refactor encodings

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)
         }
     }