cassandra-trunk/src/java/org/apache/cassandra/utils/ByteBufferUtil.java
/*
 * 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;

/*
 * BE ADVISED: New imports added here might introduce new dependencies for
 * the clientutil jar.  If in doubt, run the `ant test-clientutil-jar' target
 * afterward, and ensure the tests still pass.
 */

import java.io.DataInput;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.UUID;

import net.nicoulaj.compilecommand.annotations.Inline;
import org.apache.cassandra.db.TypeSizes;
import org.apache.cassandra.io.compress.BufferType;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.io.util.FileUtils;

/**
 * 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(new byte[0]);
    /** Represents an unset value in bound variables */
    public static final ByteBuffer UNSET_BYTE_BUFFER = ByteBuffer.wrap(new byte[]{});

    public static final ByteBuffer[] EMPTY_ARRAY = new ByteBuffer[0];

    @Inline
    public static int compareUnsigned(ByteBuffer o1, ByteBuffer o2)
    {
        return FastByteOperations.compareUnsigned(o1, o2);
    }

    @Inline
    public static int compare(byte[] o1, ByteBuffer o2)
    {
        return FastByteOperations.compareUnsigned(o1, 0, o1.length, o2);
    }

    @Inline
    public static int compare(ByteBuffer o1, byte[] o2)
    {
        return FastByteOperations.compareUnsigned(o1, o2, 0, o2.length);
    }

    public static int compare(ByteBuffer o1, int s1, int l1, byte[] o2)
    {
        return FastByteOperations.compareUnsigned(o1, s1, l1, o2, 0, o2.length);
    }

    public static int compare(byte[] o1, ByteBuffer o2, int s2, int l2)
    {
        return FastByteOperations.compareUnsigned(o1, 0, o1.length, o2, s2, l2);
    }

    /**
     * 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, StandardCharsets.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, StandardCharsets.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)
    {
        return getArray(buffer, buffer.position(), buffer.remaining());
    }

    /**
     * You should almost never use this.  Instead, use the write* methods to avoid copies.
     */
    public static byte[] getArray(ByteBuffer buffer, int position, int length)
    {
        if (buffer.hasArray())
        {
            int boff = buffer.arrayOffset() + position;
            return Arrays.copyOfRange(buffer.array(), boff, boff + length);
        }

        // else, DirectByteBuffer.get() is the fastest route
        byte[] bytes = new byte[length];
        ByteBuffer dup = buffer.duplicate();
        dup.position(position).limit(position + length);
        dup.get(bytes);
        return bytes;
    }

    /**
     * ByteBuffer adaptation of org.apache.commons.lang3.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(StandardCharsets.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 copyBytes(ByteBuffer src, int srcPos, byte[] dst, int dstPos, int length)
    {
        FastByteOperations.copy(src, srcPos, dst, dstPos, length);
    }

    /**
     * Transfer bytes from one ByteBuffer to another.
     * This function acts as System.arrayCopy() but for ByteBuffers, and operates safely on direct memory.
     *
     * @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 copyBytes(ByteBuffer src, int srcPos, ByteBuffer dst, int dstPos, int length)
    {
        FastByteOperations.copy(src, srcPos, dst, dstPos, length);
    }

    public static int put(ByteBuffer src, ByteBuffer trg)
    {
        int length = Math.min(src.remaining(), trg.remaining());
        copyBytes(src, src.position(), trg, trg.position(), length);
        trg.position(trg.position() + length);
        src.position(src.position() + length);
        return length;
    }

    public static void writeZeroes(ByteBuffer dest, int count)
    {
        if (count >= 8)
        {
            // align
            while ((dest.position() & 0x7) != 0)
            {
                dest.put((byte) 0);
                --count;
            }
        }
        // write aligned longs
        while (count >= 8)
        {
            dest.putLong(0L);
            count -= 8;
        }
        // finish up
        while (count > 0)
        {
            dest.put((byte) 0);
            --count;
        }
    }

    public static void writeWithLength(ByteBuffer bytes, DataOutputPlus out) throws IOException
    {
        out.writeInt(bytes.remaining());
        out.write(bytes);
    }

    public static void writeWithVIntLength(ByteBuffer bytes, DataOutputPlus out) throws IOException
    {
        out.writeUnsignedVInt32(bytes.remaining());
        out.write(bytes);
    }

    public static void writeWithShortLength(ByteBuffer buffer, DataOutputPlus out) throws IOException
    {
        int length = buffer.remaining();
        assert 0 <= length && length <= FBUtilities.MAX_UNSIGNED_SHORT
            : String.format("Attempted serializing to buffer exceeded maximum of %s bytes: %s", FBUtilities.MAX_UNSIGNED_SHORT, length);
        out.writeShort(length);
        out.write(buffer);
    }

    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);
    }

    public static ByteBuffer readWithVIntLength(DataInputPlus in) throws IOException
    {
        int length = in.readUnsignedVInt32();
        if (length < 0)
            throw new IOException("Corrupt (negative) value length encountered");

        return ByteBufferUtil.read(in, length);
    }

    public static int serializedSizeWithLength(ByteBuffer buffer)
    {
        int size = buffer.remaining();
        return TypeSizes.sizeof(size) + size;
    }

    public static int serializedSizeWithVIntLength(ByteBuffer buffer)
    {
        int size = buffer.remaining();
        return TypeSizes.sizeofUnsignedVInt(size) + size;
    }

    public static void skipWithVIntLength(DataInputPlus in) throws IOException
    {
        int length = in.readUnsignedVInt32();
        if (length < 0)
            throw new IOException("Corrupt (negative) value length encountered");

        in.skipBytesFully(length);
    }

    /* @return An unsigned short in an integer. */
    public static int readShortLength(DataInput in) throws IOException
    {
        return in.readUnsignedShort();
    }

    /**
     * @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));
    }

    public static int serializedSizeWithShortLength(ByteBuffer buffer)
    {
        int size = buffer.remaining();
        return TypeSizes.sizeof((short)size) + size;
    }

    /**
     * @param in data input
     * @throws IOException if an I/O error occurs.
     */
    public static void skipShortLength(DataInputPlus in) throws IOException
    {
        int skip = readShortLength(in);
        in.skipBytesFully(skip);
    }

    public static ByteBuffer read(DataInput in, int length) throws IOException
    {
        if (length == 0)
            return EMPTY_BYTE_BUFFER;

        byte[] buff = new byte[length];
        in.readFully(buff);
        return ByteBuffer.wrap(buff);
    }

    public static byte[] readBytes(DataInput in, int length) throws IOException
    {
        assert length > 0 : "length is not > 0: " + length;
        byte[] bytes = new byte[length];
        in.readFully(bytes);
        return bytes;
    }

    public static byte[] readBytesWithLength(DataInput in) throws IOException
    {
        int length = in.readInt();
        if (length < 0)
            throw new IOException("Corrupt (negative) value length encountered");

        return readBytes(in, length);
    }

    /**
     * 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());
    }

    /**
     * Convert a byte buffer to a short.
     * Does not change the byte buffer position.
     *
     * @param bytes byte buffer to convert to short
     * @return short representation of the byte buffer
     */
    public static short toShort(ByteBuffer bytes)
    {
        return bytes.getShort(bytes.position());
    }

    /**
     * Convert a byte buffer to a short.
     * Does not change the byte buffer position.
     *
     * @param bytes byte buffer to convert to byte
     * @return byte representation of the byte buffer
     */
    public static byte toByte(ByteBuffer bytes)
    {
        return bytes.get(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 objectToBytes(Object obj)
    {
        if (obj instanceof Integer)
            return ByteBufferUtil.bytes((int) obj);
        else if (obj instanceof Byte)
            return ByteBufferUtil.bytes((byte) obj);
        else if (obj instanceof Short)
            return ByteBufferUtil.bytes((short) obj);
        else if (obj instanceof Long)
            return ByteBufferUtil.bytes((long) obj);
        else if (obj instanceof Float)
            return ByteBufferUtil.bytes((float) obj);
        else if (obj instanceof Double)
            return ByteBufferUtil.bytes((double) obj);
        else if (obj instanceof UUID)
            return ByteBufferUtil.bytes((UUID) obj);
        else if (obj instanceof InetAddress)
            return ByteBufferUtil.bytes((InetAddress) obj);
        else if (obj instanceof String)
            return ByteBufferUtil.bytes((String) obj);
        else if (obj instanceof byte[])
            return ByteBuffer.wrap((byte[]) obj);
        else if (obj instanceof ByteBuffer)
            return (ByteBuffer) obj;
        else
            throw new IllegalArgumentException(String.format("Cannot convert value %s of type %s",
                                                             obj,
                                                             obj.getClass()));
    }

    public static ByteBuffer bytes(byte b)
    {
        return ByteBuffer.allocate(1).put(0, b);
    }

    public static ByteBuffer bytes(short s)
    {
        return ByteBuffer.allocate(2).putShort(0, s);
    }

    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()
            {
                if (!copy.hasRemaining())
                    return -1;

                return copy.get() & 0xFF;
            }

            @Override
            public int read(byte[] bytes, int off, int len)
            {
                if (!copy.hasRemaining())
                    return -1;

                len = Math.min(len, copy.remaining());
                copy.get(bytes, off, len);
                return len;
            }

            @Override
            public int available()
            {
                return copy.remaining();
            }
        };
    }

    /*
     * Does not modify position or limit of buffer even temporarily
     * so this is safe even without duplication.
     */
    public static String bytesToHex(ByteBuffer bytes)
    {
        if (bytes.hasArray())
        {
            return Hex.bytesToHex(bytes.array(), bytes.arrayOffset() + bytes.position(), bytes.remaining());
        }

        final int offset = bytes.position();
        final int size = bytes.remaining();
        final char[] c = new char[size * 2];
        for (int i = 0; i < size; i++)
        {
            final int bint = bytes.get(i+offset);
            c[i * 2] = Hex.byteToChar[(bint & 0xf0) >> 4];
            c[1 + i * 2] = Hex.byteToChar[bint & 0x0f];
        }
        return Hex.wrapCharArray(c);
    }

    public static ByteBuffer hexToBytes(String str)
    {
        return ByteBuffer.wrap(Hex.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 (bytes1 == null)
            return bytes2 == null ? 0 : -1;
        if (bytes2 == null) 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;
    }

    public static ByteBuffer bytes(InetAddress address)
    {
        return ByteBuffer.wrap(address.getAddress());
    }

    public static ByteBuffer bytes(UUID uuid)
    {
        return ByteBuffer.wrap(UUIDGen.decompose(uuid));
    }

    public static ByteBuffer bytes(TimeUUID uuid)
    {
        return bytes(uuid.asUUID());
    }

    // Returns whether {@code prefix} is a prefix of {@code value}.
    public static boolean isPrefix(ByteBuffer prefix, ByteBuffer value)
    {
        if (prefix.remaining() > value.remaining())
            return false;

        int diff = value.remaining() - prefix.remaining();
        return prefix.equals(value.duplicate().limit(value.remaining() - diff));
    }

    public static boolean canMinimize(ByteBuffer buf)
    {
        return buf != null && (!buf.hasArray() || buf.array().length > buf.remaining());
        // Note: buf.array().length is different from buf.capacity() for sliced buffers.
    }

    /** trims size of bytebuffer to exactly number of bytes in it, to do not hold too much memory */
    public static ByteBuffer minimalBufferFor(ByteBuffer buf)
    {
        return !buf.hasArray() || buf.array().length > buf.remaining() ? ByteBuffer.wrap(getArray(buf)) : buf;
    }

    public static ByteBuffer[] minimizeBuffers(ByteBuffer[] src)
    {
        ByteBuffer[] dst = new ByteBuffer[src.length];
        for (int i=0; i<src.length; i++)
            dst[i] = src[i] != null ? minimalBufferFor(src[i]) : null;
        return dst;
    }

    public static boolean canMinimize(ByteBuffer[] src)
    {
        for (ByteBuffer buffer : src)
        {
            if (canMinimize(buffer))
                return true;
        }
        return false;
    }

    public static int getUnsignedShort(ByteBuffer bb, int position)
    {
        return ((bb.get(position) & 0xFF) << 8) | (bb.get(position + 1) & 0xFF);
    }

    // Doesn't change bb position
    public static int getShortLength(ByteBuffer bb, int position)
    {
        return getUnsignedShort(bb, position);
    }

    // changes bb position
    public static int readShortLength(ByteBuffer bb)
    {
        int length = (bb.get() & 0xFF) << 8;
        return length | (bb.get() & 0xFF);
    }

    // changes bb position
    public static void writeShortLength(ByteBuffer bb, int length)
    {
        if (length > FBUtilities.MAX_UNSIGNED_SHORT)
            throw new IllegalArgumentException(String.format("Length %d > max length %d", length, FBUtilities.MAX_UNSIGNED_SHORT));
        bb.put((byte) ((length >> 8) & 0xFF));
        bb.put((byte) (length & 0xFF));
    }

    // changes bb position
    public static ByteBuffer readBytes(ByteBuffer bb, int length)
    {
        ByteBuffer copy = bb.duplicate();
        copy.limit(copy.position() + length);
        bb.position(bb.position() + length);
        return copy;
    }

    // changes bb position
    public static ByteBuffer readBytesWithShortLength(ByteBuffer bb)
    {
        int length = readShortLength(bb);
        return readBytes(bb, length);
    }

    /**
     * Ensure {@code buf} is large enough for {@code outputLength}. If not, it is cleaned up and a new buffer is allocated;
     * else; buffer has it's position/limit set appropriately.
     *
     * @param buf buffer to test the size of; may be null, in which case, a new buffer is allocated.
     * @param outputLength the minimum target size of the buffer
     * @param allowBufferResize true if resizing (reallocating) the buffer is allowed
     * @return {@code buf} if it was large enough, else a newly allocated buffer.
     */
    public static ByteBuffer ensureCapacity(ByteBuffer buf, int outputLength, boolean allowBufferResize)
    {
        BufferType bufferType = buf != null ? BufferType.typeOf(buf) : BufferType.ON_HEAP;
        return ensureCapacity(buf, outputLength, allowBufferResize, bufferType);
    }

    /**
     * Ensure {@code buf} is large enough for {@code outputLength}. If not, it is cleaned up and a new buffer is allocated;
     * else; buffer has it's position/limit set appropriately.
     *
     * @param buf buffer to test the size of; may be null, in which case, a new buffer is allocated.
     * @param outputLength the minimum target size of the buffer
     * @param allowBufferResize true if resizing (reallocating) the buffer is allowed
     * @param bufferType on- or off- heap byte buffer
     * @return {@code buf} if it was large enough, else a newly allocated buffer.
     */
    public static ByteBuffer ensureCapacity(ByteBuffer buf, int outputLength, boolean allowBufferResize, BufferType bufferType)
    {
        if (0 > outputLength)
            throw new IllegalArgumentException("invalid size for output buffer: " + outputLength);
        if (buf == null || buf.capacity() < outputLength)
        {
            if (!allowBufferResize)
                throw new IllegalStateException(String.format("output buffer is not large enough for data: current capacity %d, required %d", buf.capacity(), outputLength));
            FileUtils.clean(buf);
            buf = bufferType.allocate(outputLength);
        }
        else
        {
            buf.position(0).limit(outputLength);
        }
        return buf;
    }

    /**
     * Check is the given buffer contains a given sub-buffer.
     *
     * @param buffer The buffer to search for sequence of bytes in.
     * @param subBuffer The buffer to match.
     *
     * @return true if buffer contains sub-buffer, false otherwise.
     */
    public static boolean contains(ByteBuffer buffer, ByteBuffer subBuffer)
    {
        int len = subBuffer.remaining();
        if (buffer.remaining() - len < 0)
            return false;

        // adapted form the JDK's String.indexOf()
        byte first = subBuffer.get(subBuffer.position());
        int max = buffer.position() + (buffer.remaining() - len);

        for (int i = buffer.position(); i <= max; i++)
        {
            /* Look for first character. */
            if (buffer.get(i) != first)
            {
                while (++i <= max && buffer.get(i) != first)
                {}
            }

            /* (maybe) Found first character, now look at the rest of v2 */
            if (i <= max)
            {
                int j = i + 1;
                int end = j + len - 1;
                for (int k = 1 + subBuffer.position(); j < end && buffer.get(j) == subBuffer.get(k); j++, k++)
                {}

                if (j == end)
                    return true;
            }
        }
        return false;
    }

    public static boolean startsWith(ByteBuffer src, ByteBuffer prefix)
    {
        return startsWith(src, prefix, 0);
    }

    public static boolean endsWith(ByteBuffer src, ByteBuffer suffix)
    {
        return startsWith(src, suffix, src.remaining() - suffix.remaining());
    }

    private static boolean startsWith(ByteBuffer src, ByteBuffer prefix, int offset)
    {
        if (offset < 0)
            return false;

        int sPos = src.position() + offset;
        int pPos = prefix.position();

        if (src.remaining() - offset < prefix.remaining())
            return false;

        int len = Math.min(src.remaining() - offset, prefix.remaining());

        while (len-- > 0)
        {
            if (src.get(sPos++) != prefix.get(pPos++))
                return false;
        }

        return true;
    }

    /**
     * Returns true if the buffer at the current position in the input matches given buffer.
     * If true, the input is positioned at the end of the consumed buffer.
     * If false, the position of the input is undefined.
     * <p>
     * The matched buffer is unchanged
     */
    public static boolean equalsWithShortLength(DataInput in, ByteBuffer toMatch) throws IOException
    {
        int length = readShortLength(in);
        if (length != toMatch.remaining())
            return false;
        int limit = toMatch.limit();
        for (int i = toMatch.position(); i < limit; ++i)
            if (toMatch.get(i) != in.readByte())
                return false;

        return true;
    }

    public static void readFully(FileChannel channel, ByteBuffer dst, long position) throws IOException
    {
        while (dst.hasRemaining())
        {
            int read = channel.read(dst, position);
            if (read == -1)
                throw new EOFException();
            position += read;
        }
    }
}