C / C++ / MFC

Re: Assign file type to an application in Windows

21-Dec-06 5:48

The easiest way, IMO, is to create an SDI application, and look at the .reg file that gets created as a result. That will show you the minimum registry keys/values that need to be created.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

James R. Twine21-Dec-06 8:58

Re: Assign file type to an application in Windows

21-Dec-06 8:58

Directly from MSDN:

REGEDIT
   HKEY_CLASSES_ROOT\.riy = FMA000_File_assoc 
   HKEY_CLASSES_ROOT\FMA000_File_assoc = File_assoc 
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\open\command = fileasso.EXE 
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\open\ddeexec = [Open(%1)]
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\open\ddeexec\application
         = Myserver
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\open\ddeexec\topic = system
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\print\command = fileasso.EXE
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\print\ddeexec = [Open(%1)]
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\print\ddeexec\application 
         = MYServer
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\print\ddeexec\topic = System
   HKEY_CLASSES_ROOT\FMA000_File_assoc\shell\print\ddeexec\ifexec =
   [Test(%1)]

Peace!

-=- James

If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
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Cristian Amarie26-Dec-06 6:45

Cristian Amarie

26-Dec-06 6:45

Have a look also on IQueryAssociations (retrieve using AssocCreate). This won't work for rewrite, but for query will do it.

create a constructor for a struct

cy163@hotmail.com21-Dec-06 5:07

21-Dec-06 5:07

In my MFC project, I declare a struct Stru_A,
struct Stru_A{

char Name[30];
int Age;
}

I would like to initialize the member variable Name with sth like a constructor used for a class. Does this make sense?

James R. Twine21-Dec-06 5:12

21-Dec-06 5:12

Yes.

Peace!

-=- James

Maximilien21-Dec-06 5:27

Maximilien

21-Dec-06 5:27

it depends if you allocate your struct with new or with malloc.

if it's with new, then, yeah, add a constructor.

If it's with malloc, even if you have a constructor, it will not be called, juste create a wrapper function to allocate and initialize the structure.

something like :

Stru_A* MallocStru_A( char* name, int age )
{
 /// malloc the structure
 /// zero the structure,
 /// assign the default values.
}

Maximilien Lincourt
Your Head A Splode - Strong Bad

cy163@hotmail.com21-Dec-06 5:38

21-Dec-06 5:38

Thanks, Maximilien

Would you please more specific about how to create a constructor for the struct

struct Stru_A{
char Name[30];
int Age;
};

And, how to use

<br />
Stru_A* MallocStru_A( char* name, int age )<br />
{ <br />
/// malloc the structure <br />
/// zero the structure, <br />
/// assign the default values.<br />
}<br />
<br />

to initialize a struct for later use.

David Crow21-Dec-06 5:46

21-Dec-06 5:46

cy163@hotmail.com wrote:
Would you please more specific about how to create a constructor for the struct

In exactly the same way you'd create one for a class:

struct Stru_A
{
    Stru_A() {}
    char Name[30];
    int Age;
};

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

cy163@hotmail.com21-Dec-06 5:58

21-Dec-06 5:58

Is the following way correct for inckuding a constructor in a struct

<br />
struct Stru_A{<br />
    Stru_A(char Name[30], int Age) <br />
    {<br />
<br />
         strcpy(this->Name, Name);<br />
         this->Age = Age;<br />
     }<br />
    char Name[30];<br />
    int Age;<br />
<br />
}*pStru_A;<br />
<br />
<br />
pStru_A xyz = new Stru_A("ABC", 123);<br />
<br />

David Crow21-Dec-06 7:08

21-Dec-06 7:08

Rather than use C-style types such as char, use the C++ type string. This will avoid the use of memset(), strcpy() and strncpy(). Hard-coding numbers (e.g, 30) is usually not a good thing.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

James R. Twine21-Dec-06 8:42

21-Dec-06 8:42

Might want to make sure that the OP is not going to be doing memory-style copies with the structure first before suggesting something like that. For example, if passing the address of an instance of the structure to something like fwrite(...) or WriteFile(...), it will likely not work as expected if you have a dynamic-allocating string object in it.

DavidCrow wrote:
Hard-coding numbers (e.g, 30) is usually not a good thing.

Usually? Limits are what normally define the functionality of a system. They just have to be enforced in order to prevent problems.

Peace!

-=- James

David Crow21-Dec-06 8:53

21-Dec-06 8:53

James R. Twine wrote:
Usually?

I was erroring on the side of "there might be an exception." I know of no reason to use:

foo(char Name[30]);

especialy if multiple of them exist. Once the size of the variable changes, every function prototype would also have to be changed.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

James R. Twine21-Dec-06 9:16

21-Dec-06 9:16

DavidCrow wrote:
I was erroring on the side of "there might be an exception." I know of no reason to use:
foo(char Name[30]);
especialy if multiple of them exist. Once the size of the variable changes, every function prototype would also have to be changed.

You are correct - there is no reason to write a prototype that way (except for documentation purposes) because array types in a prototype decay into pointers. So even if you did write it that way, the specified lengths would not enforced. So if you did change lengths, the functions would still compile. That is why you cannot write code like this:

void    foox( char caData[ 30 ] ) { TRACE1( "foo %s\n", caData ); }
void    foox( char *cpData ) { TRACE1( "foo2 %s\n", cpData ); }
void    foox( char cvData[] ) { TRACE1( "foo3 %s\n", cvData ); }

Because all three are really the same thing - the compiler will likely complain about duplicate function bodies. That is also why you can do the following:

void    foo( char caData[ 30 ] ) { TRACE1( "foo %s\n", caData ); }
void    foo2( char *cpData ) { TRACE1( "foo2 %s\n", cpData ); }
void    foo3( char cvData[] ) { TRACE1( "foo3 %s\n", cvData ); }
 
    char    *cpTest = "Test";
    char    caTest30[ 30 ] = { "Test" };
    char    caTest10[ 10 ] = { "Test" };
    char    cvTest[] = "Test";
 
    foo( cpTest );    foo( caTest30 );
    foo( caTest10 );  foo( cvTest );
     
    foo2( cpTest );    foo2( caTest30 );
    foo2( caTest10 );  foo2( cvTest );
 
    foo3( cpTest );    foo3( caTest30 );
    foo3( caTest10 );  foo3( cvTest )

And the compiler will not complain, allowing all of the variable types to be passed to foo1/foo2/foo3 without issue.

<HR>

   First rule of buffers: when you pass a buffer, pass its usable length.

   The point about changing lengths is exactly why you use something like const DWORD IDENTIFIERs to manage buffer lengths - change it once, change it everywhere. Combine that with a strategy like Size+1 and you have a way to manage string limits without risk of buffer overruns. All it takes to use and limit buffers correctly is a little discipline.

   Peace!

-=- James

markkuk21-Dec-06 5:47

markkuk

21-Dec-06 5:47

In C++ the only difference between struct and class is the default visibility of members. A constructor for a struct is defined just like a constructor for a class.

VonHagNDaz21-Dec-06 5:32

VonHagNDaz

21-Dec-06 5:32

struct Stru_A{

char Name[30];
int Age;
}Stru_A, *pStru_A;

pStru_A foo = new Stru_A;

foo->Name(blah blah blah);
foo->Age(blah blah blah);

I win because I have the most fun in life...

krmed21-Dec-06 5:48

krmed

21-Dec-06 5:48

I believe this may be what you are looking for:

struct Stru_A
{
    char Name[30];
    int Age;
    Stru_A::Stru_A()
    {
        Age = 0;
        memset(Name,0,30);
    }
}

Hope that helps.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

cy163@hotmail.com21-Dec-06 5:59

Re: create a constructor for a struct [modified]

21-Dec-06 5:59

Is the following way correct for inckuding a constructor in a struct

<br />
<br />
struct Stru_A{<br />
Stru_A(char Name[30], int Age) <br />
{<br />
<br />
strcpy(this->Name, Name);<br />
this->Age = Age;<br />
}<br />
char Name[30];<br />
int Age;<br />
<br />
}*pStru_A;<br />
<br />
<br />
pStru_A xyz = new Stru_A("ABC", 123);<br />
<br />

krmed21-Dec-06 7:00

krmed

21-Dec-06 7:00

I believe for what you're trying to do, you'll need this (note there are two constructors here - one with no parameters and the one you are trying to use):

struct Stru_A{
    char Name[30];
    int Age;
    Stru_A::Stru_A() 
    {
        memset(Name, 0, 30);
        Age = 0;
    }

    Stru_A::Stru_A(char* inName, int inAge) 
    {
        memset(Name, 0, 30);    // this insures a null terminator
        strncpy(Name, inName, 29);
        Age = inAge;
    }
}*pStru_A;

pStru_A xyz = new Stru_A("ABC", 123);

Note also that you should use strncpy to be sure the copy doesn't overwrite the 30 character size you have, and still leaves space for the null terminator.

Hope that helps.

-- modified at 16:32 Thursday 21st December, 2006

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

James R. Twine21-Dec-06 8:48