从字节表示的 Int 计算

Question

Given bytes as HEX: 710e00fe I do the following:

int value = (*(int*)([bytes bytes]));
int exp = value >> 24; 
int mantissa = value & 0x00FFFFFF;

And I get mantissa = 3697 and exponent = -2 .

I tried doing this manually but I can't figure out how I got those values. I can actually get the exp right, but mantissa is a huge number when I manually calculate. Is there something wrong?

Answer 1

You have a little-endian CPU.
So, the exponent is the last byte in bytes, ie 0xfe == -2 in two's complement.

And the mantissa is 0x000e71, ie 3697.