summaryrefslogtreecommitdiffstats
path: root/storage/maria/ma_cache.c
diff options
context:
space:
mode:
Diffstat (limited to 'storage/maria/ma_cache.c')
-rw-r--r--storage/maria/ma_cache.c119
1 files changed, 119 insertions, 0 deletions
diff --git a/storage/maria/ma_cache.c b/storage/maria/ma_cache.c
new file mode 100644
index 00000000..59cc0ad6
--- /dev/null
+++ b/storage/maria/ma_cache.c
@@ -0,0 +1,119 @@
+/* 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 */