problem to use java class from vc++ - C / C++ / MFC Discussion Boards

Re: Apply a Low Pass filter on data with irregular time stamp

Nelek15-May-08 6:04

15-May-08 6:04

I don't understand your problem very well, but a low pass filter doesn't need to be so periodical (at least the analogic ones), it just check the values and if the data/frecuency of the signal is bigger than the cutoff value, then it does nothing, otherwise block it.

In grosso modo it should be like (assuming you are getting the data from a file... doing in a loop till you read all the values you have):

go to the beggining of the data
do
{
   read data
   if (data <= cutoff_value)
   {   go one position foward;
       continue;   //it doesn't read further and goes directly to the next iteration of the loop
   }
   else
   {
       do whatever you want to do with the values that passed the filter;
   }

   go one position foward;
}
while (data not ended)

But if you are just want to call the function in the moment you make a data aquirement you can use a function like...

bool apply_filter (cutoff_value, read_data)
{
   if (read_data > cutoff_value)
   {   do whatever you want;
       return TRUE; //given data passed the filter
   }


   return FALSE;   //given data didn't pass the filter
}

is it what you were asking? If not, please explain yourself better.

Greetings.
--------
M.D.V. Wink | ;)

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?
Help me to understand what I'm saying, and I'll explain it better to you
“The First Rule of Program Optimization: Don't do it. The Second Rule of Program Optimization (for experts only!): Don't do it yet.” - Michael A. Jackson

Re: Apply a Low Pass filter on data with irregular time stamp

jeremie.delaitre15-May-08 21:10

jeremie.delaitre

15-May-08 21:10

Well, a code snippet is really what I needed, it is crystal clear now ! Thanks a lot.
I think the articles I have read was too detailed for such a simple thing.

Just one last question, what is the order of the filter and how to apply it ?

Re: Apply a Low Pass filter on data with irregular time stamp

Nelek16-May-08 1:19

Nelek

16-May-08 1:19

The order of a filter determines how the filter atenuates the incoming signal. If it is first order the atenuation will be 20 db/dec, second order 40 db/dec, and so on... This 20/40/.. db/dec is the grade of the angle that makes the caracteristical graphic of the filter's transfer function.

This is a concept that is important when you are creating an analogic filter where not only the frecuency has to be filtered. The amplitude of the signal can be modified as well using the order of the filter.

I try to make a example

for first order it should be something like:

     .....
    .
   .
  .
..
 10  500

and, for second order

         .....
       .
     .
   .
..
 10      500

This graphics will let you now how the incoming signal is going to be related to the outgoing signal. In analogic filters the output is not so "matematical". With the examples above. a signal of more than 500 hz will have almost no problems to pass the filter and will be almost not modified (1 to 1 in amplitude) but a signal of 400 will pass the filter because the cutoff frec in these graphics is less than 400, but the output will be different according to the order. For example: In the first order it can be reduced in a ratio of 1 : 0.8 in the second in a ratio of 1 : 0.9

This is theory of analogic electronichs, and is quite extended and pretty difficult just to explain it here. If you need to use the order of the filters as well, I recommend you to search in the web/wiki and so on to see graphic examples that can help you to understand it better.

Greetings.
--------
M.D.V. Wink | ;)

Re: Apply a Low Pass filter on data with irregular time stamp

jeremie.delaitre16-May-08 1:59

jeremie.delaitre

16-May-08 1:59

Ok, that is a little bit clearer know.
Thank you very much.

Difference between similar calls

ilgale15-May-08 5:01

ilgale

15-May-08 5:01

Hi guys, can somone explain me the difference between
following calls ?

CCriticalSection mySection;<br />
<br />
mySection.Lock();<br />
....<br />
mySection.Unlock();

--------------------------

<br />
CCriticalSection mySection<br />
CSingleLock  myLock(&mySection);<br />
<br />
myLock.Lock();<br />
....<br />
myLock.Unlock();

Thanks a lot !!

Re: Difference between similar calls

Nelek15-May-08 5:57

Nelek

15-May-08 5:57

I don't know it as well but... as you are giving a reference to the CCriticalSection in the constructor of your CSingleLock, I guess you can access its methodes from the second one as well. It maybe is so to create an object based in one type and having access to functions in both (created and referenced).

Let see what the others say. (BTW, nice question Smile | :)

)

Greetings.
--------
M.D.V. Wink | ;)

Re: Difference between similar calls

Matthew Faithfull15-May-08 6:13

Matthew Faithfull

15-May-08 6:13

The purpose of CSingleLock is to prevent cases where you might accidentally do this

<br />
<br />
mySection.Lock();<br />
....<br />
<br />
 return;<br />
<br />
mySection.Unlock();<br />
<br />

If you use CSingleLock then when return is called CSingleLock is destroyed and its destructor calls Unlock() preventing disaster. Smile | :)

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

problem to use java class from vc++

intermediate15-May-08 4:13

intermediate

15-May-08 4:13

Hi,

I am trying to call a java class from vc++ program.I had added the jvm.lib in project setting. Also used loadlibrary or afxloadlibrary to load the jvm.dll. but while i am running that ,before the control comes in the initinstance of app class it is showing following error.
"The application has failed to start because jvm.dll was not found"
So basically the loadlibrary is not getting chance to load the dll as the error is ocuuring before control comes to the iniinstance function .

So i am confused how to use jvm.dll.

My code is

JavaVM* jvm;
JNIEnv* env;
JavaVMInitArgs args;
JavaVMOption options[1];
args.version = JNI_VERSION_1_4;
args.nOptions = 1;
options[0].optionString = "-Djava.class.path=C:\\Asset Migration\\converter";

args.options = options;
args.ignoreUnrecognized = TRUE;//JNI_FALSE;
AfxMessageBox("JVM start");
int res =JNI_CreateJavaVM(&jvm, (void **)&env, &args);
if(res<0)
{
AfxMessageBox("JVM failed");
return TRUE;
}
jclass cls = env->FindClass("TestJNI");
jmethodID mid = env->GetStaticMethodID(cls, "dis", "(I)V");
env->CallStaticVoidMethod(cls, mid, 100);

Re: problem to use java class from vc++

CPallini15-May-08 4:21

CPallini

15-May-08 4:21

intermediate wrote:
I had added the jvm.lib in project setting. Also used loadlibrary or afxloadlibrary to load the jvm.dll.

If you link with jvm.lib the your application will perform load-time linking with jvm.dll (hence you have to call neither AfxLoadLibrary nor LoadLibrary). Anyway you have to make sure that jvm.dll can be found by the loader, see [^].
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

Re: problem to use java class from vc++

Nelek15-May-08 5:52

Nelek

15-May-08 5:52

Mmmm, if the *.lib has a header, and it is included as well you don't need to use LoadLibrary (), do you?

Greetings.
--------
M.D.V. Wink | ;)

Re: problem to use java class from vc++

CPallini15-May-08 6:01

CPallini

15-May-08 6:01

CPallini wrote:
(hence you have to call neither AfxLoadLibrary nor LoadLibrary)

.
Maybe my English is misleading (I supposed neither and nor doing the trick of negation).
Anyway, to state it clearly:
If you use load-time DLL linking (i.e. the import library *.lib in the project) then you don't need AfxLoadLibrary (and you don't need LoadLibrary as well).
Is it OK now?
Poke tongue | ;-P

Re: problem to use java class from vc++

intermediate15-May-08 18:13

intermediate

15-May-08 18:13

I cannot keep the jvm.dll in the application path.It need to be in the install path.Also though i had declared the #include "jni.h" but if i don't include jvm.lib in setting then it gives linking error.

So how loader will find the dll in the installed path.As normally loader finds it in the exe path.

Re: problem to use java class from vc++

CPallini15-May-08 21:00

CPallini

15-May-08 21:00

MSDN [^] states the loader will search also in folders specified by the PATH environment variable:

6. The directories that are listed in the PATH environment variable. Note that this does not include the per-application path specified by the App Paths registry key. The App Paths key is not used when computing the DLL search path.

Hence you can augment PATH, adding jvm.dll folder.
Smile | :)

Hash table source code [modified]

fawadnasim15-May-08 3:28

fawadnasim

15-May-08 3:28

I need optimised hash table code implementted in C++ for my project.Can any body post me the source code?

fawadNaseeem

modified on Thursday, May 15, 2008 11:12 PM

Can a dll understand which program calls it.

maxMESA15-May-08 3:04

maxMESA

15-May-08 3:04

Hi.

I want to understand that which program is using my dll. Can dll understand itself or , another program.Anybody have idea about this.

Re: Can a dll understand which program calls it.

Matthew Faithfull15-May-08 3:15

Matthew Faithfull

15-May-08 3:15

No reason why your Dll can't call GetStartupInfo[^]. That should get you at least the basic information you're after.

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

RTTI problem

Karismatic15-May-08 2:53

Karismatic

15-May-08 2:53

Hi experts,

I have an activex control that is placed on a dialog. At runtime I have the nIDs of all the controls so, by using function GetDlgItem I am able to get the pointer to that activex control as CWnd*.

So, My question is how can I get that activex class name or how can i identify whether the pointer is of activex class or not. I have already used typeid, CRuntimeClass, and dynamic_cast but unable to get the required result.

Please help me in resolving it.

Regards,
Pankaj Sachdeva

There is no future lies in any job but future lies in the person who holds the job

Re: RTTI problem

Matthew Faithfull15-May-08 3:09

Matthew Faithfull

15-May-08 3:09

I can't see why GetRuntimeClass wouldn't work for ordinary controls and dynamic_cast to IUnknown wouldn't work for Ax Controls. Just be prepared to handle the exceptions when you try the wrong one. I have no idea why you'd want to do this anyway, don't you know which controls are ActiveX control already, having put them on the dialog Confused | :confused:

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

Re: RTTI problem

Paresh Chitte15-May-08 18:56

Paresh Chitte

15-May-08 18:56

Hi,

Have you tried CObject::IsKindOf ?

Regards,
Paresh.

How to check for filesize..

pl_kode15-May-08 2:52

pl_kode

15-May-08 2:52

How do I get the size of any file that I am reading in VC++.

ifstream myfile;
myfile.open(path);

THANKS

Re: How to check for filesize..

Rajesh R Subramanian15-May-08 2:57

Rajesh R Subramanian

15-May-08 2:57

Is it to solve this problem? If yes, please use the registry or an ini file to store your application related information. Those APIs exist for this very purpose.

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

Re: How to check for filesize..

toxcct15-May-08 3:02

toxcct

15-May-08 3:02

and you're going to delete your question once someone replied to you ?

check the CFile class for any File related operations...

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

Re: How to check for filesize..

Hamid_RT15-May-08 4:15

Hamid_RT

15-May-08 4:15

toxcct wrote:
and you're going to delete your question once someone replied to you

Well said. Wink | ;)

Re: How to check for filesize..

David Crow15-May-08 4:33

David Crow

15-May-08 4:33

Have you considering using GetFileSize() or GetFileAttributesEx()?

"Love people and use things, not love things and use people." - Unknown

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: How to check for filesize..

onlinewan15-May-08 17:20

onlinewan

15-May-08 17:20

long file_len;
ifstream myfile;
myfile.open(path);
myfile.seekg(0, ios::end);
file_len = myfile.tellg();

myfile.close();

------------------------------------------
variable file_len's value is file length.

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