python: move MakeVars class into separate module

... so I can reuse it.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 50 insertions, 0 deletions

diff --git a/python/makevars.py b/python/makevars.py
new file mode 100644
index 000000000..e0e2031a0
--- /dev/null
+++ b/python/makevars.py
@@ -0,0 +1,50 @@
+#
+# helper class to grab variables from FRR's Makefile
+#
+
+import os
+import subprocess
+
+class MakeVars(object):
+    '''
+    makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
+    '''
+    def __init__(self):
+        self._data = dict()
+
+    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
+
+    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[k] or defval