C/C++ Programming Help Thread

[psp_jono]

Maybe have a go at the psp-programming.com 'getting started' tutorials, they go through the basics, you can then build from there.

[pspballer07]

uh, isn't it completely the opposite?

try it. I think thats right.

[MaTiAz]

try it. I think thats right.

I've used paths like ms0:/PSP/PHOTO/ many times and they've all worked with only one slash. I've never bothered trying to use backslashes, but it's definitely the other way around when you're sprintf'ing paths (like ms0:/ requires no escape characters but ms0:\ requires another \).

[myschoo]

i always use / and it works perfect

[hallo007]

a file got always hexadecimales , like 0xFF , that a character cant handle

but i need to make a if statement like this

//read data of file x to y
//if y[0x08] == 0xFF

with wich type do I do that?

[pspballer07]

I've used paths like ms0:/PSP/PHOTO/ many times and they've all worked with only one slash. I've never bothered trying to use backslashes, but it's definitely the other way around when you're sprintf'ing paths (like ms0:/ requires no escape characters but ms0:\ requires another \).

ok well i'll fix my post

[coolguy5678]

Only a backwards OS (i.e. Windows) uses backslashes :) . Just use forward slashes on the PSP.

[Mr305]

a file got always hexadecimales , like 0xFF , that a character cant handle

but i need to make a if statement like this

//read data of file x to y
//if y[0x08] == 0xFF

with wich type do I do that?

long int.

[Moca]

a file got always hexadecimales , like 0xFF , that a character cant handle
but i need to make a if statement like this
//read data of file x to y
//if y[0x08] == 0xFF

with wich type do I do that?

Going by those two things I highlighted in bold, I assume you are reading 1 byte at a time. In that case, use type char. a character CAN handle 0xFF without losing any data. :\ 0xFF is the highest a char can handle.

long int.

Why is that? If he is checking 1 byte at a time, then an unsigned char would be sufficient.

[Auraomega]

Say I make a file called global.c and store all my global variables inside it, could I then in the makefile type global.o to allow all my other files access to these globals? I've not used globals often before, and I don't feel like messing up any code just to test this theory.

Thanks.
-Aura

[pspballer07]

Say I make a file called global.c and store all my global variables inside it, could I then in the makefile type global.o to allow all my other files access to these globals? I've not used globals often before, and I don't feel like messing up any code just to test this theory.

Thanks.
-Aura

what i did for global vars for all .c files to use is did this:

global.h

typedef struct Global
{
      //put all global vars here
     float Varf;
};

extern Global global;

global.c

#include "global.h"

Global global;

which u can use it like this:

global.Varf = 1.0f;

then u would add global.o to ur makefile

[Auraomega]

Ah cheers, this will certainly save having to use globals all in the same file (which is what scared me away from doing it in the past).

Thanks.
-Aura

[MrChaos]

Noobish question time:

I'm using printTextScreen, and I want to be able to print the value of a function on the screen.

(Ex: if LinkLevel = 1, I want to display this on the screen: Level: 1).
I couldn't figure out how to do this, and I even looked at some tutorials...Help?

Heres what I tried:

printTextScreen(3, 3, "Level: %LinkLevel", RGB(255, 255, 255));
And obviously...That's not how you do it.
Help?

[Auraomega]

Noobish question time:

I'm using printTextScreen, and I want to be able to print the value of a function on the screen.

(Ex: if LinkLevel = 1, I want to display this on the screen: Level: 1).
I couldn't figure out how to do this, and I even looked at some tutorials...Help?

Heres what I tried:

printTextScreen(3, 3, "Level: %LinkLevel", RGB(255, 255, 255));
And obviously...That's not how you do it.
Help?

You have to sprint the values (lets PLEASE PLEASE refrain from another big argument...)

char text[10];
sprintf(text, "Level: %d", LinkLevel);
printTextScreen(3, 3, text, RGB(255, 255, 255);

Hope that helps

-Aura

[MrChaos]

You have to sprint the values (lets PLEASE PLEASE refrain from another big argument...)

char text[10];
sprintf(text, "Level: %d", LinkLevel);
printTextScreen(3, 3, text, RGB(255, 255, 255);

Hope that helps

-Aura

Woked perfect. Thanks. :)

[_dysfunctional]

...

#include <stdarg.h>

...

int screenPrintf(int x, int y, unsigned int color, char* text, ...)
{
	char buffer[256];

	va_list ap;                             // Pointer To List Of Arguments
  	va_start(ap, text);                // Parses The String For Variables
  	vsprintf(buffer, text, ap);      // Converts Symbols To Actual Numbers
  	va_end(ap);                          // Results Are Stored In 'buffer'

        printTextScreen(x, y, buffer, color);
        return 0;
}

...

screenPrintf(0, 0, GU_RGBA(0, 0, 255, 255), "Hello %s!", "World");

[Auraomega]

Hmm, I'm having problems with the extern thingy, when I try and compile I get

global/global.h:19: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'global'

Any ideas what I've done wrong, baring in mind I only copied what you typed (so its most likely the way I'm linking the files)?

-Aura

[Grimfate126]

if you want to use globals, just use them the normal way. (declare them outside all functions, including main.) they're underrated. as long as you dont have like 5 billion (hyperbole), you'll be fine.

[Auraomega]

if you want to use globals, just use them the normal way. (declare them outside all functions, including main.) they're underrated. as long as you dont have like 5 billion (hyperbole), you'll be fine.

Thats all fine except I'm using globals over 5-6 different files, doing this does not allow them to be declared in the normal way.

-Aura

[pspballer07]

Hmm, I'm having problems with the extern thingy, when I try and compile I get

Any ideas what I've done wrong, baring in mind I only copied what you typed (so its most likely the way I'm linking the files)?

-Aura

did you put this in all the files?

#include "global.h"

[psp_jono]

...

#include <stdarg.h>

...

int screenPrintf(int x, int y, unsigned int color, char* text, ...)
{
	char buffer[256];

	va_list ap;                             // Pointer To List Of Arguments
  	va_start(ap, text);                // Parses The String For Variables
  	vsprintf(buffer, text, ap);      // Converts Symbols To Actual Numbers
  	va_end(ap);                          // Results Are Stored In 'buffer'

        printTextScreen(x, y, buffer, color);
        return 0;
}

...

screenPrintf(0, 0, GU_RGBA(0, 0, 255, 255), "Hello %s!", "World");

This variable length arguement list stuff is pretty cool, I knew it was possible but had never tried it. Thanks for the example.

About all the globals, are they constants? If not its much better to keep regular variables local.
Maybe rather than containing them all in a seperate file, you could contain them all in a structure like pspballer07 said, except then you could just pass a pointer to the globals to any function that needs them. Even that is pretty messy.

Have a search for the 'principle of least privilege', it explians why it's a good idea to only allow code to see data that it requires but nothing else. Trying to follow it can save you alot of time finding bugs :).

[yaustar]

Heavy use of globals is considered bad programming practice due to the amount of maintenance and extra debugging needed when something goes wrong. It also breaks encapsulation and promotes heavy coupling between code modules.

Strictly speaking, globals shouldn't be needed at all with C and C++ and you should pass the variables needed by parameter.

http://c2.com/cgi/wiki?GlobalVariablesAreBad
http://c2.com/cgi/wiki?GlobalVariablesConsideredHarmful

[hallo007]

Going by those two things I highlighted in bold, I assume you are reading 1 byte at a time. In that case, use type char. a character CAN handle 0xFF without losing any data. :\ 0xFF is the highest a char can handle.

Why is that? If he is checking 1 byte at a time, then an unsigned char would be sufficient.

char y = 0xFF;
if(y == 0xFF)

:290: let op: vergelijking is altijd vals omwille van het beperkte bereik van het datatype

translation

warning : statement is always false because of the limit of the data type

so why does the compiller say that then?

[brethren]

char y = 0xFF;
if(y == 0xFF)

:290: let op: vergelijking is altijd vals omwille van het beperkte bereik van het datatype

translation

warning : statement is always false because of the limit of the data type

so why does the compiller say that then?

it needs to be an unsigned char data type if your using values between 0 - 255

char data types range is -128 to 127

[yaustar]

char is 0-255. It is unsigned by default.

The problem is that the compiler sees you trying to assign an int to a char so it assumes you are giving it a value out of range of a char.

Try:

// C
char blah = (char)(0xFF);

// C++
char blah = static_cast<char>(0xFF);

[brethren]

char is 0-255. It is unsigned by default.

The problem is that the compiler sees you trying to assign an int to a char so it assumes you are giving it a value out of range of a char.

Try:

// C
char blah = (char)(0xFF);

// C++
char blah = static_cast<char>(0xFF);

i got my char info from here
http://www.eee.bham.ac.uk/dsvp_gr/ro...e3/tsld003.htm

[hallo007]

unsigned char works perfect for me , thnx=)

[brethren]

no problem, hallo007

[myschoo]

now we are about unsigned so what exactly does it mean?

unsigned int for example or unsigned char ... when do you use it

[yaustar]

Just checked with my debugger, looks like I was wrong and got confused with the extended ASCII table. char's range is actually -127 to 127.