1/* Copyright (C) 2006 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; version 2 of the License.
6
7 This program is distributed in the hope that it will be useful,
8 but WITHOUT ANY WARRANTY; without even the implied warranty of
9 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 GNU General Public License for more details.
11
12 You should have received a copy of the GNU General Public License
13 along with this program; if not, write to the Free Software
14 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
15
16/*
17 Functions for read record cacheing with maria
18 Used for reading dynamic/compressed records from datafile.
19
20 Can fetch data directly from file (outside cache),
21 if reading a small chunk straight before the cached part (with possible
22 overlap).
23
24 Can be explicitly asked not to use cache (by not setting READING_NEXT in
25 flag) - useful for occasional out-of-cache reads, when the next read is
26 expected to hit the cache again.
27
28 Allows "partial read" errors in the record header (when READING_HEADER flag
29 is set) - unread part is bzero'ed
30
31 Note: out-of-cache reads are enabled for shared IO_CACHE's too,
32 as these reads will be cached by OS cache (and my_pread is always atomic)
33*/
34
35
36#include "maria_def.h"
37
38my_bool _ma_read_cache(MARIA_HA *handler, IO_CACHE *info, uchar *buff,
39 my_off_t pos, size_t length, uint flag)
40{
41 size_t read_length,in_buff_length;
42 my_off_t offset;
43 uchar *in_buff_pos;
44 DBUG_ENTER("_ma_read_cache");
45 DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
46
47 if (pos < info->pos_in_file)
48 {
49 read_length=length;
50 if ((my_off_t) read_length > (my_off_t) (info->pos_in_file-pos))
51 read_length=(uint) (info->pos_in_file-pos);
52 info->seek_not_done=1;
53 if (mysql_file_pread(info->file,buff,read_length,pos,MYF(MY_NABP)))
54 DBUG_RETURN(1);
55 if (!(length-=read_length))
56 DBUG_RETURN(0);
57 pos+=read_length;
58 buff+=read_length;
59 }
60 if (pos >= info->pos_in_file &&
61 (offset= (my_off_t) (pos - info->pos_in_file)) <
62 (my_off_t) (info->read_end - info->request_pos))
63 {
64 in_buff_pos=info->request_pos+(uint) offset;
65 in_buff_length= MY_MIN(length,(size_t) (info->read_end-in_buff_pos));
66 memcpy(buff,info->request_pos+(uint) offset,(size_t) in_buff_length);
67 if (!(length-=in_buff_length))
68 DBUG_RETURN(0);
69 pos+=in_buff_length;
70 buff+=in_buff_length;
71 }
72 else
73 in_buff_length=0;
74 if (flag & READING_NEXT)
75 {
76 if (pos != (info->pos_in_file +
77 (uint) (info->read_end - info->request_pos)))
78 {
79 info->pos_in_file=pos; /* Force start here */
80 info->read_pos=info->read_end=info->request_pos; /* Everything used */
81 info->seek_not_done=1;
82 }
83 else
84 info->read_pos=info->read_end; /* All block used */
85 if (!_my_b_read(info,buff,length))
86 DBUG_RETURN(0);
87 read_length=info->error;
88 }
89 else
90 {
91 info->seek_not_done=1;
92 if ((read_length=mysql_file_pread(info->file,buff,length,pos,MYF(0))) == length)
93 DBUG_RETURN(0);
94 }
95 if (!(flag & READING_HEADER) || (int) read_length == -1 ||
96 read_length+in_buff_length < 3)
97 {
98 DBUG_PRINT("error",
99 ("Error %d reading next-multi-part block (Got %d bytes)",
100 my_errno, (int) read_length));
101 if (!my_errno || my_errno == HA_ERR_FILE_TOO_SHORT)
102 {
103 if (!handler->in_check_table)
104 _ma_set_fatal_error(handler->s, HA_ERR_WRONG_IN_RECORD);
105 else
106 my_errno= HA_ERR_WRONG_IN_RECORD;
107 }
108 DBUG_RETURN(1);
109 }
110 bzero(buff+read_length,MARIA_BLOCK_INFO_HEADER_LENGTH - in_buff_length -
111 read_length);
112 DBUG_RETURN(0);
113} /* _ma_read_cache */
114