[PATCH 6 of 8] libxl: add KeyedUnion type

[Ian Campbell <ian.campbell@citrix.com>]

# HG changeset patch
# User Ian Campbell <ian.campbell@citrix.com>
# Date 1280829586 -3600
# Node ID 5d51a404379e3e91c08c07c8292abefa1440a655
# Parent  c87dd259a8ed069d8786aadf9e1f6e555aa6778e
libxl: add KeyedUnion type

Use this to express the construct where a union is differentiated on a
variable in the containing struct.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

diff -r c87dd259a8ed -r 5d51a404379e tools/libxl/libxltypes.py
--- a/tools/libxl/libxltypes.py	Tue Aug 03 10:59:46 2010 +0100
+++ b/tools/libxl/libxltypes.py	Tue Aug 03 10:59:46 2010 +0100
@@ -35,12 +35,13 @@ class BitField(Type):
 
 class Field(Type):
     """An element of an Aggregate type"""
-    def __init__(self, type, name, const = False, comment = None):
+    def __init__(self, type, name, const = False, comment = None, keyvar_expr = None):
         Type.__init__(self,type.typename)
         self.type = type
         self.name = name
         self.const = const
         self.comment = comment
+        self.keyvar_expr = keyvar_expr
 
 class Aggregate(Type):
     """A type containing a collection of other types"""
@@ -79,6 +80,19 @@ class KeyValueList(Type):
         
         Type.__init__(self, "char **", namespace = None)
 
+class KeyedUnion(Aggregate):
+    """A union which is keyed of another variable"""
+    def __init__(self, name, keyvar_name, fields, comment = None):
+        self.keyvar = keyvar_name
+        Aggregate.__init__(self, "union", name, [], comment)
+        for f in fields:
+            # (name, keyvar_expr, type)
+
+            # keyvar_expr must contain exactly one %s which will be replaced with the keyvar_name
+            
+            n, kve, ty = f
+            self.fields.append(Field(ty, n, False, None, kve))
+                 
 class Reference(Type):
     """A reference to another type"""
     def __init__(self, ty):
@@ -199,26 +213,26 @@ libxl_domain_build_info = Struct("domain
     ("disable_migrate", bool),
     ("kernel",          libxl_file_reference),
     ("hvm",             integer),
-    ("u", Union(None,
-                [("hvm", Struct(None,
-                                [("pae", bool),
-                                 ("apic", bool),
-                                 ("acpi", bool),
-                                 ("nx", bool),
-                                 ("viridian", bool),
-                                 ("timeoffset", string),
-                                 ("hpet", bool),
-                                 ("vpt_align", bool),
-                                 ("timer_mode", integer),
-                                 ])),
-                 ("pv", Struct(None,
-                               [("slack_memkb", uint32),
-                                ("bootloader", string, True),
-                                ("bootloader_args", string, True),
-                                ("cmdline", string),
-                                ("ramdisk", libxl_file_reference),
-                                ("features", string, True),
-                                ])),
+    ("u", KeyedUnion(None, "hvm",
+                [("hvm", "%s", Struct(None,
+                                       [("pae", bool),
+                                        ("apic", bool),
+                                        ("acpi", bool),
+                                        ("nx", bool),
+                                        ("viridian", bool),
+                                        ("timeoffset", string),
+                                        ("hpet", bool),
+                                        ("vpt_align", bool),
+                                        ("timer_mode", integer),
+                                        ])),
+                 ("pv", "!%s", Struct(None,
+                                       [("slack_memkb", uint32),
+                                        ("bootloader", string, True),
+                                        ("bootloader_args", string, True),
+                                        ("cmdline", string),
+                                        ("ramdisk", libxl_file_reference),
+                                        ("features", string, True),
+                                        ])),
                  ])),
     ],
     comment =