Create a block / wait function?

Posted on 2004-08-17
Medium Priority
Last Modified: 2011-04-14
I am looking for a way to create a function that, like the sockets accept function,
blocks / waits untill a specific variable is set or a specific function is called.
At the moment I am using the very system expensive code:

I need a function that can be called inside a thread procedure to keep the thread from consuming all of the processors power.

Any ideas?

Question by:chrille_p
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
LVL 39

Expert Comment

ID: 11819148
On Windows platform use

    Sleep(1);    // wait 1 millisecond

in your loop.

Regards, Alex
LVL 39

Expert Comment

ID: 11819159
OS/2 you have to use DosSleep, and *NIX it is sleep (as far as i remember).

Regards, Alex
LVL 39

Accepted Solution

itsmeandnobodyelse earned 1000 total points
ID: 11819214
On Windows platform you also may wait on an event rather than on some time elapsed. You may either use WaitForSingleObject or WaitForMultipleObjects:

MSDN says:

The WaitForSingleObject function can wait for the following objects:

Change notification
Console input
Waitable timer

Regards, Alex

Industry Leaders: 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!


Author Comment

ID: 11819311
Im not looking for a function that waits for a couple of seconds.
What I want is a thread-procedure (A) that waits untill function (B) is called...

I could use sleep() in my loop and check a flag every n second, but that would make
the reaction of my function slow. I want it to stop waiting and continue its work
directly when (B) is called.


Author Comment

ID: 11819344
WaitForSingleObject is perfect.


LVL 22

Expert Comment

ID: 11819346
Depending on the OS, there may be a Sleep() function that is calibrated in milliseconds.

Otherwise you could find some API, any API, that will do a task-switch for you.
On Windows that puts your thread to sleep for about 20-30 milliseconds, a nice ballpark sleep time.

LVL 39

Expert Comment

ID: 11819381
>> Im not looking for a function that waits for a couple of seconds.

Ok, but before using

you should have

    while(!input) { sleep(1); }

>> What I want is a thread-procedure (A) that waits untill function (B) is called...

You could use a mutex that gets locked by your main thread, then your thread is waiting on the mutex to be unlocked, what is done at the beginning of function B .

What OS are you working on?

Regards, Alex



Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Unlike C#, C++ doesn't have native support for sealing classes (so they cannot be sub-classed). At the cost of a virtual base class pointer it is possible to implement a pseudo sealing mechanism The trick is to virtually inherit from a base class…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
Suggested Courses

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question