Add a ByteBufUtils class

src/main/java/com/flowpowered/networking/ByteBufUtils.java

@@ -0,0 +1,111 @@
+/*
+ * This file is part of Flow Networking, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2013 Spout LLC <http://www.spout.org/>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.flowpowered.networking;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import io.netty.buffer.ByteBuf;
+
+/**
+ * A class containing various utility methods that act on byte buffers.
+ */
+public class ByteBufUtils {
+    /**
+     * Reads an UTF8 string from a byte buffer.
+     *
+     * @param buf The byte buffer to read from
+     * @return The read string
+     * @throws java.io.IOException If the reading fails
+     */
+    public static String readUTF8(ByteBuf buf) throws IOException {
+        // Read the string's length
+        final int len = readVarInt(buf);
+        final byte[] bytes = new byte[len];
+        buf.readBytes(bytes);
+        return new String(bytes, StandardCharsets.UTF_8);
+    }
+
+    /**
+     * Writes an UTF8 string to a byte buffer.
+     *
+     * @param buf The byte buffer to write too
+     * @param value The string to write
+     * @throws java.io.IOException If the writing fails
+     */
+    public static void writeUTF8(ByteBuf buf, String value) throws IOException {
+        final byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
+        if (bytes.length >= Short.MAX_VALUE) {
+            throw new IOException("Attempt to write a string with a length greater than Short.MAX_VALUE to ByteBuf!");
+        }
+        // Write the string's length
+        writeVarInt(buf, bytes.length);
+        buf.writeBytes(bytes);
+    }
+
+    /**
+     * Reads an integer written into the byte buffer as one of various bit sizes.
+     *
+     * @param buf The byte buffer to read from
+     * @return The read integer
+     * @throws java.io.IOException If the reading fails
+     */
+    public static int readVarInt(ByteBuf buf) throws IOException {
+        int out = 0;
+        int bytes = 0;
+        byte in;
+        while (true) {
+            in = buf.readByte();
+            out |= (in & 0x7F) << (bytes * 7);
+            if (bytes > 32) {
+                throw new IOException("Attempt to read int bigger than allowed for a varint!");
+            }
+            if ((in & 0x80) != 0x80) {
+                break;
+            }
+        }
+        return out;
+    }
+
+    /**
+     * Writes an integer into the byte buffer using the least possible amount of bits.
+     *
+     * @param buf The byte buffer to write too
+     * @param value The integer value to write
+     */
+    public static void writeVarInt(ByteBuf buf, int value) {
+        int part;
+        while (true) {
+            part = value & 0x7F;
+            value >>>= 7;
+            if (value != 0) {
+                part |= 0x80;
+            }
+            buf.writeByte(part);
+            if (value == 0) {
+                break;
+            }
+        }
+    }
+}

src/test/java/com/flowpowered/networking/ByteBufUtilsTest.java

@@ -0,0 +1,61 @@
+/*
+ * This file is part of Flow Networking, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2013 Spout LLC <http://www.spout.org/>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.flowpowered.networking;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import org.junit.Test;
+
+import static org.junit.Assert.fail;
+
+public class ByteBufUtilsTest {
+    @Test
+    public void testVarInt() throws Exception {
+        final ByteBuf test = Unpooled.buffer();
+        ByteBufUtils.writeVarInt(test, 1);
+        final int varInt = ByteBufUtils.readVarInt(test);
+        if (varInt != 1) {
+            fail("The buffer had 1 wrote to it but received " + varInt + " instead!");
+        }
+    }
+
+    @Test
+    public void testUtf8() throws Exception {
+        final ByteBuf test = Unpooled.buffer();
+        ByteBufUtils.writeUTF8(test, "Hello");
+        final String utf8String = ByteBufUtils.readUTF8(test);
+        if (!"Hello".equals(utf8String)) {
+            fail("The buffer had hello wrote to it but received " + utf8String + " instead!");
+        }
+        boolean exceptionThrown = false;
+        try {
+            ByteBufUtils.writeUTF8(test, new String(new byte[Short.MAX_VALUE + 1]));
+        } catch (Exception ignore) {
+            exceptionThrown = true;
+        }
+        if (!exceptionThrown) {
+            fail("Writing more than Short.MAX_VALUE as a UTF8 String to the ByteBuf should have thrown an exception but it did not!");
+        }
+    }
+}