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// mmap.h
/* Copyright 2009 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
namespace mongo {
/* the administrative-ish stuff here */
class MongoFile : boost::noncopyable {
public:
/** Flushable has to fail nicely if the underlying object gets killed */
class Flushable {
public:
virtual ~Flushable(){}
virtual void flush() = 0;
};
protected:
virtual void close() = 0;
virtual void flush(bool sync) = 0;
/**
* returns a thread safe object that you can call flush on
* Flushable has to fail nicely if the underlying object gets killed
*/
virtual Flushable * prepareFlush() = 0;
void created(); /* subclass must call after create */
void destroyed(); /* subclass must call in destructor */
// only supporting on posix mmap
virtual void _lock() {}
virtual void _unlock() {}
public:
virtual ~MongoFile() {}
virtual long length() = 0;
enum Options {
SEQUENTIAL = 1 // hint - e.g. FILE_FLAG_SEQUENTIAL_SCAN on windows
};
static int flushAll( bool sync ); // returns n flushed
static long long totalMappedLength();
static void closeAllFiles( stringstream &message );
// Locking allows writes. Reads are always allowed
static void lockAll();
static void unlockAll();
/* can be "overriden" if necessary */
static bool exists(boost::filesystem::path p) {
return boost::filesystem::exists(p);
}
};
#ifndef _DEBUG
// no-ops in production
inline void MongoFile::lockAll() {}
inline void MongoFile::unlockAll() {}
#endif
struct MongoFileAllowWrites {
MongoFileAllowWrites(){
MongoFile::lockAll();
}
~MongoFileAllowWrites(){
MongoFile::unlockAll();
}
};
/** template for what a new storage engine's class definition must implement
PRELIMINARY - subject to change.
*/
class StorageContainerTemplate : public MongoFile {
protected:
virtual void close();
virtual void flush(bool sync);
public:
virtual long length();
/** pointer to a range of space in this storage unit */
class Pointer {
public:
/** retried address of buffer at offset 'offset' withing the storage unit. returned range is a contiguous
buffer reflecting what is in storage. caller will not read or write past 'len'.
note calls may be received that are at different points in a range and different lengths. however
for now assume that on writes, if a call is made, previously returned addresses are no longer valid. i.e.
p = at(10000, 500);
q = at(10000, 600);
after the second call it is ok if p is invalid.
*/
void* at(int offset, int len);
/** indicate that we wrote to the range (from a previous at() call) and that it needs
flushing to disk.
*/
void written(int offset, int len);
bool isNull() const;
};
/** commit written() calls from above. */
void commit();
Pointer open(const char *filename);
Pointer open(const char *_filename, long &length, int options=0);
};
class MemoryMappedFile : public MongoFile {
public:
class Pointer {
char *_base;
public:
Pointer() : _base(0) { }
Pointer(void *p) : _base((char*) p) { }
void* at(int offset, int maxLen) { return _base + offset; }
void grow(int offset, int len) { /* no action required with mem mapped file */ }
bool isNull() const { return _base == 0; }
};
MemoryMappedFile();
~MemoryMappedFile() {
destroyed();
close();
}
void close();
// Throws exception if file doesn't exist. (dm may2010: not sure if this is always true?)
void* map( const char *filename );
/*To replace map():
Pointer open( const char *filename ) {
void *p = map(filename);
uassert(13077, "couldn't open/map file", p);
return Pointer(p);
}*/
/* Creates with length if DNE, otherwise uses existing file length,
passed length.
*/
void* map(const char *filename, long &length, int options = 0 );
void flush(bool sync);
virtual Flushable * prepareFlush();
/*void* viewOfs() {
return view;
}*/
long length() {
return len;
}
string filename() const { return _filename; }
private:
static void updateLength( const char *filename, long &length );
HANDLE fd;
HANDLE maphandle;
void *view;
long len;
string _filename;
protected:
// only posix mmap implementations will support this
virtual void _lock();
virtual void _unlock();
};
void printMemInfo( const char * where );
#include "ramstore.h"
//#define _RAMSTORE
#if defined(_RAMSTORE)
typedef RamStoreFile MMF;
#else
typedef MemoryMappedFile MMF;
#endif
} // namespace mongo
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