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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 :
38 : my_bool _ma_read_cache(IO_CACHE *info, uchar *buff, my_off_t pos,
39 : size_t length, uint flag)
40 108969 : {
41 : size_t read_length,in_buff_length;
42 : my_off_t offset;
43 : uchar *in_buff_pos;
44 108969 : DBUG_ENTER("_ma_read_cache");
45 :
46 108988 : if (pos < info->pos_in_file)
47 : {
48 350 : read_length=length;
49 350 : if ((my_off_t) read_length > (my_off_t) (info->pos_in_file-pos))
50 0 : read_length=(uint) (info->pos_in_file-pos);
51 350 : info->seek_not_done=1;
52 350 : if (my_pread(info->file,buff,read_length,pos,MYF(MY_NABP)))
53 0 : DBUG_RETURN(1);
54 372 : if (!(length-=read_length))
55 372 : DBUG_RETURN(0);
56 0 : pos+=read_length;
57 0 : buff+=read_length;
58 : }
59 108695 : if (pos >= info->pos_in_file &&
60 : (offset= (my_off_t) (pos - info->pos_in_file)) <
61 : (my_off_t) (info->read_end - info->request_pos))
62 : {
63 108104 : in_buff_pos=info->request_pos+(uint) offset;
64 108104 : in_buff_length= min(length,(size_t) (info->read_end-in_buff_pos));
65 108104 : memcpy(buff,info->request_pos+(uint) offset,(size_t) in_buff_length);
66 108104 : if (!(length-=in_buff_length))
67 108047 : DBUG_RETURN(0);
68 57 : pos+=in_buff_length;
69 57 : buff+=in_buff_length;
70 : }
71 : else
72 534 : in_buff_length=0;
73 591 : if (flag & READING_NEXT)
74 : {
75 315 : if (pos != (info->pos_in_file +
76 : (uint) (info->read_end - info->request_pos)))
77 : {
78 30 : info->pos_in_file=pos; /* Force start here */
79 30 : info->read_pos=info->read_end=info->request_pos; /* Everything used */
80 30 : info->seek_not_done=1;
81 : }
82 : else
83 285 : info->read_pos=info->read_end; /* All block used */
84 315 : if (!(*info->read_function)(info,buff,length))
85 271 : DBUG_RETURN(0);
86 44 : read_length=info->error;
87 : }
88 : else
89 : {
90 276 : info->seek_not_done=1;
91 276 : if ((read_length=my_pread(info->file,buff,length,pos,MYF(0))) == length)
92 276 : DBUG_RETURN(0);
93 : }
94 44 : if (!(flag & READING_HEADER) || (int) read_length == -1 ||
95 : read_length+in_buff_length < 3)
96 : {
97 43 : DBUG_PRINT("error",
98 : ("Error %d reading next-multi-part block (Got %d bytes)",
99 : my_errno, (int) read_length));
100 43 : if (!my_errno || my_errno == HA_ERR_FILE_TOO_SHORT)
101 31 : my_errno= HA_ERR_WRONG_IN_RECORD;
102 43 : DBUG_RETURN(1);
103 : }
104 1 : bzero(buff+read_length,MARIA_BLOCK_INFO_HEADER_LENGTH - in_buff_length -
105 : read_length);
106 1 : DBUG_RETURN(0);
107 : } /* _ma_read_cache */
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