~drizzle-trunk/drizzle/development

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
/* 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
  {
    dont_break();		/* Dont allow SIGHUP or SIGINT */
    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;
    allow_break();		/* Allow SIGHUP & SIGINT */
  }
  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 */
}