mariadb/storage/innobase/include/buf0buddy.h

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/**************************************************//**
@file include/buf0buddy.h
Binary buddy allocator for compressed pages

Created December 2006 by Marko Makela
*******************************************************/

#ifndef buf0buddy_h
#define buf0buddy_h

#include "buf0types.h"

/**
@param[in]	block size in bytes
@return index of buf_pool.zip_free[], or BUF_BUDDY_SIZES */
inline
ulint
buf_buddy_get_slot(ulint size)
{
	ulint	i;
	ulint	s;

	ut_ad(ut_is_2pow(size));
	ut_ad(size >= UNIV_ZIP_SIZE_MIN);
	ut_ad(size <= srv_page_size);

	for (i = 0, s = BUF_BUDDY_LOW; s < size; i++, s <<= 1) {
	}
	ut_ad(i <= BUF_BUDDY_SIZES);
	return i;
}

/** Allocate a ROW_FORMAT=COMPRESSED block.
@param i      index of buf_pool.zip_free[] or BUF_BUDDY_SIZES
@param lru    assigned to true if buf_pool.mutex was temporarily released
@return allocated block, never NULL */
byte *buf_buddy_alloc_low(ulint i, bool *lru) MY_ATTRIBUTE((malloc));

/** Allocate a ROW_FORMAT=COMPRESSED block.
@param size   compressed page size in bytes
@param lru    assigned to true if buf_pool.mutex was temporarily released
@return allocated block, never NULL */
inline byte *buf_buddy_alloc(ulint size, bool *lru= nullptr)
{
  return buf_buddy_alloc_low(buf_buddy_get_slot(size), lru);
}

/** Deallocate a block.
@param[in]	buf	block to be freed, must not be pointed to
			by the buffer pool
@param[in]	i	index of buf_pool.zip_free[], or BUF_BUDDY_SIZES */
void buf_buddy_free_low(void* buf, ulint i);

/** Deallocate a block.
@param[in]	buf	block to be freed, must not be pointed to
			by the buffer pool
@param[in]	size	block size in bytes */
inline void buf_buddy_free(void* buf, ulint size)
{
	buf_buddy_free_low(buf, buf_buddy_get_slot(size));
}

/** Try to reallocate a block.
@param[in]	buf		block to be reallocated, must be pointed
to by the buffer pool
@param[in]	size		block size, up to srv_page_size
@retval false	if failed because of no free blocks. */
bool buf_buddy_realloc(void* buf, ulint size);

/** Combine all pairs of free buddies. */
void buf_buddy_condense_free();
#endif /* buf0buddy_h */