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colorhash.go
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colorhash.go
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package colorhash
import (
"math/big"
"github.com/status-im/status-go/multiaccounts"
"github.com/status-im/status-go/protocol/identity"
)
const (
colorHashSegmentMaxLen = 5
colorHashColorsCount = 32
)
var colorHashAlphabet [][]int
func GenerateFor(pubkey string) (hash multiaccounts.ColourHash, err error) {
if len(colorHashAlphabet) == 0 {
colorHashAlphabet = makeColorHashAlphabet(colorHashSegmentMaxLen, colorHashColorsCount)
}
compressedKey, err := identity.ToCompressedKey(pubkey)
if err != nil {
return nil, err
}
slices, err := identity.Slices(compressedKey)
if err != nil {
return nil, err
}
return toColorHash(new(big.Int).SetBytes(slices[2]), &colorHashAlphabet, colorHashColorsCount), nil
}
// [[1 0] [1 1] [1 2] ... [units, colors-1]]
// [3 12] => 3 units length, 12 color index
func makeColorHashAlphabet(units, colors int) (res [][]int) {
res = make([][]int, units*colors)
idx := 0
for i := 0; i < units; i++ {
for j := 0; j < colors; j++ {
res[idx] = make([]int, 2)
res[idx][0] = i + 1
res[idx][1] = j
idx++
}
}
return
}
func toColorHash(value *big.Int, alphabet *[][]int, colorsCount int) (hash multiaccounts.ColourHash) {
alphabetLen := len(*alphabet)
indexes := identity.ToBigBase(value, uint64(alphabetLen))
hash = make(multiaccounts.ColourHash, len(indexes))
for i, v := range indexes {
hash[i] = [2]int{}
hash[i][0] = (*alphabet)[v][0]
hash[i][1] = (*alphabet)[v][1]
}
// colors can't repeat themselves
// this makes color hash not fully collision resistant
prevColorIdx := hash[0][1]
hashLen := len(hash)
for i := 1; i < hashLen; i++ {
colorIdx := hash[i][1]
if colorIdx == prevColorIdx {
hash[i][1] = (colorIdx + 1) % colorsCount
}
prevColorIdx = hash[i][1]
}
return
}