79 lines
1.5 KiB
Go
79 lines
1.5 KiB
Go
package struc
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"io"
|
|
"math"
|
|
"strconv"
|
|
)
|
|
|
|
type Float16 float64
|
|
|
|
func (f *Float16) Pack(p []byte, opt *Options) (int, error) {
|
|
order := opt.Order
|
|
if order == nil {
|
|
order = binary.BigEndian
|
|
}
|
|
sign := uint16(0)
|
|
if *f < 0 {
|
|
sign = 1
|
|
}
|
|
var frac, exp uint16
|
|
if math.IsInf(float64(*f), 0) {
|
|
exp = 0x1f
|
|
frac = 0
|
|
} else if math.IsNaN(float64(*f)) {
|
|
exp = 0x1f
|
|
frac = 1
|
|
} else {
|
|
bits := math.Float64bits(float64(*f))
|
|
exp64 := (bits >> 52) & 0x7ff
|
|
if exp64 != 0 {
|
|
exp = uint16((exp64 - 1023 + 15) & 0x1f)
|
|
}
|
|
frac = uint16((bits >> 42) & 0x3ff)
|
|
}
|
|
var out uint16
|
|
out |= sign << 15
|
|
out |= exp << 10
|
|
out |= frac & 0x3ff
|
|
order.PutUint16(p, out)
|
|
return 2, nil
|
|
}
|
|
func (f *Float16) Unpack(r io.Reader, length int, opt *Options) error {
|
|
order := opt.Order
|
|
if order == nil {
|
|
order = binary.BigEndian
|
|
}
|
|
var tmp [2]byte
|
|
if _, err := r.Read(tmp[:]); err != nil {
|
|
return err
|
|
}
|
|
val := order.Uint16(tmp[:2])
|
|
sign := (val >> 15) & 1
|
|
exp := int16((val >> 10) & 0x1f)
|
|
frac := val & 0x3ff
|
|
if exp == 0x1f {
|
|
if frac != 0 {
|
|
*f = Float16(math.NaN())
|
|
} else {
|
|
*f = Float16(math.Inf(int(sign)*-2 + 1))
|
|
}
|
|
} else {
|
|
var bits uint64
|
|
bits |= uint64(sign) << 63
|
|
bits |= uint64(frac) << 42
|
|
if exp > 0 {
|
|
bits |= uint64(exp-15+1023) << 52
|
|
}
|
|
*f = Float16(math.Float64frombits(bits))
|
|
}
|
|
return nil
|
|
}
|
|
func (f *Float16) Size(opt *Options) int {
|
|
return 2
|
|
}
|
|
func (f *Float16) String() string {
|
|
return strconv.FormatFloat(float64(*f), 'g', -1, 32)
|
|
}
|