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