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Diffstat (limited to 'wallet/src/main/java/net/taler/wallet/crypto/Encoding.kt')
-rw-r--r--wallet/src/main/java/net/taler/wallet/crypto/Encoding.kt134
1 files changed, 134 insertions, 0 deletions
diff --git a/wallet/src/main/java/net/taler/wallet/crypto/Encoding.kt b/wallet/src/main/java/net/taler/wallet/crypto/Encoding.kt
new file mode 100644
index 0000000..25a59be
--- /dev/null
+++ b/wallet/src/main/java/net/taler/wallet/crypto/Encoding.kt
@@ -0,0 +1,134 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
+ */
+
+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
+ */
+ @Suppress("unused")
+ 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
+ */
+ @Suppress("unused")
+ fun calculateDecodedDataLength(stringSize: Int): Int {
+ return stringSize * 5 / 8
+ }
+}
+