grokify/mogo

// base36 supports Base36 encoding and decoding.
package base36

import (
    "crypto/md5" // #nosec G501
    "encoding/hex"
    "fmt"
    "strings"

    "github.com/grokify/base36"
    "github.com/grokify/mogo/math/bigint"
)

// Md5Base36Length is the length for a MD5 Base36 string
const (
    Md5Base36Length int    = 25
    md5base36format string = `%025s`
)

// Decode36 returns a decoded byte array given an encoded byte array.
func Decode36(b36 []byte) ([]byte, error) {
    return Decode36String(string(b36))
}

// Decode36String returns a decoded byte array given an encoded string.
func Decode36String(s36 string) ([]byte, error) {
    bi := base36.DecodeBigInt(s36)
    return hex.DecodeString(bigint.IntToHex(bi))
}

// Encode36 returns an encoded string given a byte array.
func Encode36(ba []byte) (string, error) {
    return Encode36HexString(hex.EncodeToString(ba))
}

// Encode36String returns an encoded string given a string.
func Encode36String(s string) (string, error) {
    return Encode36([]byte(s))
}

// Encode36HexString returns an encoded string given a string.
func Encode36HexString(s16 string) (string, error) {
    i, err := bigint.NewIntHex(s16)
    if err != nil {
        return "", err
    }
    return strings.ToLower(base36.EncodeBigInt(i)), nil
}

// Md5Base36 returns a Base36 encoded MD5 hash of a string.
func Md5Base36(s string) string {
    b36Hex, err := Encode36HexString(fmt.Sprintf("%x", md5.Sum([]byte(s)))) // #nosec G401
    if err != nil {
        panic(err)
    }
    return fmt.Sprintf(md5base36format, b36Hex) // #nosec G401
}

// Md5String is an alias for Md5Base36.
func Md5String(s string) string {
    return Md5Base36(s)
}

/*
GMP Versions

//import "github.com/grokify/gmp"

// Encode36String returns an encoded string given a byte array.
func Encode36(ba []byte) string {
    s16 := hex.EncodeToString(ba)
    bi := gmp.NewInt(0)
    bi.SetString(s16, 16)
    return bi.InBase(36)
}

// Decode36String returns a decoded byte array given an encoded string.
func Decode36String(s36 string) ([]byte, error) {
    bi := gmp.NewInt(0)
    bi.SetString(s36, 36)
    s16 := bi.InBase(16)
    return hex.DecodeString(s16)
}

// Md5Base36 returns a Base36 encoded MD5 hash of a string.
func Md5Base36(s string) string {
    h := md5.New()
    io.WriteString(h, s)
    s16 := fmt.Sprintf("%x", h.Sum(nil))
    bi := gmp.NewInt(0)
    bi.SetString(s16, 16)
    return fmt.Sprintf("%025s", bi.InBase(36))
}
*/