trie/encoding.go


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package trie

import (
    "bytes"
    "encoding/hex"
    "strings"
)

func CompactEncode(hexSlice []byte) string {
    terminator := 0
    if hexSlice[len(hexSlice)-1] == 16 {
        terminator = 1
    }

    if terminator == 1 {
        hexSlice = hexSlice[:len(hexSlice)-1]
    }

    oddlen := len(hexSlice) % 2
    flags := byte(2*terminator + oddlen)
    if oddlen != 0 {
        hexSlice = append([]byte{flags}, hexSlice...)
    } else {
        hexSlice = append([]byte{flags, 0}, hexSlice...)
    }

    var buff bytes.Buffer
    for i := 0; i < len(hexSlice); i += 2 {
        buff.WriteByte(byte(16*hexSlice[i] + hexSlice[i+1]))
    }

    return buff.String()
}

func CompactDecode(str string) []byte {
    base := CompactHexDecode(str)
    base = base[:len(base)-1]
    if base[0] >= 2 {
        base = append(base, 16)
    }
    if base[0]%2 == 1 {
        base = base[1:]
    } else {
        base = base[2:]
    }

    return base
}

func CompactHexDecode(str string) []byte {
    base := "0123456789abcdef"
    var hexSlice []byte

    enc := hex.EncodeToString([]byte(str))
    for _, v := range enc {
        hexSlice = append(hexSlice, byte(strings.IndexByte(base, byte(v))))
    }
    hexSlice = append(hexSlice, 16)

    return hexSlice
}

func DecodeCompact(key []byte) string {
    const base = "0123456789abcdef"
    var str string

    for _, v := range key {
        if v < 16 {
            str += string(base[v])
        }
    }

    res, err := hex.DecodeString(str)

    return string(res)
}