src/commonMain/kotlin/com/infendro/encoding/Base16.kt

@@ -1,5 +1,10 @@
 package com.infendro.encoding
 
-private val alphabet = "0123456789ABCDEF".encodeToByteArray()
+private val uppercase = "0123456789ABCDEF".encodeToByteArray()
+private val lowercase = "0123456789abcdef".encodeToByteArray()
 
-object Base16 : Encoding by StreamEncoding(alphabet)
+object Base16 : Encoding by StreamEncoding(uppercase) {
+    val UPPERCASE = this
+
+    object LOWERCASE : Encoding by StreamEncoding(lowercase)
+}

src/commonMain/kotlin/com/infendro/encoding/Base32.kt

@@ -3,4 +3,4 @@ package com.infendro.encoding
 private val alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567".encodeToByteArray()
 private const val padding = '='.code.toByte()
 
-object Base32 : Encoding by PaddedStreamEncoding(alphabet, padding)
+object Base32 : Encoding by StreamEncoding(alphabet, padding)

src/commonMain/kotlin/com/infendro/encoding/Base64.kt

@@ -1,6 +1,11 @@
 package com.infendro.encoding
 
-private val alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".encodeToByteArray()
+private val standard = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".encodeToByteArray()
+private val url = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".encodeToByteArray()
 private const val padding = '='.code.toByte()
 
-object Base64 : Encoding by PaddedStreamEncoding(alphabet, padding)
+object Base64 : Encoding by StreamEncoding(standard, padding) {
+    val STANDARD = this
+
+    object URL : Encoding by StreamEncoding(url)
+}

src/commonMain/kotlin/com/infendro/encoding/Encoding.kt

@@ -1,10 +1,6 @@
 package com.infendro.encoding
 
 interface Encoding {
-    val alphabet: ByteArray
-    val base: Int
-        get() = alphabet.size
-
     fun encode(bytes: ByteArray): ByteArray
     fun decode(bytes: ByteArray): ByteArray
 }

src/commonMain/kotlin/com/infendro/encoding/NumericEncoding.kt

@@ -4,8 +4,10 @@ import com.infendro.encoding.exception.IllegalByteException
 import com.infendro.encoding.util.BigInt
 
 class NumericEncoding internal constructor(
-    override val alphabet: ByteArray,
+    private val alphabet: ByteArray,
 ) : Encoding {
+    private val base: Int = alphabet.size
+
     override fun encode(bytes: ByteArray): ByteArray {
         if (bytes.isEmpty()) return byteArrayOf()
 
@@ -27,10 +29,8 @@ class NumericEncoding internal constructor(
         var value = BigInt.zero
         for (i in 0..<bytes.size) {
             val byte = bytes[i]
-
             val index = alphabet.indexOf(byte)
             if (index == -1) throw IllegalByteException(byte)
-
             value = value.timesAdd(base, index)
         }
 

src/commonMain/kotlin/com/infendro/encoding/PaddedStreamEncoding.kt

@@ -1,78 +0,0 @@
-package com.infendro.encoding
-
-import com.infendro.encoding.exception.IllegalByteException
-import com.infendro.encoding.util.align
-import com.infendro.encoding.util.divCeil
-import com.infendro.encoding.util.lcm
-import com.infendro.encoding.util.log2
-
-class PaddedStreamEncoding internal constructor(
-    override val alphabet: ByteArray,
-    private val padding: Byte,
-) : Encoding {
-    override fun encode(bytes: ByteArray): ByteArray {
-        val bits = log2(base).toInt()
-
-        val block = lcm(bits, 8) / bits
-        val size = (bytes.size * 8).divCeil(bits).align(block)
-        val result = ByteArray(size)
-
-        var r = 0
-        var buffer = 0
-        var bufferBits = 0
-        for (i in bytes.indices) {
-            buffer = (buffer shl 8) + bytes[i]
-            bufferBits += 8
-
-            while (bufferBits >= bits) {
-                val offset = bufferBits - bits
-                val index = (buffer ushr offset)
-                buffer = buffer and ((base - 1) shl offset).inv()
-                bufferBits -= bits
-
-                result[r++] = alphabet[index]
-            }
-        }
-        if (bufferBits > 0) {
-            val index = buffer shl (bits - bufferBits)
-            result[r++] = alphabet[index]
-        }
-        while (r < result.size) {
-            result[r++] = padding
-        }
-
-        return result
-    }
-
-    override fun decode(bytes: ByteArray): ByteArray {
-        val bits = log2(base).toInt()
-
-        val end = bytes.indexOf(padding).takeIf { it != -1 } ?: bytes.size
-        val size = end * bits / 8
-        val result = ByteArray(size)
-
-        var r = 0
-        var buffer = 0
-        var bufferBits = 0
-        for (i in 0..<end) {
-            val byte = bytes[i]
-
-            val value = alphabet.indexOf(byte)
-            if (value == -1) throw IllegalByteException(byte)
-
-            buffer = (buffer shl bits) + value.toByte()
-            bufferBits += bits
-
-            if (bufferBits >= 8) {
-                val offset = bufferBits - 8
-                val character = (buffer ushr offset).toByte()
-                buffer = buffer and (0xFF shl offset).inv()
-                bufferBits -= 8
-
-                result[r++] = character
-            }
-        }
-
-        return result
-    }
-}

src/commonMain/kotlin/com/infendro/encoding/StreamEncoding.kt

@@ -1,70 +1,80 @@
 package com.infendro.encoding
 
 import com.infendro.encoding.exception.IllegalByteException
+import com.infendro.encoding.util.align
 import com.infendro.encoding.util.divCeil
+import com.infendro.encoding.util.lcm
 import com.infendro.encoding.util.log2
 
 class StreamEncoding internal constructor(
-    override val alphabet: ByteArray,
+    private val alphabet: ByteArray,
+    private val padding: Byte? = null,
 ) : Encoding {
+    private val base: Int = alphabet.size
+    private val bits: Int = log2(base).toInt()
+    private val block: Int = lcm(bits, 8) / bits
+    private val mask: Int = (0x01 shl bits) - 1
+
     override fun encode(bytes: ByteArray): ByteArray {
-        val bits = log2(base).toInt()
+        val size = when (padding) {
+            null -> (bytes.size * 8).divCeil(bits)
+            else -> (bytes.size * 8).divCeil(bits).align(block)
+        }
+        val encoded = ByteArray(size)
+        var i = 0
 
-        val size = (bytes.size * 8).divCeil(bits)
-        val result = ByteArray(size)
-
-        var r = 0
         var buffer = 0
         var bufferBits = 0
-        for (i in bytes.indices) {
-            buffer = (buffer shl 8) + bytes[i]
+        for (byte in bytes) {
+            buffer = (buffer shl 8) or (byte.toInt() and 0xFF)
             bufferBits += 8
 
             while (bufferBits >= bits) {
-                val offset = bufferBits - bits
-                val index = (buffer ushr offset)
-                buffer = buffer and ((base - 1) shl offset).inv()
+                val index = (buffer shr (bufferBits - bits)) and mask
                 bufferBits -= bits
-
-                result[r++] = alphabet[index]
+                encoded[i++] = alphabet[index]
             }
         }
         if (bufferBits > 0) {
-            val index = buffer shl (bits - bufferBits)
-            result[r] = alphabet[index]
+            val index = (buffer shl (bits - bufferBits)) and mask
+            encoded[i++] = alphabet[index]
         }
 
-        return result
+        while (i < encoded.size) {
+            encoded[i++] = padding!!
+        }
+
+        return encoded
     }
 
     override fun decode(bytes: ByteArray): ByteArray {
-        val bits = log2(base).toInt()
+        val end = when (padding) {
+            null -> bytes.size
+            else -> when (val index = bytes.indexOf(padding)) {
+                -1 -> bytes.size
+                else -> index
+            }
+        }
+        val size = end * bits / 8
+        val decoded = ByteArray(size)
+        var i = 0
 
-        val size = bytes.size * bits / 8
-        val result = ByteArray(size)
-
-        var r = 0
         var buffer = 0
         var bufferBits = 0
-        for (i in bytes.indices) {
-            val byte = bytes[i]
-
-            val value = alphabet.indexOf(byte)
-            if (value == -1) throw IllegalByteException(byte)
-
-            buffer = (buffer shl bits) + value.toByte()
+        for (b in 0..<end) {
+            val byte = bytes[b]
+            val index = alphabet.indexOf(byte)
+            if (index == -1) throw IllegalByteException(byte)
+            buffer = (buffer shl bits) or index
             bufferBits += bits
 
             if (bufferBits >= 8) {
-                val offset = bufferBits - 8
-                val character = (buffer ushr offset).toByte()
-                buffer = buffer and (0xFF shl offset).inv()
+                val byte = (buffer shr (bufferBits - 8)) and 0xFF
                 bufferBits -= 8
-
-                result[r++] = character
+                decoded[i++] = byte.toByte()
             }
         }
 
-        return result
+        return decoded
     }
 }

src/commonMain/kotlin/com/infendro/encoding/util/BigInt.kt

@@ -49,40 +49,24 @@ internal class BigInt private constructor(
     }
 
     fun toByteArray(): ByteArray {
-        val msw = words.last()
-        val mswBytes = when {
-            (msw ushr 24) != 0 -> 4
-            (msw ushr 16) != 0 -> 3
-            (msw ushr 8) != 0 -> 2
-            else -> 1
+        val bytes = ByteArray((words.size * 4) - words.last().countLeadingZeroBytes())
+        for (i in bytes.indices) {
+            val (wi, bi) = (bytes.lastIndex - i).divRem(4)
+            bytes[i] = (words[wi] ushr (bi * 8)).toByte()
         }
-        val size = ((words.size - 1) * 4) + mswBytes
-        val result = ByteArray(size)
-
-        for (i in 0..<size) {
-            val index = size - 1 - i
-            val shift = (index % 4) * 8
-            result[i] = (words[index / 4] ushr shift).toByte()
-        }
-
-        return result
+        return bytes
     }
 
     companion object {
         val zero: BigInt
             get() = BigInt(intArrayOf(0))
 
-        fun from(value: ByteArray): BigInt {
-            val size = value.size.divCeil(4)
-            val words = IntArray(size)
-
-            for (i in value.indices) {
-                val byte = value[i].toInt() and 0xFF
-                val index = value.lastIndex - i
-                val shift = (index % 4) * 8
-                words[index / 4] = words[index / 4] or (byte shl shift)
+        fun from(bytes: ByteArray): BigInt {
+            val words = IntArray(bytes.size.divCeil(4))
+            for (i in bytes.indices) {
+                val (wi, bi) = (bytes.lastIndex - i).divRem(4)
+                words[wi] = words[wi] or ((bytes[i].toInt() and 0xFF) shl (bi * 8))
             }
-
             return BigInt(words)
         }
     }

src/commonMain/kotlin/com/infendro/encoding/util/Int.kt

@@ -0,0 +1,7 @@
+package com.infendro.encoding.util
+
+fun Int.divRem(divisor: Int): Pair<Int, Int> =
+    Pair(this / divisor, this % divisor)
+
+fun Int.countLeadingZeroBytes(): Int =
+    countLeadingZeroBits() / 8

src/commonMain/kotlin/com/infendro/encoding/util/Math.kt

@@ -2,15 +2,15 @@ package com.infendro.encoding.util
 
 import kotlin.math.log2
 
-internal fun log2(value: Int): Double =
-    log2(value.toDouble())
-
 internal fun Int.divCeil(n: Int): Int =
     (this + n - 1) / n
 
 internal fun Int.align(n: Int): Int =
     divCeil(n) * n
 
+internal fun log2(value: Int): Double =
+    log2(value.toDouble())
+
 internal fun gcd(a: Int, b: Int): Int {
     var x = a
     var y = b

src/commonTest/kotlin/com/infendro/encoding/Base56.kt

@@ -24,7 +24,7 @@ class `Base56 Test` {
 
     @Test
     fun encode() {
-        val actual = encoding.encode(original).also { println(it.decodeToString()) }
+        val actual = encoding.encode(original)
         assertContentEquals(encoded, actual)
     }