src/include/cdb/htupfifo.h

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*-------------------------------------------------------------------------
 *
 * htupfifo.h
 *	   A FIFO queue for HeapTuples.
 *
 * NOTES:
 *	   This FIFO doesn't do any tuple-copying right now.  It may be that we
 *	   need to take memory-contexts into account in the future, and that
 *	   would mean we would possibly need to make copies of tuples when they
 *	   are added and/or when they are retrieved.
 *
 *
 *-------------------------------------------------------------------------
 */
#ifndef HTUPFIFO_H
#define HTUPFIFO_H

#ifdef WIN32
typedef unsigned int uint;
#endif


/* An entry in the HeapTuple FIFO.	Entries are formed into queues. */
typedef struct htf_entry_data
{
	/* The HeapTuple itself. */
	HeapTuple	htup;

	/* The next entry in the FIFO. */
	struct htf_entry_data *p_next;

}	htf_entry_data, *htf_entry;


/* A HeapTuple FIFO.  The FIFO is dynamically sizable, since there is no
 * specified upper bound on the number of entries in the FIFO.
 */
typedef struct htup_fifo_state
{
	htf_entry	p_first;
	htf_entry	p_last;

	htf_entry	freelist;
	int			freelist_count;

	/* A count of HeapTuples in the FIFO. */
	int			tup_count;

	/*
	 * An estimate of the current in-memory size of the FIFO's contents, in
	 * bytes.
	 */
	int			curr_mem_size;

	/*
	 * The maximum size that the FIFO is allowed to grow to, in bytes, before
	 * it will cause an error to be reported.
	 */
	uint		max_mem_size;

}	htup_fifo_state, *htup_fifo;


#define MIN_HTUPFIFO_KB 8


extern htup_fifo htfifo_create(int max_mem_kb);
extern void htfifo_init(htup_fifo htf, int max_mem_kb);
extern void htfifo_destroy(htup_fifo htf);

extern void htfifo_addtuple(htup_fifo htf, HeapTuple htup);
extern HeapTuple htfifo_gettuple(htup_fifo htf);

#endif   /* HTUPFIFO_H */