From 3a59547f237b87ac551efc515884f342cd08b543 Mon Sep 17 00:00:00 2001
From: =?utf8?q?David=20=E2=80=98Bombe=E2=80=99=20Roden?=
 <bombe@freenetproject.org>
Date: Tue, 14 Jul 2015 20:46:18 +0200
Subject: [PATCH] Add Freenet-specific base64 implementation

---
 .../java/net/pterodactylus/fcp/FreenetBase64.java  | 85 ++++++++++++++++++++++
 .../net/pterodactylus/fcp/FreenetBase64Test.java   | 39 ++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 src/main/java/net/pterodactylus/fcp/FreenetBase64.java
 create mode 100644 src/test/java/net/pterodactylus/fcp/FreenetBase64Test.java

diff --git a/src/main/java/net/pterodactylus/fcp/FreenetBase64.java b/src/main/java/net/pterodactylus/fcp/FreenetBase64.java
new file mode 100644
index 0000000..9c70858
--- /dev/null
+++ b/src/main/java/net/pterodactylus/fcp/FreenetBase64.java
@@ -0,0 +1,85 @@
+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) & 0b111111]);
+				result.append(FREENET_BASE64_ALPHABET[(currentValue >> 12) & 0b111111]);
+				result.append(FREENET_BASE64_ALPHABET[(currentValue >> 6) & 0b111111]);
+				result.append(FREENET_BASE64_ALPHABET[currentValue & 0b111111]);
+			}
+			index++;
+		}
+		if (index % 3 == 1) {
+			result.append(FREENET_BASE64_ALPHABET[(currentValue >> 2) & 0b111111]);
+			result.append(FREENET_BASE64_ALPHABET[(currentValue << 4) & 0b111111]);
+			result.append("==");
+		} else if (index % 3 == 2) {
+			result.append(FREENET_BASE64_ALPHABET[(currentValue >> 10) & 0b111111]);
+			result.append(FREENET_BASE64_ALPHABET[(currentValue >> 4) & 0b111111]);
+			result.append(FREENET_BASE64_ALPHABET[(currentValue << 2) & 0b111111]);
+			result.append("=");
+		}
+		return result.toString();
+	}
+
+	public byte[] decode(String data) {
+		try (ByteArrayOutputStream dataOutput = new ByteArrayOutputStream(data.length() * 3 / 4)) {
+			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) & 0b11111111);
+					dataOutput.write((currentValue >> 8) & 0b11111111);
+					dataOutput.write(currentValue & 0b11111111);
+				}
+				index++;
+			}
+			if (index % 4 == 2) {
+				dataOutput.write((currentValue >> 4) & 0b11111111);
+			} else if (index % 4 == 3) {
+				dataOutput.write((currentValue >> 10) & 0b11111111);
+				dataOutput.write((currentValue >> 2) & 0b11111111);
+			}
+			return dataOutput.toByteArray();
+		} catch (IOException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+}
diff --git a/src/test/java/net/pterodactylus/fcp/FreenetBase64Test.java b/src/test/java/net/pterodactylus/fcp/FreenetBase64Test.java
new file mode 100644
index 0000000..45838e2
--- /dev/null
+++ b/src/test/java/net/pterodactylus/fcp/FreenetBase64Test.java
@@ -0,0 +1,39 @@
+package net.pterodactylus.fcp;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+
+import org.junit.Test;
+
+/**
+ * Unit test for {@link FreenetBase64}.
+ *
+ * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
+ */
+public class FreenetBase64Test {
+
+	private final FreenetBase64 freenetBase64 = new FreenetBase64();
+
+	@Test
+	public void canEncodeString() {
+		assertThat(freenetBase64.encode("".getBytes()), is(""));
+		assertThat(freenetBase64.encode("f".getBytes()), is("Zg=="));
+		assertThat(freenetBase64.encode("fo".getBytes()), is("Zm8="));
+		assertThat(freenetBase64.encode("foo".getBytes()), is("Zm9v"));
+		assertThat(freenetBase64.encode("foob".getBytes()), is("Zm9vYg=="));
+		assertThat(freenetBase64.encode("fooba".getBytes()), is("Zm9vYmE="));
+		assertThat(freenetBase64.encode("foobar".getBytes()), is("Zm9vYmFy"));
+	}
+
+	@Test
+	public void canDecodeStrings() {
+		assertThat(freenetBase64.decode(""), is("".getBytes()));
+		assertThat(freenetBase64.decode("Zg=="), is("f".getBytes()));
+		assertThat(freenetBase64.decode("Zm8="), is("fo".getBytes()));
+		assertThat(freenetBase64.decode("Zm9v"), is("foo".getBytes()));
+		assertThat(freenetBase64.decode("Zm9vYg=="), is("foob".getBytes()));
+		assertThat(freenetBase64.decode("Zm9vYmE="), is("fooba".getBytes()));
+		assertThat(freenetBase64.decode("Zm9vYmFy"), is("foobar".getBytes()));
+	}
+
+}
-- 
2.7.4