[Xen-devel] [PATCH RFC 2/9] libxl idl: allow implicit enum values

[Rob Hoes <rob.hoes@xxxxxxxxxx>]

Introducing two special enum values:
* ENUM_NEXT: equal to the previous value in the enum plus 1
* ENUM_PREV: equal to the previous value in the enum minus 1

This makes it a little easier to maintain enums for which we do not care too
much about the exact enum values.

Signed-off-by: Rob Hoes <rob.hoes@xxxxxxxxxx>
---
 tools/libxl/idl.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/libxl/idl.py b/tools/libxl/idl.py
index 437049e..9fccefa 100644
--- a/tools/libxl/idl.py
+++ b/tools/libxl/idl.py
@@ -8,6 +8,9 @@ DIR_IN   = 1
 DIR_OUT  = 2
 DIR_BOTH = 3
 
+ENUM_NEXT = sys.maxint
+ENUM_PREV = sys.maxint - 1
+
 _default_namespace = ""
 def namespace(s):
     if type(s) != str:
@@ -174,9 +177,18 @@ class Enumeration(Type):
             self.namespace)
 
         self.values = []
+        last = None
         for v in values:
             # (value, name)
             (num,name) = v
+            if num == ENUM_NEXT or num == ENUM_PREV:
+               if last == None:
+                       raise ValueError
+               elif num == ENUM_NEXT:
+                       num = last + 1
+               else:
+                       num = last - 1
+            last = num
             self.values.append(EnumerationValue(self, num, name,
                                                 typename=self.rawname))
     def lookup(self, name):
@@ -354,6 +366,7 @@ def parse(f):
             globs[n] = t
         elif n in ['PASS_BY_REFERENCE', 'PASS_BY_VALUE',
                    'DIR_NONE', 'DIR_IN', 'DIR_OUT', 'DIR_BOTH',
+                   'ENUM_NEXT', 'ENUM_PREV',
                    'namespace', 'hidden']:
             globs[n] = t
 
-- 
2.4.1


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