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.cassandra.utils; import java.io.DataInput; import java.io.DataOutput; import java.io.EOFException; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.nio.ByteBuffer; import java.nio.charset.CharacterCodingException; import java.nio.charset.Charset; import java.util.Arrays; import static com.google.common.base.Charsets.UTF_8; import org.apache.cassandra.io.util.FileDataInput; import org.apache.cassandra.io.util.FileUtils; import org.apache.commons.lang.ArrayUtils; /** * Utility methods to make ByteBuffers less painful * The following should illustrate the different ways byte buffers can be used * * public void testArrayOffet() * { * * byte[] b = "test_slice_array".getBytes(); * ByteBuffer bb = ByteBuffer.allocate(1024); * * assert bb.position() == 0; * assert bb.limit() == 1024; * assert bb.capacity() == 1024; * * bb.put(b); * * assert bb.position() == b.length; * assert bb.remaining() == bb.limit() - bb.position(); * * ByteBuffer bb2 = bb.slice(); * * assert bb2.position() == 0; * * //slice should begin at other buffers current position * assert bb2.arrayOffset() == bb.position(); * * //to match the position in the underlying array one needs to * //track arrayOffset * assert bb2.limit()+bb2.arrayOffset() == bb.limit(); * * * assert bb2.remaining() == bb.remaining(); * * } * * } * */ public class ByteBufferUtil { public static final ByteBuffer EMPTY_BYTE_BUFFER = ByteBuffer.wrap(ArrayUtils.EMPTY_BYTE_ARRAY); public static int compareUnsigned(ByteBuffer o1, ByteBuffer o2) { assert o1 != null; assert o2 != null; int minLength = Math.min(o1.remaining(), o2.remaining()); for (int x = 0, i = o1.position(), j = o2.position(); x < minLength; x++, i++, j++) { if (o1.get(i) == o2.get(j)) continue; // compare non-equal bytes as unsigned return (o1.get(i) & 0xFF) < (o2.get(j) & 0xFF) ? -1 : 1; } return (o1.remaining() == o2.remaining()) ? 0 : ((o1.remaining() < o2.remaining()) ? -1 : 1); } public static int compare(byte[] o1, ByteBuffer o2) { return compareUnsigned(ByteBuffer.wrap(o1), o2); } public static int compare(ByteBuffer o1, byte[] o2) { return compareUnsigned(o1, ByteBuffer.wrap(o2)); } /** * Decode a String representation. * This method assumes that the encoding charset is UTF_8. * * @param buffer a byte buffer holding the string representation * @return the decoded string */ public static String string(ByteBuffer buffer) throws CharacterCodingException { return string(buffer, UTF_8); } /** * Decode a String representation. * This method assumes that the encoding charset is UTF_8. * * @param buffer a byte buffer holding the string representation * @param position the starting position in {@code buffer} to start decoding from * @param length the number of bytes from {@code buffer} to use * @return the decoded string */ public static String string(ByteBuffer buffer, int position, int length) throws CharacterCodingException { return string(buffer, position, length, UTF_8); } /** * Decode a String representation. * * @param buffer a byte buffer holding the string representation * @param position the starting position in {@code buffer} to start decoding from * @param length the number of bytes from {@code buffer} to use * @param charset the String encoding charset * @return the decoded string */ public static String string(ByteBuffer buffer, int position, int length, Charset charset) throws CharacterCodingException { ByteBuffer copy = buffer.duplicate(); copy.position(position); copy.limit(copy.position() + length); return string(copy, charset); } /** * Decode a String representation. * * @param buffer a byte buffer holding the string representation * @param charset the String encoding charset * @return the decoded string */ public static String string(ByteBuffer buffer, Charset charset) throws CharacterCodingException { return charset.newDecoder().decode(buffer.duplicate()).toString(); } /** * You should almost never use this. Instead, use the write* methods to avoid copies. */ public static byte[] getArray(ByteBuffer buffer) { int length = buffer.remaining(); if (buffer.hasArray()) { int start = buffer.position(); if (buffer.arrayOffset() == 0 && start == 0 && length == buffer.array().length) return buffer.array(); else return Arrays.copyOfRange(buffer.array(), start + buffer.arrayOffset(), start + length + buffer.arrayOffset()); } // else, DirectByteBuffer.get() is the fastest route byte[] bytes = new byte[length]; buffer.duplicate().get(bytes); return bytes; } /** * ByteBuffer adaptation of org.apache.commons.lang.ArrayUtils.lastIndexOf method * * @param buffer the array to traverse for looking for the object, may be <code>null</code> * @param valueToFind the value to find * @param startIndex the start index (i.e. BB position) to travers backwards from * @return the last index (i.e. BB position) of the value within the array * [between buffer.position() and buffer.limit()]; <code>-1</code> if not found. */ public static int lastIndexOf(ByteBuffer buffer, byte valueToFind, int startIndex) { assert buffer != null; if (startIndex < buffer.position()) { return -1; } else if (startIndex >= buffer.limit()) { startIndex = buffer.limit() - 1; } for (int i = startIndex; i >= buffer.position(); i--) { if (valueToFind == buffer.get(i)) return i; } return -1; } /** * Encode a String in a ByteBuffer using UTF_8. * * @param s the string to encode * @return the encoded string */ public static ByteBuffer bytes(String s) { return ByteBuffer.wrap(s.getBytes(UTF_8)); } /** * Encode a String in a ByteBuffer using the provided charset. * * @param s the string to encode * @param charset the String encoding charset to use * @return the encoded string */ public static ByteBuffer bytes(String s, Charset charset) { return ByteBuffer.wrap(s.getBytes(charset)); } /** * @return a new copy of the data in @param buffer * USUALLY YOU SHOULD USE ByteBuffer.duplicate() INSTEAD, which creates a new Buffer * (so you can mutate its position without affecting the original) without copying the underlying array. */ public static ByteBuffer clone(ByteBuffer buffer) { assert buffer != null; if (buffer.remaining() == 0) return EMPTY_BYTE_BUFFER; ByteBuffer clone = ByteBuffer.allocate(buffer.remaining()); if (buffer.hasArray()) { System.arraycopy(buffer.array(), buffer.arrayOffset() + buffer.position(), clone.array(), 0, buffer.remaining()); } else { clone.put(buffer.duplicate()); clone.flip(); } return clone; } public static void arrayCopy(ByteBuffer buffer, int position, byte[] bytes, int offset, int length) { if (buffer.hasArray()) System.arraycopy(buffer.array(), buffer.arrayOffset() + position, bytes, offset, length); else ((ByteBuffer) buffer.duplicate().position(position)).get(bytes, offset, length); } /** * Transfer bytes from one ByteBuffer to another. * This function acts as System.arrayCopy() but for ByteBuffers. * * @param src the source ByteBuffer * @param srcPos starting position in the source ByteBuffer * @param dst the destination ByteBuffer * @param dstPos starting position in the destination ByteBuffer * @param length the number of bytes to copy */ public static void arrayCopy(ByteBuffer src, int srcPos, ByteBuffer dst, int dstPos, int length) { if (src.hasArray() && dst.hasArray()) { System.arraycopy(src.array(), src.arrayOffset() + srcPos, dst.array(), dst.arrayOffset() + dstPos, length); } else { if (src.limit() - srcPos < length || dst.limit() - dstPos < length) throw new IndexOutOfBoundsException(); for (int i = 0; i < length; i++) { dst.put(dstPos++, src.get(srcPos++)); } } } public static void writeWithLength(ByteBuffer bytes, DataOutput out) throws IOException { out.writeInt(bytes.remaining()); write(bytes, out); // writing data bytes to output source } public static void write(ByteBuffer buffer, DataOutput out) throws IOException { if (buffer.hasArray()) { out.write(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining()); } else { for (int i = buffer.position(); i < buffer.limit(); i++) { out.writeByte(buffer.get(i)); } } } public static void writeWithShortLength(ByteBuffer buffer, DataOutput out) { int length = buffer.remaining(); assert 0 <= length && length <= FBUtilities.MAX_UNSIGNED_SHORT : length; try { out.writeByte((length >> 8) & 0xFF); out.writeByte(length & 0xFF); write(buffer, out); // writing data bytes to output source } catch (IOException e) { throw new RuntimeException(e); } } public static ByteBuffer readWithLength(DataInput in) throws IOException { int length = in.readInt(); if (length < 0) { throw new IOException("Corrupt (negative) value length encountered"); } return ByteBufferUtil.read(in, length); } /* @return An unsigned short in an integer. */ private static int readShortLength(DataInput in) throws IOException { int length = (in.readByte() & 0xFF) << 8; return length | (in.readByte() & 0xFF); } /** * @param in data input * @return An unsigned short in an integer. * @throws IOException if an I/O error occurs. */ public static ByteBuffer readWithShortLength(DataInput in) throws IOException { return ByteBufferUtil.read(in, readShortLength(in)); } /** * @param in data input * @return null * @throws IOException if an I/O error occurs. */ public static ByteBuffer skipShortLength(DataInput in) throws IOException { int skip = readShortLength(in); FileUtils.skipBytesFully(in, skip); return null; } private static ByteBuffer read(DataInput in, int length) throws IOException { ByteBuffer array; if (in instanceof FileDataInput) { array = ((FileDataInput) in).readBytes(length); } else { byte[] buff = new byte[length]; in.readFully(buff); array = ByteBuffer.wrap(buff); } return array; } /** * Convert a byte buffer to an integer. * Does not change the byte buffer position. * * @param bytes byte buffer to convert to integer * @return int representation of the byte buffer */ public static int toInt(ByteBuffer bytes) { return bytes.getInt(bytes.position()); } public static long toLong(ByteBuffer bytes) { return bytes.getLong(bytes.position()); } public static float toFloat(ByteBuffer bytes) { return bytes.getFloat(bytes.position()); } public static double toDouble(ByteBuffer bytes) { return bytes.getDouble(bytes.position()); } public static ByteBuffer bytes(int i) { return ByteBuffer.allocate(4).putInt(0, i); } public static ByteBuffer bytes(long n) { return ByteBuffer.allocate(8).putLong(0, n); } public static ByteBuffer bytes(float f) { return ByteBuffer.allocate(4).putFloat(0, f); } public static ByteBuffer bytes(double d) { return ByteBuffer.allocate(8).putDouble(0, d); } public static InputStream inputStream(ByteBuffer bytes) { final ByteBuffer copy = bytes.duplicate(); return new InputStream() { public int read() throws IOException { if (!copy.hasRemaining()) return -1; return copy.get() & 0xFF; } @Override public int read(byte[] bytes, int off, int len) throws IOException { if (!copy.hasRemaining()) return -1; len = Math.min(len, copy.remaining()); copy.get(bytes, off, len); return len; } @Override public int available() throws IOException { return copy.remaining(); } }; } public static String bytesToHex(ByteBuffer bytes) { StringBuilder sb = new StringBuilder(); for (int i = bytes.position(); i < bytes.limit(); i++) { int bint = bytes.get(i) & 0xff; if (bint <= 0xF) // toHexString does not 0 pad its results. sb.append("0"); sb.append(Integer.toHexString(bint)); } return sb.toString(); } public static ByteBuffer hexToBytes(String str) { return ByteBuffer.wrap(FBUtilities.hexToBytes(str)); } /** * Compare two ByteBuffer at specified offsets for length. * Compares the non equal bytes as unsigned. * @param bytes1 First byte buffer to compare. * @param offset1 Position to start the comparison at in the first array. * @param bytes2 Second byte buffer to compare. * @param offset2 Position to start the comparison at in the second array. * @param length How many bytes to compare? * @return -1 if byte1 is less than byte2, 1 if byte2 is less than byte1 or 0 if equal. */ public static int compareSubArrays(ByteBuffer bytes1, int offset1, ByteBuffer bytes2, int offset2, int length) { if (null == bytes1) { if (null == bytes2) return 0; else return -1; } if (null == bytes2) return 1; assert bytes1.limit() >= offset1 + length : "The first byte array isn't long enough for the specified offset and length."; assert bytes2.limit() >= offset2 + length : "The second byte array isn't long enough for the specified offset and length."; for (int i = 0; i < length; i++) { byte byte1 = bytes1.get(offset1 + i); byte byte2 = bytes2.get(offset2 + i); if (byte1 == byte2) continue; // compare non-equal bytes as unsigned return (byte1 & 0xFF) < (byte2 & 0xFF) ? -1 : 1; } return 0; } }