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# © Copyright 2020-2025 Mikołaj Kuranowski
# SPDX-License-Identifier: MIT
# pyright: reportUnnecessaryComparison=false
import csv
import sys
from enum import IntEnum, auto
from typing import Any, AsyncIterator, Awaitable, Final, Generator, List, Optional, Sequence, Union
from .protocols import DialectLike, WithAsyncRead
class ParserState(IntEnum):
START_RECORD = auto()
START_FIELD = auto()
IN_FIELD = auto()
ESCAPE = auto()
IN_QUOTED_FIELD = auto()
ESCAPE_IN_QUOTED = auto()
QUOTE_IN_QUOTED = auto()
EAT_NEWLINE = auto()
def is_end_of_record(self) -> bool:
return self is ParserState.START_RECORD or self is ParserState.EAT_NEWLINE
def is_unexpected_at_eof(self) -> bool:
return self in (
ParserState.ESCAPE,
ParserState.IN_QUOTED_FIELD,
ParserState.ESCAPE_IN_QUOTED,
)
class Decision(IntEnum):
CONTINUE = auto()
DONE = auto()
DONE_WITHOUT_CONSUMING = auto()
QUOTE_MINIMAL = csv.QUOTE_MINIMAL
QUOTE_ALL = csv.QUOTE_ALL
QUOTE_NONNUMERIC = csv.QUOTE_NONNUMERIC
QUOTE_NONE = csv.QUOTE_NONE
if sys.version_info >= (3, 12):
QUOTE_STRINGS = csv.QUOTE_STRINGS
QUOTE_NOTNULL = csv.QUOTE_NOTNULL
else:
QUOTE_STRINGS: Final = 4
QUOTE_NOTNULL: Final = 5
class Parser:
def __init__(self, reader: WithAsyncRead, dialect: DialectLike) -> None:
self.dialect = dialect
self.reader = reader
self.current_read: Optional[Generator[Any, None, str]] = None
self.buffer: str = ""
self.eof: bool = False
self.line_num: int = 0
self.state = ParserState.START_RECORD
self.record_so_far: List[str] = []
self.field_so_far: List[str] = []
self.field_limit: int = csv.field_size_limit()
self.field_was_quoted: bool = False
self.last_char_was_cr: bool = False
# AsyncIterator[List[str]] interface
def __aiter__(self) -> AsyncIterator[List[str]]:
return self
def __anext__(self) -> Awaitable[List[str]]:
return self
# Awaitable[List[str]] interface
def __await__(self) -> Generator[Any, None, List[str]]:
return self # type: ignore
# Generator[Any, None, List[str]] interface
def __iter__(self) -> Generator[Any, None, List[str]]:
return self # type: ignore
def __next__(self) -> Any:
# Loop until a record has been successfully parsed or EOF has been hit
record: Optional[List[str]] = None
while record is None and (self.buffer or not self.eof):
# No pending read and no data available - initiate one
if not self.buffer and self.current_read is None:
self.current_read = self.reader.read(4096).__await__()
# Await on the pending read
if self.current_read is not None:
try:
return next(self.current_read)
except StopIteration as e:
assert not self.buffer, "a read was pending even though data was available"
self.current_read.close()
self.current_read = None
self.buffer = e.value
self.eof = not e.value
# Advance parsing
record = self.try_parse()
# Generate a row, or stop iteration altogether
if record is None:
raise StopAsyncIteration
else:
raise StopIteration(record)
# Straightforward parser interface
def try_parse(self) -> Optional[List[str]]:
decision = Decision.CONTINUE
while decision is Decision.CONTINUE and self.buffer:
decision = self.process_char(self.get_char_and_increment_line_num())
if decision is not Decision.DONE_WITHOUT_CONSUMING:
self.buffer = self.buffer[1:]
if decision is not Decision.CONTINUE or (self.eof and not self.state.is_end_of_record()):
if self.dialect.strict and self.state.is_unexpected_at_eof():
raise csv.Error("unexpected end of data")
self.add_field_at_eof()
return self.extract_record()
else:
return None
def process_char(self, c: str) -> Decision:
if self.state == ParserState.START_RECORD:
return self.process_char_in_start_record(c)
elif self.state == ParserState.START_FIELD:
return self.process_char_in_start_field(c)
elif self.state == ParserState.ESCAPE:
return self.process_char_in_escape(c)
elif self.state == ParserState.IN_FIELD:
return self.process_char_in_field(c)
elif self.state == ParserState.IN_QUOTED_FIELD:
return self.process_char_in_quoted_field(c)
elif self.state == ParserState.ESCAPE_IN_QUOTED:
return self.process_char_in_escape_in_quoted(c)
elif self.state == ParserState.QUOTE_IN_QUOTED:
return self.process_char_in_quote_in_quoted(c)
elif self.state == ParserState.EAT_NEWLINE:
return self.process_char_in_eat_newline(c)
else:
raise RuntimeError(f"unhandled parser state: {self.state}")
def process_char_in_start_record(self, c: str) -> Decision:
if c == "\r":
self.state = ParserState.EAT_NEWLINE
return Decision.CONTINUE
elif c == "\n":
self.state = ParserState.START_RECORD
return Decision.DONE
else:
return self.process_char_in_start_field(c)
def process_char_in_start_field(self, c: str) -> Decision:
if c == "\r":
self.save_field()
self.state = ParserState.EAT_NEWLINE
elif c == "\n":
self.save_field()
self.state = ParserState.START_RECORD
return Decision.DONE
elif c == self.dialect.quotechar and self.dialect.quoting != QUOTE_NONE:
self.field_was_quoted = True
self.state = ParserState.IN_QUOTED_FIELD
elif c == self.dialect.escapechar:
self.state = ParserState.ESCAPE
# XXX: skipinitialspace handling is done in save_field()
elif c == self.dialect.delimiter:
self.save_field()
self.state = ParserState.START_FIELD
else:
self.add_char(c)
self.state = ParserState.IN_FIELD
return Decision.CONTINUE
def process_char_in_escape(self, c: str) -> Decision:
self.add_char(c)
self.state = ParserState.IN_FIELD
return Decision.CONTINUE
def process_char_in_field(self, c: str) -> Decision:
if c == "\r":
self.save_field()
self.state = ParserState.EAT_NEWLINE
elif c == "\n":
self.save_field()
self.state = ParserState.START_RECORD
return Decision.DONE
elif c == self.dialect.escapechar:
self.state = ParserState.ESCAPE
elif c == self.dialect.delimiter:
self.save_field()
self.state = ParserState.START_FIELD
else:
self.add_char(c)
return Decision.CONTINUE
def process_char_in_quoted_field(self, c: str) -> Decision:
if c == self.dialect.escapechar:
self.state = ParserState.ESCAPE_IN_QUOTED
elif c == self.dialect.quotechar and self.dialect.quoting != QUOTE_NONE:
# XXX: Is this check for quoting necessary?
if self.dialect.doublequote:
self.state = ParserState.QUOTE_IN_QUOTED
else:
self.state = ParserState.IN_FIELD
else:
self.add_char(c)
return Decision.CONTINUE
def process_char_in_escape_in_quoted(self, c: str) -> Decision:
self.add_char(c)
self.state = ParserState.IN_QUOTED_FIELD
return Decision.CONTINUE
def process_char_in_quote_in_quoted(self, c: str) -> Decision:
if c == self.dialect.quotechar and self.dialect.quoting != QUOTE_NONE:
# XXX: Is this check for quoting necessary?
self.add_char(c)
self.state = ParserState.IN_QUOTED_FIELD
elif c == self.dialect.delimiter:
self.save_field()
self.state = ParserState.START_FIELD
elif c == "\r":
self.save_field()
self.state = ParserState.EAT_NEWLINE
elif c == "\n":
self.save_field()
self.state = ParserState.START_RECORD
return Decision.DONE
elif not self.dialect.strict:
self.add_char(c)
self.state = ParserState.IN_FIELD
else:
raise csv.Error(
f"{self.dialect.delimiter!r} expected after {self.dialect.quotechar!r}",
)
return Decision.CONTINUE
def process_char_in_eat_newline(self, c: str) -> Decision:
self.state = ParserState.START_RECORD
return Decision.DONE if c == "\n" else Decision.DONE_WITHOUT_CONSUMING
def add_char(self, c: str) -> None:
if len(self.field_so_far) == self.field_limit:
raise csv.Error(f"field larger than field limit ({self.field_limit})")
self.field_so_far.append(c)
def save_field(self) -> None:
field: Union[str, float, None]
if self.dialect.skipinitialspace:
field = "".join(self.field_so_far[self.find_first_non_space(self.field_so_far) :])
else:
field = "".join(self.field_so_far)
# Handle unquoted fields for special quote modes
if self.dialect.quoting == QUOTE_NONNUMERIC and not self.field_was_quoted:
field = float(field) if field else ""
elif self.dialect.quoting == QUOTE_STRINGS and not self.field_was_quoted:
field = float(field) if field else None
elif self.dialect.quoting == QUOTE_NOTNULL and not self.field_was_quoted:
field = field if field else None
self.field_was_quoted = False
self.record_so_far.append(field) # type: ignore
self.field_so_far.clear()
def add_field_at_eof(self) -> None:
# Decide if self.record_so_far needs to be added at an EOF
if self.state in (ParserState.ESCAPE, ParserState.ESCAPE_IN_QUOTED):
self.add_char("\n")
if not self.state.is_end_of_record():
self.save_field()
def extract_record(self) -> List[str]:
r = self.record_so_far.copy()
self.record_so_far.clear()
return r
def get_char_and_increment_line_num(self) -> str:
c = self.buffer[0]
if c == "\r":
self.line_num += 1
self.last_char_was_cr = True
elif c == "\n":
if self.last_char_was_cr:
self.last_char_was_cr = False
else:
self.line_num += 1
else:
self.last_char_was_cr = False
return c
@staticmethod
def find_first_non_space(x: Sequence[str]) -> int:
for i, c in enumerate(x):
if not c.isspace():
return i
return len(x)
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