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package bn256
import (
"errors"
"fmt"
)
type gfP [4]uint64
func newGFp(x int64) (out *gfP) {
if x >= 0 {
out = &gfP{uint64(x)}
} else {
out = &gfP{uint64(-x)}
gfpNeg(out, out)
}
montEncode(out, out)
return out
}
func (e *gfP) String() string {
return fmt.Sprintf("%16.16x%16.16x%16.16x%16.16x", e[3], e[2], e[1], e[0])
}
func (e *gfP) Set(f *gfP) {
e[0] = f[0]
e[1] = f[1]
e[2] = f[2]
e[3] = f[3]
}
func (e *gfP) Invert(f *gfP) {
bits := [4]uint64{0x3c208c16d87cfd45, 0x97816a916871ca8d, 0xb85045b68181585d, 0x30644e72e131a029}
sum, power := &gfP{}, &gfP{}
sum.Set(rN1)
power.Set(f)
for word := 0; word < 4; word++ {
for bit := uint(0); bit < 64; bit++ {
if (bits[word]>>bit)&1 == 1 {
gfpMul(sum, sum, power)
}
gfpMul(power, power, power)
}
}
gfpMul(sum, sum, r3)
e.Set(sum)
}
func (e *gfP) Marshal(out []byte) {
for w := uint(0); w < 4; w++ {
for b := uint(0); b < 8; b++ {
out[8*w+b] = byte(e[3-w] >> (56 - 8*b))
}
}
}
func (e *gfP) Unmarshal(in []byte) error {
// Unmarshal the bytes into little endian form
for w := uint(0); w < 4; w++ {
for b := uint(0); b < 8; b++ {
e[3-w] += uint64(in[8*w+b]) << (56 - 8*b)
}
}
// Ensure the point respects the curve modulus
for i := 3; i >= 0; i-- {
if e[i] < p2[i] {
return nil
}
if e[i] > p2[i] {
return errors.New("bn256: coordinate exceeds modulus")
}
}
return errors.New("bn256: coordinate equals modulus")
}
func montEncode(c, a *gfP) { gfpMul(c, a, r2) }
func montDecode(c, a *gfP) { gfpMul(c, a, &gfP{1}) }
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