Thread: Weird problem with sscanf

Hi, I've got a weird problem here:

I have a routine of reading from a file and getting some values for the variables from it. Here's the problem:

Code:

...
	sscanf ( buffer,"%d : %d : %d : %d : %d",&mWidth, &mHeight, &mTransCol.transR, &mTransCol.transG , &mTransCol.transB);
...

and the buffer's value (from debug) is:

Code:

buffer = "22 : 21 : 1 : 2 : 3\r\n\000..."

the value of variables are:

Code:

mWidth=0 
mHeight=21
mTransCol.transR=1
mTransCol.transG=2
mTransCol.transB=3

I'm confused. Why does the mWidth is 0 whereas in the buffer string it's clearly 22 ?? Can anybody help me with this?

What type is mWidth, how are you printing the results? What is sscanf returning?

Originally Posted by SKeane

What type is mWidth, how are you printing the results? What is sscanf returning?

mWidth is an int. And when I cout-ed the buffer, it displays the same as the value of buffer. And sscanf returned 5 (so I guess all the variables are successfully read).

BTW, before the troublesome line, there's a sequence of reading with fgets and sscanf. And the pervious sequence worked fine.

Code:

        int scanBuff;

	fgets (buffer, 255, fp);
        //looping through comments (#)
	while (buffer[0] == '#' || buffer[0] == '\r' || buffer[0] == '\0' || buffer[0] == '\n' || strlen(buffer) == 0)
	{
		fgets (buffer, 255, fp);
	}

	scanBuff = sscanf ( buffer, "%s : %s : %s : %s : %d", nametemp, dirName, filename, widthfile, &mNumFonts);
	
	fgets (buffer, 255, fp);
        //looping through comments (#)
	while (buffer[0] == '#' || buffer[0] == '\r' || buffer[0] == '\0' || buffer[0] == '\n' || strlen(buffer) == 0)
	{
		fgets (buffer, 255, fp);
	}
	scanBuff = sscanf ( buffer, "%d : %d : %d : %d : %d : %d : %d : %d", &mIndexLargeA, &mIndexSmallA, &mIndex0, &mIndexKoma, &mIndexDot, &mIndexDot2, &mIndexEq, &mIndexEs);

	fgets (buffer, 255, fp);
        //looping through comments (#)
	while (buffer[0] == '#' || buffer[0] == '\r' || buffer[0] == '\0' || buffer[0] == '\n' || strlen(buffer) == 0)
	{
		fgets (buffer, 255, fp);
	}
	scanBuff=sscanf ( buffer,"%d : %d : %d : %d : %d",&mWidth, &mHeight, &mTransCol.transR, &mTransCol.transG , &mTransCol.transB);

You know, I've solved the problem with a little bit of tinkering. I defined a local temporary variable and then used it in the sscanf. After that the I set mWidth equivalent the temporary variable like so:

Code:

        int tempW;
	scanBuff=sscanf ( buffer,"%d : %d : %d : %d : %d", &tempW, &mHeight, &mTransCol.transR, &mTransCol.transG , &mTransCol.transB);

	mWidth= tempW;

And it worked (At last!!!!!!). BTW, I forgot to mention that mWidth is a private member variable (as well as mHeight and mTransCol in that matter). But still, the cause of the problem isn't solved and I'm still curious. But I'm happy with that, for now.

Originally Posted by SlyMaelstrom

Well, now that you got that solved... may I suggest using stringstreams or lexical_cast instead? This is C++, after all, and sprintf is a very C solution... those very acceptable.

Yeah, that's what I thought too. But alas, the code was already in C (my application is in the most part C++, but in a few exceptions still in C like this one). And I kind of lazy to rewrite in in C++ style :P

Originally Posted by Salem

Can you post a small and complete program which demonstrates the problem.

Your answer doesn't solve anything, it sweeps it under the carpet for it to reappear later on.

Well, this is not the complete program, just the faulty function:

Code:

int CFont::init(char *infoPath, char *infoFile)
{
	char buffer[255];
	char *strState; 
	char filename[255], filename2[255];
	char dirName[255];
	char nametemp[255];
	char widthfile[255];

	//int bogusVar;
	FILE *fp; //buffer config file


	//Path&filename config file
	strcpy(filename,infoPath);
	strcat(filename,"/");
	strcat(filename,infoFile);

	int scanBuff, tempW;
	
	//open config file
	if((fp=fopen(filename, "r")) == NULL)
	{
		printf("ERROR opening file %s\n\n", filename);
		return -1;
	}

	//Reading configuration
	strState = fgets (buffer, 255, fp);
        //looping through comments (#)
	while (buffer[0] == '#' || buffer[0] == '\r' || buffer[0] == '\0' || buffer[0] == '\n' || strlen(buffer) == 0)
	{
		strState = fgets (buffer, 255, fp);
	}

	scanBuff = sscanf ( buffer, "%s : %s : %s : %s : %d", nametemp, dirName, filename, widthfile, &mNumFonts);
	
	strState = fgets (buffer, 255, fp);
        //looping through comments (#)
	while (buffer[0] == '#' || buffer[0] == '\r' || buffer[0] == '\0' || buffer[0] == '\n' || strlen(buffer) == 0)
	{
		strState = fgets (buffer, 255, fp);
	}
	scanBuff = sscanf ( buffer, "%d : %d : %d : %d : %d : %d : %d : %d", &mIndexLargeA, &mIndexSmallA, &mIndex0, &mIndexKoma, &mIndexDot, &mIndexDot2, &mIndexEq, &mIndexEs);

	strState = fgets (buffer, 255, fp);
        //looping through comments (#)
	while (buffer[0] == '#' || buffer[0] == '\r' || buffer[0] == '\0' || buffer[0] == '\n' || strlen(buffer) == 0)
	{
		strState = fgets (buffer, 255, fp);
	}
	scanBuff=sscanf ( buffer,"%d : %d : %d : %d : %d",&mWidth, &mHeight, &mTransCol.transR, &mTransCol.transG , &mTransCol.transB);

	//mWidth= tempW;
      	fclose(fp);
}

The class itself:

Code:

class CFont  
{
public:
	CPicFont* getPicFont(int no);
	int getCharWidth(char nama);
	string getName();
	void draw(int xx, int yy, char huruf);
	void createFont(char* folder, char* nama, SDL_Rect blit_Reg, char huruf);
	CFont();
	CFont(char *fontInfoPath, char *fontInfoFile, CSurface* screen);
	int getHeight();
	int getWidth();
	virtual ~CFont();

private:
	CSurface* mScreen;
	int init(char *infoPath, char *infoFile);
	int mNumFonts;
	string mNamaFont;
	TransparentColor mTransCol;
	int mWidth;
	int mHeight;
	lstFontName mFontName;
	lstFontHandle mFontHandle;
	int mIndexLargeA; 
	int mIndexSmallA; 
	int mIndex0; 
	int mIndexKoma;
	int mIndexDot; 
	int mIndexDot2;
	int mIndexEq; 
	int mIndexEs; 
};

The init function is called under the constructor.

On a side note, it is not usually a good idea to mix C and C++ code. Either do it one way or the other

Originally Posted by swgh

On a side note, it is not usually a good idea to mix C and C++ code. Either do it one way or the other

Yeah, I know that. The code is done because I didn't know the proper way to do it in C++. And because my application is getting bigger, I somewhat reluctant to rewrite it. After all, there's still many things to do than tweaking the code.

2 Salem:

Okay, I've made a new app with only the class, the constructor of the class, and the init function. And guess what, it didn't show any error and worked fine. BTW, the faulty code was actually worked fine at first. Then I added five more integer input before mWidth (the IndexKoma to IndexEs) and after that the code always read mWidth = 0 regardless of the actual value in the file.