GuidFromName

guid.go

testName := "Bagaaqy23kudbhchAaq5u2chNd"
testGuid := "{20001801-5DE6-11D1-8E38-00C04FB9386D}"


func GuidFromName(n string) (Guid, error) {
n = strings.ToLower(n)
buf, err := charConvert([]byte(n))
if err != nil {
 return Guid{}, err
}
return makeGuid(buf, binary.LittleEndian), nil
}

func charConvert(in []byte) ([]byte, error) {
  if len(in) != 26 {
    return nil, errors.New("invalid GUID: expecting 26 characters")
  }
  out := make([]byte, 16)
  idx, right, left := 0, 0, 3
  var b byte
  for _, v := range in {
    this, ok := characterMapping[v]
    if !ok {
      return nil, errors.New("invalid Guid: invalid character")
    }
    if right > 0 || left == 0 {
      b = b | this >> right
      out[idx] = b
      b = 0
      idx++
    }
    if left > 0 {
        b = b | this << left
   }
    rem := 5 - l
    if rem <= 0 {
       rem = 8 + rem
       r = 0
    } else {
       r = rem
    }
   l = 8 - rem
  }
  return out, nil
}

const (
   charA byte = iota
   charB
   charC
   charD
   charE
   charF
   charG
   charH
   charI
   charJ
   charK
   charL
   charM
   charN
   charO
   charP
   charQ
   charR
   charS
   charT
   charU
   charV
   charW
   charX
   charY
   charZ
   char0
   char1
   char2
   char3
   char4
   char5
)

var characterMapping  = map[byte]byte{
  'a': charA,
  'b': charB,
  'c': charC,
  'd': charD,
  'e': charE,
  'f': charF,
  'g': charG,
  'h': charH,
  'i': charI,
  'j': charJ,
  'k': charK,
  'l': charL,
  'm': charM,
  'n': charN,
  'o': charO,
  'p': charP,
  'q': charQ,
  'r': charR,
  's': charS,
  't': charT,
  'u': charU,
  'v': charV,
  'w': charW,
  'x': charX,
  'y': charY,
  'z': charZ,
  '0': char0,
  '1': char1,
  '2': char2,
  '3': char3,
  '4': char4,
  '5': char5,
}