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
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
|
// @file dur_journalformat.h The format of our journal files.
/**
* Copyright (C) 2010 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 "../util/md5.hpp"
namespace mongo {
namespace dur {
#pragma pack(1)
/** beginning header for a journal/j._<n> file
there is nothing important int this header at this time. except perhaps version #.
*/
struct JHeader {
JHeader() { }
JHeader(string fname);
char magic[2]; // "j\n". j means journal, then a linefeed, fwiw if you were to run "less" on the file or something...
// x4142 is asci--readable if you look at the file with head/less -- thus the starting values were near
// that. simply incrementing the version # is safe on a fwd basis.
enum { CurrentVersion = 0x4147 };
unsigned short _version;
// these are just for diagnostic ease (make header more useful as plain text)
char n1; // '\n'
char ts[20]; // ascii timestamp of file generation. for user reading, not used by code.
char n2; // '\n'
char dbpath[128]; // path/filename of this file for human reading and diagnostics. not used by code.
char n3, n4; // '\n', '\n'
unsigned long long fileId; // unique identifier that will be in each JSectHeader. important as we recycle prealloced files
char reserved3[8026]; // 8KB total for the file header
char txt2[2]; // "\n\n" at the end
bool versionOk() const { return _version == CurrentVersion; }
bool valid() const { return magic[0] == 'j' && txt2[1] == '\n' && fileId; }
};
/** "Section" header. A section corresponds to a group commit.
len is length of the entire section including header and footer.
*/
struct JSectHeader {
unsigned len; // length in bytes of the whole section
unsigned long long seqNumber; // sequence number that can be used on recovery to not do too much work
unsigned long long fileId; // matches JHeader::fileId
};
/** an individual write operation within a group commit section. Either the entire section should
be applied, or nothing. (We check the md5 for the whole section before doing anything on recovery.)
*/
struct JEntry {
enum OpCodes {
OpCode_Footer = 0xffffffff,
OpCode_DbContext = 0xfffffffe,
OpCode_FileCreated = 0xfffffffd,
OpCode_DropDb = 0xfffffffc,
OpCode_Min = 0xfffff000
};
union {
unsigned len; // length in bytes of the data of the JEntry. does not include the JEntry header
OpCodes opcode;
};
unsigned ofs; // offset in file
// sentinel and masks for _fileNo
enum {
DotNsSuffix = 0x7fffffff, // ".ns" file
LocalDbBit = 0x80000000 // assuming "local" db instead of using the JDbContext
};
int _fileNo; // high bit is set to indicate it should be the <dbpath>/local database
// char data[len] follows
const char * srcData() const {
const int *i = &_fileNo;
return (const char *) (i+1);
}
int getFileNo() const { return _fileNo & (~LocalDbBit); }
void setFileNo(int f) { _fileNo = f; }
bool isNsSuffix() const { return getFileNo() == DotNsSuffix; }
void setLocalDbContextBit() { _fileNo |= LocalDbBit; }
bool isLocalDbContext() const { return _fileNo & LocalDbBit; }
void clearLocalDbContextBit() { _fileNo = getFileNo(); }
static string suffix(int fileno) {
if( fileno == DotNsSuffix ) return "ns";
stringstream ss;
ss << fileno;
return ss.str();
}
};
/** group commit section footer. md5 is a key field. */
struct JSectFooter {
JSectFooter(const void* begin, int len) { // needs buffer to compute hash
sentinel = JEntry::OpCode_Footer;
reserved = 0;
magic[0] = magic[1] = magic[2] = magic[3] = '\n';
// skip section header since size modified after hashing
(const char*&)begin += sizeof(JSectHeader);
len -= sizeof(JSectHeader);
md5(begin, len, hash);
}
unsigned sentinel;
md5digest hash; // unsigned char[16]
unsigned long long reserved;
char magic[4]; // "\n\n\n\n"
bool checkHash(const void* begin, int len) const {
// skip section header since size modified after hashing
(const char*&)begin += sizeof(JSectHeader);
len -= sizeof(JSectHeader);
md5digest current;
md5(begin, len, current);
DEV log() << "checkHash len:" << len << " hash:" << toHex(hash, 16) << " current:" << toHex(current, 16) << endl;
return (memcmp(hash, current, sizeof(hash)) == 0);
}
};
/** declares "the next entry(s) are for this database / file path prefix" */
struct JDbContext {
JDbContext() : sentinel(JEntry::OpCode_DbContext) { }
const unsigned sentinel; // compare to JEntry::len -- zero is our sentinel
//char dbname[];
};
/** "last sequence number" */
struct LSNFile {
unsigned ver;
unsigned reserved2;
unsigned long long lsn;
unsigned long long checkbytes;
unsigned long long reserved[8];
void set(unsigned long long lsn);
unsigned long long get();
};
#pragma pack()
}
}
|
