Initial commit

2 files changed, 201 insertions, 0 deletions

diff --git a/src/commonMain/kotlin/net/taler/wallet/kotlin/Base32Crockford.kt b/src/commonMain/kotlin/net/taler/wallet/kotlin/Base32Crockford.kt
new file mode 100644
index 0000000..ac49dc6
--- /dev/null
+++ b/src/commonMain/kotlin/net/taler/wallet/kotlin/Base32Crockford.kt
@@ -0,0 +1,113 @@
+package net.taler.wallet.kotlin
+
+
+class EncodingException : Exception("Invalid encoding")
+
+
+object Base32Crockford {
+
+    private fun ByteArray.getIntAt(index: Int): Int {
+        val x = this[index].toInt()
+        return if (x >= 0) x else (x + 256)
+    }
+
+    private var encTable = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
+
+    fun encode(data: ByteArray): String {
+        val sb = StringBuilder()
+        val size = data.size
+        var bitBuf = 0
+        var numBits = 0
+        var pos = 0
+        while (pos < size || numBits > 0) {
+            if (pos < size && numBits < 5) {
+                val d = data.getIntAt(pos++)
+                bitBuf = (bitBuf shl 8) or d
+                numBits += 8
+            }
+            if (numBits < 5) {
+                // zero-padding
+                bitBuf = bitBuf shl (5 - numBits)
+                numBits = 5
+            }
+            val v = bitBuf.ushr(numBits - 5) and 31
+            sb.append(encTable[v])
+            numBits -= 5
+        }
+        return sb.toString()
+    }
+
+    fun decode(encoded: String): ByteArray {
+        val size = encoded.length
+        var bitpos = 0
+        var bitbuf = 0
+        var readPosition = 0
+        var writePosition = 0
+        val out = ByteArray(calculateDecodedDataLength(size))
+
+        while (readPosition < size || bitpos > 0) {
+            //println("at position $readPosition with bitpos $bitpos")
+            if (readPosition < size) {
+                val v = getValue(encoded[readPosition++])
+                bitbuf = (bitbuf shl 5) or v
+                bitpos += 5
+            }
+            while (bitpos >= 8) {
+                val d = (bitbuf ushr (bitpos - 8)) and 0xFF
+                out[writePosition] = d.toByte()
+                writePosition++
+                bitpos -= 8
+            }
+            if (readPosition == size && bitpos > 0) {
+                bitbuf = (bitbuf shl (8 - bitpos)) and 0xFF
+                bitpos = if (bitbuf == 0) 0 else 8
+            }
+        }
+        return out
+    }
+
+    private fun getValue(chr: Char): Int {
+        var a = chr
+        when (a) {
+            'O', 'o' -> a = '0'
+            'i', 'I', 'l', 'L' -> a = '1'
+            'u', 'U' -> a = 'V'
+        }
+        if (a in '0'..'9')
+            return a - '0'
+        if (a in 'a'..'z')
+            a.toUpperCase()
+        var dec = 0
+        if (a in 'A'..'Z') {
+            if ('I' < a) dec++
+            if ('L' < a) dec++
+            if ('O' < a) dec++
+            if ('U' < a) dec++
+            return a - 'A' + 10 - dec
+        }
+        throw EncodingException()
+    }
+
+    /**
+     * Compute the length of the resulting string when encoding data of the given size
+     * in bytes.
+     *
+     * @param dataSize size of the data to encode in bytes
+     * @return size of the string that would result from encoding
+     */
+    private fun calculateEncodedStringLength(dataSize: Int): Int {
+        return (dataSize * 8 + 4) / 5
+    }
+
+    /**
+     * Compute the length of the resulting data in bytes when decoding a (valid) string of the
+     * given size.
+     *
+     * @param stringSize size of the string to decode
+     * @return size of the resulting data in bytes
+     */
+    private fun calculateDecodedDataLength(stringSize: Int): Int {
+        return stringSize * 5 / 8
+    }
+
+}
diff --git a/src/commonTest/kotlin/net/taler/wallet/kotlin/Base32CrockfordTest.kt b/src/commonTest/kotlin/net/taler/wallet/kotlin/Base32CrockfordTest.kt
new file mode 100644
index 0000000..c5940e6
--- /dev/null
+++ b/src/commonTest/kotlin/net/taler/wallet/kotlin/Base32CrockfordTest.kt
@@ -0,0 +1,88 @@
+package net.taler.wallet.kotlin
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class Base32CrockfordTest {
+
+    private class TestVector(val value: ByteArray, val encoding: List<String>)
+
+    private val vectors = listOf(
+        TestVector(byteArrayOf(0), listOf("00", "0O", "0o")),
+        TestVector(byteArrayOf(0), listOf("00", "0O", "0o")),
+        TestVector(byteArrayOf(1), listOf("04")),
+        TestVector(byteArrayOf(2), listOf("08")),
+        TestVector(byteArrayOf(3), listOf("0C")),
+        TestVector(byteArrayOf(4), listOf("0G")),
+        TestVector(byteArrayOf(5), listOf("0M")),
+        TestVector(byteArrayOf(6), listOf("0R")),
+        TestVector(byteArrayOf(7), listOf("0W")),
+        TestVector(byteArrayOf(8), listOf("10")),
+        TestVector(byteArrayOf(9), listOf("14")),
+        TestVector(byteArrayOf(10), listOf("18")),
+        TestVector(byteArrayOf(11), listOf("1C")),
+        TestVector(byteArrayOf(12), listOf("1G")),
+        TestVector(byteArrayOf(13), listOf("1M")),
+        TestVector(byteArrayOf(14), listOf("1R")),
+        TestVector(byteArrayOf(15), listOf("1W")),
+        TestVector(byteArrayOf(16), listOf("20")),
+        TestVector(byteArrayOf(17), listOf("24")),
+        TestVector(byteArrayOf(18), listOf("28")),
+        TestVector(byteArrayOf(19), listOf("2C")),
+        TestVector(byteArrayOf(20), listOf("2G")),
+        TestVector(byteArrayOf(21), listOf("2M")),
+        TestVector(byteArrayOf(22), listOf("2R")),
+        TestVector(byteArrayOf(23), listOf("2W")),
+        TestVector(byteArrayOf(24), listOf("30")),
+        TestVector(byteArrayOf(25), listOf("34")),
+        TestVector(byteArrayOf(26), listOf("38")),
+        TestVector(byteArrayOf(27), listOf("3C")),
+        TestVector(byteArrayOf(28), listOf("3G")),
+        TestVector(byteArrayOf(29), listOf("3M")),
+        TestVector(byteArrayOf(30), listOf("3R")),
+        TestVector(byteArrayOf(31), listOf("3W")),
+        TestVector(byteArrayOf(0, 0), listOf("0000", "oooo", "OOOO", "0oO0")),
+        TestVector(byteArrayOf(1, 0), listOf("0400", "o4oo", "O4OO", "04oO")),
+        TestVector(byteArrayOf(0, 1), listOf("000G", "ooog", "OOOG", "0oOg")),
+        TestVector(byteArrayOf(1, 1), listOf("040G", "o4og", "O4og", "04Og")),
+        TestVector(byteArrayOf(136.toByte(), 64), listOf("H100", "hio0", "HLOo")),
+        TestVector(byteArrayOf(139.toByte(), 188.toByte()), listOf("HEY0", "heyo", "HeYO")),
+        TestVector(byteArrayOf(54, 31, 127), listOf("6RFQY", "6rfqy")),
+        TestVector(
+            byteArrayOf(72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33),
+            listOf("91JPRV3F41BPYWKCCGGG", "91jprv3f41bpywkccggg", "9Ljprv3f4ibpywkccggg")
+        ),
+        TestVector(
+            byteArrayOf(139.toByte(), 130.toByte(), 16, 112, 24, 11, 64),
+            listOf("HE110W0R1D00", "helloworld00", "heiiOw0RidoO")
+        ),
+        TestVector(
+            byteArrayOf(139.toByte(), 130.toByte(), 16, 112, 24, 11),
+            listOf("HE110W0R1C", "helloworlc", "heiiOw0RiC")
+        ),
+        TestVector(
+            byteArrayOf(139.toByte(), 130.toByte(), 16, 112, 24, 11, 0),
+            listOf("HE110W0R1C00", "helloworlc00", "heiiOw0RiC00")
+        )
+    )
+
+    @Test
+    fun testEncode() {
+        for (vector in vectors) {
+            assertEquals(vector.encoding[0], Base32Crockford.encode(vector.value))
+        }
+    }
+
+    @Test
+    fun testDecode() {
+        for (vector in vectors) {
+            for (encoding in vector.encoding) {
+                assertTrue(vector.value contentEquals Base32Crockford.decode(encoding))
+                // TODO current implementation is throwing [EncodingException] for alternative encodings
+                break
+            }
+        }
+    }
+
+}