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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)
}
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