'] = True257 return LegacyRawFrame(**fields), None258 if not tail:259 raise ValueError('经典CAN数据帧缺少DLC')260 dlc_text, *payload = tail261 code = length = _unsigned(dlc_text, base, 8, '经典CAN DLC')262 fields['is_remote_frame'] = frame_type == 'r'263 if fields['is_remote_frame']:264 length = 0265 if len(payload) != length:266 raise ValueError('ASC实际载荷与声明长度不一致')267 fields['dlc'] = code if fields['is_remote_frame'] else length268 fields['data'] = bytes(_unsigned(item, base, 255, 'ASC载荷字节') for item in payload)269 return LegacyRawFrame(**fields), code270271272def _repository_frame(tokens, base, seconds, version):273 """同次解析标准统计尾或显式Sclicer布局，再复用标准字段检查。274275 参数: tokens为不含时间的有界字段；base为头部进制；seconds为兼容秒；version为选定版本。276 返回: (原帧快照, DLC编码)。异常: ValueError/IndexError为布局、统计身份或载荷错误。277 不探测后重新读取；同文件可含该版本规定的经典及FD行，未声明变体拒绝。278 """279 if not tokens:280 raise ValueError('ASC行缺少帧或事件内容')281 if tokens[0] == 'CANFD':282 if version != 'sclicer-asc-v1':283 return _frame(tokens, base, seconds)284 # Sclicer样例顺序固定为CANFD 通道 ID 方向 BRS ESI d 十进制DLC 十进制长度。285 _, channel, identifier, direction, brs, esi, frame_type, code_text, length, *payload = tokens286 if frame_type != 'd':287 raise ValueError('sclicer-asc-v1只接受明确的CAN FD数据行')288 code = _unsigned(code_text, 10, 15, 'Sclicer十进制DLC编码')289 if len(payload) != _unsigned(length, 10, 64, 'Sclicer载荷长度'):290 raise ValueError('Sclicer实际载荷与声明长度不一致')291 normalized = ['CANFD', channel, direction, identifier, brs, esi,292 format(code, 'x') if base == 16 else str(code), length, *payload]293 return _frame(normalized, base, seconds)294 # 错误帧的诊断Length属于独立布局，不能当成普通报文的统计尾。295 if len(tokens) > 1 and tokens[1].lower() == 'errorframe':296 return _frame(tokens, base, seconds)297 # 统计尾必须完整且字段名/顺序正确；不能把任意多余内容当注释丢掉。298 if 'Length' not in tokens:299 return _frame(tokens, base, seconds)300 position = tokens.index('Length')301 tail = tokens[position:]302 if (len(tail) != 9 or tail[0::3] != ['Length', 'BitCount', 'ID']303 or tail[1::3] != ['=', '=', '=']):304 raise ValueError('ASC统计尾需Length = n BitCount = n ID = n')305 for item in tail[2::3]:306 _unsigned(item, 10, 0xffffffffffffffff, 'ASC统计字段')307 frame, code = _frame(tokens[:position], base, seconds)308 if int(tail[8], 10) != frame.arbitration_id:309 raise ValueError('ASC统计ID与报文ID不一致')310 return frame, code311312313class ASCRead:314 """拥有单个文件及固定行缓冲预算；完成、错误和取消均关闭，禁止中途重读。"""315316 def __init__(self, spec, budget, *, check_cancel=None, retain_original=True, retain_source_time=True, time_selector=None, previous_exact_time=None):317 """预约后打开一次。参数: spec为ASCSpec；budget为共享账本；check_cancel为可选无参回调。318319 time_selector可选接收原帧并返回bool，仅核选中帧的先后顺序；None严格核所有时间。320 所有帧仍返回原时间供必要的来源范围统计，relative增量仍逐行累加。321 previous_exact_time为上一文件最近参与检查的Decimal秒，已含偏移；只作比较状态。322 返回: 可迭代reader。异常: 类型、预算、打开失败；清理失败附asc_read_cleanup_owner。323 """324 if type(retain_original) is not bool or type(retain_source_time) is not bool:325 raise TypeError('原文/导出时间选择需要bool')326 self._retain_original=retain_original327 self._retain_source_time=retain_source_time328 if time_selector is not None and not callable(time_selector):329 raise TypeError('ASC时间选择器必须可调用')330 if previous_exact_time is not None and (type(previous_exact_time) is not Decimal331 or not previous_exact_time.is_finite()):332 raise TypeError('ASC前序比较时刻需要有限Decimal秒')333 self._time_selector = time_selector334 if type(spec) is not ASCSpec or not isinstance(budget, ResourceBudget):335 raise TypeError('ASCRead需要ASCSpec和ResourceBudget')336 if check_cancel is not None and not callable(check_cancel):337 raise TypeError('取消检查必须可调用')338 # 先安装关闭责任，再预约/打开；构造失败也保留恢复owner。339 self.spec, self._budget, self._check_cancel = spec, budget, check_cancel340 self._file, self._fixed_cost, self._held_cost, self._closed = None, 0, 0, False341 self.line_number = self.count = 0342 self._base = self._mode = self._date_origin = self._header_date = None343 self._block_ns, self._elapsed = 0, Decimal(0)344 self._last_exact = previous_exact_time345 self.first_exact_time = None # 当前文件首个参与顺序检查的时刻，含无CAN帧的计时行。346 try:347 _reserve_owned_ram(self, MAX_ASC_LINE_CHARS * 64 + 8192, '_fixed_cost')348 self._file = spec.path.open('rb')349 except BaseException as error:350 _cleanup_owner(self, error, 'asc_read_cleanup_owner', 'ASC读取')351 raise352353 @property354 def closed(self):355 """提供真实关闭状态。参数: 无。返回: bool。异常: 无。356 """357 return self._closed358359 @property360 def last_exact_time(self):361 """返回最近参与检查的精确秒值，供连续文件接续比较。362363 参数: 无。返回: Decimal或None，已含日期参考和offset；空文件保留前序值。364 异常: 无。不向逐帧记录或输出增加另一套时间，关闭后仍可取得该比较状态。365 """366 return self._last_exact367368 def __iter__(self):369 """返回本次读取。参数: 无。返回: self。异常: 无；不启动第二次扫描。370 """371 return self372373 def _set_date(self, value, trigger=False):374 """设置段基准。参数: value日期；trigger是否真实触发块。返回: None。异常: 时间越界。375 """376 if self._date_origin is None or trigger and not self.count:377 self._date_origin = value378 self._header_date = value379 # relative参考按段日期差保持连续；epoch用显式时区，不经过float timestamp。380 if self.spec.time_reference == 'epoch':381 zone = timezone(timedelta(minutes=self.spec.timezone_offset_minutes))382 delta = value.replace(tzinfo=zone) - datetime(1970, 1, 1, tzinfo=timezone.utc)383 else:384 delta = value - self._date_origin385 self._block_ns = require_int64_ns((delta.days * 86400 + delta.seconds) * 10**9386 + delta.microseconds * 1000)387 self._elapsed = Decimal(0)388389 def _line(self, line):390 """解释一行。参数: line有界去空白文本。返回: RawCANRecord或元数据None。异常: 格式错误。391 """392 # 注释和已知非数据头不参与时间；未知内容拒绝，不能静默漏帧。393 if not line or line.startswith('//'):394 return None395 lower = line.lower()396 if lower.startswith('date '):397 if self.count:398 raise ValueError('数据中途不允许重新定义ASC日期')399 self._set_date(_date(line.split(None, 2)[2]))400 return None401 if lower.startswith('base '):402 if self.count or self._base is not None:403 raise ValueError('ASC进制只允许在头部定义一次')404 match = re.fullmatch(r'base\s+(hex|dec)\s+timestamps\s+(absolute|relative)', lower)405 if match is None:406 raise ValueError('ASC头需base hex/dec timestamps absolute/relative')407 self._base, self._mode = (16 if match[1] == 'hex' else 10), match[2]408 return None409 if lower in ('internal events logged', 'no internal events logged', 'end triggerblock'):410 return None411 if lower.startswith('begin triggerblock '):412 self._set_date(_date(line.split(None, 3)[3]), trigger=True)413 return None414 if self._base is None:415 raise ValueError('ASC数据前缺少明确base/timestamps头')416 if self.spec.time_reference == 'epoch' and self._header_date is None:417 raise ValueError('日历时间ASC缺少日期头')418 timestamp, *tokens = line.split()419 if not re.fullmatch(r'\d+(?:\.\d+)?', timestamp):420 raise ValueError('ASC时间需要非负十进制秒')421 # relative先精确累加再舍入；逐条先舍入会把两次0.5ns都变成0，丢掉真实的1ns。422 with localcontext() as context:423 context.prec = MAX_ASC_LINE_CHARS + 32424 value = Decimal(timestamp)425 self._elapsed = self._elapsed + value if self._mode == 'relative' else value426 exact = Decimal(self._block_ns).scaleb(-9) + self._elapsed427 converted = convert_time(exact, 's')428 ns = checked_add_ns(converted.time_ns, self.spec.offset_ns)429 # 完整读取保留先核时间再核载荷的错误顺序；选择模式元数据只推进relative时钟。430 if self._time_selector is None:431 self._check_order(exact)432 if ' '.join(tokens).lower() == 'start of measurement':433 return None434 # 状态事件也占relative时间，只在完成上面的时钟推进后跳过。435 if _status_event(tokens):436 return None437 # 标准入口同次处理可选统计尾；Sclicer FD仍须显式选择，不在失败后重读或换格式。438 frame, code = _repository_frame(tokens, self._base, ns / 10**9, self.spec.parser_version)439 # 不把无关帧当作已选时间序列的前点，仍保留其原始时间供范围统计。440 if self._time_selector is not None and self._time_selector(frame):441 self._check_order(exact)442 return RawCANRecord(frame, ns, self.spec.path, self.line_number, self.count,443 timestamp if self._retain_original else None, self.spec.parser_version, code, converted.quantized,444 converted.time_ns if self._retain_source_time else None)445446 def _check_order(self, exact):447 """拒绝所需时间序列回退，包括舍入后相同的亚纳秒回退。448449 参数: exact为已解析、尚未加offset的Decimal秒。返回: None。异常: ValueError为回退。450 只保存最近参与检查的时刻；不排序、不钳平，也不改写返回报文。451 """452 # 每个文件可能使用不同显式偏移；比较状态必须与返回坐标使用相同原点。453 shifted = exact454 if self.spec.offset_ns:455 with localcontext() as context:456 context.prec = MAX_ASC_LINE_CHARS + 32457 shifted = exact + Decimal(self.spec.offset_ns).scaleb(-9)458 if self._last_exact is not None and shifted < self._last_exact:459 raise ValueError('ASC来源时间回退')460 if self.first_exact_time is None:461 self.first_exact_time = shifted462 self._last_exact = shifted463464 def __next__(self):465 """读取到下一帧或EOF。参数: 无。返回: RawCANRecord。异常: 定位格式错、I/O或取消原错。466467 完成/失败后释放自有资源；已返回前缀不会重复。取消回调在每个物理行前检查。468 """469 if self._closed:470 raise StopIteration471 try:472 while True:473 if self._check_cancel is not None:474 self._check_cancel()475 # 先按有界原字节取得一个物理行，再解码，避免文本缓冲提前解码后续坏行。476 raw = self._file.readline(MAX_ASC_LINE_CHARS * 4 + 1)477 if not raw:478 self.close()479 raise StopIteration480 self.line_number += 1481 if len(raw) > MAX_ASC_LINE_CHARS * 4:482 raise CANTextError(self.spec.path, self.line_number, 'ASC行超过65536字节')483 try:484 encoding = ('utf-8' if self.spec.encoding.lower() == 'utf-8-sig'485 and self.line_number != 1 else self.spec.encoding)486 line = raw.decode(encoding, errors='strict')487 except UnicodeError as error:488 raise CANTextError(self.spec.path, self.line_number, 'ASC编码错误') from error489 if len(line) > MAX_ASC_LINE_CHARS:490 raise CANTextError(self.spec.path, self.line_number, 'ASC行超过16384字符')491 try:492 record = self._line(line.strip())493 except (ValueError, IndexError, OverflowError) as error:494 raise CANTextError(self.spec.path, self.line_number, str(error)) from error495 if record is not None:496 self.count += 1497 return record498 except BaseException as error:499 _cleanup_owner(self, error, 'asc_read_cleanup_owner', 'ASC读取')500 raise501502 def close(self):503 """关闭自有文件再归还预算，可重试。参数: 无。返回: None。异常: 关闭或预算原错。504 """505 if self._closed:506 return507 if self._file is not None:508 self._file.close()509 self._file = None510 if self._fixed_cost:511 _release_owned_ram(self, self._fixed_cost, '_fixed_cost')512 self._time_selector = None513 self._closed = True514515 def __enter__(self):516 """支持显式读取上下文。参数: 无。返回: self。异常: 无。517 """518 return self519520 def __exit__(self, exception_type, error, traceback):521 """保留原错并收尾。参数: exception_type/error/traceback异常信息。返回: False。异常: 无原错时的关闭失败。522 """523 if error is None:524 self.close()525 else:526 _cleanup_owner(self, error, 'asc_read_cleanup_owner', 'ASC读取')527 return False528