1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
// extent.h
/**
* Copyright (C) 2013 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include "mongo/db/diskloc.h"
#include "mongo/db/storage/namespace.h"
namespace mongo {
/* extents are datafile regions where all the records within the region
belong to the same namespace.
(11:12:35 AM) dm10gen: when the extent is allocated, all its empty space is stuck into one big DeletedRecord
(11:12:55 AM) dm10gen: and that is placed on the free list
*/
#pragma pack(1)
class Extent {
public:
enum { extentSignature = 0x41424344 };
unsigned magic;
DiskLoc myLoc;
DiskLoc xnext, xprev; /* next/prev extent for this namespace */
/* which namespace this extent is for. this is just for troubleshooting really
and won't even be correct if the collection were renamed!
*/
Namespace nsDiagnostic;
int length; /* size of the extent, including these fields */
DiskLoc firstRecord;
DiskLoc lastRecord;
char _extentData[4];
static int HeaderSize() { return sizeof(Extent)-4; }
bool validates(const DiskLoc diskLoc, BSONArrayBuilder* errors = NULL);
BSONObj dump();
void dump(iostream& s);
/* assumes already zeroed -- insufficient for block 'reuse' perhaps
Returns a DeletedRecord location which is the data in the extent ready for us.
Caller will need to add that to the freelist structure in namespacedetail.
*/
DiskLoc init(const char *nsname, int _length, int _fileNo, int _offset, bool capped);
/* like init(), but for a reuse case */
DiskLoc reuse(const char *nsname, bool newUseIsAsCapped);
bool isOk() const { return magic == extentSignature; }
void assertOk() const { verify(isOk()); }
Record* getRecord(DiskLoc dl) {
verify( !dl.isNull() );
verify( dl.sameFile(myLoc) );
int x = dl.getOfs() - myLoc.getOfs();
verify( x > 0 );
return (Record *) (((char *) this) + x);
}
Extent* getNextExtent();
Extent* getPrevExtent();
static int maxSize();
static int minSize() { return 0x1000; }
/**
* @param len lengt of record we need
* @param lastRecord size of last extent which is a factor in next extent size
*/
static int followupSize(int len, int lastExtentLen);
/** get a suggested size for the first extent in a namespace
* @param len length of record we need to insert
*/
static int initialSize(int len);
struct FL {
DiskLoc firstRecord;
DiskLoc lastRecord;
};
/** often we want to update just the firstRecord and lastRecord fields.
this helper is for that -- for use with getDur().writing() method
*/
FL* fl() { return (FL*) &firstRecord; }
/** caller must declare write intent first */
void markEmpty();
private:
DiskLoc _reuse(const char *nsname, bool newUseIsAsCapped); // recycle an extent and reuse it for a different ns
};
#pragma pack()
}
|