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/* Copyright (C) 2006 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; version 2 of the License.
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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
/*
Functions for read record cacheing with maria
Used for reading dynamic/compressed records from datafile.
Can fetch data directly from file (outside cache),
if reading a small chunk straight before the cached part (with possible
overlap).
Can be explicitly asked not to use cache (by not setting READING_NEXT in
flag) - useful for occasional out-of-cache reads, when the next read is
expected to hit the cache again.
Allows "partial read" errors in the record header (when READING_HEADER flag
is set) - unread part is bzero'ed
Note: out-of-cache reads are enabled for shared IO_CACHE's too,
as these reads will be cached by OS cache (and my_pread is always atomic)
*/
#include "maria_def.h"
my_bool _ma_read_cache(MARIA_HA *handler, IO_CACHE *info, uchar *buff,
my_off_t pos, size_t length, uint flag)
{
size_t read_length,in_buff_length;
my_off_t offset;
uchar *in_buff_pos;
DBUG_ENTER("_ma_read_cache");
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
if (unlikely(pos >= info->end_of_file) && (flag & READING_HEADER))
DBUG_RETURN(-1);
if (pos < info->pos_in_file)
{
read_length=length;
if ((my_off_t) read_length > (my_off_t) (info->pos_in_file-pos))
read_length=(uint) (info->pos_in_file-pos);
info->seek_not_done=1;
if (mysql_file_pread(info->file,buff,read_length,pos,MYF(MY_NABP)))
DBUG_RETURN(1);
if (!(length-=read_length))
DBUG_RETURN(0);
pos+=read_length;
buff+=read_length;
}
if (pos >= info->pos_in_file &&
(offset= (my_off_t) (pos - info->pos_in_file)) <
(my_off_t) (info->read_end - info->request_pos))
{
in_buff_pos=info->request_pos+(uint) offset;
in_buff_length= MY_MIN(length,(size_t) (info->read_end-in_buff_pos));
memcpy(buff,info->request_pos+(uint) offset,(size_t) in_buff_length);
if (!(length-=in_buff_length))
DBUG_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 (!_my_b_read(info,buff,length))
DBUG_RETURN(0);
read_length=info->error;
}
else
{
info->seek_not_done=1;
if ((read_length=mysql_file_pread(info->file,buff,length,pos,MYF(0))) == length)
DBUG_RETURN(0);
}
if (!(flag & READING_HEADER) || (int) read_length == -1 ||
read_length+in_buff_length < 3)
{
if ((flag & READING_HEADER) && read_length + in_buff_length == 0)
DBUG_RETURN(-1); /* End of file */
DBUG_PRINT("error",
("Error %d reading next-multi-part block (Got %d of %d bytes)",
my_errno, (int) read_length, (int) length));
if (!my_errno || my_errno == HA_ERR_FILE_TOO_SHORT)
{
if (!handler->in_check_table)
_ma_set_fatal_error(handler, HA_ERR_FILE_TOO_SHORT);
if (!my_errno)
my_errno= HA_ERR_WRONG_IN_RECORD;
}
DBUG_RETURN(1);
}
bzero(buff+read_length,MARIA_BLOCK_INFO_HEADER_LENGTH - in_buff_length -
read_length);
DBUG_RETURN(0);
} /* _ma_read_cache */
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