1 files changed, 90 insertions, 0 deletions
diff --git a/python/makevars.py b/python/makevars.py
new file mode 100644
index 0000000000..1a85fbd6f5
--- /dev/null
+++ b/python/makevars.py
@@ -0,0 +1,90 @@
+#
+# helper class to grab variables from FRR's Makefile
+#
+
+import os
+import subprocess
+import re
+
+class MakeVarsBase(object):
+    '''
+    common code between MakeVars and MakeReVars
+    '''
+    def __init__(self):
+        self._data = dict()
+
+    def __getitem__(self, k):
+        if k not in self._data:
+            self.getvars([k])
+        return self._data[k]
+
+    def get(self, k, defval = None):
+        if k not in self._data:
+            self.getvars([k])
+        return self._data.get(k) or defval
+
+class MakeVars(MakeVarsBase):
+    '''
+    makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
+
+    This variant works by invoking make as a subprocess, i.e. Makefile must
+    be valid and working.  (This is sometimes a problem if depfiles have not
+    been generated.)
+    '''
+    def getvars(self, varlist):
+        '''
+        get a batch list of variables from make.  faster than individual calls.
+        '''
+        rdfd, wrfd = os.pipe()
+
+        shvars = ['shvar-%s' % s for s in varlist]
+        make = subprocess.Popen(['make', '-s', 'VARFD=%d' % wrfd] + shvars, pass_fds = [wrfd])
+        os.close(wrfd)
+        data = b''
+
+        rdf = os.fdopen(rdfd, 'rb')
+        while True:
+            rdata = rdf.read()
+            if len(rdata) == 0:
+                break
+            data += rdata
+
+        del rdf
+        make.wait()
+
+        data = data.decode('US-ASCII').strip().split('\n')
+        for row in data:
+            k, v = row.split('=', 1)
+            v = v[1:-1]
+            self._data[k] = v
+
+class MakeReVars(MakeVarsBase):
+    '''
+    makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
+
+    This variant works by regexing through Makefile.  This means the Makefile
+    does not need to be fully working, but on the other hand it doesn't support
+    fancy complicated make expressions.
+    '''
+    var_re = re.compile(r'^([^=#\n\s]+)[ \t]*=[ \t]*([^#\n]*)(?:#.*)?$', flags=re.MULTILINE)
+    repl_re = re.compile(r'\$(?:([A-Za-z])|\(([^\)]+)\))')
+
+    def __init__(self, maketext):
+        super().__init__()
+        self._vars = dict(self.var_re.findall(maketext.replace('\\\n', '')))
+
+    def replacevar(self, match):
+        varname = match.group(1) or match.group(2)
+        return self._vars.get(varname, '')
+
+    def getvars(self, varlist):
+        for varname in varlist:
+            if varname not in self._vars:
+                continue
+
+            val, prevval = self._vars[varname], None
+            while val != prevval:
+                prevval = val
+                val = self.repl_re.sub(self.replacevar, val)
+
+            self._data[varname] = val