template class - C / C++ / MFC Discussion Boards

Re: File I/O que

LiYS26-Dec-05 22:51

LiYS

26-Dec-05 22:51

toxcct wrote:
change the LPCTSTR(...) into (LPCTSTR)....

if ( ! file.Open( (LPCTSTR)"C:\\Test.xml", CFile::modeRead ) )

doesn't works either!

Re: File I/O que

Prakash Nadar27-Dec-05 0:03

Prakash Nadar

27-Dec-05 0:03

try

if ( ! file.Open( _T("C:\\Test.xml"), CFile::modeRead ) )

<hr<span style="color:gray;size:15px;">Prakash
Prakash

Re: File I/O que

vikas amin27-Dec-05 0:43

vikas amin

27-Dec-05 0:43

Is the file been used by another application

i tried a code similer to the above one and it worked fine

Vikas Amin
Embin Technology
Bombay
vikas.amin@embin.com

Re: File I/O que

Owner drawn26-Dec-05 23:22

Owner drawn

26-Dec-05 23:22

Are you sure there is a file with that name. Check the extension,name etc... to make sure

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Re: File I/O que

krmed27-Dec-05 4:57

krmed

27-Dec-05 4:57

LiYS wrote:
CFile file;
if ( ! file.Open(LPCTSTR ("C:\\Test.xml"), CFile::modeRead ) ) { return; }

If this code is in function X, then as soon as you leave function X, the CFile object is destroyed (it goes out of scope). Thus the file will be closed.

Hope that helps.

Karl - WK5M
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HOT TO TYPE CAST OJBECT TO VARIANT

gpshadrach26-Dec-05 21:45

gpshadrach

26-Dec-05 21:45

hi friends

i have created one object called pIImage. I have to give the object pIImage as A argument to AddImage(). IN VARIANT type. how to convert one object to VARIANT type Sigh | :sigh:

eg.

hr = CoCreateInstance(CLSID_Image,NULL,CLSCTX_INPROC_SERVER,IID_IImage,(void **)&pIImage);

pDoc->AddImage(pIImage)

error C2664: 'AddImage' : cannot convert parameter 1 from 'struct XYZ5::IImage *' to 'struct tagVARIANT'

Shadrach

Re: HOT TO TYPE CAST OJBECT TO VARIANT

AntonGogolev26-Dec-05 21:58

AntonGogolev

26-Dec-05 21:58

If you look more closely at VARIANT constructors (more precisely, at _variant_t, you'll notice that one of them accepts IUnknown* and bool arguments. This is exactly what you need:

pDoc->AddImage(_variant_t(pIImage, true));

template class

Nishad S26-Dec-05 21:29

Nishad S

26-Dec-05 21:29

Hi,

I created a template class, just like:

template < typename TYPE, typename TYPE_ARG = TYPE > class DataList
{
public:
    void AddNode( TYPE_ARG val_i )
    {
        // some code to handle linked list.

        SetVal( val_i, valNew );

        // some code
    }
protected:
    struct NODE
    {
        NODE* pNext;
        TYPE val;
    };
    virtual void SetVal( TYPE_ARG valSrc_i, TYPE& valDst_o )
    {
        val = val_i;
    }
};

This is only a model. I use this class for a general purpose linked list.
I derived a class for string handling, just like:

class StringDataList : public DataList < LPTSTR, LPCTSTR >
{
private:
    void SetVal( LPCTSTR valSrc_i, LPTSTR& valDst_o )
    {
        // copy the string
        valDst_o = new TCHAR[ lstrlen( valSrc_i ) ];
        lstrcpy( valDst_o, valSrc_i );
    }
};

Thus I can use the template class for both numeric data handling and string handling.
For example:
DataList < int, int > intDataList;
StringDataList strDataList;
The real problem is, we assume that the input parameters should be const, especially for pointers (that's why I use LPCTSTR as TYPE_ARG in StringDataList).
So the compiler shows error in the base class while compiling StringDataList.
The error is error C2440: '=' : cannot convert from 'const char *' to 'char *'
If I change the TYPE_ARG to TYPE in the SetVal of template class, another problem arises. That is in the AddNode. It is written as to pass the const input value to the SetVal. To clear it, I have to change the input from TYPE_ARG to TYPE. It is OK for all the classes passing value, but for string type, it is not advisable.

One solution is, I think, use type cast in SetVal, just like
val = TYPE( val_i )

Is there any other better solution?

Thank you.

- NS -

Re: template class

vikas amin27-Dec-05 0:49

vikas amin

27-Dec-05 0:49

I think we had a discussion on constant string
when u had put up a question before few days.
I have already lost that data but will try again
for the same
but the changes u have done in the class are
quiet good.
Pls put up ur class on codeproj when u acomplish it

Vikas Amin
Embin Technology
Bombay
vikas.amin@embin.com

GUId of a COM object

ragavan26-Dec-05 21:25

ragavan

26-Dec-05 21:25

Hi Is the GUID of a COM object unique through out the network or unique through out the world

Re: GUId of a COM object

AntonGogolev26-Dec-05 22:05

AntonGogolev

26-Dec-05 22:05

Theoretically, it's unique, as they call it, 'both in time and in space', but it depends on the actual algorithm used to generate UUIDs. However, you can be reasonably confident that these are unique.

warning C4509: nonstandard extension used:

Chintoo72326-Dec-05 20:43

Chintoo723

26-Dec-05 20:43

I have code like this:

<br />
BOOL f() {<br />
...<br />
__try {<br />
   ...<br />
}__except(EXCEPTION_EXECUTE_HANDLER)<br />
{<br />
  ...<br />
}<br />
<br />
Object o;<br />
}<br />

The object declaration of variable 'o' is outside the __try/__except construct. I get the error:
warning C4509: nonstandard extension used: 'f' uses SEH and 'o' has destructor

Why is this so? I was thinking this should not be an issue as even if an exception is thrown, it will be handled by the __except block, and the exception stuff would end there. The object o is then created.

What can I do to fix this error?

thanks!

Re: warning C4509: nonstandard extension used:

toxcct26-Dec-05 22:49

toxcct

26-Dec-05 22:49

firstly, it is not an error, it is a warning. that means that the compiler saw that there is some coude that may cause some trouble, but non blocking for the execution of the program.

i have one question however. why are you using __try/__except instead of try/catch ?

refering to the MSDN[^], you have to declare o before the exception handling... (SEH means structured exception handling).

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VisualCalc 3.0]

-- modified at 4:56 Tuesday 27th December, 2005

C\C++ with Expat

praveenanil0426-Dec-05 20:06

praveenanil04

26-Dec-05 20:06

I am writing a C/C++ code using EXPAT parser which convert a text file to XML file. Can someone pls let me know how to go about, sample application is appreciated? Confused | :confused:

Anil

Are static members auto removed from HEAP ?

Owner drawn26-Dec-05 18:01

Owner drawn

26-Dec-05 18:01

I have a question? D'Oh! | :doh:

Are static members automatically removed from the HEAP or do we have to remove it manually. Roll eyes | :rolleyes:

Thanks.

Re: Are static members auto removed from HEAP ?

asdfkjsodifuweior26-Dec-05 18:34

asdfkjsodifuweior

26-Dec-05 18:34

I think your question is invalid.
Static members are never allocated on heap.

Vipin - MVP

Re: Are static members auto removed from HEAP ?

vikas amin26-Dec-05 18:52

vikas amin

26-Dec-05 18:52

Is there any good article on net
for the allocation for memory .
regarding diffrent variables and fuctions .

thank u

Vikas Amin
Embin Technology
Bombay
vikas.amin@embin.com

Then where are they allocated!

Owner drawn26-Dec-05 18:57

Owner drawn

26-Dec-05 18:57

asdfkjsodifuweior wrote:
Static members are never allocated on heap.

Then where are they allocated buddy. Tell me.

-- modified at 0:58 Tuesday 27th December, 2005

[Message Deleted]

Sheng Jiang 蒋晟26-Dec-05 19:41

Sheng Jiang 蒋晟

26-Dec-05 19:41

[Message Deleted]

Re: Then where are they allocated!

Owner drawn26-Dec-05 19:53

Owner drawn

26-Dec-05 19:53

JIANG, Sheng[MVP] wrote:
on the stack.

[Message Deleted]

Sheng Jiang 蒋晟26-Dec-05 20:08

Sheng Jiang 蒋晟

26-Dec-05 20:08

[Message Deleted]

Re: Then where are they allocated!

Owner drawn26-Dec-05 20:39

Owner drawn

26-Dec-05 20:39

JIANG, Sheng[MVP] wrote:
depends on the compiler

Thanks for that.

But now if it is allocated on the HEAP do we have to do the cleaning by ourselves. D'Oh! | :doh:

Re: Then where are they allocated!

Sheng Jiang 蒋晟26-Dec-05 20:44

Sheng Jiang 蒋晟

26-Dec-05 20:44

No. It won't be allocated on the heap.

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Conquer what is not
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Re: Then where are they allocated!

asdfkjsodifuweior26-Dec-05 21:17

asdfkjsodifuweior

26-Dec-05 21:17

Static variables are in the read/write data segment when the loader loads the binary.
Info as to how much the size is, is embedded in the binary at link time.

Vipin -MVP

Re: Then where are they allocated!

Prakash Nadar27-Dec-05 0:16

Prakash Nadar

27-Dec-05 0:16

Owner drawn wrote:
But now if it is allocated on the HEAP do we have to do the cleaning by ourselves.

static variables are not allocated on the heap, so u dont free them. simple rule is that, what u dont allocated u dont have to free it.

Typically a binary is divided into sections, also called as the segments.

data segment
code segment &
stack segment.

so your application may have additional data segment for static data also which are typicaly a read/write segment.

Constant data are stored in read only segment.

All these segments are calculated at link time. i.e. the memory is allocated statically and not dynamically so u dont have to clean up anything.

Prakash

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