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Diffstat (limited to 'src/prompt_toolkit/input/posix_utils.py')
| -rw-r--r-- | src/prompt_toolkit/input/posix_utils.py | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/src/prompt_toolkit/input/posix_utils.py b/src/prompt_toolkit/input/posix_utils.py new file mode 100644 index 0000000..4a78dc4 --- /dev/null +++ b/src/prompt_toolkit/input/posix_utils.py @@ -0,0 +1,97 @@ +from __future__ import annotations + +import os +import select +from codecs import getincrementaldecoder + +__all__ = [ + "PosixStdinReader", +] + + +class PosixStdinReader: + """ + Wrapper around stdin which reads (nonblocking) the next available 1024 + bytes and decodes it. + + Note that you can't be sure that the input file is closed if the ``read`` + function returns an empty string. When ``errors=ignore`` is passed, + ``read`` can return an empty string if all malformed input was replaced by + an empty string. (We can't block here and wait for more input.) So, because + of that, check the ``closed`` attribute, to be sure that the file has been + closed. + + :param stdin_fd: File descriptor from which we read. + :param errors: Can be 'ignore', 'strict' or 'replace'. + On Python3, this can be 'surrogateescape', which is the default. + + 'surrogateescape' is preferred, because this allows us to transfer + unrecognized bytes to the key bindings. Some terminals, like lxterminal + and Guake, use the 'Mxx' notation to send mouse events, where each 'x' + can be any possible byte. + """ + + # By default, we want to 'ignore' errors here. The input stream can be full + # of junk. One occurrence of this that I had was when using iTerm2 on OS X, + # with "Option as Meta" checked (You should choose "Option as +Esc".) + + def __init__( + self, stdin_fd: int, errors: str = "surrogateescape", encoding: str = "utf-8" + ) -> None: + self.stdin_fd = stdin_fd + self.errors = errors + + # Create incremental decoder for decoding stdin. + # We can not just do `os.read(stdin.fileno(), 1024).decode('utf-8')`, because + # it could be that we are in the middle of a utf-8 byte sequence. + self._stdin_decoder_cls = getincrementaldecoder(encoding) + self._stdin_decoder = self._stdin_decoder_cls(errors=errors) + + #: True when there is nothing anymore to read. + self.closed = False + + def read(self, count: int = 1024) -> str: + # By default we choose a rather small chunk size, because reading + # big amounts of input at once, causes the event loop to process + # all these key bindings also at once without going back to the + # loop. This will make the application feel unresponsive. + """ + Read the input and return it as a string. + + Return the text. Note that this can return an empty string, even when + the input stream was not yet closed. This means that something went + wrong during the decoding. + """ + if self.closed: + return "" + + # Check whether there is some input to read. `os.read` would block + # otherwise. + # (Actually, the event loop is responsible to make sure that this + # function is only called when there is something to read, but for some + # reason this happens in certain situations.) + try: + if not select.select([self.stdin_fd], [], [], 0)[0]: + return "" + except OSError: + # Happens for instance when the file descriptor was closed. + # (We had this in ptterm, where the FD became ready, a callback was + # scheduled, but in the meantime another callback closed it already.) + self.closed = True + + # Note: the following works better than wrapping `self.stdin` like + # `codecs.getreader('utf-8')(stdin)` and doing `read(1)`. + # Somehow that causes some latency when the escape + # character is pressed. (Especially on combination with the `select`.) + try: + data = os.read(self.stdin_fd, count) + + # Nothing more to read, stream is closed. + if data == b"": + self.closed = True + return "" + except OSError: + # In case of SIGWINCH + data = b"" + + return self._stdin_decoder.decode(data) |