131 lines
3.3 KiB
Go
131 lines
3.3 KiB
Go
package encoder
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import (
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"unsafe"
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)
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var endianness int
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func init() {
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var b [2]byte
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*(*uint16)(unsafe.Pointer(&b)) = uint16(0xABCD)
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switch b[0] {
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case 0xCD:
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endianness = 0 // LE
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case 0xAB:
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endianness = 1 // BE
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default:
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panic("could not determine endianness")
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}
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}
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// "00010203...96979899" cast to []uint16
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var intLELookup = [100]uint16{
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0x3030, 0x3130, 0x3230, 0x3330, 0x3430, 0x3530, 0x3630, 0x3730, 0x3830, 0x3930,
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0x3031, 0x3131, 0x3231, 0x3331, 0x3431, 0x3531, 0x3631, 0x3731, 0x3831, 0x3931,
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0x3032, 0x3132, 0x3232, 0x3332, 0x3432, 0x3532, 0x3632, 0x3732, 0x3832, 0x3932,
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0x3033, 0x3133, 0x3233, 0x3333, 0x3433, 0x3533, 0x3633, 0x3733, 0x3833, 0x3933,
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0x3034, 0x3134, 0x3234, 0x3334, 0x3434, 0x3534, 0x3634, 0x3734, 0x3834, 0x3934,
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0x3035, 0x3135, 0x3235, 0x3335, 0x3435, 0x3535, 0x3635, 0x3735, 0x3835, 0x3935,
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0x3036, 0x3136, 0x3236, 0x3336, 0x3436, 0x3536, 0x3636, 0x3736, 0x3836, 0x3936,
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0x3037, 0x3137, 0x3237, 0x3337, 0x3437, 0x3537, 0x3637, 0x3737, 0x3837, 0x3937,
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0x3038, 0x3138, 0x3238, 0x3338, 0x3438, 0x3538, 0x3638, 0x3738, 0x3838, 0x3938,
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0x3039, 0x3139, 0x3239, 0x3339, 0x3439, 0x3539, 0x3639, 0x3739, 0x3839, 0x3939,
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}
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var intBELookup = [100]uint16{
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0x3030, 0x3031, 0x3032, 0x3033, 0x3034, 0x3035, 0x3036, 0x3037, 0x3038, 0x3039,
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0x3130, 0x3131, 0x3132, 0x3133, 0x3134, 0x3135, 0x3136, 0x3137, 0x3138, 0x3139,
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0x3230, 0x3231, 0x3232, 0x3233, 0x3234, 0x3235, 0x3236, 0x3237, 0x3238, 0x3239,
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0x3330, 0x3331, 0x3332, 0x3333, 0x3334, 0x3335, 0x3336, 0x3337, 0x3338, 0x3339,
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0x3430, 0x3431, 0x3432, 0x3433, 0x3434, 0x3435, 0x3436, 0x3437, 0x3438, 0x3439,
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0x3530, 0x3531, 0x3532, 0x3533, 0x3534, 0x3535, 0x3536, 0x3537, 0x3538, 0x3539,
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0x3630, 0x3631, 0x3632, 0x3633, 0x3634, 0x3635, 0x3636, 0x3637, 0x3638, 0x3639,
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0x3730, 0x3731, 0x3732, 0x3733, 0x3734, 0x3735, 0x3736, 0x3737, 0x3738, 0x3739,
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0x3830, 0x3831, 0x3832, 0x3833, 0x3834, 0x3835, 0x3836, 0x3837, 0x3838, 0x3839,
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0x3930, 0x3931, 0x3932, 0x3933, 0x3934, 0x3935, 0x3936, 0x3937, 0x3938, 0x3939,
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}
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var intLookup = [2]*[100]uint16{&intLELookup, &intBELookup}
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func numMask(numBitSize uint8) uint64 {
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return 1<<numBitSize - 1
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}
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func AppendInt(_ *RuntimeContext, out []byte, u64 uint64, code *Opcode) []byte {
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mask := numMask(code.NumBitSize)
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n := u64 & mask
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negative := (u64>>(code.NumBitSize-1))&1 == 1
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if !negative {
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if n < 10 {
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return append(out, byte(n+'0'))
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} else if n < 100 {
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u := intLELookup[n]
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return append(out, byte(u), byte(u>>8))
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}
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} else {
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n = -n & mask
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}
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lookup := intLookup[endianness]
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var b [22]byte
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u := (*[11]uint16)(unsafe.Pointer(&b))
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i := 11
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for n >= 100 {
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j := n % 100
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n /= 100
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i--
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u[i] = lookup[j]
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}
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i--
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u[i] = lookup[n]
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i *= 2 // convert to byte index
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if n < 10 {
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i++ // remove leading zero
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}
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if negative {
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i--
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b[i] = '-'
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}
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return append(out, b[i:]...)
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}
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func AppendUint(_ *RuntimeContext, out []byte, u64 uint64, code *Opcode) []byte {
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mask := numMask(code.NumBitSize)
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n := u64 & mask
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if n < 10 {
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return append(out, byte(n+'0'))
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} else if n < 100 {
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u := intLELookup[n]
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return append(out, byte(u), byte(u>>8))
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}
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lookup := intLookup[endianness]
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var b [22]byte
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u := (*[11]uint16)(unsafe.Pointer(&b))
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i := 11
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for n >= 100 {
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j := n % 100
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n /= 100
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i--
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u[i] = lookup[j]
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}
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i--
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u[i] = lookup[n]
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i *= 2 // convert to byte index
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if n < 10 {
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i++ // remove leading zero
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}
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return append(out, b[i:]...)
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}
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