147 lines
2.7 KiB
Go
147 lines
2.7 KiB
Go
package filter
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// Filter exposes Decode and Encode methods for data manipulation
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type Filter struct {
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index int32
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error int32
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round int32
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shift uint32
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qm [8]int32
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dx [24]int32
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dl [24]int32
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}
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type codec func(fs *Filter, in *int32)
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var (
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decode codec = CompatDecode
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encode codec = CompatEncode
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)
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// New creates a Filter based on data and shift
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func New(data [8]byte, shift uint32) *Filter {
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f := Filter{}
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f.shift = shift
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f.round = 1 << uint32(shift-1)
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f.qm[0] = int32(int8(data[0]))
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f.qm[1] = int32(int8(data[1]))
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f.qm[2] = int32(int8(data[2]))
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f.qm[3] = int32(int8(data[3]))
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f.qm[4] = int32(int8(data[4]))
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f.qm[5] = int32(int8(data[5]))
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f.qm[6] = int32(int8(data[6]))
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f.qm[7] = int32(int8(data[7]))
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return &f
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}
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func (f *Filter) Decode(in *int32) {
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decode(f, in)
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}
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func (f *Filter) Encode(in *int32) {
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encode(f, in)
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}
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func CompatDecode(f *Filter, in *int32) {
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pa := f.dl[:]
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pb := f.qm[:]
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pm := f.dx[:]
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sum := f.round
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if f.error < 0 {
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pb[0] -= pm[0]
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pb[1] -= pm[1]
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pb[2] -= pm[2]
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pb[3] -= pm[3]
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pb[4] -= pm[4]
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pb[5] -= pm[5]
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pb[6] -= pm[6]
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pb[7] -= pm[7]
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} else if f.error > 0 {
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pb[0] += pm[0]
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pb[1] += pm[1]
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pb[2] += pm[2]
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pb[3] += pm[3]
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pb[4] += pm[4]
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pb[5] += pm[5]
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pb[6] += pm[6]
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pb[7] += pm[7]
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}
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sum += pa[0]*pb[0] + pa[1]*pb[1] + pa[2]*pb[2] + pa[3]*pb[3] +
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pa[4]*pb[4] + pa[5]*pb[5] + pa[6]*pb[6] + pa[7]*pb[7]
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pm[0] = pm[1]
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pm[1] = pm[2]
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pm[2] = pm[3]
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pm[3] = pm[4]
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pa[0] = pa[1]
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pa[1] = pa[2]
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pa[2] = pa[3]
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pa[3] = pa[4]
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pm[4] = ((pa[4] >> 30) | 1)
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pm[5] = ((pa[5] >> 30) | 2) & ^1
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pm[6] = ((pa[6] >> 30) | 2) & ^1
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pm[7] = ((pa[7] >> 30) | 4) & ^3
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f.error = *in
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*in += (sum >> uint32(f.shift))
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pa[4] = -pa[5]
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pa[5] = -pa[6]
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pa[6] = *in - pa[7]
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pa[7] = *in
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pa[5] += pa[6]
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pa[4] += pa[5]
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}
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func CompatEncode(f *Filter, in *int32) {
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pa := f.dl[:]
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pb := f.qm[:]
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pm := f.dx[:]
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sum := f.round
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if f.error < 0 {
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pb[0] -= pm[0]
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pb[1] -= pm[1]
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pb[2] -= pm[2]
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pb[3] -= pm[3]
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pb[4] -= pm[4]
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pb[5] -= pm[5]
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pb[6] -= pm[6]
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pb[7] -= pm[7]
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} else if f.error > 0 {
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pb[0] += pm[0]
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pb[1] += pm[1]
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pb[2] += pm[2]
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pb[3] += pm[3]
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pb[4] += pm[4]
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pb[5] += pm[5]
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pb[6] += pm[6]
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pb[7] += pm[7]
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}
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sum += pa[0]*pb[0] + pa[1]*pb[1] + pa[2]*pb[2] + pa[3]*pb[3] +
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pa[4]*pb[4] + pa[5]*pb[5] + pa[6]*pb[6] + pa[7]*pb[7]
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pm[0] = pm[1]
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pm[1] = pm[2]
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pm[2] = pm[3]
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pm[3] = pm[4]
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pa[0] = pa[1]
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pa[1] = pa[2]
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pa[2] = pa[3]
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pa[3] = pa[4]
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pm[4] = ((pa[4] >> 30) | 1)
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pm[5] = ((pa[5] >> 30) | 2) & ^1
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pm[6] = ((pa[6] >> 30) | 2) & ^1
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pm[7] = ((pa[7] >> 30) | 4) & ^3
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pa[4] = -pa[5]
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pa[5] = -pa[6]
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pa[6] = *in - pa[7]
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pa[7] = *in
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pa[5] += pa[6]
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pa[4] += pa[5]
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*in -= (sum >> uint32(f.shift))
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f.error = *in
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}
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