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Convert Float to Int using Assembly Language Programming

, 15 Jun 2005
An article on Converting Float value to an integer value trimming off the decimal part
ftoi_src.zip
ftoi
ftoi.dsp
ftoi.dsw
ftoi.opt
ftoi.plg
test.opt
test.plg
#include <stdio.h>
int ftoi(float flt)
{
	int i;
	_asm
	{
		mov  eax,flt; //loaded mem to acc
		rcl  eax,1;   //left shift acc to remove the sign
		mov  ebx,eax; //save the acc
		mov	 edx,4278190080; //clear reg edx;
		and  eax,edx; //and acc to retrieve the exponent
		shr  eax,24;
		sub  eax,7fh; //subtract 7fh(127) to get the actual power 
		mov  edx,eax; //save acc val power
		mov  eax,ebx; //retrieve from ebx
		rcl  eax,8;	 //trim the left 8 bits that contain the power
		mov  ebx,eax; //store
        mov  ecx, 1fh; //subtract 17 h
		sub  ecx,edx; 
        mov  edx,00000000h;
        cmp  ecx,0;
		je   loop2;
		shr  eax,1;
		or   eax,80000000h;		
loop1:	
		shr  eax,1; //shift (total bits - power bits);
		sub  ecx,1;
		add  edx,1;
		cmp  ecx,0;
		ja   loop1;
loop2:  
		mov  i, eax;		
	
//check sign +/-		
sign:
		mov  eax,flt;
		and  eax,80000000h;
		cmp  eax,80000000h;
		je	 putsign;
	}

	return i;

putsign:
	return -i;
}


void main()
{
	float f = 0;
	while (true)
	{
		printf("Enter the Float value\n");
		scanf("%f", &f);
		printf("float %f\n", f);
		printf("int %d\n",ftoi(f)); 
	}
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Jayadev MV
Web Developer
India India
Hi.. I have been working on C/C++ for more than 2 years. My areas of interest are Network programming and System Level programming.
I work with C/C++ over Windows and Solaris.

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