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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 */
/* Functions for read record cacheing with nisam */
/* Used instead of my_b_read() to allow for no-cacheed seeks */
#include "isamdef.h"
#define READING_NEXT 1
#define READING_HEADER 2
/* Copy block from cache if it`s in it. If re_read_if_possibly is */
/* set read to cache (if after current file-position) else read to */
/* buff */
int _nisam_read_cache(IO_CACHE *info, byte *buff, ulong pos, uint length,
int flag)
{
uint read_length,in_buff_length;
ulong offset;
char *in_buff_pos;
if (pos < info->pos_in_file)
{
read_length= (uint) min((ulong) length,(ulong) (info->pos_in_file-pos));
info->seek_not_done=1;
VOID(my_seek(info->file,pos,MY_SEEK_SET,MYF(0)));
if (my_read(info->file,buff,read_length,MYF(MY_NABP)))
return 1;
if (!(length-=read_length))
return 0;
pos+=read_length;
buff+=read_length;
}
if ((offset=pos - (ulong) info->pos_in_file) <
(ulong) (info->read_end - info->request_pos))
{
in_buff_pos=info->request_pos+(uint) offset;
in_buff_length= min(length,(uint) (info->read_end-in_buff_pos));
memcpy(buff,info->request_pos+(uint) offset,(size_t) in_buff_length);
if (!(length-=in_buff_length))
return 0;
pos+=in_buff_length;
buff+=in_buff_length;
}
else
in_buff_length=0;
if (flag & READING_NEXT)
{
if (pos != ((info)->pos_in_file +
(uint) ((info)->read_end - (info)->request_pos)))
{
info->pos_in_file=pos; /* Force start here */
info->read_pos=info->read_end=info->request_pos; /* Everything used */
info->seek_not_done=1;
}
else
info->read_pos=info->read_end; /* All block used */
if (!(*info->read_function)(info,buff,length))
return 0;
if (!(flag & READING_HEADER) || info->error == -1 ||
(uint) info->error+in_buff_length < 3)
return 1;
if (BLOCK_INFO_HEADER_LENGTH < in_buff_length + (uint) info->error)
bzero(buff+info->error,BLOCK_INFO_HEADER_LENGTH - in_buff_length -
(uint) info->error);
return 0;
}
info->seek_not_done=1;
VOID(my_seek(info->file,pos,MY_SEEK_SET,MYF(0)));
if ((read_length=my_read(info->file,buff,length,MYF(0))) == length)
return 0;
if (!(flag & READING_HEADER) || (int) read_length == -1 ||
read_length+in_buff_length < 3)
return 1;
bzero(buff+read_length,BLOCK_INFO_HEADER_LENGTH - in_buff_length -
read_length);
return 0;
} /* _nisam_read_cache */
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