1 /* Copyright (c) 2000-2002, 2005-2007 MySQL AB
2 Use is subject to license terms
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; version 2 of the License.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
16
17 /*
18 Read a record with random-access. The position to the record must
19 get by myrg_info(). The next record can be read with pos= -1 */
20
21
22 #include "myrg_def.h"
23
24 static MYRG_TABLE *find_table(MYRG_TABLE *start,MYRG_TABLE *end,ulonglong pos);
25
26 /*
27 If filepos == HA_OFFSET_ERROR, read next
28 Returns same as mi_rrnd:
29 0 = Ok.
30 HA_ERR_RECORD_DELETED = Record is deleted.
31 HA_ERR_END_OF_FILE = EOF.
32 */
33
myrg_rrnd(MYRG_INFO * info,uchar * buf,ulonglong filepos)34 int myrg_rrnd(MYRG_INFO *info,uchar *buf,ulonglong filepos)
35 {
36 int error;
37 MI_INFO *isam_info;
38 DBUG_ENTER("myrg_rrnd");
39 DBUG_PRINT("info",("offset: %lu", (ulong) filepos));
40
41 if (filepos == HA_OFFSET_ERROR)
42 {
43 if (!info->current_table)
44 {
45 if (info->open_tables == info->end_table)
46 { /* No tables */
47 DBUG_RETURN(my_errno=HA_ERR_END_OF_FILE);
48 }
49 isam_info=(info->current_table=info->open_tables)->table;
50 if (info->cache_in_use)
51 mi_extra(isam_info,HA_EXTRA_CACHE,(uchar*) &info->cache_size);
52 filepos=isam_info->s->pack.header_length;
53 isam_info->lastinx= (uint) -1; /* Can't forward or backward */
54 }
55 else
56 {
57 isam_info=info->current_table->table;
58 filepos= isam_info->nextpos;
59 }
60
61 for (;;)
62 {
63 isam_info->update&= HA_STATE_CHANGED;
64 if ((error=(*isam_info->s->read_rnd)(isam_info,(uchar*) buf,
65 (my_off_t) filepos,1)) !=
66 HA_ERR_END_OF_FILE)
67 DBUG_RETURN(error);
68 if (info->cache_in_use)
69 mi_extra(info->current_table->table, HA_EXTRA_NO_CACHE,
70 (uchar*) &info->cache_size);
71 if (info->current_table+1 == info->end_table)
72 DBUG_RETURN(HA_ERR_END_OF_FILE);
73 info->current_table++;
74 info->last_used_table=info->current_table;
75 if (info->cache_in_use)
76 mi_extra(info->current_table->table, HA_EXTRA_CACHE,
77 (uchar*) &info->cache_size);
78 info->current_table->file_offset=
79 info->current_table[-1].file_offset+
80 info->current_table[-1].table->state->data_file_length;
81
82 isam_info=info->current_table->table;
83 filepos=isam_info->s->pack.header_length;
84 isam_info->lastinx= (uint) -1;
85 }
86 }
87 info->current_table=find_table(info->open_tables,
88 info->end_table-1,filepos);
89 isam_info=info->current_table->table;
90 isam_info->update&= HA_STATE_CHANGED;
91 DBUG_RETURN((*isam_info->s->read_rnd)
92 (isam_info, (uchar*) buf,
93 (my_off_t) (filepos - info->current_table->file_offset),
94 0));
95 }
96
97
98 /* Find which table to use according to file-pos */
99
find_table(MYRG_TABLE * start,MYRG_TABLE * end,ulonglong pos)100 static MYRG_TABLE *find_table(MYRG_TABLE *start, MYRG_TABLE *end,
101 ulonglong pos)
102 {
103 MYRG_TABLE *mid;
104 DBUG_ENTER("find_table");
105
106 while (start != end)
107 {
108 mid=start+((uint) (end-start)+1)/2;
109 if (mid->file_offset > pos)
110 end=mid-1;
111 else
112 start=mid;
113 }
114 DBUG_PRINT("info",("offset: %lu, table: %s",
115 (ulong) pos, start->table->filename));
116 DBUG_RETURN(start);
117 }
118