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Create short GUIDs with a custom alphabet
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using System; | |
using System.Numerics; | |
namespace Cuppster | |
{ | |
/// <summary> | |
/// converted from the python version at https://github.com/stochastic-technologies/shortuuid | |
/// </summary> | |
class ShortUUID | |
{ | |
private char[] _alphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".ToCharArray(); | |
private int _alphaLen; | |
public ShortUUID() | |
{ | |
_alphaLen = _alphabet.Length; | |
} | |
public ShortUUID(char[] alphabet) | |
{ | |
_alphabet = alphabet; | |
_alphaLen = _alphabet.Length; | |
} | |
public string Uuid() | |
{ | |
var uuid = Guid.NewGuid(); | |
return Encode(uuid); | |
} | |
private string Encode(Guid uuid) | |
{ | |
var uuidBytes = uuid.ToByteArray(); | |
// ensure that the most-significant bit of the last byte (because it's little endian) is zero | |
// see: http://stackoverflow.com/questions/6141745/shift-a-128-bit-signed-biginteger-to-always-be-positive | |
byte[] padded = new byte[uuidBytes.Length + 1]; | |
uuidBytes.CopyTo(padded, 0); | |
padded[uuidBytes.Length] = 0; | |
BigInteger big = new BigInteger(padded); | |
return NumToString(big); | |
} | |
private string NumToString(BigInteger number) | |
{ | |
var output = string.Empty; | |
var len = new BigInteger(_alphaLen); | |
BigInteger digit; | |
while (0 < number) | |
{ | |
number = BigInteger.DivRem(number, len, out digit); | |
output += _alphabet[(int)digit]; | |
} | |
return output; | |
} | |
} | |
} |
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