1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
|
#!/usr/bin/env python
# ******************************************************
# Michael Cohen <scudette@users.sourceforge.net>
#
# ******************************************************
# Version: FLAG $Version: 0.87-pre1 Date: Thu Jun 12 00:48:38 EST 2008$
# ******************************************************
#
# * This program is free software; you can redistribute it and/or
# * modify it under the terms of the GNU General Public License
# * as published by the Free Software Foundation; either version 2
# * of the License, or (at your option) any later version.
# *
# * This program is distributed in the hope that it will be useful,
# * but WITHOUT ANY WARRANTY; without even the implied warranty of
# * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# * GNU General Public License for more details.
# *
# * You should have received a copy of the GNU General Public License
# * along with this program; if not, write to the Free Software
# * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
# ******************************************************
""" A simple feed lexer.
"""
import re,sys
class Lexer:
""" A generic feed lexer """
## The following is a description of the states we have and the
## way we move through them: format is an array of
## [ state_re, re, token/action, next state ]
tokens = []
state = "INITIAL"
buffer = ''
error = 0
verbose = 0
state_stack = []
processed = 0
processed_buffer = ''
saved_state = None
flags = 0
def __init__(self, verbose=0, fd=None):
if not self.verbose:
self.verbose = verbose
if len(self.tokens[0])==4:
for row in self.tokens:
row.append(re.compile(row[0], re.DOTALL))
row.append(re.compile(row[1], re.DOTALL | re.M | re.S | self.flags ))
self.fd = fd
def save_state(self, t=None, m=None):
""" Returns a dict which represents the current state of the lexer.
When provided to restore_state, the lexer is guaranteed to be
in the same state as when the save_state was called.
Note that derived classes may need to extend this.
"""
## Cant save our state if we have errors. We need to guarantee
## that we rewind to a good part of the file.
if self.error: return
try:
end = m.end()
except: end = 0
self.saved_state = dict(state_stack = self.state_stack[:],
processed = self.processed - end,
processed_buffer = self.processed_buffer,
readptr = self.fd.tell() - len(self.buffer) - end,
state = self.state,
objects = self.objects[:],
error = self.error,
)
if self.verbose>1:
print "Saving state %s" % self.processed
def restore_state(self):
state = self.saved_state
if not state: return
self.state_stack = state['state_stack']
self.processed = state['processed']
self.processed_buffer = state['processed_buffer']
self.buffer = ''
self.fd.seek(state['readptr'])
self.state = state['state']
self.objects = state['objects']
self.error = state['error']
if self.verbose>1:
print "Restoring state to offset %s" % self.processed
def next_token(self, end = True):
## Now try to match any of the regexes in order:
current_state = self.state
for state_re, re_str, token, next, state, regex in self.tokens:
## Does the rule apply for us now?
if state.match(current_state):
if self.verbose > 2:
print "%s: Trying to match %r with %r" % (self.state, self.buffer[:10], re_str)
m = regex.match(self.buffer)
if m:
if self.verbose > 3:
print "%s matched %s" % (re_str, m.group(0).encode("utf8"))
## The match consumes the data off the buffer (the
## handler can put it back if it likes)
self.processed_buffer += self.buffer[:m.end()]
self.buffer = self.buffer[m.end():]
self.processed += m.end()
## Try to iterate over all the callbacks specified:
for t in token.split(','):
try:
if self.verbose > 0:
print "0x%X: Calling %s %r" % (self.processed, t, m.group(0))
cb = getattr(self, t, self.default_handler)
except AttributeError:
continue
## Is there a callback to handle this action?
next_state = cb(t, m)
if next_state == "CONTINUE":
continue
elif next_state:
next = next_state
self.state = next
if next:
self.state = next
return token
## Check that we are making progress - if we are too full, we
## assume we are stuck:
if end and len(self.buffer)>0 or len(self.buffer)>1024:
self.processed_buffer += self.buffer[:1]
self.buffer = self.buffer[1:]
self.ERROR("Lexer Stuck, discarding 1 byte (%r) - state %s" % (self.buffer[:10], self.state))
return "ERROR"
## No token were found
return None
def feed(self, data):
self.buffer += data
def empty(self):
return not len(self.buffer)
def default_handler(self, token, match):
if self.verbose > 2:
print "Default handler: %s with %r" % (token,match.group(0))
def ERROR(self, message = None, weight =1):
if self.verbose > 0 and message:
print "Error(%s): %s" % (weight,message)
self.error += weight
def PUSH_STATE(self, token = None, match = None):
if self.verbose > 1:
print "Storing state %s" % self.state
self.state_stack.append(self.state)
def POP_STATE(self, token = None, match = None):
try:
state = self.state_stack.pop()
if self.verbose > 1:
print "Returned state to %s" % state
return state
except IndexError:
print "Tried to pop the state but failed - possible recursion error"
return None
def close(self):
""" Just a conveniece function to force us to parse all the data """
while self.next_token(): pass
class SelfFeederMixIn(Lexer):
""" This mixin is used to make a lexer which feeds itself one
sector at the time.
Note that self.fd must be the fd we read from.
"""
def parse_fd(self, fd):
self.feed(fd.read())
while self.next_token(): pass
|
