Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.hadoop.io; import java.io.IOException; import java.io.DataInput; import java.io.DataOutput; import org.apache.commons.logging.*; /** A WritableComparable for strings that uses the UTF8 encoding. * * <p>Also includes utilities for efficiently reading and writing UTF-8. * * @deprecated replaced by Text */ public class UTF8 implements WritableComparable { private static final Log LOG = LogFactory.getLog(UTF8.class); private static final DataInputBuffer IBUF = new DataInputBuffer(); private static final ThreadLocal<DataOutputBuffer> OBUF_FACTORY = new ThreadLocal<DataOutputBuffer>() { @Override protected DataOutputBuffer initialValue() { return new DataOutputBuffer(); } }; private static final byte[] EMPTY_BYTES = new byte[0]; private byte[] bytes = EMPTY_BYTES; private int length; public UTF8() { //set(""); } /** Construct from a given string. */ public UTF8(String string) { set(string); } /** Construct from a given string. */ public UTF8(UTF8 utf8) { set(utf8); } /** The raw bytes. */ public byte[] getBytes() { return bytes; } /** The number of bytes in the encoded string. */ public int getLength() { return length; } /** Set to contain the contents of a string. */ public void set(String string) { if (string.length() > 0xffff / 3) { // maybe too long LOG.warn("truncating long string: " + string.length() + " chars, starting with " + string.substring(0, 20)); string = string.substring(0, 0xffff / 3); } length = utf8Length(string); // compute length if (length > 0xffff) // double-check length throw new RuntimeException("string too long!"); if (bytes == null || length > bytes.length) // grow buffer bytes = new byte[length]; try { // avoid sync'd allocations DataOutputBuffer obuf = OBUF_FACTORY.get(); obuf.reset(); writeChars(obuf, string, 0, string.length()); System.arraycopy(obuf.getData(), 0, bytes, 0, length); } catch (IOException e) { throw new RuntimeException(e); } } /** Set to contain the contents of a string. */ public void set(UTF8 other) { length = other.length; if (bytes == null || length > bytes.length) // grow buffer bytes = new byte[length]; System.arraycopy(other.bytes, 0, bytes, 0, length); } public void readFields(DataInput in) throws IOException { length = in.readUnsignedShort(); if (bytes == null || bytes.length < length) bytes = new byte[length]; in.readFully(bytes, 0, length); } /** Skips over one UTF8 in the input. */ public static void skip(DataInput in) throws IOException { int length = in.readUnsignedShort(); WritableUtils.skipFully(in, length); } public void write(DataOutput out) throws IOException { out.writeShort(length); out.write(bytes, 0, length); } /** Compare two UTF8s. */ public int compareTo(Object o) { UTF8 that = (UTF8) o; return WritableComparator.compareBytes(bytes, 0, length, that.bytes, 0, that.length); } /** Convert to a String. */ public String toString() { StringBuffer buffer = new StringBuffer(length); try { synchronized (IBUF) { IBUF.reset(bytes, length); readChars(IBUF, buffer, length); } } catch (IOException e) { throw new RuntimeException(e); } return buffer.toString(); } /** Returns true iff <code>o</code> is a UTF8 with the same contents. */ public boolean equals(Object o) { if (!(o instanceof UTF8)) return false; UTF8 that = (UTF8) o; if (this.length != that.length) return false; else return WritableComparator.compareBytes(bytes, 0, length, that.bytes, 0, that.length) == 0; } public int hashCode() { return WritableComparator.hashBytes(bytes, length); } /** A WritableComparator optimized for UTF8 keys. */ public static class Comparator extends WritableComparator { public Comparator() { super(UTF8.class); } public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) { int n1 = readUnsignedShort(b1, s1); int n2 = readUnsignedShort(b2, s2); return compareBytes(b1, s1 + 2, n1, b2, s2 + 2, n2); } } static { // register this comparator WritableComparator.define(UTF8.class, new Comparator()); } /// STATIC UTILITIES FROM HERE DOWN /// These are probably not used much anymore, and might be removed... /** Convert a string to a UTF-8 encoded byte array. * @see String#getBytes(String) */ public static byte[] getBytes(String string) { byte[] result = new byte[utf8Length(string)]; try { // avoid sync'd allocations DataOutputBuffer obuf = OBUF_FACTORY.get(); obuf.reset(); writeChars(obuf, string, 0, string.length()); System.arraycopy(obuf.getData(), 0, result, 0, obuf.getLength()); } catch (IOException e) { throw new RuntimeException(e); } return result; } /** Read a UTF-8 encoded string. * * @see DataInput#readUTF() */ public static String readString(DataInput in) throws IOException { int bytes = in.readUnsignedShort(); StringBuffer buffer = new StringBuffer(bytes); readChars(in, buffer, bytes); return buffer.toString(); } private static void readChars(DataInput in, StringBuffer buffer, int nBytes) throws IOException { DataOutputBuffer obuf = OBUF_FACTORY.get(); obuf.reset(); obuf.write(in, nBytes); byte[] bytes = obuf.getData(); int i = 0; while (i < nBytes) { byte b = bytes[i++]; if ((b & 0x80) == 0) { buffer.append((char) (b & 0x7F)); } else if ((b & 0xE0) != 0xE0) { buffer.append((char) (((b & 0x1F) << 6) | (bytes[i++] & 0x3F))); } else { buffer.append((char) (((b & 0x0F) << 12) | ((bytes[i++] & 0x3F) << 6) | (bytes[i++] & 0x3F))); } } } /** Write a UTF-8 encoded string. * * @see DataOutput#writeUTF(String) */ public static int writeString(DataOutput out, String s) throws IOException { if (s.length() > 0xffff / 3) { // maybe too long LOG.warn("truncating long string: " + s.length() + " chars, starting with " + s.substring(0, 20)); s = s.substring(0, 0xffff / 3); } int len = utf8Length(s); if (len > 0xffff) // double-check length throw new IOException("string too long!"); out.writeShort(len); writeChars(out, s, 0, s.length()); return len; } /** Returns the number of bytes required to write this. */ private static int utf8Length(String string) { int stringLength = string.length(); int utf8Length = 0; for (int i = 0; i < stringLength; i++) { int c = string.charAt(i); if ((c >= 0x0001) && (c <= 0x007F)) { utf8Length++; } else if (c > 0x07FF) { utf8Length += 3; } else { utf8Length += 2; } } return utf8Length; } private static void writeChars(DataOutput out, String s, int start, int length) throws IOException { final int end = start + length; for (int i = start; i < end; i++) { int code = s.charAt(i); if (code >= 0x01 && code <= 0x7F) { out.writeByte((byte) code); } else if (code <= 0x07FF) { out.writeByte((byte) (0xC0 | ((code >> 6) & 0x1F))); out.writeByte((byte) (0x80 | code & 0x3F)); } else { out.writeByte((byte) (0xE0 | ((code >> 12) & 0X0F))); out.writeByte((byte) (0x80 | ((code >> 6) & 0x3F))); out.writeByte((byte) (0x80 | (code & 0x3F))); } } } }