UI tweaks

1 files changed, 116 insertions, 0 deletions

diff --git a/app/src/main/java/net/taler/wallet/crypto/Encoding.kt b/app/src/main/java/net/taler/wallet/crypto/Encoding.kt
new file mode 100644
index 0000000..f64dcae
--- /dev/null
+++ b/app/src/main/java/net/taler/wallet/crypto/Encoding.kt
@@ -0,0 +1,116 @@
+package net.taler.wallet.crypto
+
+import java.io.ByteArrayOutputStream
+
+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, out: ByteArrayOutputStream) {
+        val size = encoded.length
+        var bitpos = 0
+        var bitbuf = 0
+        var readPosition = 0
+
+        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.write(d)
+                bitpos -= 8
+            }
+            if (readPosition == size && bitpos > 0) {
+                bitbuf = (bitbuf shl (8 - bitpos)) and 0xFF
+                bitpos = if (bitbuf == 0) 0 else 8
+            }
+        }
+    }
+
+    fun decode(encoded: String): ByteArray {
+        val out = ByteArrayOutputStream()
+        decode(encoded, out)
+        return out.toByteArray()
+    }
+
+    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 = Character.toUpperCase(a)
+        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
+     */
+    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
+     */
+    fun calculateDecodedDataLength(stringSize: Int): Int {
+        return stringSize * 5 / 8
+    }
+}
+