Support inheriting tp_as_buffer

Author: fangerer

graalpython/com.oracle.graal.python.cext/src/capi.c

@@ -358,6 +358,11 @@ freefunc get_tp_free(PyTypeObject* obj) {
 	return obj->tp_free;
 }
 
+/** to be used from Java code only; reads native 'tp_as_buffer' field */
+PyBufferProcs* get_tp_as_buffer(PyTypeObject* obj) {
+	return obj->tp_as_buffer;
+}
+
 /** to be used from Java code only; reads native 'tp_flags' field */
 unsigned long get_tp_flags(PyTypeObject* obj) {
 	return obj->tp_flags;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/DynamicObjectNativeWrapper.java

@@ -433,6 +433,7 @@ static Object doTpAsBuffer(PythonManagedClass object, @SuppressWarnings("unused"
                         @Cached BranchProfile notMemoryview,
                         @Cached BranchProfile notBuffer,
                         @Cached BranchProfile notMmap,
+                        @Cached LookupNativeMemberInMRONode lookupTpAsBufferNode,
                         @Shared("getNativeNullNode") @Cached GetNativeNullNode getNativeNullNode,
                         @Shared("nullToSulongNode") @Cached ToSulongNode toSulongNode) {
             PythonBuiltinClass pBytes = context.getCore().lookupType(PythonBuiltinClassType.PBytes);
@@ -460,8 +461,16 @@ static Object doTpAsBuffer(PythonManagedClass object, @SuppressWarnings("unused"
                 return new PyBufferProcsWrapper(pMmap);
             }
             notMmap.enter();
-            // NULL pointer
-            return toSulongNode.execute(getNativeNullNode.execute());
+            /*
+             * Managed classes don't store PyBufferProcs objects and so there is no attribute. This
+             * is why we use managedMemberName == "".
+             */
+            Object result = lookupTpAsBufferNode.execute(object, NativeMember.TP_AS_BUFFER, "");
+            if (result == PNone.NO_VALUE) {
+                // NULL pointer
+                return toSulongNode.execute(getNativeNullNode.execute());
+            }
+            return toSulongNode.execute(result);
         }
 
         @Specialization(guards = "eq(TP_AS_SEQUENCE, key)")

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/NativeCAPISymbol.java

@@ -79,6 +79,7 @@ public enum NativeCAPISymbol implements NativeCExtSymbol {
     FUN_GET_TP_DICTOFFSET("get_tp_dictoffset"),
     FUN_GET_TP_BASICSIZE("get_tp_basicsize"),
     FUN_GET_TP_ITEMSIZE("get_tp_itemsize"),
+    FUN_GET_TP_AS_BUFFER("get_tp_as_buffer"),
     FUN_GET_BYTE_ARRAY_TYPE_ID("get_byte_array_typeid"),
     FUN_GET_PTR_ARRAY_TYPE_ID("get_ptr_array_typeid"),
     FUN_PTR_COMPARE("truffle_ptr_compare"),