SSEDecoder Class — anthropic-sdk-python Architecture

Source Code

src/anthropic/_streaming.py lines 299–401

class SSEDecoder:
    _data: list[str]
    _event: str | None
    _retry: int | None
    _last_event_id: str | None

    def __init__(self) -> None:
        self._event = None
        self._data = []
        self._last_event_id = None
        self._retry = None

    def iter_bytes(self, iterator: Iterator[bytes]) -> Iterator[ServerSentEvent]:
        """Given an iterator that yields raw binary data, iterate over it & yield every event encountered"""
        for chunk in self._iter_chunks(iterator):
            # Split before decoding so splitlines() only uses \r and \n
            for raw_line in chunk.splitlines():
                line = raw_line.decode("utf-8")
                sse = self.decode(line)
                if sse:
                    yield sse

    def _iter_chunks(self, iterator: Iterator[bytes]) -> Iterator[bytes]:
        """Given an iterator that yields raw binary data, iterate over it and yield individual SSE chunks"""
        data = b""
        for chunk in iterator:
            for line in chunk.splitlines(keepends=True):
                data += line
                if data.endswith((b"\r\r", b"\n\n", b"\r\n\r\n")):
                    yield data
                    data = b""
        if data:
            yield data

    async def aiter_bytes(self, iterator: AsyncIterator[bytes]) -> AsyncIterator[ServerSentEvent]:
        """Given an iterator that yields raw binary data, iterate over it & yield every event encountered"""
        async for chunk in self._aiter_chunks(iterator):
            # Split before decoding so splitlines() only uses \r and \n
            for raw_line in chunk.splitlines():
                line = raw_line.decode("utf-8")
                sse = self.decode(line)
                if sse:
                    yield sse

    async def _aiter_chunks(self, iterator: AsyncIterator[bytes]) -> AsyncIterator[bytes]:
        """Given an iterator that yields raw binary data, iterate over it and yield individual SSE chunks"""
        data = b""
        async for chunk in iterator:
            for line in chunk.splitlines(keepends=True):
                data += line
                if data.endswith((b"\r\r", b"\n\n", b"\r\n\r\n")):
                    yield data
                    data = b""
        if data:
            yield data

    def decode(self, line: str) -> ServerSentEvent | None:
        # See: https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation  # noqa: E501

        if not line:
            if not self._event and not self._data and not self._last_event_id and self._retry is None:
                return None

            sse = ServerSentEvent(
                event=self._event,
                data="\n".join(self._data),
                id=self._last_event_id,
                retry=self._retry,
            )

            # NOTE: as per the SSE spec, do not reset last_event_id.
            self._event = None
            self._data = []
            self._retry = None

            return sse

        if line.startswith(":"):
            return None

        fieldname, _, value = line.partition(":")