Java tutorial
/** * Copyright 2011-2016 Asakusa Framework Team. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.asakusafw.runtime.flow.join; import java.io.IOException; import java.util.Arrays; import org.apache.hadoop.io.Writable; import com.asakusafw.runtime.io.util.DataBuffer; /** * A key for {@link LookUpTable}. * @since 0.1.0 * @version 0.8.0 */ public class LookUpKey { private static final int INITIAL_SIZE = 256; private final DataBuffer buffer; private final DirectView view; /** * Creates a new instance w/ default initial buffer size. */ public LookUpKey() { this(INITIAL_SIZE); } /** * Creates a new instance. * @param bufferSize the initial buffer size */ public LookUpKey(int bufferSize) { this.buffer = new DataBuffer(bufferSize); this.view = new DirectView(buffer); } /** * Clears the buffer. * @throws IOException if failed to initialize the buffer */ public void reset() throws IOException { buffer.reset(0, 0); } /** * Appends an element into the buffer. * @param writable the target element * @throws IOException if error occurred while appending the element * @throws IllegalArgumentException if the parameter is {@code null} */ public void add(Writable writable) throws IOException { if (writable == null) { throw new IllegalArgumentException("writable must not be null"); //$NON-NLS-1$ } writable.write(buffer); } /** * Returns a copy of this key. * @return a copy of this * @throws IOException if error occurred while creating a copy */ public LookUpKey copy() throws IOException { LookUpKey result = new LookUpKey(0); byte[] contents = Arrays.copyOfRange(buffer.getData(), buffer.getReadPosition(), buffer.getReadLimit()); result.buffer.reset(contents, 0, contents.length); return result; } /** * Returns a direct view of this key. * @return a direct view * @since 0.8.0 */ public LookUpKey.View getDirectView() { return view; } /** * Returns a frozen view of this key. * @return a frozen view * @since 0.8.0 */ public LookUpKey.View getFrozenView() { return new FrozenView(buffer); } @Override public int hashCode() { final int prime = 31; int result = 1; byte[] b = buffer.getData(); for (int i = buffer.getReadPosition(), n = buffer.getReadLimit(); i < n; i++) { result = result * prime + b[i]; } return result; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } LookUpKey other = (LookUpKey) obj; if (buffer.getReadRemaining() != other.buffer.getReadRemaining()) { return false; } byte[] b1 = buffer.getData(); byte[] b2 = other.buffer.getData(); int o1 = buffer.getReadPosition(); int o2 = other.buffer.getReadPosition(); for (int i = 0, n = buffer.getReadRemaining(); i < n; i++) { if (b1[o1 + i] != b2[o2 + i]) { return false; } } return true; } /** * Represents a view of {@link LookUpKey}. * @since 0.8.0 */ public interface View { // no special members } private static final class DirectView implements View { final DataBuffer entity; public DirectView(DataBuffer entity) { this.entity = entity; } @Override public int hashCode() { DataBuffer b = entity; return hashCodeInBytes(b.getData(), b.getReadPosition(), b.getReadLimit()); } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof DirectView) { DataBuffer b1 = entity; DataBuffer b2 = ((DirectView) obj).entity; return equalsInBytes(b1.getData(), b1.getReadPosition(), b1.getReadLimit(), b2.getData(), b2.getReadPosition(), b2.getReadLimit()); } else if (obj instanceof FrozenView) { DataBuffer b1 = entity; byte[] b2 = ((FrozenView) obj).entity; return equalsInBytes(b1.getData(), b1.getReadPosition(), b1.getReadLimit(), b2, 0, b2.length); } else { return false; } } } private static final class FrozenView implements View { final byte[] entity; public FrozenView(DataBuffer entity) { this.entity = Arrays.copyOfRange(entity.getData(), entity.getReadPosition(), entity.getReadLimit()); } @Override public int hashCode() { byte[] b = entity; return hashCodeInBytes(b, 0, b.length); } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof DirectView) { byte[] b1 = entity; DataBuffer b2 = ((DirectView) obj).entity; return equalsInBytes(b1, 0, b1.length, b2.getData(), b2.getReadPosition(), b2.getReadLimit()); } else if (obj instanceof FrozenView) { byte[] b1 = entity; byte[] b2 = ((FrozenView) obj).entity; return equalsInBytes(b1, 0, b1.length, b2, 0, b2.length); } else { return false; } } } static int hashCodeInBytes(byte[] buffer, int from, int to) { final int prime = 31; int result = 1; for (int i = from; i < to; i++) { result = result * prime + buffer[i]; } return result; } static boolean equalsInBytes(byte[] b1, int from1, int to1, byte[] b2, int from2, int to2) { if (to1 - from1 != to2 - from2) { return false; } for (int i = 0, n = to1 - from1; i < n; i++) { if (b1[from1 + i] != b2[from2 + i]) { return false; } } return true; } }