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/* 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 mrg_info(). The next record can be read with pos= -1 */
#include "mrg_def.h"
static MRG_TABLE *find_table(MRG_TABLE *start,MRG_TABLE *end,mrg_off_t pos);
/*
If filepos == -1, read next
Returns same as nisam_rrnd:
0 = Ok.
1 = Record deleted.
-1 = EOF (or something, errno should be HA_ERR_END_OF_FILE)
*/
int mrg_rrnd(MRG_INFO *info,byte *buf,mrg_off_t filepos)
{
int error;
N_INFO *isam_info;
if (filepos == ~(mrg_off_t) 0) /* Can't use HA_POS_ERROR */
{
if (!info->current_table)
{
if (info->open_tables == info->end_table)
{ /* No tables */
my_errno=HA_ERR_END_OF_FILE;
return -1;
}
isam_info=(info->current_table=info->open_tables)->table;
if (info->cache_in_use)
nisam_extra(isam_info,HA_EXTRA_CACHE);
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,
filepos,1)) >= 0 ||
my_errno != HA_ERR_END_OF_FILE)
return (error);
if (info->cache_in_use)
nisam_extra(info->current_table->table,HA_EXTRA_NO_CACHE);
if (info->current_table+1 == info->end_table)
return(-1);
info->current_table++;
info->last_used_table=info->current_table;
if (info->cache_in_use)
nisam_extra(info->current_table->table,HA_EXTRA_CACHE);
info->current_table->file_offset=
info->current_table[-1].file_offset+
info->current_table[-1].table->s->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;
return ((*isam_info->s->read_rnd)(isam_info,(byte*) buf,
(ulong) (filepos -
info->current_table->file_offset),
0));
}
/* Find which table to use according to file-pos */
static MRG_TABLE *find_table(MRG_TABLE *start,MRG_TABLE *end,mrg_off_t pos)
{
MRG_TABLE *mid;
while (start != end)
{
mid=start+((uint) (end-start)+1)/2;
if (mid->file_offset > pos)
end=mid-1;
else
start=mid;
}
return start;
}
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