polardbxengine/storage/heap/hp_block.cc

/* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

/* functions on blocks; Keys and records are saved in blocks */

#include <stddef.h>
#include <sys/types.h>

#include "my_inttypes.h"
#include "mysql/service_mysql_alloc.h"
#include "storage/heap/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) {
  int i;
  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) {
  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 +
                  (ulonglong)block->records_in_block * block->recbuffer;
  if (!(root = (HP_PTRS *)my_malloc(hp_key_memory_HP_PTRS, *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(pos);
    return last_pos;
  }
  return next_ptr; /* next memory position */
}