bindings/python/codegen/scmexpr.py

   1 #!/usr/bin/env python
   2 # -*- Mode: Python; py-indent-offset: 4 -*-
   3 from __future__ import generators
   4
   5 import string
   6 from cStringIO import StringIO
   7
   8 class error(Exception):
   9     def __init__(self, filename, lineno, msg):
  10         Exception.__init__(self, msg)
  11         self.filename = filename
  12         self.lineno = lineno
  13         self.msg = msg
  14     def __str__(self):
  15         return '%s:%d: error: %s' % (self.filename, self.lineno, self.msg)
  16
  17 trans = [' '] * 256
  18 for i in range(256):
  19     if chr(i) in string.letters + string.digits + '_':
  20         trans[i] = chr(i)
  21     else:
  22         trans[i] = '_'
  23 trans = string.join(trans, '')
  24
  25 def parse(filename):
  26     if isinstance(filename, str):
  27         fp = open(filename, 'r')
  28     else: # if not string, assume it is some kind of iterator
  29         fp = filename
  30         filename = getattr(fp, 'name', '<unknown>')
  31     whitespace = ' \t\n\r\x0b\x0c'
  32     nonsymbol = whitespace + '();\'"'
  33     stack = []
  34     openlines = []
  35     lineno = 0
  36     for line in fp:
  37         pos = 0
  38         lineno += 1
  39         while pos < len(line):
  40             if line[pos] in whitespace: # ignore whitespace
  41                 pass
  42             elif line[pos] == ';': # comment
  43                 break
  44             elif line[pos:pos+2] == "'(":
  45                 pass # the open parenthesis will be handled next iteration
  46             elif line[pos] == '(':
  47                 stack.append(())
  48                 openlines.append(lineno)
  49             elif line[pos] == ')':
  50                 if len(stack) == 0:
  51                     raise error(filename, lineno, 'close parenthesis found when none open')
  52                 closed = stack[-1]
  53                 del stack[-1]
  54                 del openlines[-1]
  55                 if stack:
  56                     stack[-1] += (closed,)
  57                 else:
  58                     yield closed
  59             elif line[pos] == '"': # quoted string
  60                 if not stack:
  61                     raise error(filename, lineno,
  62                                 'string found outside of s-expression')
  63                 endpos = pos + 1
  64                 chars = []
  65                 while endpos < len(line):
  66                     if endpos+1 < len(line) and line[endpos] == '\\':
  67                         endpos += 1
  68                         if line[endpos] == 'n':
  69                             chars.append('\n')
  70                         elif line[endpos] == 'r':
  71                             chars.append('\r')
  72                         elif line[endpos] == 't':
  73                             chars.append('\t')
  74                         else:
  75                             chars.append('\\')
  76                             chars.append(line[endpos])
  77                     elif line[endpos] == '"':
  78                         break
  79                     else:
  80                         chars.append(line[endpos])
  81                     endpos += 1
  82                 if endpos >= len(line):
  83                     raise error(filename, lineno, "unclosed quoted string")
  84                 pos = endpos
  85                 stack[-1] += (''.join(chars),)
  86             else: # symbol/number
  87                 if not stack:
  88                     raise error(filename, lineno,
  89                                 'identifier found outside of s-expression')
  90                 endpos = pos
  91                 while endpos < len(line) and line[endpos] not in nonsymbol:
  92                     endpos += 1
  93                 symbol = line[pos:endpos]
  94                 pos = max(pos, endpos-1)
  95                 try: symbol = int(symbol)
  96                 except ValueError:
  97                     try: symbol = float(symbol)
  98                     except ValueError: pass
  99                 stack[-1] += (symbol,)
 100             pos += 1
 101     if len(stack) != 0:
 102         msg = '%d unclosed parentheses found at end of ' \
 103               'file (opened on line(s) %s)' % (len(stack),
 104                                                ', '.join(map(str, openlines)))
 105         raise error(filename, lineno, msg)
 106
 107 class Parser:
 108     def __init__(self, filename):
 109         """Argument is either a string, a parse tree, or file object"""
 110         self.filename = filename
 111     def startParsing(self, filename=None):
 112         statements = parse(filename or self.filename)
 113         for statement in statements:
 114             self.handle(statement)
 115     def handle(self, tup):
 116         cmd = string.translate(tup[0], trans)
 117         if hasattr(self, cmd):
 118             getattr(self, cmd)(*tup[1:])
 119         else:
 120             self.unknown(tup)
 121     def unknown(self, tup):
 122         pass
 123
 124 _testString = """; a scheme file
 125 (define-func gdk_font_load    ; a comment at end of line
 126   GdkFont
 127   ((string name)))
 128
 129 (define-boxed GdkEvent
 130   gdk_event_copy
 131   gdk_event_free
 132   "sizeof(GdkEvent)")
 133 """
 134
 135 if __name__ == '__main__':
 136     import sys
 137     if sys.argv[1:]:
 138         fp = open(sys.argv[1])
 139     else:
 140         fp = StringIO(_testString)
 141     statements = parse(fp)
 142     for s in statements:
 143         print `s`