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diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
new file mode 100644
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+++ b/include/qapi/visitor-impl.h
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+/*
+ * Core Definitions for QAPI Visitor implementations
+ *
+ * Copyright (C) 2012-2016 Red Hat, Inc.
+ *
+ * Author: Paolo Bonizni <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+#ifndef QAPI_VISITOR_IMPL_H
+#define QAPI_VISITOR_IMPL_H
+
+#include "qapi/visitor.h"
+
+/*
+ * This file describes the callback interface for implementing a QAPI
+ * visitor.  For the client interface, see visitor.h.  When
+ * implementing the callbacks, it is easiest to declare a struct with
+ * 'Visitor visitor;' as the first member.  A callback's contract
+ * matches the corresponding public functions' contract unless stated
+ * otherwise.  In the comments below, some callbacks are marked "must
+ * be set for $TYPE visits to work"; if a visitor implementation omits
+ * that callback, it should also document that it is only useful for a
+ * subset of QAPI.
+ */
+
+/*
+ * There are four classes of visitors; setting the class determines
+ * how QAPI enums are visited, as well as what additional restrictions
+ * can be asserted.  The values are intentionally chosen so as to
+ * permit some assertions based on whether a given bit is set (that
+ * is, some assertions apply to input and clone visitors, some
+ * assertions apply to output and clone visitors).
+ */
+typedef enum VisitorType {
+    VISITOR_INPUT = 1,
+    VISITOR_OUTPUT = 2,
+    VISITOR_CLONE = 3,
+    VISITOR_DEALLOC = 4,
+} VisitorType;
+
+struct Visitor
+{
+    /*
+     * Only input visitors may fail!
+     */
+
+    /* Must be set to visit structs */
+    bool (*start_struct)(Visitor *v, const char *name, void **obj,
+                         size_t size, Error **errp);
+
+    /* Optional; intended for input visitors */
+    bool (*check_struct)(Visitor *v, Error **errp);
+
+    /* Must be set to visit structs */
+    void (*end_struct)(Visitor *v, void **obj);
+
+    /* Must be set; implementations may require @list to be non-null,
+     * but must document it. */
+    bool (*start_list)(Visitor *v, const char *name, GenericList **list,
+                       size_t size, Error **errp);
+
+    /* Must be set */
+    GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size);
+
+    /* Optional; intended for input visitors */
+    bool (*check_list)(Visitor *v, Error **errp);
+
+    /* Must be set */
+    void (*end_list)(Visitor *v, void **list);
+
+    /* Must be set by input and clone visitors to visit alternates */
+    bool (*start_alternate)(Visitor *v, const char *name,
+                            GenericAlternate **obj, size_t size,
+                            Error **errp);
+
+    /* Optional */
+    void (*end_alternate)(Visitor *v, void **obj);
+
+    /* Must be set */
+    bool (*type_int64)(Visitor *v, const char *name, int64_t *obj,
+                       Error **errp);
+
+    /* Must be set */
+    bool (*type_uint64)(Visitor *v, const char *name, uint64_t *obj,
+                        Error **errp);
+
+    /* Optional; fallback is type_uint64() */
+    bool (*type_size)(Visitor *v, const char *name, uint64_t *obj,
+                      Error **errp);
+
+    /* Must be set */
+    bool (*type_bool)(Visitor *v, const char *name, bool *obj, Error **errp);
+
+    /* Must be set */
+    bool (*type_str)(Visitor *v, const char *name, char **obj, Error **errp);
+
+    /* Must be set to visit numbers */
+    bool (*type_number)(Visitor *v, const char *name, double *obj,
+                        Error **errp);
+
+    /* Must be set to visit arbitrary QTypes */
+    bool (*type_any)(Visitor *v, const char *name, QObject **obj,
+                     Error **errp);
+
+    /* Must be set to visit explicit null values.  */
+    bool (*type_null)(Visitor *v, const char *name, QNull **obj,
+                      Error **errp);
+
+    /* Must be set for input visitors to visit structs, optional otherwise.
+       The core takes care of the return type in the public interface. */
+    void (*optional)(Visitor *v, const char *name, bool *present);
+
+    /* Optional */
+    bool (*policy_reject)(Visitor *v, const char *name,
+                          unsigned special_features, Error **errp);
+
+    /* Optional */
+    bool (*policy_skip)(Visitor *v, const char *name,
+                        unsigned special_features);
+
+    /* Must be set */
+    VisitorType type;
+
+    /* Optional */
+    struct CompatPolicy compat_policy;
+
+    /* Must be set for output visitors, optional otherwise. */
+    void (*complete)(Visitor *v, void *opaque);
+
+    /* Must be set */
+    void (*free)(Visitor *v);
+};
+
+#endif