Go Premium for a chance to win a PS4. Enter to Win

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 311
  • Last Modified:

Memeory allocation in COM Components and Clinet programs

Hi,

This is related to allocation/deallocation of memory in the COM Component(server) and client application.

In COM programming a situation may arise when you allocate memory in the client, pass it to the server where its freed and reallocated or visa versa. In such situations since the clinet  and server objects can be in different machine and hence in different address spaces, we cannot use malloc/free instead COM library functions CoTaskMemAlloc/CoTaskMemFree has to be used. My question is :
Can I use these COM lib functions throught my client and server code for all my dynamic memory requirement other than the cases where its a must(as mentioned in the above paragraph)totally discarding malloc/free. This way I can have one consistant way of handling memory.

Is using CoTaskMemAlloc/CoTaskMemFree instead of malloc/free for the local dynamic memory requirement affects the performance ?

Hope I am clear..

Thank you
FidoDido
0
fidodido
Asked:
fidodido
  • 4
  • 3
1 Solution
 
Answers2000Commented:
1. You can use them throughout, it's just memory.  

2. It's probably going to be a bit slower especially if you allocate and free many small blocks, as most compilers include quite powerful optimizations around malloc/free new/delete and the runtime library.   However given your app is probably doing I/O, network operations and so on, these may be the slowest parts of your app, so you may not notice the difference.  [slowest parts of the app are usually the major constraints on performance]

3. If using C++ you can overload new and delete to work with these blocks.  If using MFC have a look at the DEBUG_NEW stuff and this should give you some pointers on how to do this.

I've never measured this.  If you use approach #3 then you can flip between the 2 ways of doing this and compare - that way you can get a timing measurement specific for your app.


0
 
fidodidoAuthor Commented:
Hi,

Thnak you ! Can you give some more information on CoTaskMemAlloc()/CoTaskMemeFree() implenetation/working/behaviour ? I tried to find in MFC help but its not very clear.

Thanks agin
Prashanth
0
 
Answers2000Commented:
To allocate

LPVOID lpvoid = CoTaskMemAlloc( how_many_bytes ) ;

if ( lpvoid == NULL )
{
  // memory allocation failed, you need to add checks for this
}

You can then access memory through a normal pointer.

The initial state of the memory is undefined, use memset if you want to set all initial contents to 0.  You can use memcpy and other similar library functions to poke around in the memory, or simply access the memory using a pointer (casting if necessary)

e.g.
char * pMemoryAsChars = (char *)lpvoid ;
*pMemoryAsChars = 'A' ; /* First char in memory is now an 'A' */


To free (only do this if CoTaskMemAlloc succeeded)

CoTaskMemFree( lpvoid ) ;

Is this the info you need ?
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
fidodidoAuthor Commented:
Thank you

Prashanth


0
 
fidodidoAuthor Commented:
Thank you

Prashanth


0
 
fidodidoAuthor Commented:
Hi Answer2000,

While I was rating your answer, accidently I clicked on 'reject'. Actually I wanted to 'accept' it. So please respond again so that I can accept your answer.

Thank you again
Prashanth
0
 
Answers2000Commented:
Responding again Prashanth

See you round
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

  • 4
  • 3
Tackle projects and never again get stuck behind a technical roadblock.
Join Now