mirror of
https://github.com/MariaDB/server.git
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97 lines
3.3 KiB
C
97 lines
3.3 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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/* Functions for read record cacheing with myisam */
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/* Used instead of my_b_read() to allow for no-cacheed seeks */
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#include "myisamdef.h"
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/* Copy block from cache if it`s in it. If re_read_if_possibly is */
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/* set read to cache (if after current file-position) else read to */
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/* buff */
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int _mi_read_cache(IO_CACHE *info, byte *buff, my_off_t pos, uint length,
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int flag)
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{
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uint read_length,in_buff_length;
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my_off_t offset;
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char *in_buff_pos;
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DBUG_ENTER("_mi_read_cache");
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if (pos < info->pos_in_file)
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{
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read_length=length;
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if ((my_off_t) read_length > (my_off_t) (info->pos_in_file-pos))
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read_length=(uint) (info->pos_in_file-pos);
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info->seek_not_done=1;
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if (my_pread(info->file,buff,read_length,pos,MYF(MY_NABP)))
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DBUG_RETURN(1);
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if (!(length-=read_length))
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DBUG_RETURN(0);
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pos+=read_length;
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buff+=read_length;
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}
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if ((offset= (my_off_t) (pos - info->pos_in_file)) <
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(my_off_t) (info->rc_end - info->rc_request_pos))
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{
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in_buff_pos=info->rc_request_pos+(uint) offset;
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in_buff_length= min(length,(uint) (info->rc_end-in_buff_pos));
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memcpy(buff,info->rc_request_pos+(uint) offset,(size_t) in_buff_length);
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if (!(length-=in_buff_length))
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DBUG_RETURN(0);
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pos+=in_buff_length;
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buff+=in_buff_length;
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}
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else
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in_buff_length=0;
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if (flag & READING_NEXT)
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{
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if (pos != (info->pos_in_file +
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(uint) (info->rc_end - info->rc_request_pos)))
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{
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info->pos_in_file=pos; /* Force start here */
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info->rc_pos=info->rc_end=info->rc_request_pos; /* Everything used */
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info->seek_not_done=1;
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}
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else
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info->rc_pos=info->rc_end; /* All block used */
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if (!(*info->read_function)(info,buff,length))
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DBUG_RETURN(0);
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if (!(flag & READING_HEADER) || info->error == -1 ||
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(uint) info->error+in_buff_length < 3)
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{
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if (!my_errno || my_errno == -1)
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my_errno=HA_ERR_WRONG_IN_RECORD;
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DBUG_RETURN(1);
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}
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bzero(buff+info->error,MI_BLOCK_INFO_HEADER_LENGTH - in_buff_length -
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(uint) info->error);
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DBUG_RETURN(0);
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}
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info->seek_not_done=1;
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if ((read_length=my_pread(info->file,buff,length,pos,MYF(0))) == length)
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DBUG_RETURN(0);
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if (!(flag & READING_HEADER) || (int) read_length == -1 ||
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read_length+in_buff_length < 3)
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{
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if (!my_errno || my_errno == -1)
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my_errno=HA_ERR_WRONG_IN_RECORD;
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DBUG_RETURN(1);
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}
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bzero(buff+read_length,MI_BLOCK_INFO_HEADER_LENGTH - in_buff_length -
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read_length);
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DBUG_RETURN(0);
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} /* _mi_read_cache */
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