Java ReadableByteChannel Read readLengthAndString(ReadableByteChannel channel, ByteBuffer buffer)

Description

read Length And String

License

Open Source License

Declaration

public static String readLengthAndString(ReadableByteChannel channel, ByteBuffer buffer) throws IOException 

Method Source Code

//package com.java2s;
/**/*from   ww  w  .ja va2 s. c  o m*/
 * Copyright (c) 2002-2014 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.io.IOException;

import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;

public class Main {
    public static String readLengthAndString(ReadableByteChannel channel, ByteBuffer buffer) throws IOException {
        Integer length = readInt(channel, buffer);
        if (length != null) {
            char[] chars = new char[length];
            chars = readCharArray(channel, buffer, chars);
            return chars == null ? null : new String(chars);
        } else
            return null;
    }

    public static Integer readInt(ReadableByteChannel channel, ByteBuffer buffer) throws IOException {
        return readAndFlip(channel, buffer, 4) ? buffer.getInt() : null;
    }

    private static char[] readCharArray(ReadableByteChannel channel, ByteBuffer buffer, char[] charArray)
            throws IOException {
        buffer.clear();
        int charsLeft = charArray.length;
        int maxSize = buffer.capacity() / 2;
        int offset = 0; // offset in chars
        while (charsLeft > 0) {
            if (charsLeft > maxSize) {
                buffer.limit(maxSize * 2);
                charsLeft -= maxSize;
            } else {
                buffer.limit(charsLeft * 2);
                charsLeft = 0;
            }
            if (channel.read(buffer) != buffer.limit()) {
                return null;
            }
            buffer.flip();
            int length = buffer.limit() / 2;
            buffer.asCharBuffer().get(charArray, offset, length);
            offset += length;
            buffer.clear();
        }
        return charArray;
    }

    public static boolean readAndFlip(ReadableByteChannel channel, ByteBuffer buffer, int bytes)
            throws IOException {
        buffer.clear();
        buffer.limit(bytes);
        while (buffer.hasRemaining()) {
            int read = channel.read(buffer);

            if (read == -1) {
                return false;
            }
        }
        buffer.flip();
        return true;
    }
}

Related

1. readFull(ReadableByteChannel ch, ByteBuffer dst)
2. readFully(final ReadableByteChannel channel, final ByteBuffer buf)
3. readFully(final ReadableByteChannel channel, final ByteBuffer buf)
4. readFully(ReadableByteChannel channel, ByteBuffer b)
5. readFully(ReadableByteChannel channel, ByteBuffer buffer)
6. readMap(ReadableByteChannel channel, ByteBuffer buffer)
7. readObjFromChannel(ReadableByteChannel chan, ByteBuffer buffer, AtomicBoolean endPointCrashed)
8. readToBuffer(ReadableByteChannel src, ByteBuffer dst)
9. retryRead(ReadableByteChannel channel, ByteBuffer buffer)