Created
May 13, 2020 20:07
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Base62 encoding/decoding
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| import java.math.BigInteger | |
| /** | |
| * Base62 encoder/decoder. | |
| */ | |
| object Base62 { | |
| private val BASE = BigInteger.valueOf(62) | |
| private val DIGITS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" | |
| /** | |
| * Encodes a number using Base62 encoding. | |
| * | |
| * @param number a positive integer | |
| * @return a Base62 string | |
| * @throws IllegalArgumentException if `number` is a negative integer | |
| */ | |
| fun encode(number: BigInteger): String { | |
| require(number >= BigInteger.ZERO) | |
| val result = StringBuilder() | |
| var quotient = number | |
| while (quotient > BigInteger.ZERO) { | |
| val divmod = quotient.divideAndRemainder(BASE) | |
| quotient = divmod[0] | |
| val remainder = divmod[1].intValueExact() | |
| result.append(DIGITS[remainder]) | |
| } | |
| return when (result.isEmpty()) { | |
| true -> DIGITS.take(1) | |
| else -> result.reverse().toString() | |
| } | |
| } | |
| fun encode(number: Long) = encode(BigInteger.valueOf(number)) | |
| /** | |
| * Decodes a string using Base62 encoding. | |
| * | |
| * @param string a Base62 string | |
| * @return a positive integer | |
| * @throws IllegalArgumentException if `string` is empty | |
| */ | |
| fun decode(string: String): BigInteger { | |
| require(string.isNotEmpty()) | |
| var result = BigInteger.ZERO | |
| string.forEachIndexed { index, c -> | |
| val digit = DIGITS.indexOf(c) | |
| result = result.add( | |
| BigInteger | |
| .valueOf(digit.toLong()) | |
| .multiply(BASE.pow(index)) | |
| ) | |
| } | |
| return result | |
| } | |
| } |
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