third_party/cython/src/Cython/Plex/Scanners.py

   1 #=======================================================================
   2 #
   3 #   Python Lexical Analyser
   4 #
   5 #
   6 #   Scanning an input stream
   7 #
   8 #=======================================================================
   9
  10 import cython
  11 cython.declare(BOL=object, EOL=object, EOF=object, NOT_FOUND=object)
  12
  13 import Errors
  14 from Regexps import BOL, EOL, EOF
  15
  16 NOT_FOUND = object()
  17
  18 class Scanner(object):
  19   """
  20   A Scanner is used to read tokens from a stream of characters
  21   using the token set specified by a Plex.Lexicon.
  22
  23   Constructor:
  24
  25     Scanner(lexicon, stream, name = '')
  26
  27       See the docstring of the __init__ method for details.
  28
  29   Methods:
  30
  31     See the docstrings of the individual methods for more
  32     information.
  33
  34     read() --> (value, text)
  35       Reads the next lexical token from the stream.
  36
  37     position() --> (name, line, col)
  38       Returns the position of the last token read using the
  39       read() method.
  40
  41     begin(state_name)
  42       Causes scanner to change state.
  43
  44     produce(value [, text])
  45       Causes return of a token value to the caller of the
  46       Scanner.
  47
  48   """
  49
  50 #  lexicon = None        # Lexicon
  51 #  stream = None         # file-like object
  52 #  name = ''
  53 #  buffer = ''
  54 #  buf_start_pos = 0     # position in input of start of buffer
  55 #  next_pos = 0          # position in input of next char to read
  56 #  cur_pos = 0           # position in input of current char
  57 #  cur_line = 1          # line number of current char
  58 #  cur_line_start = 0    # position in input of start of current line
  59 #  start_pos = 0         # position in input of start of token
  60 #  start_line = 0        # line number of start of token
  61 #  start_col = 0         # position in line of start of token
  62 #  text = None           # text of last token read
  63 #  initial_state = None  # Node
  64 #  state_name = ''       # Name of initial state
  65 #  queue = None          # list of tokens to be returned
  66 #  trace = 0
  67
  68   def __init__(self, lexicon, stream, name = '', initial_pos = None):
  69     """
  70     Scanner(lexicon, stream, name = '')
  71
  72       |lexicon| is a Plex.Lexicon instance specifying the lexical tokens
  73       to be recognised.
  74
  75       |stream| can be a file object or anything which implements a
  76       compatible read() method.
  77
  78       |name| is optional, and may be the name of the file being
  79       scanned or any other identifying string.
  80     """
  81     self.trace = 0
  82
  83     self.buffer = u''
  84     self.buf_start_pos = 0
  85     self.next_pos = 0
  86     self.cur_pos = 0
  87     self.cur_line = 1
  88     self.start_pos = 0
  89     self.start_line = 0
  90     self.start_col = 0
  91     self.text = None
  92     self.state_name = None
  93
  94     self.lexicon = lexicon
  95     self.stream = stream
  96     self.name = name
  97     self.queue = []
  98     self.initial_state = None
  99     self.begin('')
 100     self.next_pos = 0
 101     self.cur_pos = 0
 102     self.cur_line_start = 0
 103     self.cur_char = BOL
 104     self.input_state = 1
 105     if initial_pos is not None:
 106         self.cur_line, self.cur_line_start = initial_pos[1], -initial_pos[2]
 107
 108   def read(self):
 109     """
 110     Read the next lexical token from the stream and return a
 111     tuple (value, text), where |value| is the value associated with
 112     the token as specified by the Lexicon, and |text| is the actual
 113     string read from the stream. Returns (None, '') on end of file.
 114     """
 115     queue = self.queue
 116     while not queue:
 117       self.text, action = self.scan_a_token()
 118       if action is None:
 119         self.produce(None)
 120         self.eof()
 121       else:
 122         value = action.perform(self, self.text)
 123         if value is not None:
 124           self.produce(value)
 125     result = queue[0]
 126     del queue[0]
 127     return result
 128
 129   def scan_a_token(self):
 130     """
 131     Read the next input sequence recognised by the machine
 132     and return (text, action). Returns ('', None) on end of
 133     file.
 134     """
 135     self.start_pos = self.cur_pos
 136     self.start_line = self.cur_line
 137     self.start_col = self.cur_pos - self.cur_line_start
 138     action = self.run_machine_inlined()
 139     if action is not None:
 140       if self.trace:
 141         print("Scanner: read: Performing %s %d:%d" % (
 142           action, self.start_pos, self.cur_pos))
 143       text = self.buffer[self.start_pos - self.buf_start_pos :
 144                          self.cur_pos   - self.buf_start_pos]
 145       return (text, action)
 146     else:
 147       if self.cur_pos == self.start_pos:
 148         if self.cur_char is EOL:
 149           self.next_char()
 150         if self.cur_char is None or self.cur_char is EOF:
 151           return (u'', None)
 152       raise Errors.UnrecognizedInput(self, self.state_name)
 153
 154   def run_machine_inlined(self):
 155     """
 156     Inlined version of run_machine for speed.
 157     """
 158     state = self.initial_state
 159     cur_pos = self.cur_pos
 160     cur_line = self.cur_line
 161     cur_line_start = self.cur_line_start
 162     cur_char = self.cur_char
 163     input_state = self.input_state
 164     next_pos = self.next_pos
 165     buffer = self.buffer
 166     buf_start_pos = self.buf_start_pos
 167     buf_len = len(buffer)
 168     b_action, b_cur_pos, b_cur_line, b_cur_line_start, b_cur_char, b_input_state, b_next_pos = \
 169               None, 0, 0, 0, u'', 0, 0
 170     trace = self.trace
 171     while 1:
 172       if trace: #TRACE#
 173         print("State %d, %d/%d:%s -->" % ( #TRACE#
 174           state['number'], input_state, cur_pos, repr(cur_char)))  #TRACE#
 175       # Begin inlined self.save_for_backup()
 176       #action = state.action #@slow
 177       action = state['action'] #@fast
 178       if action is not None:
 179         b_action, b_cur_pos, b_cur_line, b_cur_line_start, b_cur_char, b_input_state, b_next_pos = \
 180                   action, cur_pos, cur_line, cur_line_start, cur_char, input_state, next_pos
 181       # End inlined self.save_for_backup()
 182       c = cur_char
 183       #new_state = state.new_state(c) #@slow
 184       new_state = state.get(c, NOT_FOUND) #@fast
 185       if new_state is NOT_FOUND: #@fast
 186         new_state = c and state.get('else') #@fast
 187       if new_state:
 188         if trace: #TRACE#
 189           print("State %d" % new_state['number'])  #TRACE#
 190         state = new_state
 191         # Begin inlined: self.next_char()
 192         if input_state == 1:
 193           cur_pos = next_pos
 194           # Begin inlined: c = self.read_char()
 195           buf_index = next_pos - buf_start_pos
 196           if buf_index < buf_len:
 197             c = buffer[buf_index]
 198             next_pos = next_pos + 1
 199           else:
 200             discard = self.start_pos - buf_start_pos
 201             data = self.stream.read(0x1000)
 202             buffer = self.buffer[discard:] + data
 203             self.buffer = buffer
 204             buf_start_pos = buf_start_pos + discard
 205             self.buf_start_pos = buf_start_pos
 206             buf_len = len(buffer)
 207             buf_index = buf_index - discard
 208             if data:
 209               c = buffer[buf_index]
 210               next_pos = next_pos + 1
 211             else:
 212               c = u''
 213           # End inlined: c = self.read_char()
 214           if c == u'\n':
 215             cur_char = EOL
 216             input_state = 2
 217           elif not c:
 218             cur_char = EOL
 219             input_state = 4
 220           else:
 221             cur_char = c
 222         elif input_state == 2:
 223           cur_char = u'\n'
 224           input_state = 3
 225         elif input_state == 3:
 226           cur_line = cur_line + 1
 227           cur_line_start = cur_pos = next_pos
 228           cur_char = BOL
 229           input_state = 1
 230         elif input_state == 4:
 231           cur_char = EOF
 232           input_state = 5
 233         else: # input_state = 5
 234           cur_char = u''
 235         # End inlined self.next_char()
 236       else: # not new_state
 237         if trace: #TRACE#
 238           print("blocked")  #TRACE#
 239         # Begin inlined: action = self.back_up()
 240         if b_action is not None:
 241           (action, cur_pos, cur_line, cur_line_start,
 242            cur_char, input_state, next_pos) = \
 243                    (b_action, b_cur_pos, b_cur_line, b_cur_line_start,
 244                     b_cur_char, b_input_state, b_next_pos)
 245         else:
 246           action = None
 247         break # while 1
 248         # End inlined: action = self.back_up()
 249     self.cur_pos = cur_pos
 250     self.cur_line = cur_line
 251     self.cur_line_start = cur_line_start
 252     self.cur_char = cur_char
 253     self.input_state = input_state
 254     self.next_pos     = next_pos
 255     if trace: #TRACE#
 256       if action is not None: #TRACE#
 257         print("Doing %s" % action) #TRACE#
 258     return action
 259
 260   def next_char(self):
 261     input_state = self.input_state
 262     if self.trace:
 263       print("Scanner: next: %s [%d] %d" % (" "*20, input_state, self.cur_pos))
 264     if input_state == 1:
 265       self.cur_pos = self.next_pos
 266       c = self.read_char()
 267       if c == u'\n':
 268         self.cur_char = EOL
 269         self.input_state = 2
 270       elif not c:
 271         self.cur_char = EOL
 272         self.input_state = 4
 273       else:
 274         self.cur_char = c
 275     elif input_state == 2:
 276       self.cur_char = u'\n'
 277       self.input_state = 3
 278     elif input_state == 3:
 279       self.cur_line = self.cur_line + 1
 280       self.cur_line_start = self.cur_pos = self.next_pos
 281       self.cur_char = BOL
 282       self.input_state = 1
 283     elif input_state == 4:
 284       self.cur_char = EOF
 285       self.input_state = 5
 286     else: # input_state = 5
 287       self.cur_char = u''
 288     if self.trace:
 289       print("--> [%d] %d %s" % (input_state, self.cur_pos, repr(self.cur_char)))
 290
 291   def position(self):
 292     """
 293     Return a tuple (name, line, col) representing the location of
 294     the last token read using the read() method. |name| is the
 295     name that was provided to the Scanner constructor; |line|
 296     is the line number in the stream (1-based); |col| is the
 297     position within the line of the first character of the token
 298     (0-based).
 299     """
 300     return (self.name, self.start_line, self.start_col)
 301
 302   def get_position(self):
 303     """Python accessible wrapper around position(), only for error reporting.
 304     """
 305     return self.position()
 306
 307   def begin(self, state_name):
 308     """Set the current state of the scanner to the named state."""
 309     self.initial_state = (
 310       self.lexicon.get_initial_state(state_name))
 311     self.state_name = state_name
 312
 313   def produce(self, value, text = None):
 314     """
 315     Called from an action procedure, causes |value| to be returned
 316     as the token value from read(). If |text| is supplied, it is
 317     returned in place of the scanned text.
 318
 319     produce() can be called more than once during a single call to an action
 320     procedure, in which case the tokens are queued up and returned one
 321     at a time by subsequent calls to read(), until the queue is empty,
 322     whereupon scanning resumes.
 323     """
 324     if text is None:
 325       text = self.text
 326     self.queue.append((value, text))
 327
 328   def eof(self):
 329     """
 330     Override this method if you want something to be done at
 331     end of file.
 332     """