help with strings

[Ajhacksu]

hi trad

i have an integer and i want to do sth like a IntToStr()
and use the string in the command glutSetWindowTitle
but i dunno how to do it, strings in C is too complicated for me cuz i'm corrupted by delphi

like thisbr]
int i = 1;
char *str;

sprintf(&str, "%d", i);
glutSetWindowTitle (str);

it doesnt works... the program crashes...

the definition of that functionbr]GLUTAPI void APIENTRY glutSetWindowTitle(const char *title);

... so any help?

[Trad]

Well, dont make any function like IntToStr, you can try this..

wsprintf(str,"%d",i);
glutSetWindowTitle(str);

i havent really looked into the print functions, but i use wprintf to convert a DWORD to CHAR, so im presuming it will work in your program too.

[Ajhacksu]

warning C4700: local variable 'str' used without having been initialized

and then program crash

thx anyway!

/me goes back to delphi

[Trad]

you shouldnt get that...

hmm.

if you like send me the source and ill get it to work.

[Trad]

first of all try making str an array of char's not a pointer.

[Ajhacksu]

the code is this... its an opengl program
i want to put the milisseconds beteween each frame in the caption
#include <windows.h>
#include <gl/glut.h>
#include <math.h>

void PutPoint (int i)
{
switch (i)
{
case 0: glColor3f(1.0, 1.0, 0.0); break;
case 1: glColor3f(0.0, 0.0, 1.0); break;
case 2: glColor3f(0.5, 0.5, 0.5); break;
}
glBegin (GL_POINTS);
glVertex3f(0.0, 0.0, 0.0);
glEnd ();
}

int p = 0; // planeta trans
int s = 0; // satelite trans

float rx; // mouse rot x
float ry; // mouse rot y
float rz; // mouse rot z

void glutDisplay (void)
{
glClear (GL_COLOR_BUFFER_BIT);

glMatrixMode (GL_MODELVIEW);
glLoadIdentity ();
glTranslatef (0.0, 0.0, -10.0);
glRotatef (rx, 1.0, 0.0, 0.0);
glRotatef (ry, 0.0, 1.0, 0.0);
glRotatef (rz, 0.0, 0.0, 1.0);

glutWireTorus (2.0, 5.0, 10.0, 18.0);

PutPoint (0);

glRotatef(p, 0.0, 0.0, 1.0); p = p++ % 360;
glTranslatef(5.0, 0.0, 0.0);

PutPoint (1);

glRotatef(s, 0.0, 0.0, 1.0); s = (s + 5) % 360;
glTranslatef(1.0, 0.0, 0.0);

PutPoint (2);

glutSwapBuffers();
}

SYSTEMTIME st0;
int i = 1;

void glutIdle (void)
{
SYSTEMTIME st1;
int dt;
char str[5];

if (i % 10 == 0)
{
GetLocalTime(&st1);
dt = ( ( (st1.wMinute * 60000) + (st1.wSecond * 1000) + st1.wMilliseconds ) - ( (st0.wMinute * 60000) + (st0.wSecond * 1000) + st0.wMilliseconds ) ) / 10;
if (dt < 0)
return;
wsprintf(str, "msecs: %d", dt);
//sprintf(&str, "msecs: %d", dt);
glutSetWindowTitle (str);
GetLocalTime(&st0);
}
i++;

glutPostRedisplay ();
}

int m;
int xo;
int yo;
int rxo;
int ryo;
int rzo;

float clamp (float f)
{
if (f > 360) f -= 360;
if (f < 000) f += 360;
return f;
}

void glutMotion(int x, int y)
{
if (m == 1)
{
rx = clamp(rxo - ((yo - y) / 5.0f));
ry = clamp(ryo - ((xo - x) / 5.0f));
}  
if (m == 2)
{
rx = clamp(rxo - ((yo - y) / 5.0f));
rz = clamp(rzo - ((xo - x) / 5.0f));
}
}

void glutMouse(int button, int state, int x, int y)
{
if (state == GLUT_DOWN)
{
if (button == GLUT_LEFT_BUTTON) { m = 1; }
if (button == GLUT_RIGHT_BUTTON) { m = 2; }
xo = x;
yo = y;
rxo = rx;
ryo = ry;
rzo = rz;
}
else if (state == GLUT_UP)
{
m = 0;
rxo = rx;
ryo = ry;
rzo = rz;
}
}

void glutKeyboard (unsigned char key, int x, int y)
{
switch (key)
{
case 0x1b: // esc
exit (1);
break;
}
}

void glutResize (int w, int h)
{
if (!h)
return;

glViewport (0, 0, w, h);

glMatrixMode (GL_PROJECTION);
glLoadIdentity ();

gluPerspective (90, w / h, 1, 1024);

glutPostRedisplay ();
}

void glInit (void)
{
GetLocalTime(&st0);
glPointSize(2.5);
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{

int w = 300;
int h = 300;
int x = (GetSystemMetrics (SM_CXSCREEN) - w) / 2;
int y = (GetSystemMetrics (SM_CYSCREEN) - h) / 2;

glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE);
glutInitWindowPosition (x, y);
glutInitWindowSize (w, h);
glutCreateWindow ("Orbe. Orbiter Particles.");

glutDisplayFunc (glutDisplay);
glutIdleFunc (glutIdle);
   glutMotionFunc (glutMotion);
   glutMouseFunc (glutMouse);
glutKeyboardFunc (glutKeyboard);
glutReshapeFunc (glutResize);

glInit ();

glutMainLoop(); // we never return...

return 0;
}

[Leonardo]

Hi LZM

I would do thisbr]
int i=1;
char strCad[5];

sprintf(strCad,"%d",i);

THe reason that ur program crashes is because str has no memory allocated so u r writing to a location that its either invalid or maybe a location that is being used by another program or something like that

Hope helps

Leonardo

[Trad]

you COULD try........

int ticks GetTickCount();

and inbetween the frames... use

'GetTickCount() - ticks'

and that will return the amount of miliseconds from when you set ticks to when you use GetTickCount() - ticks.

[Ajhacksu]

Thanks Trad and Leonardo
funfou namoral
ticks are much better than systemtime

int t0;

void glutIdle (void)
{
int dt;
char str[10];

dt = GetTickCount() - t0;
sprintf(str, "msecs: %d", dt);
glutSetWindowTitle (str);
t0 = GetTickCount();

glutPostRedisplay ();
}

these strings are still confused for me.. i dont know when/why to use array of chars, pointers, array of pointers, pointers to pointers, etc and how to convert them. pascal strings rlz but thanks for the help. deus abençoe vcs:p

[Leonardo]

I would say thisbr]
If you are declaring a string u need to create a space for allocation, so u need an array of characters, remember in C/C++ all strings are an array of characters.

If you are passing this string, array, to another function, you will receive it as a pointer.

If you want to create an array of stings, then u need an array of pointerrs.

Pointers to Pointers... u will use this when u want to change the actual pointer within a function other than where u declared the pointer...... let me use an example

void f(){
int *p,i;
getElements(&p);
for(i=0;i<n;i++){
cout << p;
}
delete []p;
}

void getElements( int **p){
int i,n;
cout << "# ELements";
cin >> n;
*p=new int[n];
for(i=0;i<n;i++){
cin >> (*p);
}
}

In this case in the f function p is actually non determinded yet, there is no space allocated for it, therefore u r going to change the actual value of the pointer, thats why u use a pointer to pointer.

Generally for pointer speaking... before putting any information of the pointer.... just ask urself... does the pointer has memory allocated?? And you can answer this question by asking u another 2 questions
-Does it has its own memory allocated ( you used new or malloc or any other function that allocates memory dynamically)
-It is using the space of another variable, that has its space already allocated

Hope this is clear enough, if not let me know and I will ellaborate more

Leonardo

[Ajhacksu]

heh
that will help me next time i code a c program
freshed my mind about low level variables and pointers
was very clear to me
big thanks