As an example of a real-life application which might
benefit from a fast switch-statement in Python, I'd
like to offer the following excerpt from Plex, which
runs as part of a tight loop once per input character.
if input_state == 1:
cur_pos = next_pos
# Begin inlined: c = self.read_char()
buf_index = next_pos - buf_start_pos
if buf_index < buf_len:
c = buffer[buf_index]
next_pos = next_pos + 1
else:
discard = self.start_pos - buf_start_pos
data = self.stream.read(0x1000)
buffer = self.buffer[discard:] + data
self.buffer = buffer
buf_start_pos = buf_start_pos + discard
self.buf_start_pos = buf_start_pos
buf_len = len(buffer)
buf_index = buf_index - discard
if data:
c = buffer[buf_index]
next_pos = next_pos + 1
else:
c = ''
# End inlined: c = self.read_char()
if c == '\n':
cur_char = EOL
input_state = 2
elif not c:
cur_char = EOL
input_state = 4
else:
cur_char = c
elif input_state == 2:
cur_char = '\n'
input_state = 3
elif input_state == 3:
cur_line = cur_line + 1
cur_line_start = cur_pos = next_pos
cur_char = BOL
input_state = 1
elif input_state == 4:
cur_char = EOF
input_state = 5
else: # input_state = 5
cur_char = ''
# End inlined self.next_char()
else: # not new_state
if trace: #TRACE#
print "blocked" #TRACE#
# Begin inlined: action = self.back_up()
if backup_state:
(action, cur_pos, cur_line, cur_line_start,
cur_char, input_state, next_pos) = backup_state
else:
action = None
break # while 1
# End inlined: action = self.back_up()
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury, | A citizen of NewZealandCorp, a |
Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. |
greg@cosc.canterbury.ac.nz +--------------------------------------+
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