Tools/modulator/varsubst.py

   1 #
   2 # Variable substitution. Variables are $delimited$
   3 #
   4 import re
   5
   6 error = 'varsubst.error'
   7
   8 class Varsubst:
   9     def __init__(self, dict):
  10         self.dict = dict
  11         self.prog = re.compile('\$([a-zA-Z0-9_]*)\$')
  12         self.do_useindent = 0
  13
  14     def useindent(self, onoff):
  15         self.do_useindent = onoff
  16
  17     def subst(self, s):
  18         rv = ''
  19         while 1:
  20             m = self.prog.search(s)
  21             if not m:
  22                 return rv + s
  23             rv = rv + s[:m.start()]
  24             s = s[m.end():]
  25             if m.end() - m.start() == 2:
  26                 # Escaped dollar
  27                 rv = rv + '$'
  28                 s = s[2:]
  29                 continue
  30             name = m.group(1)
  31             if not self.dict.has_key(name):
  32                 raise error, 'No such variable: '+name
  33             value = self.dict[name]
  34             if self.do_useindent and '\n' in value:
  35                 value = self._modindent(value, rv)
  36             rv = rv + value
  37
  38     def _modindent(self, value, old):
  39         lastnl = old.rfind('\n', 0) + 1
  40         lastnl = len(old) - lastnl
  41         sub = '\n' + (' '*lastnl)
  42         return re.sub('\n', sub, value)
  43
  44 def _test():
  45     import sys
  46     import os
  47
  48     sys.stderr.write('-- Copying stdin to stdout with environment map --\n')
  49     c = Varsubst(os.environ)
  50     c.useindent(1)
  51     d = sys.stdin.read()
  52     sys.stdout.write(c.subst(d))
  53     sys.exit(1)
  54
  55 if __name__ == '__main__':
  56     _test()