memory_pool.h

/*
 * Copyright 2009 Nicolai Hähnle <[email protected]>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * on the rights to use, copy, modify, merge, publish, distribute, sub
 * license, and/or sell copies of the Software, and to permit persons to whom
 * the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE. */

#ifndef MEMORY_POOL_H
#define MEMORY_POOL_H

struct memory_block;

/**
 * Provides a pool of memory that can quickly be allocated from, at the
 * cost of being unable to explicitly free one of the allocated blocks.
 * Instead, the entire pool can be freed at once.
 *
 * The idea is to allow one to quickly allocate a flexible amount of
 * memory during operations like shader compilation while avoiding
 * reference counting headaches.
 */
struct memory_pool {
	unsigned char * head;
	unsigned char * end;
	unsigned int total_allocated;
	struct memory_block * blocks;
};


void memory_pool_init(struct memory_pool * pool);
void memory_pool_destroy(struct memory_pool * pool);
void * memory_pool_malloc(struct memory_pool * pool, unsigned int bytes);


/**
 * Generic helper for growing an array that has separate size/count
 * and reserved counters to accommodate up to num new element.
 *
 *  type * Array;
 *  unsigned int Size;
 *  unsigned int Reserved;
 *
 * memory_pool_array_reserve(pool, type, Array, Size, Reserved, k);
 * assert(Size + k < Reserved);
 *
 * \note Size is not changed by this macro.
 *
 * \warning Array, Size, Reserved have to be lvalues and may be evaluated
 * several times.
 */
#define memory_pool_array_reserve(pool, type, array, size, reserved, num) do { \
	unsigned int _num = (num); \
	if ((size) + _num > (reserved)) { \
		unsigned int newreserve = (reserved) * 2; \
		type * newarray; \
		if (newreserve < _num) \
			newreserve = 4 * _num; /* arbitrary heuristic */ \
		newarray = memory_pool_malloc((pool), newreserve * sizeof(type)); \
		memcpy(newarray, (array), (size) * sizeof(type)); \
		(array) = newarray; \
		(reserved) = newreserve; \
	} \
} while(0)

#endif /* MEMORY_POOL_H */