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/**
* Copyright (C) 2008 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/>.
*/
/* @file diskloc.h
Storage subsystem management.
Lays out our datafiles on disk, manages disk space.
*/
#pragma once
#include "mongo/db/jsobj.h"
#include "mongo/platform/cstdint.h"
#include "mongo/platform/unordered_set.h"
namespace mongo {
class Record;
class DeletedRecord;
class Extent;
class MongoDataFile;
class DiskLoc;
template< class Version > class BtreeBucket;
#pragma pack(1)
/** represents a disk location/offset on disk in a database. 64 bits.
it is assumed these will be passed around by value a lot so don't do anything to make them large
(such as adding a virtual function)
*/
class DiskLoc {
int _a; // this will be volume, file #, etc. but is a logical value could be anything depending on storage engine
int ofs;
public:
enum SentinelValues {
/* note NullOfs is different. todo clean up. see refs to NullOfs in code - use is valid but outside DiskLoc context so confusing as-is. */
NullOfs = -1,
// Caps the number of files that may be allocated in a database, allowing about 32TB of
// data per db. Note that the DiskLoc and DiskLoc56Bit types supports more files than
// this value, as does the data storage format.
MaxFiles=16000
};
DiskLoc(int a, int Ofs) : _a(a), ofs(Ofs) { }
DiskLoc() { Null(); }
DiskLoc(const DiskLoc& l) {
_a=l._a;
ofs=l.ofs;
}
bool questionable() const {
return ofs < -1 ||
_a < -1 ||
_a > 524288;
}
bool isNull() const { return _a == -1; }
void Null() {
_a = -1;
ofs = 0; /* note NullOfs is different. todo clean up. see refs to NullOfs in code - use is valid but outside DiskLoc context so confusing as-is. */
}
void assertOk() { verify(!isNull()); }
void setInvalid() {
_a = -2;
ofs = 0;
}
bool isValid() const { return _a != -2; }
string toString() const {
if ( isNull() )
return "null";
stringstream ss;
ss << _a << ':' << hex << ofs;
return ss.str();
}
BSONObj toBSONObj() const { return BSON( "file" << _a << "offset" << ofs ); }
int a() const { return _a; }
int& GETOFS() { return ofs; }
int getOfs() const { return ofs; }
void set(int a, int b) {
_a=a;
ofs=b;
}
void inc(int amt) {
verify( !isNull() );
ofs += amt;
}
bool sameFile(DiskLoc b) {
return _a== b._a;
}
bool operator==(const DiskLoc& b) const {
return _a==b._a&& ofs == b.ofs;
}
bool operator!=(const DiskLoc& b) const {
return !(*this==b);
}
const DiskLoc& operator=(const DiskLoc& b) {
_a=b._a;
ofs = b.ofs;
//verify(ofs!=0);
return *this;
}
int compare(const DiskLoc& b) const {
int x = _a - b._a;
if ( x )
return x;
return ofs - b.ofs;
}
bool operator<(const DiskLoc& b) const {
return compare(b) < 0;
}
/**
* Hash value for this disk location. The hash implementation may be modified, and its
* behavior may differ across platforms. Hash values should not be persisted.
*/
struct Hasher {
size_t operator()( DiskLoc loc ) const;
};
/**
* Marks this disk loc for writing
* @returns a non const reference to this disk loc
* This function explicitly signals we are writing and casts away const
*/
DiskLoc& writing() const; // see dur.h
/* Get the "thing" associated with this disk location.
it is assumed the object is what you say it is -- you must assure that
(think of this as an unchecked type cast)
Note: set your Context first so that the database to which the diskloc applies is known.
*/
BSONObj obj() const;
Record* rec() const;
DeletedRecord* drec() const;
Extent* ext() const;
template< class V >
const BtreeBucket<V> * btree() const;
// Explicitly signals we are writing and casts away const
template< class V >
BtreeBucket<V> * btreemod() const;
/*MongoDataFile& pdf() const;*/
};
#pragma pack()
inline size_t DiskLoc::Hasher::operator()( DiskLoc loc ) const {
// Older tr1 implementations do not support hashing 64 bit integers. This implementation
// delegates to hashing 32 bit integers.
return
unordered_set<uint32_t>::hasher()( loc.a() ) ^
unordered_set<uint32_t>::hasher()( loc.getOfs() );
}
inline std::ostream& operator<<( std::ostream &stream, const DiskLoc &loc ) {
return stream << loc.toString();
}
// Minimum allowed DiskLoc. No Record may begin at this location because file and extent
// headers must precede Records in a file.
const DiskLoc minDiskLoc(0, 0);
// Maximum allowed DiskLoc. Note that only three bytes are used to represent the file number
// for consistency with the v1 index DiskLoc storage format, which uses only 7 bytes total.
// No Record may begin at this location because the minimum size of a Record is larger than one
// byte.
const DiskLoc maxDiskLoc(0x00ffffff, 0x7fffffff);
} // namespace mongo
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