postgresql/src/include/nodes/extensible.h

/*-------------------------------------------------------------------------
 *
 * extensible.h
 *    Definitions for extensible node type
 *
 *
 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/nodes/extensible.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef EXTENSIBLE_H
#define EXTENSIBLE_H

#include "nodes/nodes.h"

#define EXTNODENAME_MAX_LEN					64

/*
 * An extensible node is a new type of node defined by an extension.  The
 * type is always T_ExtensibleNode, while the extnodename identifies the
 * specific type of node.  extnodename can be looked up to find the
 * ExtensibleNodeMethods for this node type.
 */
typedef struct ExtensibleNode
{
	NodeTag		type;
	const char *extnodename;	/* identifier of ExtensibleNodeMethods */
} ExtensibleNode;

/*
 * node_size is the size of an extensible node of this type in bytes.
 *
 * nodeCopy is a function which performs a deep copy from oldnode to newnode.
 * It does not need to copy type or extnodename, which are copied by the
 * core system.
 *
 * nodeEqual is a function which performs a deep equality comparison between
 * a and b and returns true or false accordingly.  It does not need to compare
 * type or extnodename, which are compared by the core system.
 *
 * nodeOut is a serialization function for the node type.  It should use the
 * output conventions typical for outfuncs.c.  It does not need to output
 * type or extnodename; the core system handles those.
 *
 * nodeRead is a deserialization function for the node type.  It does not need
 * to read type or extnodename; the core system handles those.  It should fetch
 * the next token using pg_strtok() from the current input stream, and then
 * reconstruct the private fields according to the manner in readfuncs.c.
 *
 * All callbacks are mandatory.
 */
typedef struct ExtensibleNodeMethods
{
	const char *extnodename;
	Size		node_size;
	void	  (*nodeCopy)(struct ExtensibleNode *newnode,
						  const struct ExtensibleNode *oldnode);
	bool	  (*nodeEqual)(const struct ExtensibleNode *a,
						   const struct ExtensibleNode *b);
	void	  (*nodeOut)(struct StringInfoData *str,
						 const struct ExtensibleNode *node);
	void	  (*nodeRead)(struct ExtensibleNode *node);
} ExtensibleNodeMethods;

extern void RegisterExtensibleNodeMethods(const ExtensibleNodeMethods *method);
extern const ExtensibleNodeMethods *GetExtensibleNodeMethods(const char *name,
						 bool missing_ok);

#endif	/* EXTENSIBLE_H */