Get the hexadecimal notation of floating point numbers (SW)

Last time About Verilog-HDL implementation of Float calculation circuit-Part 1

4/26 Added simulation results 5/17 Fixed a negative number bug

Contents of this time

Is 32bit float (single) the correct value? Create a tool to convert between float value and hexadecimal notation value

use cgo

Great pioneer (references)

Let's get the internal representation of floating point numbers

Whole code

Code created this time

`check.go`


package main

/*
union {float f; unsigned i;} uv;

int f2b(float inp) {
	uv.f = inp;
	return uv.i;
}

float b2f(unsigned inp) {
	uv.i = inp;
	return uv.f;
}
*/
import "C"
import (
	"fmt"
	"os"
	"strconv"
)

func main() {
	if os.Args[1] == "f" {
		fmt.Println("float -> hx")
		fv, _ := strconv.ParseFloat(os.Args[2], 32)
		f2h(float32(fv))
	} else if os.Args[1] == "h" {
		fmt.Println("hx -> float")
		hv, _ := strconv.ParseUint(os.Args[2], 16, 32)
		h2f(uint(hv))
	}
}

func h2f(inp uint) {
	float := float32(C.b2f(_Ctype_uint(inp)))
	fmt.Println(float)
}

func f2h(inp float32) {
	bits := int(C.f2b(_Ctype_float(inp)))

	fmt.Printf("Hex:%08X\n", bits)
	fmt.Printf("Exp:%02X\n", bits >> 23 & 0xFF)
	fmt.Printf("Fra:%X\n", bits & 0x7FFFFF)
}

Converting values in a union

I don't do anything special, so I think it can be implemented in C as well. (Rather, can it be implemented only with Go?)

test

$ go run check.go f 7.25
float -> hx
Hex:40E80000
Exp:81
Fra:680000

Exp bias value 127 is 7F The value of the exponent part is 81, which is +2.

Also, since 680000 = 110 1000 0 0 0 0 You can see that 7.25 = 111.01 = 680000 x 2 ^ 2

$ go run check.go h 40E80000
hx -> float
7.25

You can see that it can be returned correctly

Verification of simulation results

7.25 + 11.625

7.25 + 11.625 = 18.875 \\
-> 40E8\_0000 + 413A\_0000 = 4197\_0000\\

Screenshot from 2020-04-26 20-05-25.png

It looks like it's right

12.345 + 3.1415926

12.345 + 3.1415926 = 15.4865926\\
-> 4145\_851F + 4049\_0FDA = 4177\_C915

Screenshot from 2020-04-26 20-09-04.png