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- from __future__ import annotations
-
- from typing import Generator
-
-
- class StreamReader:
- """
- Generator-based stream reader.
-
- This class doesn't support concurrent calls to :meth:`read_line`,
- :meth:`read_exact`, or :meth:`read_to_eof`. Make sure calls are
- serialized.
-
- """
-
- def __init__(self) -> None:
- self.buffer = bytearray()
- self.eof = False
-
- def read_line(self, m: int) -> Generator[None, None, bytes]:
- """
- Read a LF-terminated line from the stream.
-
- This is a generator-based coroutine.
-
- The return value includes the LF character.
-
- Args:
- m: maximum number bytes to read; this is a security limit.
-
- Raises:
- EOFError: if the stream ends without a LF.
- RuntimeError: if the stream ends in more than ``m`` bytes.
-
- """
- n = 0 # number of bytes to read
- p = 0 # number of bytes without a newline
- while True:
- n = self.buffer.find(b"\n", p) + 1
- if n > 0:
- break
- p = len(self.buffer)
- if p > m:
- raise RuntimeError(f"read {p} bytes, expected no more than {m} bytes")
- if self.eof:
- raise EOFError(f"stream ends after {p} bytes, before end of line")
- yield
- if n > m:
- raise RuntimeError(f"read {n} bytes, expected no more than {m} bytes")
- r = self.buffer[:n]
- del self.buffer[:n]
- return r
-
- def read_exact(self, n: int) -> Generator[None, None, bytes]:
- """
- Read a given number of bytes from the stream.
-
- This is a generator-based coroutine.
-
- Args:
- n: how many bytes to read.
-
- Raises:
- EOFError: if the stream ends in less than ``n`` bytes.
-
- """
- assert n >= 0
- while len(self.buffer) < n:
- if self.eof:
- p = len(self.buffer)
- raise EOFError(f"stream ends after {p} bytes, expected {n} bytes")
- yield
- r = self.buffer[:n]
- del self.buffer[:n]
- return r
-
- def read_to_eof(self, m: int) -> Generator[None, None, bytes]:
- """
- Read all bytes from the stream.
-
- This is a generator-based coroutine.
-
- Args:
- m: maximum number bytes to read; this is a security limit.
-
- Raises:
- RuntimeError: if the stream ends in more than ``m`` bytes.
-
- """
- while not self.eof:
- p = len(self.buffer)
- if p > m:
- raise RuntimeError(f"read {p} bytes, expected no more than {m} bytes")
- yield
- r = self.buffer[:]
- del self.buffer[:]
- return r
-
- def at_eof(self) -> Generator[None, None, bool]:
- """
- Tell whether the stream has ended and all data was read.
-
- This is a generator-based coroutine.
-
- """
- while True:
- if self.buffer:
- return False
- if self.eof:
- return True
- # When all data was read but the stream hasn't ended, we can't
- # tell if until either feed_data() or feed_eof() is called.
- yield
-
- def feed_data(self, data: bytes) -> None:
- """
- Write data to the stream.
-
- :meth:`feed_data` cannot be called after :meth:`feed_eof`.
-
- Args:
- data: data to write.
-
- Raises:
- EOFError: if the stream has ended.
-
- """
- if self.eof:
- raise EOFError("stream ended")
- self.buffer += data
-
- def feed_eof(self) -> None:
- """
- End the stream.
-
- :meth:`feed_eof` cannot be called more than once.
-
- Raises:
- EOFError: if the stream has ended.
-
- """
- if self.eof:
- raise EOFError("stream ended")
- self.eof = True
-
- def discard(self) -> None:
- """
- Discard all buffered data, but don't end the stream.
-
- """
- del self.buffer[:]
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