my_alloc.h

vc连接mysql的封装类

/* Copyright (C) 2000 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; either version 2 of the License, or
   (at your option) any later version.

   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 */

/* 
   Data structures for mysys/my_alloc.c (root memory allocator)
*/

#ifndef _my_alloc_h
#define _my_alloc_h

#define ALLOC_MAX_BLOCK_TO_DROP			4096
#define ALLOC_MAX_BLOCK_USAGE_BEFORE_DROP	10

typedef struct st_used_mem
{				   /* struct for once_alloc (block) */
  struct st_used_mem *next;	   /* Next block in use */
  unsigned int	left;		   /* memory left in block  */
  unsigned int	size;		   /* size of block */
} USED_MEM;


typedef struct st_mem_root
{
  USED_MEM *free;                  /* blocks with free memory in it */
  USED_MEM *used;                  /* blocks almost without free memory */
  USED_MEM *pre_alloc;             /* preallocated block */
  /* if block have less memory it will be put in 'used' list */
  unsigned int min_malloc;
  unsigned int block_size;         /* initial block size */
  unsigned int block_num;          /* allocated blocks counter */
  /* 
     first free block in queue test counter (if it exceed 
     MAX_BLOCK_USAGE_BEFORE_DROP block will be dropped in 'used' list)
  */
  unsigned int first_block_usage;

  void (*error_handler)(void);
} MEM_ROOT;
#endif