I'm wondering if there is any way to do run-time checking for the size of
class-instances?
The only idea I've come up with is overloading operator new and saving the
size passes to it on the instance itself.
class CMyClassA
{
public:
int a;
};
class CMyClassA : public CMyClassB
{
public:
int b;
};
void test(CMyClassA *pPtr)
{
// Here I would like to know the size of the instance that pPtr points
to...
}
int main(int argc, char* argv[])
{
CMyClassB MyInstance;
test(&MyInstanc e);
}
BTW, this is for a garbagecollecto r I'm working on just for fun and learning
stuff....
--
Lasse 7 2087
"Lasse Skyum" <no spam> wrote... I'm wondering if there is any way to do run-time checking for the size of class-instances? The only idea I've come up with is overloading operator new and saving the size passes to it on the instance itself.
class CMyClassA { public: int a; };
class CMyClassA : public CMyClassB { public: int b; };
void test(CMyClassA *pPtr) { // Here I would like to know the size of the instance that pPtr points to... }
int main(int argc, char* argv[]) { CMyClassB MyInstance; test(&MyInstanc e); }
BTW, this is for a garbagecollecto r I'm working on just for fun and
learning stuff....
Most of those things (memory managers, garbage collectors (which are
memory managers of sorts)) do store either some "header" information
right in front of the pointer or in a separate table.
Doesn't seem like a language problem, though.
Victor Most of those things (memory managers, garbage collectors (which are memory managers of sorts)) do store either some "header" information right in front of the pointer or in a separate table.
Well yes, I would like to store the data on the instance, but I don't know
where to get the information from, when the object is not created with
operator new?
--
Lasse
"Lasse Skyum" <no spam> wrote in message
news:3f******** *************** @dread16.news.t ele.dk... Most of those things (memory managers, garbage collectors (which are memory managers of sorts)) do store either some "header" information right in front of the pointer or in a separate table.
Well yes, I would like to store the data on the instance, but I don't know where to get the information from, when the object is not created with operator new?
There is no standard way to obtain the size of an object created on
the stack. Platform-specific low-level tricks and guesses need to
be used...
Regards, Ivan
-- http://ivan.vecerina.com
"Lasse Skyum" <no spam> wrote:
Most of those things (memory managers, garbage collectors (which are memory managers of sorts)) do store either some "header" information right in front of the pointer or in a separate table.
Well yes, I would like to store the data on the instance, but I don't know where to get the information from, when the object is not created with operator new?
When it's not created with new, your garbage collector must not delete
it anyway, so that won't be a problem.
Well the reason is, that I'm trying to pair the smart-pointers with the
objects, so I know where the references are comming from. It works great
when I know the size of the instances.
All garbage-collected classes inherit from "CBL_Object " and I was thinking
of something with a template "SizeOf" virtual-function... but I can't quite
figure it out :-(
I was also looking at typeid (RTTI) but it doesn't look like anything I can
use...
--
Lasse Most of those things (memory managers, garbage collectors (which are memory managers of sorts)) do store either some "header" information right in front of the pointer or in a separate table.
Well yes, I would like to store the data on the instance, but I don't know where to get the information from, when the object is not created with operator new?
When it's not created with new, your garbage collector must not delete it anyway, so that won't be a problem.
"Lasse Skyum" <no spam> wrote: Well the reason is, that I'm trying to pair the smart-pointers with the objects, so I know where the references are comming from. It works great when I know the size of the instances.
All garbage-collected classes inherit from "CBL_Object " and I was thinking of something with a template "SizeOf" virtual-function... but I can't quite figure it out :-(
I was also looking at typeid (RTTI) but it doesn't look like anything I can use...
One thing you could try is to make the base class a template and derive
your other classes as template instances, like:
#include <iostream>
#include <cstdlib>
class CBL_Base
{
public:
virtual std::size_t size() const = 0;
};
template <class T>
class CBL_Object : public CBL_Base
{
public:
virtual std::size_t size() const
{
return sizeof(T);
}
//...
};
class SomeClass : public CBL_Object<Some Class>
{
double x;
double y;
};
class SomeOtherClass : public CBL_Object<Some OtherClass>
{
int x;
};
int main()
{
CBL_Base* a = new SomeClass;
CBL_Base* b = new SomeOtherClass;
std::cout << "size of a is " << a->size() << std::endl;
std::cout << "size of b is " << b->size() << std::endl;
} One thing you could try is to make the base class a template and derive your other classes as template instances, like:
Thanks Rolf, that was actually a great idea :-) This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
by: Matthias |
last post by:
Hi,
I am just reading that book by Scott Meyers. In Item 4 Meyers suggests
to always use empty() instead of size() when probing for emptyness of
STL containers. His reasoning is that size() might take linear time on
some list implementations. That makes sense at first.
However, he also says this at the very beginning:
"That being the...
|
by: Christian Berg |
last post by:
Hi,
I have got a problem with resizing the bufferpool of a DB2 v.8.2
instance.
The DB2 runs on an AIX 5.x platform.
Problem is that an "ALTER BUFFERPOOL ..." command is not persistent if
the database is stopped with the db2stop and restarted with the
db2start command.
|
by: Mariano Drago |
last post by:
Hi there.
How can i know how much memory is an instance taking, devided by internal
instances. For examples lets say i have 2 classes, C1 and C2.
C1 have an internal instance of C2
How can i know the size of:
C1 class
C2 class
C1 instance
Another question. If C1 has an instance method (1MB code), and i create 10
|
by: erdem |
last post by:
hi all,
i guess this question had been asked many times but i couldnt find a way
how can we generate a struct with managed code with fixed size
i mean
struct easy
{
|
by: TheMadHatter |
last post by:
yello,
Quick Q:
With regards to ram use, there really isnt any memory savings if I use type
bool, vs int....... is there? If I remmeber correctly from a microcontroller
course, the smallest addressable unit is an int. All rules still apply for
todays machines, right?
Thanks in advance.
| |
by: Lan W via DBMonster.com |
last post by:
I tried to restore DB2 UDB two databases into two different instances on AIX
server. the raw devices size of rShortSpace0 and rShortSpace1 on the two
instances are the same.
# lsvg -l datavg
datavg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
db2templv jfs 52 52 1 open/syncd ...
|
by: Curious |
last post by:
Hi,
I have created my own data structure. Basically it is a two way
'stack', where I can push elements and pop elements both from top and
bottom. I also included a counter to show the number of elements
currently on the data structure.
I need to calculate the size in bytes of this datastructure content at
a certain time. What I am...
|
by: Tarun |
last post by:
Hi coders,
How can check the total RAM size and the number of RAM modules and their
respective sizes using C#?
Regards,
Tarun
|
by: Frodo Baggins |
last post by:
Hi all,
We are using strcpy to copy strings in our app. This gave us problems
when the destination buffer is not large enough. As a workaround, we
wanted to replace calls to strcpy with strncpy. That is, replace calls
to strcpy with say, my_strcpy(dest,src) which will internally find the
destination buffer length.
For this we need to know...
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main...
|
by: Hystou |
last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it.
First, let's disable language...
| |
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that...
|
by: Hystou |
last post by:
Overview:
Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For...
|
by: tracyyun |
last post by:
Dear forum friends,
With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the...
|
by: conductexam |
last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one.
At the time of converting from word file to html my equations which are in the word document file was convert...
|
by: TSSRALBI |
last post by:
Hello
I'm a network technician in training and I need your help.
I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs.
The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols.
I succeeded, with both firewalls in...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
| |
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
| |