C/C++ Programming Help Thread

[Insert_Witty_Name]

Makefile:

TARGET = Select Square
OBJS = main.o
YOURLIBS=

INCDIR =
CFLAGS = -G4 -Wall -O2
CXXFLAGS = $(CFLAGS) -fno-exceptions -fno-rtti
ASFLAGS = $(CFLAGS)

LIBDIR =
LDFLAGS =
STDLIBS= -losl -lpng -lz \
		-lpspsdk -lpspctrl -lpspumd -lpsprtc -lpsppower -lpspgu -lpspaudiolib -lpspaudio -lm
LIBS=$(STDLIBS)$(YOURLIBS)

EXTRA_TARGETS = EBOOT.PBP
PSP_EBOOT_TITLE = SelectPSP

PSPSDK=$(shell psp-config --pspsdk-path)
include $(PSPSDK)/lib/build.mak

Your target can only be one word. Change it to:

TARGET = SelectSquare

[Lukeson]

Spoiler for old post:

Strings

Hi, I'm having troubles with strings recieved via TCP; I'm getting a string "[list of artists]" from a simple TCP echo server (you don't need to view this, all it does is recieve a command (string) from the client and answer "[list of artists]".

Spoiler for server code:

    for (;;) {
        len = sizeof(client);
        fd = accept(sock, (struct sockaddr*)&client, &len);
        if (fd < 0)
            error_exit("Error while accepting\n");
		
		printf("Incoming Client: %s\n", inet_ntoa(client.sin_addr));

		if((rc = recv(fd,commandbuffer,RCVCOMMSIZE,0)) < 0)
			printf("Error while recieving the command; error-code: %d\n",WSAGetLastError());
		if(rc==0)
			printf("Client has closed the connection...\n");

		commandbuffer[rc]='\0';
		printf("Client command: %s\n",commandbuffer);

		printf("Sending answer...\n");
		sprintf(answer,"[list of artists]");
		rc=send(fd,answer,strlen(answer),0);

	printf("Closing connection\n\n\n");
        closesocket(fd);

More relevant code; How the client recieves the string from the server:

    command = "get_artists";
    command_len = strlen(command);

	if (send(socket, command, command_len, 0) != command_len) {
        printf("send() sent a different length of bytes than expected!\n");
		return;
	}
	printf("sending command get_artists...\n");

	printf("recieving...\n");
	while(rc!=SOCKET_ERROR)
	{
		printf("Recieving package %d\n", i);
		rc = recv(socket,buf,256,0);
		buf[rc]='\0';
		if(rc==0)
		{
			printf("Server has closed the connnection\n");
			break;
		}
		if(rc==SOCKET_ERROR)
		{
			printf("Error: recv, error-code: %s\n",strerror(errno));
			break;
		}
		strcat(recivedMessage, " - ");
		strcat(recivedMessage, buf);
		printf("buf: %s\n", buf);
		printf("recivedMessage: %s\n", recivedMessage);
		i++;
	}
	printf("\n\nget_artists returned: %s\n", recivedMessage);

IMHO seems fine, but look what he does:

Could it be that he prints buf, which as an array has the size of 265, completely, the whole 256 chars?
-= Double Post =-
PS: Damn that psp is dirty!

I found the source of the problem;

recivedMessage was declared[4096] but not initialized.

Thanks to everyone who racked their brains...

Strings and variable length

Hi,
how can I create strings of variable length in C(non++)? I have a viariable that will be filled in a loop; I can't say when this loop will stop, I don't know how long the string will be. Do I have to use realloc(string, sizeof(string)+sizeof(add edString)) each time in the loop? Or is there a better way?

[soccerPMN]

char string[variable]; ?
I can't remember, its been so long since I've programmed, and now I'm taking a Java class in school...

[Lukeson]

char string[variable];

And what if the string gets longer than <variable>?
-= Double Post =-
I'd actually even be happy if someone could confirm that the method I thought of (using realloc each time in the loop) actually is a method and not utter bull****

[Insert_Witty_Name]

malloc & realloc.

[yaustar]

You really want to avoid reallocating memory at runtime on a console. Just make the buffer a fixed size (eg 4096) and ensure that the message sent is no longer then that.

Your method of realloc would work but might be slow depending on the implementation of the function.

Another method would be to send the size of the message of first then the actual message.

[Lukeson]

Just make the buffer a fixed size (eg 4096) and ensure that the message sent is no longer then that.

I'm retrieving a list of artists from winamp, always different and surely larger than 4096 at many PCs

Your method of realloc would work but might be slow depending on the implementation of the function.

If it makes the console run slow I think I'll go with the other solution you mentioned. Can you actually send and recieve X bytes or is there a limit? Like i need to send a list of 411 Artist (~6165bytes) at once...
-= Double Post =-
Converting numbers to char-arrays
I get a number from sizeof and need to save it in an array of chars (char length[8]). How do you do that?

[yaustar]

Number to char arrays, use sprintf.

Yes there is a limit to how much data you can send in a packet on the network. I can't remember off hand what it is though.

[Moonchild]

Converting numbers to char-arrays
I get a number from sizeof and need to save it in an array of chars (char length[8]). How do you do that?

You'd have to use the itoa function.
Or sprintf if you want.

[Lukeson]

Thanks guys
-= Double Post =-
Hmmm but how do I convert a char to an int? I tried

artist_list_length = (int)artist_list_length_c ;

but it fills artist_list_length with 16thousand-whatever-the-unsigned-int-maximum is...

[Insert_Witty_Name]

atoi

[yaustar]

atoi()

[Lukeson]

Yay, everything works fine now, thanks again!

PS: This is the first time I'm doing something in C, so please be kind to me
-= Double Post =-
i have another noob-question: I got the following code

void get_artists(int socket, char * recivedMessage)
{
	buf[recieved_size] = recieve_message_of_variable_length();
	recivedMessage = (char)malloc(recieved_size);
}

char buffer;

get_artists(socket, buffer);

to get the artists from winamp. The part with malloc freezes my PSP. How else can I make buffer the right size?

[Waterbottle]

I've been trying to get the debug text to work with a prx for devhook.

I first tried using the normal one from pspdebug.h (pspDebugScreenPrintf)
but that gave me these errors

Spoiler for errors:

/usr/local/pspdev/psp/sdk/lib/libpspdebug.a(scr_printf. o): In function `pspDebug
ScreenInit':
/tmp/pspdev/pspsdk/src/debug/scr_printf.c:52: undefined reference to `sceGeEdram
GetAddr'
/usr/local/pspdev/psp/sdk/lib/libpspdebug.a(scr_printf. o): In function `pspDebug
ScreenPrintf':
/tmp/pspdev/pspsdk/src/debug/scr_printf.c:168: undefined reference to `vsnprintf
'
collect2: ld returned 1 exit status

I also tried without defining which I thought maybe could possibly workbecouse I had -fno-builtin-printf which I have in CFLAGS. I didn't get any errors then but no text appeared..

Do I have to do something else to get it working in prx'es? Or is there some other simple text function that exists that works?

[SG57]

waterbottle - Sorry, i havent any experience with PRX printing routines... Or anything PRX that matter...

Lukeson - 'malloc' doesnt just stop working and makes it crash. Either you havent free'd the current memory in recieveMessage, you're trying to allocate memory to something whose memory already has been allocated or all else fails, something you're calling before is causing it to crash -- meaning maybe a call to malloc before yours corrupts the stack, or something of the sort... All i know for sure is malloc doesnt just stop working for no reason...

Best of luck with your problem, wish i could help more...

[psphacker12.]

Can vars have double quotes in them?
For example:

short inches = "Inches";

[SG57]

psp - character arrays, yes. Others, not so sure but you CAN add the ASCII value together and have hte same effect I suppose, but after each char you need an + operator...

int string = 'h'+'e'+'l'+'l'+'o'; // add ASCII values together, not so useful
char string[] = "hello"; // auto sizes array
char string[6] = "hello"; // make room for '\0' char

[Lukeson]

i have another noob-question: I got the following code

void get_artists(int socket, char * recivedMessage)
{
	recieved_size = recieve_message_size();
	buf[recieved_size] = recieve_message_of_variable_length();
	recivedMessage = (char)malloc(recieved_size);
}

char buffer;

get_artists(socket, buffer);

to get the artists from winamp. The part with malloc freezes my PSP. How else can I make buffer the right size?

The correct version should be:

void get_artists(int socket, char * recivedMessage)
{
	recieved_size = recieve_message_size();
	buf[recieved_size] = recieve_message_of_variable_length();
	recivedMessage = (char*)malloc(recieved_size);
	printf("recievedMessage-size: %d\n", sizeof(recivedMessage));
	return;
}

char * buffer;

get_artists(socket, buffer);
printf("get_artists returned: %s", buffer);

However this version freezes after printing "recievedMessage-size: 15" and doesn't print "get_artists returned: message".

Does anyone have an explanation for this?
-= Double Post =-
Or, if not an explanation, probably even a better solution for getting a string of variable length from a function

[snowymydog]

void get_artists(int socket, char * recivedMessage)
{
	buf[recieved_size] = recieve_message_of_variable_length();
	
}

you assign the return value from receive_message_of_variab le_length() to the array, not the variable recieved_size

	recivedMessage = (char*)malloc(recieved_size);

}

Since recieved_size is not assign a value, it contains random value. You're allocation a random number of memory.

	printf("recievedMessage-size: %d\n", sizeof(recivedMessage));
	return;
}

Memory allocated, but you didn't assign any value to it. You're trying to print some random value.

Two more things:
1. sizeof(recivedMessage), it returns the size of a char*, becoz recivedMessage is a char*. It won't return the message size.

2. If you don't use the pointer correctly, it's always result in a crash.

[hallo007]

correct;)

[Lukeson]

Ahh, sorry, what I wrote up there is simplified code just to explain the problem, here's the real deal:

void get_artists(int socket, char * recivedMessage)
{
	char *command;
	int command_len;
	char artist_list_length_c[8];
	int artist_list_length;
	long rc;

	command = "get_artists";
	command_len = strlen(command);

	if (send(socket, command, command_len, 0) != command_len) {
        printf("send() sent a different length of bytes than expected!\n");		// needs real exceptionhandling
		return;
	}
	printf("\n\nsending command get_artists...\n");


	if((rc = recv(socket, artist_list_length_c, 8,0)) < 0) {
		printf("Error while recieving the artist-list-length; error-code: %s\n",strerror(errno));
		return;
	}
	if(rc==0) {
		printf("Client has closed the connection before sending the artist-list-length\n");
		return;
	}

	printf("Recieving artist-list-length\n");
	artist_list_length_c[rc]='\0';
	artist_list_length = atoi(artist_list_length_c);
	printf("Artistlist length: %d\n", artist_list_length);
	artist_list_length++;
	char buf[artist_list_length];

	recivedMessage = (char*)malloc(artist_list_length);

	printf("recieving artist-list...\n");
	rc = recv(socket,buf,artist_list_length,0);
	if(rc==0)
	{
		printf("Server has closed the connnection before sending the artist-list\n");
		return;
	}
	if(rc==SOCKET_ERROR)
	{
		printf("Error: recv, error-code: %s\n",strerror(errno));
		return;
	}
	buf[rc]='\0';
	strcpy(recivedMessage, buf);
	printf("recivedMessage length: %d\n", strlen(recivedMessage));
	printf("buf: %s\n", buf);

	return;
}

In another function that is called in main():

char* artist_list;

	get_artists(sock, artist_list);
	printf("\n\nget_artists returned: %s\n", artist_list);

Sorry for the confusion
-= Double Post =-
Hoever it works using malloc after the initialization and the reallocating it... .

[hallo007]

i have some problem when you make array's and let the user put in the value
how can you "+" them
for exemple

int repeat()
{

int totaal , scores[5];
totaal=?????????????????
cout<<"geef de scores van de toetsen\n";
cin>>scores[1]>>scores[2]>>scores[3]>>scores[4]>>scores[5];
cout<<"de gemmidelde score voor deze test is "<<totaal /(sizeof(scores)/sizeof(int));

note two :
how cane you let the user put in more numbers for example
the user wants to put in 20 numbers expect 5

int repeat()
{

int totaal , scores[?????];
totaal=??????????;
cout<<"geef de scores van de toetsen\n";
cin>>??????????;
cout<<"de gemmidelde score voor deze test is "<<totaal /(sizeof(scores)/sizeof(int));

i use cout , but dont wory this is something for psp;)

[Lukeson]

how can you "+" them

Errm, what do you mean?
totaal = scores[1] + scores[2] + scores[3] + scores[4] + scores[5];
?

how cane you let the user put in more numbers

Example:

int n=0, max=5, z,i;
int *scores=NULL;
scores = (int *)calloc(max, sizeof(int));

printf("enter scores; end with 0\n");

while(1)
{
	printf("Enter Score #%d: ", n+1);
	scanf("%d", &z);
	if(z==0)
		break;
	if(n >= max) {
		max += max;
		scores = (int *)realloc(scores,max*sizeof(int));
	}
	scores[n++] = z;
}

printf("The following scores have been entered ->\n\n");
for(i = 0; i < n; i++)
	printf("%d ", scores[i]);
printf("\n");
free(scores);

[hallo007]

Errm, what do you mean?
totaal = scores[1] + scores[2] + scores[3] + scores[4] + scores[5];
?

lol , ofcourse i know that:ROFL:
but 1) it's a bi work
2) you answered that in question 2 , thnxxx

[Lukeson]

Now I've got a question:

if you open a file of let's say 200byte and you write 50bytes with fprintf, will it just replace the first 50 bytes an leave the rest as it it (I guess so) or will it replace the file with a new one of 50 bytes? And if you write 300bytes into that file, will there be problems, or will he just create a file of 300bytes then?

Thanks, Luke

PS: What the hell does [WiP] actually mean?
PPS: How do I remove a file? remove(filename)?

[Moonchild]

Now I've got a question:

if you open a file of let's say 200byte and you write 50bytes with fprintf, will it just replace the first 50 bytes an leave the rest as it it (I guess so) or will it replace the file with a new one of 50 bytes? And if you write 300bytes into that file, will there be problems, or will he just create a file of 300bytes then?

Thanks, Luke

PS: What the hell does [WiP] actually mean?
PPS: How do I remove a file? remove(filename)?

That depends whether you choose to truncate the file when you open it. I would suggest reading some about the fopen function.

WiP = Work in Progress ;)

Not sure if the remove function actually works, but you can use the sdk function sceIoRemove(filepath).

[Lukeson]

An answer! Thank you!

PS: How do you know so much about the SDK? The only documentation I found sucks and the samples don't include AFAIK no fileIO examples...

[Moonchild]

The includes (.h) in /usr/local/pspdev/psp/sdk/include have some documentation, like right before the functions it says what it does etc.

[Lukeson]

i c...

[SodR]

All the documentation are stored in usr/local/pspdev/psp/sdk/doc/html. Then just open main.html. I get the feeling that must stuff is documented there.