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110 lines
3.2 KiB
C
110 lines
3.2 KiB
C
/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/*
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Read a record with random-access. The position to the record must
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get by mrg_info(). The next record can be read with pos= -1 */
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#include "mrgdef.h"
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static MRG_TABLE *find_table(MRG_TABLE *start,MRG_TABLE *end,mrg_off_t pos);
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/*
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If filepos == -1, read next
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Returns same as nisam_rrnd:
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0 = Ok.
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1 = Record deleted.
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-1 = EOF (or something, errno should be HA_ERR_END_OF_FILE)
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*/
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int mrg_rrnd(MRG_INFO *info,byte *buf,mrg_off_t filepos)
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{
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int error;
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N_INFO *isam_info;
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if (filepos == ~(mrg_off_t) 0) /* Can't use HA_POS_ERROR */
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{
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if (!info->current_table)
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{
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if (info->open_tables == info->end_table)
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{ /* No tables */
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my_errno=HA_ERR_END_OF_FILE;
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return -1;
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}
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isam_info=(info->current_table=info->open_tables)->table;
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if (info->cache_in_use)
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nisam_extra(isam_info,HA_EXTRA_CACHE);
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filepos=isam_info->s->pack.header_length;
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isam_info->lastinx= (uint) -1; /* Can't forward or backward */
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}
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else
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{
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isam_info=info->current_table->table;
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filepos= isam_info->nextpos;
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}
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for (;;)
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{
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isam_info->update&= HA_STATE_CHANGED;
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if ((error=(*isam_info->s->read_rnd)(isam_info,(byte*) buf,
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filepos,1)) >= 0 ||
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my_errno != HA_ERR_END_OF_FILE)
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return (error);
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if (info->cache_in_use)
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nisam_extra(info->current_table->table,HA_EXTRA_NO_CACHE);
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if (info->current_table+1 == info->end_table)
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return(-1);
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info->current_table++;
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info->last_used_table=info->current_table;
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if (info->cache_in_use)
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nisam_extra(info->current_table->table,HA_EXTRA_CACHE);
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info->current_table->file_offset=
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info->current_table[-1].file_offset+
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info->current_table[-1].table->s->state.data_file_length;
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isam_info=info->current_table->table;
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filepos=isam_info->s->pack.header_length;
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isam_info->lastinx= (uint) -1;
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}
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}
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info->current_table=find_table(info->open_tables,
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info->end_table-1,filepos);
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isam_info=info->current_table->table;
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isam_info->update&= HA_STATE_CHANGED;
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return ((*isam_info->s->read_rnd)(isam_info,(byte*) buf,
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(ulong) (filepos -
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info->current_table->file_offset),
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0));
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}
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/* Find which table to use according to file-pos */
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static MRG_TABLE *find_table(MRG_TABLE *start,MRG_TABLE *end,mrg_off_t pos)
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{
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MRG_TABLE *mid;
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while (start != end)
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{
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mid=start+((uint) (end-start)+1)/2;
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if (mid->file_offset > pos)
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end=mid-1;
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else
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start=mid;
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}
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return start;
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}
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