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/* Copyright (C) 2000-2002, 2004 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/* functions on blocks; Keys and records are saved in blocks */
#include "heapdef.h"
/*
Find record according to record-position.
The record is located by factoring position number pos into (p_0, p_1, ...)
such that
pos = SUM_i(block->level_info[i].records_under_level * p_i)
{p_0, p_1, ...} serve as indexes to descend the blocks tree.
*/
uchar *hp_find_block(HP_BLOCK *block, ulong pos)
{
register int i;
register HP_PTRS *ptr; /* block base ptr */
for (i=block->levels-1, ptr=block->root ; i > 0 ; i--)
{
ptr=(HP_PTRS*)ptr->blocks[pos/block->level_info[i].records_under_level];
pos%=block->level_info[i].records_under_level;
}
return (uchar*) ptr+ pos*block->recbuffer;
}
/*
Get one new block-of-records. Alloc ptr to block if needed
SYNOPSIS
hp_get_new_block()
block HP_BLOCK tree-like block
alloc_length OUT Amount of memory allocated from the heap
Interrupts are stopped to allow ha_panic in interrupts
RETURN
0 OK
1 Out of memory
*/
int hp_get_new_block(HP_BLOCK *block, size_t *alloc_length)
{
register uint i,j;
HP_PTRS *root;
for (i=0 ; i < block->levels ; i++)
if (block->level_info[i].free_ptrs_in_block)
break;
/*
Allocate space for leaf block plus space for upper level blocks up to
first level that has a free slot to put the pointer.
In some cases we actually allocate more then we need:
Consider e.g. a situation where we have one level 1 block and one level 0
block, the level 0 block is full and this function is called. We only
need a leaf block in this case. Nevertheless, we will get here with i=1
and will also allocate sizeof(HP_PTRS) for non-leaf block and will never
use this space.
This doesn't add much overhead - with current values of sizeof(HP_PTRS)
and my_default_record_cache_size we get about 1/128 unused memory.
*/
*alloc_length=sizeof(HP_PTRS)*i+block->records_in_block* block->recbuffer;
if (!(root=(HP_PTRS*) my_malloc(*alloc_length,MYF(MY_WME))))
return 1;
if (i == 0)
{
block->levels=1;
block->root=block->level_info[0].last_blocks=root;
}
else
{
if ((uint) i == block->levels)
{
/* Adding a new level on top of the existing ones. */
block->levels=i+1;
/*
Use first allocated HP_PTRS as a top-level block. Put the current
block tree into the first slot of a new top-level block.
*/
block->level_info[i].free_ptrs_in_block=HP_PTRS_IN_NOD-1;
((HP_PTRS**) root)[0]= block->root;
block->root=block->level_info[i].last_blocks= root++;
}
/* Occupy the free slot we've found at level i */
block->level_info[i].last_blocks->
blocks[HP_PTRS_IN_NOD - block->level_info[i].free_ptrs_in_block--]=
(uchar*) root;
/* Add a block subtree with each node having one left-most child */
for (j=i-1 ; j >0 ; j--)
{
block->level_info[j].last_blocks= root++;
block->level_info[j].last_blocks->blocks[0]=(uchar*) root;
block->level_info[j].free_ptrs_in_block=HP_PTRS_IN_NOD-1;
}
/*
root now points to last (block->records_in_block* block->recbuffer)
allocated bytes. Use it as a leaf block.
*/
block->level_info[0].last_blocks= root;
}
return 0;
}
/* free all blocks under level */
uchar *hp_free_level(HP_BLOCK *block, uint level, HP_PTRS *pos, uchar *last_pos)
{
int i,max_pos;
uchar *next_ptr;
if (level == 1)
next_ptr=(uchar*) pos+block->recbuffer;
else
{
max_pos= (block->level_info[level-1].last_blocks == pos) ?
HP_PTRS_IN_NOD - block->level_info[level-1].free_ptrs_in_block :
HP_PTRS_IN_NOD;
next_ptr=(uchar*) (pos+1);
for (i=0 ; i < max_pos ; i++)
next_ptr=hp_free_level(block,level-1,
(HP_PTRS*) pos->blocks[i],next_ptr);
}
if ((uchar*) pos != last_pos)
{
my_free((uchar*) pos,MYF(0));
return last_pos;
}
return next_ptr; /* next memory position */
}
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