Tools/modulator/varsubst.py

   1 #
   2 # Variable substitution. Variables are $delimited$
   3 #
   4 import string
   5 import regex
   6 import regsub
   7
   8 error = 'varsubst.error'
   9
  10 class Varsubst:
  11     def __init__(self, dict):
  12         self.dict = dict
  13         self.prog = regex.compile('\$[a-zA-Z0-9_]*\$')
  14         self.do_useindent = 0
  15
  16     def useindent(self, onoff):
  17         self.do_useindent = onoff
  18
  19     def subst(self, str):
  20         rv = ''
  21         while 1:
  22             pos = self.prog.search(str)
  23             if pos < 0:
  24                 return rv + str
  25             if pos:
  26                 rv = rv + str[:pos]
  27                 str = str[pos:]
  28             len = self.prog.match(str)
  29             if len == 2:
  30                 # Escaped dollar
  31                 rv = rv + '$'
  32                 str = str[2:]
  33                 continue
  34             name = str[1:len-1]
  35             str = str[len:]
  36             if not self.dict.has_key(name):
  37                 raise error, 'No such variable: '+name
  38             value = self.dict[name]
  39             if self.do_useindent and '\n' in value:
  40                 value = self._modindent(value, rv)
  41             rv = rv + value
  42
  43     def _modindent(self, value, old):
  44         lastnl = string.rfind(old, '\n', 0) + 1
  45         lastnl = len(old) - lastnl
  46         sub = '\n' + (' '*lastnl)
  47         return regsub.gsub('\n', sub, value)
  48
  49 def _test():
  50     import sys
  51     import os
  52
  53     sys.stderr.write('-- Copying stdin to stdout with environment map --\n')
  54     c = Varsubst(os.environ)
  55     c.useindent(1)
  56     d = sys.stdin.read()
  57     sys.stdout.write(c.subst(d))
  58     sys.exit(1)
  59
  60 if __name__ == '__main__':
  61     _test()