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Hello gurus,
Please be patient with a newbie.
Everywhere I look on the web I see code with these strange vriable types written in capitals like "DWORD" or "HANDLE". Pleople just declare them without having a class of type dword or handle. When I try to use such code, ofcourse the compiler says:
'DWORD' : undeclared identifier
I am trying to use a function called CreateFile which has the attributes:
HANDLE CreateFile(
LPCTSTR lpFileName,
DWORD dwDesiredAccess,
DWORD dwShareMode,
LPSECURITY_ATTRIBUTES lpSecurityAttributes,
DWORD dwCreationDispostion,
DWORD dwFlagsAndAttributes,
HANDLE hTemplateFile
);
It return type is "HANDLE". What the? Theres no such thing. Is it an int?
MSDN says that "dwDesiredAcess" has to be either 0, GENERIC_READ or GENERIC_WRITE. Is GENERIC_READ a string or what?
When I try to use the the function. ie:
hComm = CreateFile(portname,
GENERIC_READ | GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
0,
0);
The compiler says:
'GENERIC_READ' : undeclared identifier.
Look, this is a basic question that has porbably been answered elsewhere? But what am I supposed to search for? "variable types written in CAPITALS"?
Pleas help.
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DWORD is just a typedef for unsigned long:
typedef unsigned long DWORD;
HANDLE is just a typedef for void*
typedef void *HANDLE;
handle is a kind of pointer to the windows objects, like bitmaps, brush, etc.
http://www.priyank.in/
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Priyank Bolia wrote:
HANDLE is just a typedef for void*
typedef void *HANDLE;
not always: see WINNT.H
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Hello,
Try:
<br />
#include <windows.h><br />
ans see the magic that can do!
About those types, they are all typedefs by microsoft. All the types that have 'WORD' in their name, are somekind of an int: WORD = 2 bytes unsigned integer, DWORD = 4 bytes unsigned integer and QWORD (Quad WORD) is left as a exercise...
The HANDLE object is a void* pointer to a system object that is managed by windows. The more windows programming you do, the more you see those objects.
Once you learn how to read the MS conventions (try the hongarian notation) some of those names become more easy to read. For example:
LPCTSTR becomes something like: Long Pointer Constant T (unicode, when defined) STRing, where T comes from the macro _T that you use to make unicode strings if you do a unicode build.
I hope that things are more clear now. Good luck on your quest!
I also got the blogging virus..[^]
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1.Project/ADD TO Project/Components And Controls insert SHOCKWAVE FLASH OBJECT Action
********************
The code:
CDialog::OnInitDialog()
{
...
m_ToolBar.CreateEx(this,TBSTYLE_FLAT,WS_CHILD
| WS_VISIBLE |CBRS_ALIGN_TOP,CRect(0,5,0,0));
m_ToolBar.LoadToolBar(IDR_TOOLBAR1);
RepositionBars(AFX_IDW_CONTROLBAR_FIRST,AFX_IDW_CONTROLBAR_LAST,0);
m_ToolBar.ShowWindow(true);
char cPath[_MAX_DIR];
::GetCurrentDirectory(_MAX_DIR,cPath);
strcat(cPath,"\\ss.swf");
this->m_Flash.SetMovie(cPath);
this->m_Flash.SetParent(&m_ToolBar);
this->m_Flash.MoveWindow(560,0,560,40,true);
this->m_Flash.SetPlaying(true);
....
}
It runing error!Please everybody help me!
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describe the error !
is m_Flash well initialized in the constructor ? 
TOXCCT >>> GEII power
[toxcct][VisualCalc]
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1 Please insert SHOCKWAVE FLASH OBJECT Action in a Dialog.
2 Use ClassWizar-->Member variables add CShockwaveFlash m_Flash.
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i wonder if you understand that we cannot help you if you don't give us the error message in details and if you don't give us the code that's crashing !!!
TOXCCT >>> GEII power
[toxcct][VisualCalc]
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THKS.
I find the error;P,^!^
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1) Create status bar w/panes
2) Get rect of pane that progress ctrl will be placed in using SB_GETRECT
3) Create progress control using status bar as parent, and rect value returned in 2) to set its position.
4) Manipulate progress ctrl as desired.
Pssst. You see that little light on your monitor? That's actually a government installed spy camera. Smile and wave to big brother!
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To display the ranges of values an unsigned _int64 can have,this is what I wrote:
void myDlg::ShowRanges()
{
unsigned _int64 uValue;
CString uValueStr;
uValue=(unsigned _int64)pow(2,sizeof(unsigned _int64)*8) ;
////////////////////////////////////////////////////////
uValueStr.Format("0 to %I64u",uValue-1);
AfxMessageBox(uValueStr);
}
///////////////////////////////////////////
This is displaying:
0 to 9 223 372 036 854 775 807
instead of the correct answer:
0 to 18 446 744 073 709 551 614
Obviously the answer is truncated by some statment.But where ? In the formatting perhaps?
Thanks for any help.
NB: I added the spaces between the digits to facilitate reading.
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I see two problems here:
1) pow is a floating point function, returning a double, and doubles won't maintain precision to the 20 digits you are expecting.
2) it wouldn't work anyway. You can't represent the range of an integer type as you are doing. For example, think about a byte. That has a sizeof 1, but the range is not 0 to 256, but 0 to 255. Note that 256 will not fit in a byte data type.
The range is actually 0 to 2 to the power of (number of bits) - 1
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If you look in limits.h
#if _INTEGRAL_MAX_BITS >= 64
/* minimum signed 64 bit value */
#define _I64_MIN (-9223372036854775807i64 - 1)
/* maximum signed 64 bit value */
#define _I64_MAX 9223372036854775807i64
/* maximum unsigned 64 bit value */
#define _UI64_MAX 0xffffffffffffffffui64
#endif
Sooooo,
uValueStr.Format("0 to %I64u", _UI64_MAX);
...cmk
Save the whales - collect the whole set
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And that works perfectly.
Thank you so much for your time.
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You could also do :
unsigned _int64 uValue = (unsigned _int64)~0;
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04
Within you lies the power for good - Use it!
Honoured as one of The Most Helpful Members of 2004
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You are right.
I wrote :
void CMyHexDDlg::ShowRangeOfULONGLONG()
{unsigned _int64 uValue = (unsigned _int64)~0;
CString result;
result.Format("0 to %I64u",uValue);
AfxMessageBox(result);
}
and the output is ( as expected ) :
0 to 18446744073709551615
Very elegant ,and fast solution.
Thank you so much for your time.
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I use this little template class:
template <typename T>
class Limits
{
public:
static T min() { return (T)~0 > 0 ? 0 : (T)1 << (sizeof(T) * 8 - 1); }
static T max() { return (T)~0 > 0 ? (T)~0 : (T)~0 & ~((T)1 << (sizeof(T) * 8 - 1)); }
};
unsigned _int64 ui64Max = Limits<unsigned _int64>::max();
_int64 i64Min = Limits<_int64>::min();
char cMin = Limits<char>::min();
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04
Within you lies the power for good - Use it!
Honoured as one of The Most Helpful Members of 2004
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This is a new subject to me.
My hint is taht the class you are defining can be used for all kind of data types(unsigned and signed) to find the minimum and maximum values that can be stored in them.
But if you have time,could you please tell me what header file I must include to use your class ?
Thanks for any help.
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fardak wrote:
could you please tell me what header file I must include to use your class ?
It is plain C++, no header file required.
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04
Within you lies the power for good - Use it!
Honoured as one of The Most Helpful Members of 2004
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I copied the template and class Limits and insert it (as is) in one of my header files of my code
(D:\myPrograms\myHexD\MyDTypeDlg.h)
,and the compiler displayed this list of warnings and errors.(By the way I am using VC++6.0).
warning C4003: not enough actual parameters for macro 'min'
D:\myPrograms\myHexD\MyDTypeDlg.h(17) : warning C4003: not enough actual parameters for macro 'max'
D:\myPrograms\myHexD\MyDTypeDlg.h(15) : error C2059: syntax error : 'function-style cast'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(15) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2143: syntax error : missing ')' before '}'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2059: syntax error : ')'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2143: syntax error : missing ';' before '}'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2238: unexpected token(s) preceding ';'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(17) : error C2143: syntax error : missing ';' before 'static'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
myHexDDlg.cpp
D:\myPrograms\myHexD\MyDTypeDlg.h(15) : warning C4003: not enough actual parameters for macro 'min'
D:\myPrograms\myHexD\MyDTypeDlg.h(17) : warning C4003: not enough actual parameters for macro 'max'
D:\myPrograms\myHexD\MyDTypeDlg.h(15) : error C2059: syntax error : 'function-style cast'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(15) : error C2334: unexpected token(s) preceding ':'; skipping apparent function body
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2143: syntax error : missing ')' before '}'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2059: syntax error : ')'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2143: syntax error : missing ';' before '}'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(16) : error C2238: unexpected token(s) preceding ';'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
D:\myPrograms\myHexD\MyDTypeDlg.h(17) : error C2143: syntax error : missing ';' before 'static'
D:\myPrograms\myHexD\MyDTypeDlg.h(19) : see reference to class template instantiation 'Limits<t>' being compiled
Thanks for any help.
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Sorry, but that is my fault. The functions are named Min and Max, I forgot to capitalize them when I typed them in here. In lower case the way they are now, the compiler substites the function names for the min and max macros defined in WinDef.h so it is trying to compile a line that looks like this:
static T (((a) < (b)) ? (a) : (b)) { return (T)~0 > 0 ?...and it can not find the variables a and b.
So capitalize min() and max() to Min() and Max() and it will work fine.
Sorry about that.
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04
Within you lies the power for good - Use it!
Honoured as one of The Most Helpful Members of 2004
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Pls don't worry.
This is what I wrote and got the (correct) result:
void CMyHexDDlg::Temp()
{ CString result;
unsigned _int64 ui64Max=Limits<unsigned _int64="">::Max();
result.Format("Max:%I64u",ui64Max);
AfxMessageBox(result);
_int64 i64Min=Limits<_int64>::Min();
result.Format("Min:%I64i",i64Min);
AfxMessageBox(result);
char cMin=Limits<char>::Min();
result.Format("Min:%i",cMin);
AfxMessageBox(result);
}
///////////////////////////////////////////
The output of the three message boxes is:
Max: 18446744073709551615
Min: -9223372036854775808
Min:-128
The code is very subtle and very interesting.
May I add that you are a supestar alright.
Thank you so much for your time and effort.
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I have difficulty with one part of this statement and I hope you give me a hand there.
static T Max()
{ return (T)~0 > 0 ? (T)~0 : (T)~0 & ~((T)1 << (sizeof(T) * 8 - 1)); }
/////////////////////////////////////////
Say I have a WORD:
00000000 00000000
If it is a UWORD (HOB set to 1) return
11111111 11111111
If it is a WORD (HOB set to -)
transform it to
11111111 11111111
and AND it with what exactly ?
Bearing in mind that: 1<< (sizeof(T)*8-1) is:
10000000 00000000
Thanks for any help.
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http://www.codeproject.com/cpp/bitbashing.asp[^]
In a signed value the high order bit(HOB) is the sign bit, it is zero for positive numbers and one for negative numbers. In unsigned values the HOB has no special significance.
So what is done is to first check if we are dealing with a signed or unsigned value by checking if ~0 (inverse zero) is greater than zero. For signed values ~0 will give you -1 (minus one), for unsigned values it will give you the largest possible value.
So for unsigned values we can simply return ~0.
But for signed values, we have to clear the HOB (set it zero) to get the largest possible value
ie:
BYTE bMax = Limits<BYTE>::Max();
will do the following calculations:
(T)~0 > 0 ?
00000000 inversed is 11111111
is 11111111 greater than zero?
No, it is minus one, so it is less than zero.
So we have to return: (T)~0 & ~((T)1 << (sizeof(T) * 8 - 1))
00000000 inversed is 11111111
00000001 left shifted 1 * 8 - 1 (or 7) is 10000000
10000000 inversed is 01111111
11111111 bitwise and 01111111 is 01111111
So we can return 01111111, the largest possible signed value.
And now that I have gone through the exercise of explaining it this way, I realize that I can simplify the function a little. The last step with the bitwise and can be eliminated. The function can be
static T Max() { return (T)~0 > 0 ? (T)~0 : ~((T)1 << (sizeof(T) * 8 - 1)); }
Thanks for putting me through this exercise
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04
Within you lies the power for good - Use it!
Honoured as one of The Most Helpful Members of 2004
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