C/C++ Programming Help Thread

Zitat:

---

Zitat von Raphael

That's plain utter bull. malloc shouldn't be used inside inner loops of realtime-apps, yes, but even there it is possible to some extent. Whoever told you that, don't listen to him.

---

Ok. Thank you. My format now will be

Code:

---

00517                        // First line, number of artists (5 bytes)
016                        // length of the first artist (3 bytes)
A perfect circle        // Name of the artist (#1)
3                        // Albumcount
016                        // length of the first album
Emotive                        // Name of the album (#1)
016                        // length of the second album
Mer de noms                // Name of the album (#2)
016                        // length of the third album
The thiteenth step        // Name of the album (#3)
016                        // length of the second artist
Aphex Twin                // Name of the artist (#2)
2                        // albumcount
016                        // length of the first album
Come to daddy                // Name of the album (#1)
016                        // length of the second album
Selected ambient works        // Name of the album (#2)
[...]                        // Name of the artist (#3)

---

but without the linebreaks. This way artist and album names can be of any length and nothing will be cut. I think this is the most professional solution

hi guys. i wanted to blit a png image of a crosshair in the center of my screen, but when i do it using PSPGU, the image doesnt show. is it posible to use graphics.h with pspgu? (also, the same thing happens when i use "printTextScreen()")

so ur saying text and images aren't rendering? Are you switching them from offscreen buffer to onscreen buffer?

Grimfate - graphics.h/c IS GU. IF it's not showing up, either you arent translating into view of it, or not flipping the draw/display buffers.

You also need to call initGraphics()...

all of you were right. i didnt call initGraphics or flipScreen. BUT, it still wont work. my current main function:

Code:

---

int main(void)
{

        scePowerSetClockFrequency(333, 333, 166);

        pspDebugScreenInit();
        SetupCallbacks();
        initGraphics();
       
        dList = memalign( 16, 640 );
        fbp0  = 0;
 
        InitGU();
        SetupProjection();
       
        // SET CAMERA ONE POSITION //
        cameraOne.SetPos(model_x, model_y + 1, model_z, 0.0f, 1.0f, 0.5f, 0.0f, 1.0f, 0.0f);

        crossHair = loadImage("crossHair.png");
 
        while (1)
        {
                DrawScene();
               
                blitAlphaImageToScreen(0 ,0 ,32 , 32, crossHair, 224, 120);               
               
                sceDisplayWaitVblankStart();
                fbp0 = sceGuSwapBuffers();
                flipScreen();
              }
 
        sceGuTerm();                       
 

        free( dList );
        free( fbp0 );

        return 0;
}

---

its compiles fine, but when i boot it, it just shows a blank screen. (its not crashing cause i can still exit by pressing "home".)


now whats wrong?

Grimfate - You cant initlaize the GU twice. Your trying to take the easy way out by taking 2 differ GU setup functions thus casuing unknown errors (?). Since your making that FPS, i highly suggest you get off graphics.h/c (unless you want to do vectoring and whatnot with it somehow :X) and stay with raw GU. First, load and texturize an Ortho view crosshair (texturize a quad movable via analog stick).

Hi,
what's the quickest way to read bytes/chars x-y from a char-array? Is there a better way than using a for-loop?

Zitat:

---

dList = memalign( 16, 640 );

---

Whoever brought up that code for the command list setup should get slaughtered IMO. 640 bytes is in no way enough space to store commands as soon as you do more than drawing 10 images. It's nearly as annoying as the buffer = "myfile.png"; loadImage( buffer ); crap, only that this didn't cause any problems, it just was ugly.

Zitat:

---

its compiles fine, but when i boot it, it just shows a blank screen.

---

Either your image isn't loaded correctly (wrong path/filename/anything) or anything GU specific isn't setup correctly (read further below).

Zitat:

---

free( fbp0 );

---

Remove this line. And never do that again. You cannot free VRAM memory with the free function. Also you didn't allocate fbp0 with malloc in the first place anyway, so this is double-wrong.

Zitat:

---

Grimfate - You cant initlaize the GU twice. Your trying to take the easy way out by taking 2 differ GU setup functions thus casuing unknown errors (?).

---

Wrong. You can initialize the GU as often as you want and it will not cause any unknown errors, the only thing that happens is that all your states from the previous setup get reset to the defaults each time. Therefore the initGU() call will make the initGraphics() obsolete, which in turn might be the cause for the image not showing up (because some important setup is missing then, probably something like sceGuEnable(GU_TEXTURE_2D ) or alike).

Zitat:

---

what's the quickest way to read bytes/chars x-y from a char-array? Is there a better way than using a for-loop?

---

No, there's no quicker way. Any time you read an amount of data or search for an unknown position you ALWAYS need a loop. The question if there's a BETTER way on the other side depends on the needs, but most likely there's no "better" way in this case.

Hm, wouldn't memcpy probably be faster? I mean I know the position (the offset and the length I want to read). If there's the a way to create a pointer that points to the point (omg my english *dies*), I mean a pointer that points to the offset where I want to read the string from, I could use memcpy to copy an excerpt from the string.

Like (reading array[5]-array[10]):
char * pArray = &array+5; // (pseudo-code)
memcpy(stringExcerpt, pArray, 5);

?

Zitat:

---

Zitat von Lukeson

Hm, wouldn't memcpy probably be faster? I mean I know the position (the offset and the length I want to read). If there's the a way to create a pointer that points to the point (omg my english *dies*), I mean a pointer that points to the offset where I want to read the string from, I could use memcpy to copy an excerpt from the string.

Like (reading array[5]-array[10]):
char * pArray = &array+5; // (pseudo-code)
memcpy(stringExcerpt, pArray, 5);

?

---

Yes, that's true, I somewhat misunderstood your intention with "read x-y chars". If you want to copy some strings out of a longer one, that's the best (as in cleanest/best readable) way to go yes (if its faster depends on the length of the string to copy, because the overhead of the function call is not little and on the other side, memcpy also only does a loop [but optimized] - note though that all that is not really time-critical code, so it doesn't matter which solution you take, therefore the memcpy is still preferable).
Well, at least the idea is right, the syntax not quite ;)

Code:

---

memcpy(stringExcerpt, &array[5], 5);

---

That's the same in one single line. Copys 5 bytes starting from position 5.

PS: You get my personal award for craziest funny sentence of the month :D :tup:

Zitat:

---

If there's the a way to create a pointer that points to the point (omg my english *dies*)

---

PPS: If you once really get into problems explaining yourself in english, you can always contact me in german too ;)

Thanks again, Raphael!

Now can somebody pls explain that errormessage to me?

Zitat:

---

pspwamp_commands.c:84: error: 'for' loop initial declaration used outside C99 mode

---

Line 84:

Code:

---

for(int i=1; i<=1; i++)

---

You need to set the std to c99. Simply open up your makefile and add -std=c99 to the CFLAGS.

You could also change it to

Code:

---

int i;
for(i=1; i<=1; i++)

---

Thanks!

Zitat:

---

Zitat von Lukeson

Thanks again, Raphael!

Now can somebody pls explain that errormessage to me?



Line 84:

Code:

---

for(int i=1; i<=1; i++)

---

---

thats wierd i got that error to and i just made it a c++ file. and it was gone.:PC:

C++ includes the C99 standard, that'swhy with C++ that won't occur.

Code:

---

for( leerlingen = 0; leerlingen < 21; ++leerlingen ) {
   
    cout << "geef de score van leerling " << leerlingen;
    cin >> punten[leerlingen-1];
    cout << endl;
}

---

Zitat:

---

Zitat von head_54us

Woah. That would start from -1 not 0. On the first loop, leerlingen = 0, it doesnt increment until the end of the first loop.

---

No... it increments before entering the loop, since the ++ is in the prefix position.

Over at php-resource.de (german) they say, you can simply send() a struct, recieve it, and, on the client, make it a struct again via a simple typeconversion. Can somebody confirm that?

Zitat:

---

Zitat von FreePlay

No... it increments before entering the loop, since the ++ is in the prefix position.

---

No, the increment happens at the end of loop whether it is i++, ++i, i+=1 or i = i + 1. Seriously, try it.

++i increments before the expression of i is evaluated
i++ increments after the expression of i is evaluated

Code:

---

for( int i = 0; i < 10; ++i )
        |        |    |--> Executed at the end of the loop
        |        |--> Executed at the beginning of the loop
        |--> Is initialised on entry to the for loop block

---

Zitat:

---

Zitat von Lukeson

Over at php-resource.de (german) they say, you can simply send() a struct, recieve it, and, on the client, make it a struct again via a simple typeconversion. Can somebody confirm that?

---

Yes that's possible. It's as it stands there, data is just data, and a type or struct is just an interpretation of that data which can be exchanged (through typecasts).

Zitat:

---

/*packet von irgendwo her gelesen*/
/* packet ist vom typ char* */
struct libnet_ip_hdr *ip_h = (struct libnet_ip_hdr*)packet;

---

That's the typecast (from char* to struct libnet_ip_hdr*).

kewl sh*t!
-= Double Post =-
How do I allocate memory for multidimensional arrays? I have the following problem:

Code:

---

        typedef struct {
                char * name;
                char * albums;
        } artist_entry;

        artist_entry artist_list[517];

        for(i=0;i<=517;i++)
        {
                // find out artist name and length
                artist_list[i].name = (char*)malloc(artist_name_lenght+1);
                strcpy(artist_list[i].name, artist_name);
                artist_list[i].name[artist_name_lenght]='\0';

                // find out number of albums, and album-names

                // make albums an array for X (3 for example) albums

                for(j=0;j<=X;j++)
                {
                        artist_list[i].albums[j] = (char*)malloc(album_name_lenght+1);
                        [...]
                }

        }

---

How do I create that album-array?

Zitat:

---

Zitat von head_54us

No, the increment happens at the end of loop whether it is i++, ++i, i+=1 or i = i + 1. Seriously, try it.

++i increments before the expression of i is evaluated
i++ increments after the expression of i is evaluated

Code:

---

for( int i = 0; i < 10; ++i )
        |        |    |--> Executed at the end of the loop
        |        |--> Executed at the beginning of the loop
        |--> Is initialised on entry to the for loop block

---

---

That doesn't make any sense... In my experience, it executes the third argument of 'for' at the beginning of each iteration. I mean, you don't have to just increment a variable there... you can put any kind of code there you want.

Zitat:

---

Zitat von Lukeson

kewl sh*t!
-= Double Post =-
How do I allocate memory for multidimensional arrays? I have the following problem:

Code:

---

        typedef struct {
                char * name;
                char * albums;
        } artist_entry;

        artist_entry artist_list[517];

        for(i=0;i<=517;i++)
        {
                // find out artist name and length
                artist_list[i].name = (char*)malloc(artist_name_lenght+1);
                strcpy(artist_list[i].name, artist_name);
                artist_list[i].name[artist_name_lenght]='\0';

                // find out number of albums, and album-names

                // make albums an array for X (3 for example) albums

                for(j=0;j<=X;j++)
                {
                        artist_list[i].albums[j] = (char*)malloc(album_name_lenght+1);
                        [...]
                }

        }

---

How do I create that album-array?

---

Make that albums a double pointer, ie char** albums. Then before the inner for loop, allocate the albums array like that: artist_list[i].albums = malloc( X*sizeof(char*) );
The rest is good already. Just be sure to free that array in the reverse order, ie first loop through albums[j] and free each and after that, free the albums.

crosspost

Zitat:

---

Zitat von FreePlay

That doesn't make any sense... In my experience, it executes the third argument of 'for' at the beginning of each iteration. I mean, you don't have to just increment a variable there... you can put any kind of code there you want.

---

But headus is right there. The last part in the for loop is executed at the end, therefore it doesn't matter if the increment is prefixed or postfixed. You can easily try that by doing

Code:

---

for (i=0;i<3;++i) printf("%i,", i);

---

and it will print 0,1,2,
then you can also try that to get absolutely sure that the stuff in the last part is executed AFTER the loop, by inserting another printf("++"); before the ++i. The output will now be 0,++1,++2,++

Thanks for the quick answer, just one las question; How do I set the String-null-terminator? Lke this?

Code:

---

for(j=0;j<=X;j++)
{
artist_list[i].albums[j] = (char*)malloc(album_name_length+1);
strcpy(artist_list[i].albums[j], album_name);
artist_list[i].albums[j][album_name_length]='\0';
}

---

Zitat:

---

Zitat von Lukeson

Thanks for the quick answer, just one las question; How do I set the String-null-terminator? Lke this?

Code:

---

for(j=0;j<=X;j++)
{
artist_list[i].albums[j] = (char*)malloc(album_name_length+1);
strcpy(artist_list[i].albums[j], album_name);
artist_list[i].albums[j][album_name_length]='\0';
}

---

---

Yes, exactly.

How do i clean the screen? Or make it go to sleep after displaying some txt?

1.) clearScreen(RGB(0, 0, 0));

2.) sceKernelSleepThread();

Zitat:

---

Zitat von Lukeson

1.) clearScreen(RGB(0, 0, 0));

2.) sceKernelSleepThread();

---

Thank you :)

np

This should be possible, shouldn't it? Errormessage: line 130: Constant expression expected.

Line 130:
artist_entry artist_list[num_artists];

I get that error when compiling with visual c++. I have done the same with gcc without problems!

Zitat:

---

Zitat von Raphael

But headus is right there. The last part in the for loop is executed at the end, therefore it doesn't matter if the increment is prefixed or postfixed. You can easily try that by doing

Code:

---

for (i=0;i<3;++i) printf("%i,", i);

---

and it will print 0,1,2,
then you can also try that to get absolutely sure that the stuff in the last part is executed AFTER the loop, by inserting another printf("++"); before the ++i. The output will now be 0,++1,++2,++

---

Thanks Raphael.

Zitat:

---

Zitat von Lukeson

np

This should be possible, shouldn't it? Errormessage: line 130: Constant expression expected.

Line 130:
artist_entry artist_list[num_artists];

I get that error when compiling with visual c++. I have done the same with gcc without problems!

---

Is num_artists a define or a variable? The latter won't work. If the size is not known at compile time, you need to dynamically malloc an array.

That's wierd; Using gcc this alsways worked. However I got more difficult errors:

line 158: '=': 'void *' cennot be converted in 'char **'

Code:

---

        typedef struct {
                char * name;
                int num_albums;
                char ** albums;
        } artist_entry;

        artist_entry * artist_list;
        artist_list = (artist_entry *)malloc(num_artists*sizeof(artist_entry));

        for(i=0; i<num_artists; i++)
        {
                [...]
line 158:        artist_list[i].albums = malloc( num_albums*sizeof(char*) );
                [...]
        }

---

Pretty sure you'd have to write it like this:

Code:

---

artist_list[i].albums = (char **)malloc( num_albums*sizeof(char**) );

---

Zitat:

---

Zitat von homer

Pretty sure you'd have to write it like this:

Code:

---

artist_list[i].albums = (char **)malloc( num_albums*sizeof(char**) );

---

---

Well, it should be

Code:

---

artist_list[i].albums = (char **)malloc( num_albums*sizeof(char*) );

---

but that's the same since sizeof(char*) = sizeof(char**) ;p

Ok, thanks, compiling works now, but I get wierd errors; I read a string from a file and send it to the PSP where I then decode it. Now that I found out that you can send structs via TCP I want to do the decoding-work on the server. I use exactly the same code, but it just doesn't work on the server!

Server code:

Code:

---

        pFile = fopen ( "artists.txt" , "rb" );
        fseek (pFile , 0 , SEEK_END);
        lSize = ftell (pFile);
        rewind (pFile);
        buffer = (char*) malloc (lSize);
        fread (buffer,1,lSize,pFile);
        fclose (pFile);

        memcpy(num_artists_c, &buffer, 5);
        num_artists_c[5]='\0';
        offset = 5;
        printf("%s\n", num_artists_c);
        printf("num artists: %d\n", atoi(num_artists_c));
        num_artists = atoi(num_artists_c);
        artist_entry * artist_list;
        artist_list = (artist_entry *)malloc(num_artists*sizeof(artist_entry));

---

Output is:

Zitat:

---

êO1
num artists: 0

---

-= Double Post =-

I fixed it using strncopy (which sucks... but works! :)). However the serverprogram crashes with an adress-error:

Code:

---

        int i,j;
        for(i=0; i<num_artists; i++)
        {
                // get artist- and album-data, works
                artist_list[i].num_albums = num_albums;

                artist_list[i].name = (char*)malloc(artist_name_lenght+1);
                strcpy(artist_list[i].name, artist_name);
                artist_list[i].name[artist_name_lenght]='\0';

                artist_list[i].albums = (char **)malloc( num_albums*sizeof(char**) );

                for(j=1;j<=num_albums;j++)
                {
                        // get album-name, works
                        artist_list[i].albums[j] = (char*)malloc(album_name_length+1);
                        strcpy(artist_list[i].albums[j], album_name);
                        artist_list[i].albums[j][album_name_length]='\0';
                }
        }

---

Everything works when I have these lines commented.

Zitat:

---

I fixed it using strncopy (which sucks... but works! :)). However the serverprogram crashes with an adress-error:

Code:

---

        int i,j;
        for(i=0; i<num_artists; i++)
        {
                // get artist- and album-data, works
                artist_list[i].num_albums = num_albums;

                artist_list[i].name = (char*)malloc(artist_name_lenght+1);
                strcpy(artist_list[i].name, artist_name);
                artist_list[i].name[artist_name_lenght]='\0';

                artist_list[i].albums = (char **)malloc( num_albums*sizeof(char**) );

                for(j=1;j<=num_albums;j++)
                {
                        // get album-name, works
                        artist_list[i].albums[j] = (char*)malloc(album_name_length+1);
                        strcpy(artist_list[i].albums[j], album_name);
                        artist_list[i].albums[j][album_name_length]='\0';
                }
        }

---

Everything works when I have these lines commented.

---

for(j=1;j<=num_albums;j++ ) counts from 1 to num_albums, but the albums array goes from 0 to num_albums-1

I keep getting mixed answers on this, but you can assign multiple variables to one value with use of multiple = signs...

Code:

---

int var1, var2, var3;

var1=var2=var3=123;

printf("%i%i%i",var1,var2,var3

---

That returns each var as '123'. Why is it some say it will only set var1 to 123?

Just thought Id ask why some may get confused, is it differ in C++ or are the people just... out of it.

That will set var3 to 123, var2 to var3(123) and var1 to var2(123).
Nothing strange about that...