myrg_rrnd.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:4k
- /* 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 */
- /*
- Read a record with random-access. The position to the record must
- get by myrg_info(). The next record can be read with pos= -1 */
- #include "myrg_def.h"
- static MYRG_TABLE *find_table(MYRG_TABLE *start,MYRG_TABLE *end,ulonglong pos);
- /*
- If filepos == HA_OFFSET_ERROR, read next
- Returns same as mi_rrnd:
- 0 = Ok.
- HA_ERR_RECORD_DELETED = Record is deleted.
- HA_ERR_END_OF_FILE = EOF.
- */
- int myrg_rrnd(MYRG_INFO *info,byte *buf,ulonglong filepos)
- {
- int error;
- MI_INFO *isam_info;
- DBUG_ENTER("myrg_rrnd");
- DBUG_PRINT("info",("offset: %lu", (ulong) filepos));
- if (filepos == HA_OFFSET_ERROR)
- {
- if (!info->current_table)
- {
- if (info->open_tables == info->end_table)
- { /* No tables */
- DBUG_RETURN(my_errno=HA_ERR_END_OF_FILE);
- }
- isam_info=(info->current_table=info->open_tables)->table;
- if (info->cache_in_use)
- mi_extra(isam_info,HA_EXTRA_CACHE,(byte*) &info->cache_size);
- filepos=isam_info->s->pack.header_length;
- isam_info->lastinx= (uint) -1; /* Can't forward or backward */
- }
- else
- {
- isam_info=info->current_table->table;
- filepos= isam_info->nextpos;
- }
- for (;;)
- {
- isam_info->update&= HA_STATE_CHANGED;
- if ((error=(*isam_info->s->read_rnd)(isam_info,(byte*) buf,
- (my_off_t) filepos,1)) !=
- HA_ERR_END_OF_FILE)
- DBUG_RETURN(error);
- if (info->cache_in_use)
- mi_extra(info->current_table->table, HA_EXTRA_NO_CACHE,
- (byte*) &info->cache_size);
- if (info->current_table+1 == info->end_table)
- DBUG_RETURN(HA_ERR_END_OF_FILE);
- info->current_table++;
- info->last_used_table=info->current_table;
- if (info->cache_in_use)
- mi_extra(info->current_table->table, HA_EXTRA_CACHE,
- (byte*) &info->cache_size);
- info->current_table->file_offset=
- info->current_table[-1].file_offset+
- info->current_table[-1].table->state->data_file_length;
- isam_info=info->current_table->table;
- filepos=isam_info->s->pack.header_length;
- isam_info->lastinx= (uint) -1;
- }
- }
- info->current_table=find_table(info->open_tables,
- info->end_table-1,filepos);
- isam_info=info->current_table->table;
- isam_info->update&= HA_STATE_CHANGED;
- DBUG_RETURN((*isam_info->s->read_rnd)
- (isam_info, (byte*) buf,
- (my_off_t) (filepos - info->current_table->file_offset),
- 0));
- }
- /* Find which table to use according to file-pos */
- static MYRG_TABLE *find_table(MYRG_TABLE *start, MYRG_TABLE *end,
- ulonglong pos)
- {
- MYRG_TABLE *mid;
- DBUG_ENTER("find_table");
- while (start != end)
- {
- mid=start+((uint) (end-start)+1)/2;
- if (mid->file_offset > pos)
- end=mid-1;
- else
- start=mid;
- }
- DBUG_PRINT("info",("offset: %lu, table: %s",
- (ulong) pos, start->table->filename));
- DBUG_RETURN(start);
- }