如何将十六进制转换为浮点数

Question

I have to convert hex, represeneted as strings (e.g. "0xC40C5253") to float values (IEEE-754 conversion). I did not manage to do that using the strconv.ParseFloat function. Is there anything else I have to use? I couldn't find it so far. I also tried converting it to an integer first and then to a float, but the results were wrong.

Code of my last try:

package main

import (
  "fmt"
  "strconv"
)

func main () {
  x, err := strconv.ParseInt("C40C5253", 16, 64) 
  f, err := strconv.ParseFloat(fmt.Sprintf("%d", x), 64) 

  if err != nil {
    fmt.Printf("Error in conversion: %s
", err)
  } else {
    fmt.Println(f)
  }
}

Answer 1

First it needs to be stated the bit-length of the input. Since the hex representation has 4 bytes (8 hex digits), it is most likely a float32 (needs clarification from the asker).

You can parse the bytes from the hex representation into an uint32 using strconv.ParseUint(). ParseUint() always returns uint64 which uses 8 bytes in memory so you have to convert it to uint32 which uses 4 bytes just like float32:

s := "C40C5253"
n, err := strconv.ParseUint(s, 16, 32)
if err != nil {
    panic(err)
}
n2 = uint32(n)

Now you have the bytes but they are stored in a variable of type uint32 and therefore interpreted as the bytes of an integer. And you want to interpret them as the bytes of a IEEE-754 floating point number, you can use the unsafe package to do that:

f := *(*float32)(unsafe.Pointer(&n2))
fmt.Println(f)

Output (try it on the Go Playground):

-561.2863

Note:

As JimB noted, for the 2nd part (translating uint32 to float32) the math package has a built-in function math.Float32frombits() which does exactly this under the hood:

f := math.Float32frombits(n2)