Encoding int value as an IEEE-754 float (binary32)
bit-manipulation, bitwise-operators, c, floating-point
Solution
C has the "union" to handle this type of view of data:
typedef union {
int i;
float f;
} u;
u u1;
u1.f = 45.6789;
/* now u1.i refers to the int version of the float */
printf("%d",u1.i);
Problem
Given the 32 bits that represent an IEEE 754 floating-point number, how can the number be converted to an integer, using integer or bit operations on the representation (rather than using a machine instruction or compiler operation to convert)? I have the following function but it fails in some cases: Input: int x (contains 32 bit single precision number in IEEE 754 format) ``` if(x == 0) return x; unsigned int signBit = 0; unsigned int absX = (unsigned int)x; if (x < 0) { signBit = 0x80000000u; absX = (unsigned int)-x; } unsigned int exponent = 158; while ((absX & 0x80000000) == 0) { exponent--; absX <<= 1; } unsigned int mantissa = absX >> 8; unsigned int result = signBit | (exponent << 23) | (mantissa & 0x7fffff); printf("\nfor x: %x, result: %x",x,result); return result; ```