This class implements a shared memory region mapped to a file.

Objects can be placed into this shared memory area using the Add() member function. To actually place a copy of the object is shared memory call Update() also whenever the mapped object(s) change(s) call Update() to put a fresh copy in the shared memory. This extra step is necessary since it is not possible to share objects with virtual pointers between processes (the vtbl ptr points to the originators unique address space and can not be used by the consumer process(es)). Consumer processes can map the memory region from this file and access the objects stored in it via the Get() method (which returns a copy of the object stored in the shared memory with correct vtbl ptr set). Only objects of classes with a Streamer() member function defined can be shared.

I know the current implementation is not ideal (you need to copy to and from the shared memory file) but the main problem is with the class' virtual_table pointer. This pointer points to a table unique for every process. Therefore, different options are:

One could allocate an object directly in shared memory in the producer, but the consumer still has to copy the object from shared memory into a local object which has the correct vtbl pointer for that process (copy ctor's can be used for creating the local copy).
Another possibility is to only allow objects without virtual functions in shared memory (like simple C structs), or to forbid (how?) the consumer from calling any virtual functions of the objects in shared memory.
A last option is to copy the object internals to shared memory and copy them again from there. This is what is done in the TMapFile (using the object Streamer() to make a deep copy).

Option 1) saves one copy, but requires solid copy ctor's (along the full inheritance chain) to rebuild the object in the consumer. Most classes don't provide these copy ctor's, especially not when objects contain collections, etc. 2) is too limiting or dangerous (calling accidentally a virtual function will segv). So since we have a robust Streamer mechanism I opted for 3).

Definition at line 34 of file TMapFile.h.

Public Types
enum	{ kDefaultMapSize = 0x80000 }

Public Types inherited from TObject
enum	EStatusBits { kCanDelete = BIT(0), kMustCleanup = BIT(3), kObjInCanvas = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5), kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13) }

enum	{ kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kBitMask = 0x00ffffff }

enum	{ kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }

Public Member Functions
virtual	~TMapFile ()
	TMapFiles may not be deleted, since we want to keep the complete TMapFile object in the mapped file for later re-use. More...

void	operator delete (void *vp)
	Need special "operator delete" in which we close the shared memory. More...

void	Browse (TBrowser *b)
	Browse contents of TMapFile. More...

void	Close (Option_t *option="")
	Close a mapped file. More...

void *	GetBaseAddr () const

void *	GetBreakval () const
	Return the current location in the memory region for this malloc heap which represents the end of memory in use. More...

TDirectory *	GetDirectory () const

Int_t	GetFd () const

void *	GetMmallocDesc () const

const char *	GetName () const
	Returns name of object. More...

Int_t	GetSize () const

const char *	GetOption () const

const char *	GetTitle () const
	Returns title of object. More...

TMapRec *	GetFirst () const

TMapRec *	GetLast () const

Bool_t	IsFolder () const
	Returns kTRUE in case object is a folder (i.e. contains browsable lists). More...

Bool_t	IsWritable () const

void *	OrgAddress (void *addr) const

void	Print (Option_t *option="") const
	Print some info about the mapped file. More...

void	ls (Option_t *option="") const
	List contents of TMapFile. More...

Bool_t	cd (const char *path=0)
	Cd to associated directory. More...

void	Add (const TObject obj, const char name="")
	Add an object to the list of objects to be stored in shared memory. More...

void	Update (TObject *obj=0)
	Update an object (or all objects, if obj == 0) in shared memory. More...

TObject *	Remove (TObject *obj)

TObject *	Remove (const char *name)

void	RemoveAll ()
	Remove all objects from shared memory. More...

TObject *	Get (const char name, TObject retObj=0)
	Return pointer to object retrieved from shared memory. More...

Public Member Functions inherited from TObject
	TObject ()

	TObject (const TObject &object)
	TObject copy ctor. More...

TObject &	operator= (const TObject &rhs)
	TObject assignment operator. More...

virtual	~TObject ()
	TObject destructor. More...

virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad. More...

virtual const char *	ClassName () const
	Returns name of class to which the object belongs. More...

virtual void	Clear (Option_t *="")

virtual TObject *	Clone (const char *newname="") const
	Make a clone of an object using the Streamer facility. More...

virtual Int_t	Compare (const TObject *obj) const
	Compare abstract method. More...

virtual void	Copy (TObject &object) const
	Copy this to obj. More...

virtual void	Delete (Option_t *option="")
	Delete this object. More...

virtual Int_t	DistancetoPrimitive (Int_t px, Int_t py)
	Computes distance from point (px,py) to the object. More...

virtual void	Draw (Option_t *option="")
	Default Draw method for all objects. More...

virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs. More...

virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current pad. More...

virtual void	Dump () const
	Dump contents of object on stdout. More...

virtual void	Execute (const char method, const char params, Int_t *error=0)
	Execute method on this object with the given parameter string, e.g. More...

virtual void	Execute (TMethod method, TObjArray params, Int_t *error=0)
	Execute method on this object with parameters stored in the TObjArray. More...

virtual void	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to an event at (px,py). More...

virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes. More...

virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes. More...

virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object. More...

virtual UInt_t	GetUniqueID () const
	Return the unique object id. More...

virtual const char *	GetIconName () const
	Returns mime type name of object. More...

virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py). More...

virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out. More...

virtual ULong_t	Hash () const
	Return hash value for this object. More...

virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname". More...

virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl. More...

virtual void	Inspect () const
	Dump contents of this object in a graphics canvas. More...

virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory). More...

virtual Bool_t	IsSortable () const

Bool_t	IsOnHeap () const

Bool_t	IsZombie () const

virtual Bool_t	Notify ()
	This method must be overridden to handle object notification. More...

virtual void	Paint (Option_t *option="")
	This method must be overridden if a class wants to paint itself. More...

virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list. More...

virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory. More...

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove this object from a list. More...

virtual void	SaveAs (const char filename="", Option_t option="") const
	Save this object in the file specified by filename. More...

virtual void	SavePrimitive (std::ostream &out, Option_t *option="")
	Save a primitive as a C++ statement(s) on output stream "out". More...

virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object. More...

virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id. More...

virtual void	UseCurrentStyle ()
	Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked. More...

virtual Int_t	Write (const char *name=0, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory. More...

virtual Int_t	Write (const char *name=0, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory. More...

void *	operator new (size_t sz)

void *	operator new[] (size_t sz)

void *	operator new (size_t sz, void *vp)

void *	operator new[] (size_t sz, void *vp)

void	operator delete (void *ptr)
	Operator delete. More...

void	operator delete[] (void *ptr)
	Operator delete []. More...

void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f. More...

void	SetBit (UInt_t f)

void	ResetBit (UInt_t f)

Bool_t	TestBit (UInt_t f) const

Int_t	TestBits (UInt_t f) const

void	InvertBit (UInt_t f)

virtual void	Info (const char method, const char msgfmt,...) const
	Issue info message. More...

virtual void	Warning (const char method, const char msgfmt,...) const
	Issue warning message. More...

virtual void	Error (const char method, const char msgfmt,...) const
	Issue error message. More...

virtual void	SysError (const char method, const char msgfmt,...) const
	Issue system error message. More...

virtual void	Fatal (const char method, const char msgfmt,...) const
	Issue fatal error message. More...

void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract. More...

void	MayNotUse (const char *method) const
	Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary). More...

void	Obsolete (const char method, const char asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete. More...

Static Public Member Functions
static TMapFile *	Create (const char name, Option_t option="READ", Int_t size=kDefaultMapSize, const char *title="")
	Create a memory mapped file. More...

static TMapFile *	WhichMapFile (void *addr)

static void	SetMapAddress (Long_t addr)
	Set preferred map address. More...

Static Public Member Functions inherited from TObject
static Long_t	GetDtorOnly ()
	Return destructor only flag. More...

static void	SetDtorOnly (void *obj)
	Set destructor only flag. More...

static Bool_t	GetObjectStat ()
	Get status of object stat flag. More...

static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable. More...

Protected Member Functions
	TMapFile ()

	TMapFile (const char name, const char title, Option_t option, Int_t size, TMapFile &newMapFile)
	Create a memory mapped file. More...

	TMapFile (const TMapFile &f, Long_t offset=0)
	Private copy ctor. More...

void	operator= (const TMapFile &rhs)

TMapFile *	FindShadowMapFile ()
	Returns shadow map file. More...

void	InitDirectory ()
	Create the directory associated to this mapfile. More...

TObject *	Remove (TObject *obj, Bool_t lock)
	Remove object from shared memory. More...

TObject *	Remove (const char *name, Bool_t lock)
	Remove object by name from shared memory. More...

void	SumBuffer (Int_t bufsize)
	Increment statistics for buffer sizes of objects in this file. More...

Int_t	GetBestBuffer ()
	Return the best buffer size for objects in this file. More...

void	CreateSemaphore (Int_t pid=0)
	Create semaphore used for synchronizing access to shared memory. More...

Int_t	AcquireSemaphore ()
	Acquire semaphore. Returns 0 if OK, -1 on error. More...

Int_t	ReleaseSemaphore ()
	Release semaphore. Returns 0 if OK, -1 on error. More...

void	DeleteSemaphore ()
	Delete the semaphore. More...

Protected Member Functions inherited from TObject
void	MakeZombie ()

virtual void	DoError (int level, const char location, const char fmt, va_list va) const
	Interface to ErrorHandler (protected). More...

Static Protected Member Functions
static void *	MapToAddress ()
	Return the base address at which we would like the next TMapFile's mapped data to start. More...

Private Attributes
Int_t	fFd
	Descriptor of mapped file. More...

Int_t	fVersion
	ROOT version (or -1 for shadow map file) More...

char *	fName
	Name of mapped file. More...

char *	fTitle
	Title of mapped file. More...

char *	fOption
	Directory creation options. More...

void *	fMmallocDesc
	Pointer to mmalloc descriptor. More...

ULong_t	fBaseAddr
	Base address of mapped memory region. More...

Int_t	fSize
	Original start size of memory mapped region. More...

TMapRec *	fFirst
	List of streamed objects is shared memory. More...

TMapRec *	fLast
	Last object in list of shared objects. More...

Long_t	fOffset
	Offset in bytes for region mapped by reader. More...

TDirectory *	fDirectory
	Pointer to directory associated to this mapfile. More...

TList *	fBrowseList
	List of KeyMapFile objects. More...

Bool_t	fWritable
	TRUE if mapped file opened in RDWR mode. More...

Int_t	fSemaphore
	Modification semaphore (or getpid() for WIN32) More...

ULong_t	fhSemaphore
	HANDLE of WIN32 Mutex object to implement semaphore. More...

TObject *	fGetting
	Don't deadlock in update mode, when from Get() Add() is called. More...

Int_t	fWritten
	Number of objects written sofar. More...

Double_t	fSumBuffer
	Sum of buffer sizes of objects written sofar. More...

Double_t	fSum2Buffer
	Sum of squares of buffer sizes of objects written so far. More...

Static Private Attributes
static Long_t	fgMapAddress = 0
	Map to this address, set address via SetMapAddress() More...

static void *	fgMmallocDesc = 0
	Used in Close() and operator delete() More...

Friends
class	TMapRec

#include <TMapFile.h>

Inheritance diagram for TMapFile:

[legend]

Member Enumeration Documentation

anonymous enum

Enumerator
kDefaultMapSize

Definition at line 84 of file TMapFile.h.

Constructor & Destructor Documentation

TMapFile::TMapFile ( )

protected

Referenced by Create(), and TMapFile().

TMapFile::TMapFile	(	const char *	name,
		const char *	title,
		Option_t *	option,
		Int_t	size,
		TMapFile *&	newMapFile
	)

protected

Create a memory mapped file.

This opens a file (to which the memory will be mapped) and attaches a memory region to it. Option can be either: "NEW", "CREATE", "RECREATE", "UPDATE" or "READ" (see TFile). The default open mode is "READ". The size argument specifies the maximum size of shared memory file in bytes. This protected ctor is called via the static Create() method.

Definition at line 204 of file TMapFile.cxx.

TMapFile::TMapFile	(	const TMapFile &	f,
		Long_t	offset = `0`
	)

protected

Private copy ctor.

Used by the the ctor to create a new version of TMapFile in the memory mapped heap. It's main purpose is to correctly create the string data members.

Definition at line 487 of file TMapFile.cxx.

TMapFile::~TMapFile ( )

virtual

TMapFiles may not be deleted, since we want to keep the complete TMapFile object in the mapped file for later re-use.

To enforce this the delete operator has been made private. Use Close() to properly terminate a TMapFile (also done via the TROOT dtor).

Definition at line 521 of file TMapFile.cxx.

Member Function Documentation

Int_t TMapFile::AcquireSemaphore ( )

protected

Acquire semaphore. Returns 0 if OK, -1 on error.

Definition at line 843 of file TMapFile.cxx.

Referenced by Add(), Browse(), Get(), Remove(), RemoveAll(), and Update().

void TMapFile::Add	(	const TObject *	obj,
		const char *	name = `""`
	)

Add an object to the list of objects to be stored in shared memory.

To place the object actually into shared memory call Update().

Definition at line 561 of file TMapFile.cxx.

Referenced by TDirectoryFile::Append().

void TMapFile::Browse ( TBrowser * b )

virtual

Browse contents of TMapFile.

Reimplemented from TObject.

Definition at line 1007 of file TMapFile.cxx.

Bool_t TMapFile::cd ( const char * path = 0 )

Cd to associated directory.

Definition at line 1034 of file TMapFile.cxx.

void TMapFile::Close ( Option_t * option = "" )

Close a mapped file.

First detach mapped memory then close file. No member functions of a TMapFile that was opened in write mode may be called after Close() (this includes, of course, "delete" which would call the dtors). The option="dtor" is only used when called via the ~TMapFile.

Definition at line 920 of file TMapFile.cxx.

Referenced by ~TMapFile().

TMapFile * TMapFile::Create	(	const char *	name,
		Option_t *	option = `"READ"`,
		Int_t	size = `kDefaultMapSize`,
		const char *	title = `""`
	)

static

Create a memory mapped file.

This opens a file (to which the memory will be mapped) and attaches a memory region to it. Option can be either: "NEW", "CREATE", "RECREATE", "UPDATE" or "READ" (see TFile). The default open mode is "READ". The size argument specifies the maximum size of shared memory file in bytes. TMapFile's can only be created via this method. Create() enforces that a TMapFile is always on the memory mapped heap (when "NEW", "CREATE" or "RECREATE" are used).

Definition at line 1104 of file TMapFile.cxx.

void TMapFile::CreateSemaphore ( Int_t pid = 0 )

protected

Create semaphore used for synchronizing access to shared memory.

Definition at line 788 of file TMapFile.cxx.

Referenced by TMapFile().

void TMapFile::DeleteSemaphore ( )

protected

Delete the semaphore.

Definition at line 818 of file TMapFile.cxx.

Referenced by Close().

TMapFile * TMapFile::FindShadowMapFile ( )

protected

Returns shadow map file.

Definition at line 965 of file TMapFile.cxx.

Referenced by Close().

TObject * TMapFile::Get	(	const char *	name,
		TObject *	delObj = `0`
	)

Return pointer to object retrieved from shared memory.

The object must be deleted after use. If delObj is a pointer to a previously allocated object it will be deleted. Returns 0 in case object with the given name does not exist.

Definition at line 741 of file TMapFile.cxx.

Referenced by TKeyMapFile::Browse().

void* TMapFile::GetBaseAddr ( ) const

inline

Definition at line 92 of file TMapFile.h.

Int_t TMapFile::GetBestBuffer ( )

protected

Return the best buffer size for objects in this file.

The best buffer size is estimated based on the current mean value and standard deviation of all objects written so far to this file. Returns mean value + one standard deviation.

Definition at line 1083 of file TMapFile.cxx.

Referenced by Update().

void * TMapFile::GetBreakval ( ) const

inline

Return the current location in the memory region for this malloc heap which represents the end of memory in use.

Returns 0 if map file was closed.

Definition at line 166 of file TMapFile.h.

Referenced by Print(), and WhichMapFile().

TDirectory* TMapFile::GetDirectory ( ) const

inline

Definition at line 94 of file TMapFile.h.

Int_t TMapFile::GetFd ( ) const

inline

Definition at line 95 of file TMapFile.h.

TMapRec* TMapFile::GetFirst ( ) const

inline

Definition at line 101 of file TMapFile.h.

Referenced by Browse(), Get(), and ls().

TMapRec* TMapFile::GetLast ( ) const

inline

Definition at line 102 of file TMapFile.h.

void* TMapFile::GetMmallocDesc ( ) const

inline

Definition at line 96 of file TMapFile.h.

const char* TMapFile::GetName ( ) const

inlinevirtual

Returns name of object.

This default method returns the class name. Classes that give objects a name should override this method.

Reimplemented from TObject.

Definition at line 97 of file TMapFile.h.

Referenced by InitDirectory().

const char* TMapFile::GetOption ( ) const

inlinevirtual

Reimplemented from TObject.

Definition at line 99 of file TMapFile.h.

Int_t TMapFile::GetSize ( ) const

inline

Definition at line 98 of file TMapFile.h.

const char* TMapFile::GetTitle ( ) const

inlinevirtual

Returns title of object.

This default method returns the class title (i.e. description). Classes that give objects a title should override this method.

Reimplemented from TObject.

Definition at line 100 of file TMapFile.h.

Referenced by InitDirectory().

void TMapFile::InitDirectory ( )

protected

Create the directory associated to this mapfile.

Definition at line 546 of file TMapFile.cxx.

Referenced by TMapFile().

Bool_t TMapFile::IsFolder ( ) const

virtual

Returns kTRUE in case object is a folder (i.e. contains browsable lists).

Reimplemented from TObject.

Definition at line 998 of file TMapFile.cxx.

Bool_t TMapFile::IsWritable ( ) const

inline

Definition at line 104 of file TMapFile.h.

void TMapFile::ls ( Option_t * option = "" ) const

virtual

List contents of TMapFile.

Reimplemented from TObject.

Definition at line 1044 of file TMapFile.cxx.

void * TMapFile::MapToAddress ( )

staticprotected

Return the base address at which we would like the next TMapFile's mapped data to start.

For now, we let the system decide (start address 0). There are a lot of issues to deal with here to make this work reasonably, including:

Avoid memory collisions with existing mapped address spaces
Reclaim address spaces when their mmalloc heaps are unmapped
When mmalloc heaps are shared between processes they have to be mapped at the same addresses in each

Once created, a mmalloc heap that is to be mapped back in must be mapped at the original address. I.e. each TMapFile will expect to be remapped at it's original address. This becomes a problem if the desired address is already in use.

Definition at line 1163 of file TMapFile.cxx.

Referenced by TMapFile().

void TMapFile::operator delete ( void * ptr )

Need special "operator delete" in which we close the shared memory.

This has to be done after the dtor chain has been finished.

Definition at line 1179 of file TMapFile.cxx.

void TMapFile::operator= ( const TMapFile & rhs )

protected

void* TMapFile::OrgAddress ( void * addr ) const

inline

Definition at line 105 of file TMapFile.h.

Referenced by Browse(), Get(), and ls().

void TMapFile::Print ( Option_t * option = "" ) const

virtual

Print some info about the mapped file.

Reimplemented from TObject.

Definition at line 981 of file TMapFile.cxx.

Int_t TMapFile::ReleaseSemaphore ( )

protected

Release semaphore. Returns 0 if OK, -1 on error.

Definition at line 888 of file TMapFile.cxx.

Referenced by Add(), Browse(), Get(), Remove(), RemoveAll(), and Update().

TObject * TMapFile::Remove	(	TObject *	obj,
		Bool_t	lock
	)

protected

Remove object from shared memory.

Returns pointer to removed object if successful, 0 otherwise.

Definition at line 640 of file TMapFile.cxx.

Referenced by Add().

TObject * TMapFile::Remove	(	const char *	name,
		Bool_t	lock
	)

protected

Remove object by name from shared memory.

Returns pointer to removed object if successful, 0 otherwise.

Definition at line 679 of file TMapFile.cxx.

TObject* TMapFile::Remove ( TObject * obj )

inline

Definition at line 112 of file TMapFile.h.

Referenced by Remove().

TObject* TMapFile::Remove ( const char * name )

inline

Definition at line 113 of file TMapFile.h.

Referenced by Remove().

void TMapFile::RemoveAll ( )

Remove all objects from shared memory.

Definition at line 716 of file TMapFile.cxx.

TMapFile::SetMapAddress ( Long_t addr )

static

Initial value:

{
   
   gROOT->Reset()

Set preferred map address.

Find out preferred map address as follows:

Run consumer program to find the preferred map address. Remember begin of mapped region, i.e. 0x40b4c000
$ root

root [0] m = TMapFile::Create("dummy.map", "recreate", 10000000);

root [1] m.Print()

Memory mapped file: dummy.map

Title:

Option: CREATE

Mapped Memory region: 0x40b4c000 - 0x40d95f00 (2.29 MB)

Current breakval: 0x40b53000

root [2] .q

$ rm dummy.map
Add to producer program, just before creating the TMapFile: TMapFile::SetMapAddress(0x40b4c000);

Repeat this if more than one map file is being used. The above procedure allow programs using, e.g., different number of shared libraries (that cause the default mapping address to be different) to create shared memory regions in the same location without overwriting a shared library. The above assumes the consumer program is larger (i.e. has more shared memory occupied) than the producer. If this is not true inverse the procedure.

Definition at line 1141 of file TMapFile.cxx.

void TMapFile::SumBuffer ( Int_t bufsize )

protected

Increment statistics for buffer sizes of objects in this file.

Definition at line 1069 of file TMapFile.cxx.

Referenced by Update().

void TMapFile::Update ( TObject * obj = 0 )

Update an object (or all objects, if obj == 0) in shared memory.

Definition at line 600 of file TMapFile.cxx.

TMapFile * TMapFile::WhichMapFile ( void * addr )

inlinestatic

Definition at line 174 of file TMapFile.h.