Custom CVar system

I am trying to write my own cvar system, similar to that found in quake games.

This is my prototype...

Code:

class rCVarEngine
{
	public:
		void setCVar(const char *name, const char *value);
		void setNewCVar(const char *name, const char *value);
		const char returnCVar(const char *name);
	private:
		rCVar *cvarList;
};

and I get this error for it...

rCVar.h:31: error: multiple types in one declaration

Then in this function where I return cvarList->value...

Code:

const char rCVarEngine::returnCVar(const char *name)
{
	while(cvarList)
	{
		if(cvarList->name == name)
		{
			return cvarList->value;			
		} else {
			cvarList = cvarList->next;
		}
		
	}
}

I get this error:

rCVar.h:74: error: invalud conversion from 'const char*' to 'char'

Any help on fixing this would be great! I am using GCC v 3.4.2

Code:

const char rCVarEngine::returnCVar(const char *name)

Perhaps this function is suposed to return a const char*?

Code:

const char *rCVarEngine::returnCVar(const char *name)

Code:

if(cvarList->name == name)

C strings can be compared with strcmp(..)

Thanks! I still get the multiple types in one declaration error, in the class declaration.

I get the multiple type declaration errors when I forget to put a semi-colon after the class. Could this be the case, or could you show us where the exact line is?

Code:

class rCVarEngine
{
	public:
		void setCVar(const char *name, const char *value);
		void setNewCVar(const char *name, const char *value);
		const char* returnCVar(const char *name);
	private:
		rCVar *cvarList;
}; //<-- Error here, line 31

And what is before that? I highly suspect that it's simply a missing semi-colon.

Well, you were right. I forgot a ; in my struct above my class :P

*sighs
Now I get these errors that I have no idea what they mean.

C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0xd):test.cpp: undefined reference to `std::string::size() const'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0x60):test.cpp: undefined reference to `std::string:perator[](unsigned int) const'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0x9f):test.cpp: undefined reference to `std::string:perator[](unsigned int) const'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0xce):test.cpp: undefined reference to `std::string:perator[](unsigned int) const'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0x23b):test.cpp: undefined reference to `std::cout'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0x240):test.cpp: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std:perator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0x275):test.cpp: undefined reference to `std::ios_base::Init::Init()'
C:/DOCUME~1/ryan/LOCALS~1/Temp/ccUDbaaa.o(.text+0x290):test.cpp: undefined reference to `std::ios_base::Init::~Init()'
collect2: ld returned 1 exit status

Ok, it compiles fine, but now the program crashes when I run this function:

Code:

void rCVarEngine::setNewCVar(const char *name, const char *value)
{
	cvarList->next = 0;
	
	if(cvarList == 0)
	{
		strcpy((char*)cvarList->name, name);
		strcpy((char*)cvarList->value, value);
		return;
	}
	
	rCVar *current = cvarList;
	while(current->next)
	{
		current = current->next;
	}
	
	current->next = cvarList;
	cvarList->next = (rCVar*)0;
}

Code:

	if(cvarList == 0)
	{
		strcpy((char*)cvarList->name, name);
		strcpy((char*)cvarList->value, value);
		return;
	}

Operating on a null pointer

Well, what that is doing, is if there is nothing set on cvarList, then set thoe values, instead of moving to the next object.

Originally Posted by St0rmTroop3er

Well, what that is doing, is if there is nothing set on cvarList, then set thoe values, instead of moving to the next object.

No. Look at it.

Originally Posted by Tonto

Code:

	if(cvarList == 0)
	{
		strcpy((char*)cvarList->name, name);
		strcpy((char*)cvarList->value, value);
		return;
	}

Operating on a null pointer

If cvarList is a NULL pointer, then dereference it.


"Hi, I'm pointing somewhere I can never write. Mind if I write this here?"
*Crash* means, "No, I do mind".

Ah, ok I fixed it... but it still crashes. I revamped it so I don't have two functions, one to set a new one and one to set an exisiting one. Hopefully I didn't mess it up.

Linked Lists are big ol pain in the butt...and its so hard to understand them.

Code:

void rCVarEngine::set(const char *name, const char *value,bool lock)
{
	// If our head pointer is blank, then fill that first.
	if(head == 0)
	{
		head->name = name;
		head->value = value;
		head->locked = lock;
		return;
	}
	
	while(cvarList)
	{
		// If we found an existing CVar
		// then set its value and lock
		// mode
		if(cvarList->name == name)
		{
			cvarList->value = value;
			cvarList->locked = lock;
			return;
		//Else if the next in the list is empty
		// Set its new values
		} else if(cvarList->next == 0) {
	
			// Create a temporary cvar
			rCVar *newVar = new rCVar;
			// Set its value
			newVar->name = name;
			newVar->value = value;
			newVar->locked = lock;
			newVar->next = 0;
			
			rCVar *temp = head;
			while(temp->next)
			{
				temp = temp->next;
			}
			
			// Add it to the end
			temp->next = newVar;
		// If we havn't found the end of the
		// list or if we havn't found a pre-
		// existing cvar, then move to the 
		// next in the list
		} else {
			cvarList = cvarList->next;
		} 
		
	}
	
}

NOTE* I am following examples in C++ for Dummies 4th Edition.

Code:

	if(head == 0)
	{
		head->name = name;
		head->value = value;
		head->locked = lock;
		return;
	}

You're trying to dereference a null pointer again, allocate memory for it first, then set values. You might find it useful to have two auxillary pointers, head and tail, pointing to the first and last members of the list respectively.

Code:

if(cvarList->name == name)

Probably need strcmp, unless they are std::string's now.

Ok I added strcmp.

I don't know how to allocate memory for that. :P Would it be better if I did

if(strcmp(head->name,""))

To check if it is empty?