+package net.pterodactylus.fcp;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+/**
+ * Freenet-specific Base64 implementation.
+ *
+ * @author <a href="mailto:bombe@freenetproject.org">David ‘Bombe’ Roden</a>
+ */
+public class FreenetBase64 {
+
+ private static final char[] FREENET_BASE64_ALPHABET =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789~-".toCharArray();
+ private static final int[] REVERSE_FREENET_BASE64_ALPHABET = reverse(FREENET_BASE64_ALPHABET);
+
+ private static int[] reverse(char[] alphabet) {
+ String alphabetString = new String(alphabet);
+ int[] reversedAlphabet = new int[128];
+ for (int i = 0; i < 128; i++) {
+ if (alphabetString.indexOf(i) > -1) {
+ reversedAlphabet[i] = alphabetString.indexOf(i);
+ } else {
+ reversedAlphabet[i] = -1;
+ }
+ }
+ return reversedAlphabet;
+ }
+
+ public String encode(byte[] data) {
+ StringBuilder result = new StringBuilder();
+ int currentValue = 0;
+ int index = 0;
+ while (index < data.length) {
+ currentValue = (currentValue << 8) | data[index];
+ if (index % 3 == 2) {
+ result.append(FREENET_BASE64_ALPHABET[(currentValue >> 18) & 0x3f]);
+ result.append(FREENET_BASE64_ALPHABET[(currentValue >> 12) & 0x3f]);
+ result.append(FREENET_BASE64_ALPHABET[(currentValue >> 6) & 0x3f]);
+ result.append(FREENET_BASE64_ALPHABET[currentValue & 0x3f]);
+ }
+ index++;
+ }
+ if (index % 3 == 1) {
+ result.append(FREENET_BASE64_ALPHABET[(currentValue >> 2) & 0x3f]);
+ result.append(FREENET_BASE64_ALPHABET[(currentValue << 4) & 0x3f]);
+ result.append("==");
+ } else if (index % 3 == 2) {
+ result.append(FREENET_BASE64_ALPHABET[(currentValue >> 10) & 0x3f]);
+ result.append(FREENET_BASE64_ALPHABET[(currentValue >> 4) & 0x3f]);
+ result.append(FREENET_BASE64_ALPHABET[(currentValue << 2) & 0x3f]);
+ result.append("=");
+ }
+ return result.toString();
+ }
+
+ public byte[] decode(String data) {
+ ByteArrayOutputStream dataOutput = new ByteArrayOutputStream(data.length() * 3 / 4);
+ try {
+ int currentValue = 0;
+ int index = 0;
+ for (char c : data.toCharArray()) {
+ if (c == '=') {
+ break;
+ }
+ currentValue = (currentValue << 6) | REVERSE_FREENET_BASE64_ALPHABET[c];
+ if (index % 4 == 3) {
+ dataOutput.write((currentValue >> 16) & 0xff);
+ dataOutput.write((currentValue >> 8) & 0xff);
+ dataOutput.write(currentValue & 0xff);
+ }
+ index++;
+ }
+ if (index % 4 == 2) {
+ dataOutput.write((currentValue >> 4) & 0xff);
+ } else if (index % 4 == 3) {
+ dataOutput.write((currentValue >> 10) & 0xff);
+ dataOutput.write((currentValue >> 2) & 0xff);
+ }
+ return dataOutput.toByteArray();
+ } finally {
+ try {
+ dataOutput.close();
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }
+ }
+
+}