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from enum import Enum, auto
class PtyEventType(Enum):
TEXT = auto()
BELL = auto()
class PtyParser(object):
"""
Parses a subset of special control sequences read from
a pty device. It is somewhat high level: Given a decoded,
proper Python string it will emit a series of events
which just need to be reflected in the UI while any state
is tracked in the PtyParser object.
"""
def __init__(self):
# no state, yet
pass
def parse(self, input):
"""
Main interface of PtyParser. Given a proper decoded
Python string , it yields a series of tuples of the
form (PtyEventType, payload) which the caller can
iterate through. Valid events are:
* PtyEventType.TEXT has a string slice as its payload
which should be appended to the terminal buffer as is.
* PtyEventType.BELL has no payload and indicates that
the bell character '\a' was in the terminal input.
This usually should trigger the machine to beep
and/or the window to set the urgent flag.
"""
# keep track of the start and potential end position
# of the slice we want to emit as a TEXT event
start = 0
pos = 0
# TODO: can we check for the last element more efficiently?
size = len(input)
# we expect a decoded string as input,
# so we don't need to handle incremental
# decoding here as well
for code in input:
# if flush_until is set, a slice of the buffer
# from start to flush_until will be emitted as
# a TEXT event
flush_until = None
# if not None, will be yielded as is, but only
# after any necessary flushing
special_ev = None
# control characters flush before advancing pos
# in order to not add them to the buffer -- we
# want to handle them ourselves instead of
# relying of gtk's default behavior.
if code == '\a':
flush_until = pos
special_ev = (PtyEventType.BELL, None)
pos += 1
# at the end of input, flush if we aren't already
if flush_until == None and pos >= size:
flush_until = pos
# only generate text event if it is non empty, …
if flush_until != None and flush_until > start:
yield (PtyEventType.TEXT, input[start:flush_until])
# … but advance as if we had flushed
if flush_until != None:
start = pos
if special_ev != None:
yield special_ev
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