python/makevars.py

   1 #
   2 # helper class to grab variables from FRR's Makefile
   3 #
   4
   5 import os
   6 import subprocess
   7 import re
   8
   9
  10 class MakeVarsBase(object):
  11     """
  12     common code between MakeVars and MakeReVars
  13     """
  14
  15     def __init__(self):
  16         self._data = dict()
  17
  18     def __getitem__(self, k):
  19         if k not in self._data:
  20             self.getvars([k])
  21         return self._data[k]
  22
  23     def get(self, k, defval=None):
  24         if k not in self._data:
  25             self.getvars([k])
  26         return self._data.get(k) or defval
  27
  28
  29 class MakeVars(MakeVarsBase):
  30     """
  31     makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
  32
  33     This variant works by invoking make as a subprocess, i.e. Makefile must
  34     be valid and working.  (This is sometimes a problem if depfiles have not
  35     been generated.)
  36     """
  37
  38     def getvars(self, varlist):
  39         """
  40         get a batch list of variables from make.  faster than individual calls.
  41         """
  42         rdfd, wrfd = os.pipe()
  43
  44         shvars = ["shvar-%s" % s for s in varlist]
  45         make = subprocess.Popen(
  46             ["make", "-s", "VARFD=%d" % wrfd] + shvars, pass_fds=[wrfd]
  47         )
  48         os.close(wrfd)
  49         data = b""
  50
  51         rdf = os.fdopen(rdfd, "rb")
  52         while True:
  53             rdata = rdf.read()
  54             if len(rdata) == 0:
  55                 break
  56             data += rdata
  57
  58         del rdf
  59         make.wait()
  60
  61         data = data.decode("US-ASCII").strip().split("\n")
  62         for row in data:
  63             k, v = row.split("=", 1)
  64             v = v[1:-1]
  65             self._data[k] = v
  66
  67
  68 class MakeReVars(MakeVarsBase):
  69     """
  70     makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
  71
  72     This variant works by regexing through Makefile.  This means the Makefile
  73     does not need to be fully working, but on the other hand it doesn't support
  74     fancy complicated make expressions.
  75     """
  76
  77     var_re = re.compile(
  78         r"^([^=#\n\s]+)[ \t]*=[ \t]*([^#\n]*)(?:#.*)?$", flags=re.MULTILINE
  79     )
  80     repl_re = re.compile(r"\$(?:([A-Za-z])|\(([^\)]+)\))")
  81
  82     def __init__(self, maketext):
  83         super(MakeReVars, self).__init__()
  84         self._vars = dict(self.var_re.findall(maketext.replace("\\\n", "")))
  85
  86     def replacevar(self, match):
  87         varname = match.group(1) or match.group(2)
  88         return self._vars.get(varname, "")
  89
  90     def getvars(self, varlist):
  91         for varname in varlist:
  92             if varname not in self._vars:
  93                 continue
  94
  95             val, prevval = self._vars[varname], None
  96             while val != prevval:
  97                 prevval = val
  98                 val = self.repl_re.sub(self.replacevar, val)
  99
 100             self._data[varname] = val