How can I convert a float64 variable to big endian encoded byte array?
var f float64 = 12.666512
var result []byte = float64ToByte(f);
fmt.Printf("result:%f",result)
For the sake of clarity how should I implement float64ToByte function in the following playground?
Use math.Float64bits to get the float64 as a uint64. Use shifting and conversions on the uint64 to convert to a desired sequence of bytes. For example, here's how to encode a float in big endian order:
var buf [8]byte
n := math.Float64bits(f)
buf[0] = byte(n >> 56)
buf[1] = byte(n >> 48)
buf[2] = byte(n >> 40)
buf[3] = byte(n >> 32)
buf[4] = byte(n >> 24)
buf[5] = byte(n >> 16)
buf[6] = byte(n >> 8)
buf[7] = byte(n)
You can use the encoding/binary to convert the uint64 to bytes instead of writing out the shifts and conversions directly. Here's how to encode the float64 in big endian order using that package:
var buf [8]byte
binary.BigEndian.PutUint64(buf[:], math.Float64bits(f))
The little endian code is:
var buf [8]byte
binary.LittleEndian.PutUint64(buf[:], math.Float64bits(f))
Here's the big endian implementation of the float64ToByte function in the question:
func float64ToByte(f float64) []byte {
var buf [8]byte
binary.BigEndian.PutUint64(buf[:], math.Float64bits(f))
return buf[:]
}
You can use binary.Write() from package "encoding/binary" :
func float64ToByte(f float64) []byte {
var buf bytes.Buffer
err := binary.Write(&buf, binary.BigEndian, f)
if err != nil {
fmt.Println("binary.Write failed:", err)
}
return buf.Bytes()
}
Adding yet another flavor to this question.
func float64ToBytes(f64 float64) []byte {
bts := make([]byte, 8)
(*(*[]float64)(unsafe.Pointer(&bts)))[0] = f64
return bts
}
func bytesToF64(bts []byte) float64 {
return *(*float64)(unsafe.Pointer(&bts[0]))
}
You could even make it with zero allocation like this
func float64ToBytes(f64 float64) []byte {
var bts []byte
sh := (*reflect.SliceHeader)(unsafe.Pointer(&bts))
sh.Data = uintptr(unsafe.Pointer(&f64))
sh.Len = 8
sh.Cap = sh.Len
return bts
}
https://play.golang.org/p/FO32EmWfjbL
On my system it had to be little endianed:
func float64ToByte(f float64) []byte {
var buf bytes.Buffer
err := binary.Write(&buf, binary.LittleEndian, f)
if err != nil {
fmt.Println("binary.Write failed:", err)
}
return buf.Bytes()
}
