Thread: Repeated calls to sscanf

Code:

int convert_data(int id_limb){
	char temp1[VECTOR_SIZE];
	char temp2[VECTOR_SIZE];
	char code;
	char code_temp;
	double velocities[8];
	int i;

	
	for (i=0;i<6;i++)	//initializing
	{
		memcpy(temp1,buffer+i*VECTOR_SIZE,VECTOR_SIZE);
		sscanf(temp1,"%s",temp2);
		velocities[i]=atof(temp2);  //
	}
	memcpy(&codigo_temp,buffer+6*VECTOR_SIZE,1);
	sscanf(&codigo_temp,"%c",&code);
	printf("\nCode %c \n",code);
	
return(execute_comand(velocities, code, id_limb));

}

The overall project consist of an operator sending linear and angular velocities to a robotic arm as a string of chars through the lan. As of now we need to speed up the process (it's about 0.5 ms too slow). Is there any way to optimize this particular function? For example, a way to skip the repeated calls to sscanf?

Thanks a lot

Originally Posted by grumpy

Yeah. Eliminate the temp1 buffer and also the sscanf calls. Neither are necessary. Also eliminate the printf() call, except when debugging.

When using sscanf, the %s format scans until it encounters either a whitespace or the end of the input string. As long as you guarantee you do not change buffer, you can do the same using a loop. Similarly, %c simply gets the next character. If all you're reading from the string is a single character, you are getting the first character.

I'm not sure I follow, could you please elaborate a bit more? Also, the string consist of 6 different characters at all times (3 linear components and 3 angular).

@laserlight buffer is global. As for why I don't initialize temp2, I figured I didn't need to since scanf would write there anyway

I was under the impression that memcpy simply copied the memory blocks, but but didn't format the data. Therefore I used sscanf to format them as strings, was my logic wrong?

char buffer[BUFSIZE]

As of right now there are seven different elements in the string: x,y,z linear and x,y,z angular. There's an extra character E,C or H that tells the machine to exit the program, continue or go home. So yes, the remote machine should be able to tell them apart.

Thanks everyone for the help

I'm goig to try

Code:

for (i=0;i<6;i++)    //inicializacion

    {
        strncpy(temp1,buffer+i*VECTOR_SIZE,VECTOR_SIZE);
        velocities[i]=atof(temp1);
     
}
      strncopy(&codigo,buffer+6*VECTOR_SIZE,1);

will report results and speed later