_decoders.py•4 kB
from typing import List, Optional
from ._models import ServerSentEvent
def _splitlines_sse(text: str) -> List[str]:
"""Split text on \r\n, \r, or \n only."""
if not text:
return []
if "\r" not in text:
lines = text.split("\n")
else:
normalized = text.replace("\r\n", "\n").replace("\r", "\n")
lines = normalized.split("\n")
if text[-1] in "\r\n":
lines.pop()
return lines
class SSELineDecoder:
"""
Handles incrementally reading lines from text.
Mostly a copy of httpx._decoders.LineDecoder, but as per SSE spec, only \r\n, \r,
and \n are treated as newlines, which differs from the behavior of splitlines()
used by httpx._decoders.LineDecoder.
"""
def __init__(self) -> None:
self.buffer: list[str] = []
self.trailing_cr: bool = False
def decode(self, text: str) -> list[str]:
# We always push a trailing `\r` into the next decode iteration.
if self.trailing_cr:
text = "\r" + text
self.trailing_cr = False
if text.endswith("\r"):
self.trailing_cr = True
text = text[:-1]
if not text:
# NOTE: the edge case input of empty text doesn't occur in practice,
# because other httpx internals filter out this value
return [] # pragma: no cover
trailing_newline = text[-1] in "\n\r"
lines = _splitlines_sse(text)
if len(lines) == 1 and not trailing_newline:
# No new lines, buffer the input and continue.
self.buffer.append(lines[0])
return []
if self.buffer:
# Include any existing buffer in the first portion of the
# splitlines result.
lines = ["".join(self.buffer) + lines[0]] + lines[1:]
self.buffer = []
if not trailing_newline:
# If the last segment of splitlines is not newline terminated,
# then drop it from our output and start a new buffer.
self.buffer = [lines.pop()]
return lines
def flush(self) -> list[str]:
if not self.buffer and not self.trailing_cr:
return []
lines = ["".join(self.buffer)]
self.buffer = []
self.trailing_cr = False
return lines
class SSEDecoder:
def __init__(self) -> None:
self._event = ""
self._data: List[str] = []
self._last_event_id = ""
self._retry: Optional[int] = None
def decode(self, line: str) -> Optional[ServerSentEvent]:
# 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 = ""
self._data = []
self._retry = None
return sse
if line.startswith(":"):
return None
fieldname, _, value = line.partition(":")
if value.startswith(" "):
value = value[1:]
if fieldname == "event":
self._event = value
elif fieldname == "data":
self._data.append(value)
elif fieldname == "id":
if "\0" in value:
pass
else:
self._last_event_id = value
elif fieldname == "retry":
try:
self._retry = int(value)
except (TypeError, ValueError):
pass
else:
pass # Field is ignored.
return None