1 files changed, 88 insertions, 0 deletions
diff --git a/libxcb/xcb-proto/xcbgen/expr.py b/libxcb/xcb-proto/xcbgen/expr.py
new file mode 100644
index 000000000..522e17d09
--- /dev/null
+++ b/libxcb/xcb-proto/xcbgen/expr.py
@@ -0,0 +1,88 @@
+'''
+This module contains helper classes for structure fields and length expressions.
+'''
+class Field(object):
+    '''
+    Represents a field of a structure.
+
+    type is the datatype object for the field.
+    field_type is the name of the type (string tuple)
+    field_name is the name of the structure field.
+    visible is true iff the field should be in the request API.
+    wire is true iff the field should be in the request structure.
+    auto is true iff the field is on the wire but not in the request API (e.g. opcode)
+    '''
+    def __init__(self, type, field_type, field_name, visible, wire, auto):
+        self.type = type
+        self.field_type = field_type
+        self.field_name = field_name
+        self.visible = visible
+        self.wire = wire
+        self.auto = auto
+
+
+class Expression(object):
+    '''
+    Represents a mathematical expression for a list length or exprfield.
+
+    Public fields:
+    op is the operation (text +,*,/,<<) or None.
+    lhs and rhs are the sub-Expressions if op is set.
+    lenfield_name is the name of the length field, or None for request lists.
+    lenfield is the Field object for the length field, or None.
+    bitfield is True if the length field is a bitmask instead of a number.
+    nmemb is the fixed size (value)of the expression, or None
+    '''
+    def __init__(self, elt, parent):
+        self.parent = parent
+
+        self.nmemb = None
+
+        self.lenfield_name = None
+        self.lenfield_type = None
+        self.lenfield = None
+        self.lenwire = False
+        self.bitfield = False
+
+        self.op = None
+        self.lhs = None
+        self.rhs = None
+
+        if elt.tag == 'list':
+            # List going into a request, which has no length field (inferred by server)
+            self.lenfield_name = elt.get('name') + '_len'
+            self.lenfield_type = 'CARD32'
+
+        elif elt.tag == 'fieldref':
+            # Standard list with a fieldref
+            self.lenfield_name = elt.text
+
+        elif elt.tag == 'valueparam':
+            # Value-mask.  The length bitmask is described by attributes.
+            self.lenfield_name = elt.get('value-mask-name')
+            self.lenfield_type = elt.get('value-mask-type')
+            self.lenwire = True
+            self.bitfield = True
+
+        elif elt.tag == 'op':
+            # Op field.  Need to recurse.
+            self.op = elt.get('op')
+            self.lhs = Expression(list(elt)[0], parent)
+            self.rhs = Expression(list(elt)[1], parent)
+
+            # Hopefully we don't have two separate length fields...
+            self.lenfield_name = self.lhs.lenfield_name
+            if self.lenfield_name == None:
+                self.lenfield_name = self.rhs.lenfield_name
+
+        elif elt.tag == 'value':
+            # Constant expression
+            self.nmemb = int(elt.text)
+
+        else:
+            # Notreached
+            raise Exception('XXX')
+
+
+    def fixed_size(self):
+        return self.nmemb != None