Add ctypes-based wrapper to ALPM vercmp API

This will allow us to do some additional stuff on systems that have
libalpm available; namely we can use the version comparison logic it
provides to do smarter filtering etc. of fields that use comparsion
operations.

Signed-off-by: Dan McGee <dan@archlinux.org>

1 files changed, 68 insertions, 0 deletions

diff --git a/packages/alpm.py b/packages/alpm.py
new file mode 100644
index 00000000..a7f4c3b5
--- /dev/null
+++ b/packages/alpm.py
@@ -0,0 +1,68 @@
+import ctypes
+from ctypes.util import find_library
+import operator
+
+
+def load_alpm(name=None):
+    # Load the alpm library and set up some of the functions we might use
+    if name == None:
+        name = find_library('alpm')
+    try:
+        alpm = ctypes.cdll.LoadLibrary(name)
+    except OSError:
+        return None
+    alpm.alpm_version.argtypes = ()
+    alpm.alpm_version.restype = ctypes.c_char_p
+    alpm.alpm_pkg_vercmp.argtypes = (ctypes.c_char_p, ctypes.c_char_p)
+    alpm.alpm_pkg_vercmp.restype = ctypes.c_int
+    return alpm
+
+
+ALPM = load_alpm()
+
+class AlpmAPI(object):
+    OPERATOR_MAP = {
+        '=':  operator.eq,
+        '==': operator.eq,
+        '!=': operator.ne,
+        '<':  operator.lt,
+        '<=': operator.le,
+        '>':  operator.gt,
+        '>=': operator.ge,
+    }
+
+    def __init__(self):
+        self.alpm = ALPM
+        self.available = ALPM is not None
+
+    def version(self):
+        if not self.available:
+            return None
+        return ALPM.alpm_version()
+
+    def vercmp(self, ver1, ver2):
+        if not self.available:
+            return None
+        return ALPM.alpm_pkg_vercmp(str(ver1), str(ver2))
+
+    def compare_versions(self, ver1, oper, ver2):
+        func = self.OPERATOR_MAP.get(oper, None)
+        if func is None:
+            raise Exception("Invalid operator %s specified" % oper)
+        if not self.available:
+            return None
+        res = self.vercmp(ver1, ver2)
+        return func(res, 0)
+
+
+def main():
+    api = AlpmAPI()
+    print api.version()
+    print api.vercmp(1, 2)
+    print api.compare_versions(1, '<', 2)
+
+
+if __name__ == '__main__':
+    main()
+
+# vim: set ts=4 sw=4 et: