item_buff.cpp
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:3k
- /* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult 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 */
- /* Buffers to save and compare item values */
- #include "mysql_priv.h"
- /*
- ** Create right type of item_buffer for an item
- */
- Item_buff *new_Item_buff(THD *thd, Item *item)
- {
- if (item->type() == Item::FIELD_ITEM &&
- !(((Item_field *) item)->field->flags & BLOB_FLAG))
- return new Item_field_buff((Item_field *) item);
- if (item->result_type() == STRING_RESULT)
- return new Item_str_buff(thd, (Item_field *) item);
- if (item->result_type() == INT_RESULT)
- return new Item_int_buff((Item_field *) item);
- return new Item_real_buff(item);
- }
- Item_buff::~Item_buff() {}
- /*
- ** Compare with old value and replace value with new value
- ** Return true if values have changed
- */
- Item_str_buff::Item_str_buff(THD *thd, Item *arg)
- :item(arg), value(min(arg->max_length, thd->variables.max_sort_length))
- {}
- bool Item_str_buff::cmp(void)
- {
- String *res;
- bool tmp;
- if ((res=item->val_str(&tmp_value)))
- res->length(min(res->length(), value.alloced_length()));
- if (null_value != item->null_value)
- {
- if ((null_value= item->null_value))
- return TRUE; // New value was null
- tmp=TRUE;
- }
- else if (null_value)
- return 0; // new and old value was null
- else
- tmp= sortcmp(&value,res,item->collation.collation) != 0;
- if (tmp)
- value.copy(*res); // Remember for next cmp
- return tmp;
- }
- Item_str_buff::~Item_str_buff()
- {
- item=0; // Safety
- }
- bool Item_real_buff::cmp(void)
- {
- double nr=item->val();
- if (null_value != item->null_value || nr != value)
- {
- null_value= item->null_value;
- value=nr;
- return TRUE;
- }
- return FALSE;
- }
- bool Item_int_buff::cmp(void)
- {
- longlong nr=item->val_int();
- if (null_value != item->null_value || nr != value)
- {
- null_value= item->null_value;
- value=nr;
- return TRUE;
- }
- return FALSE;
- }
- bool Item_field_buff::cmp(void)
- {
- bool tmp= field->cmp(buff) != 0; // This is not a blob!
- if (tmp)
- field->get_image(buff,length,field->charset());
- if (null_value != field->is_null())
- {
- null_value= !null_value;
- tmp=TRUE;
- }
- return tmp;
- }
- /*****************************************************************************
- ** Instansiate templates
- *****************************************************************************/
- #ifdef __GNUC__
- template class List<Item_buff>;
- template class List_iterator<Item_buff>;
- #endif