Java File Read via ByteBuffer readString(ReadableByteChannel channel)

Description

read String

License

Apache License

Declaration

public static String readString(ReadableByteChannel channel) throws IOException 

Method Source Code

//package com.java2s;
/*/*from ww  w  . j  a v  a2  s. c  o  m*/
 * 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.
 */

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

public class Main {
    public static String readString(ReadableByteChannel channel) throws IOException {
        int nameLen = readInt(channel); // name length
        if (nameLen < 0) {
            return null;
        }

        ByteBuffer buf = ByteBuffer.allocate(nameLen * 2);
        if (fillBuffer(channel, buf, true)) {
            char[] name = new char[nameLen];
            buf.rewind();
            for (int i = 0; i < nameLen; i++) {
                name[i] = buf.getChar();
            }
            return new String(name);
        }
        return null;
    }

    public static int readInt(ReadableByteChannel channel) throws IOException {
        ByteBuffer buf = ByteBuffer.allocate(4);
        if (fillBuffer(channel, buf, true)) {
            buf.rewind();
            return buf.getInt();
        }
        return -1;
    }

    public static boolean fillBuffer(ReadableByteChannel channel, ByteBuffer buf, boolean clear)
            throws IOException {
        if (clear) {
            buf.clear();
        }

        while (true) {
            int cnt = channel.read(buf);
            if (cnt < 0) {
                return false;
            }
            if (buf.position() == buf.capacity()) {
                break;// fill to capacity
            }
        }
        return true;
    }
}

Related

1. readShort(byte[] bytes, int start)
2. readShort(DataInput input)
3. readShortBuffer(DataInputStream input)
4. readShortByteArray(DataInput in)
5. readString(ByteArrayInputStream bin)
6. readStringFromFile(String path)
7. readStringFromSocketChannel(SocketChannel sc)
8. readStringInUTF8(DataInput in)
9. readToBuffer(final String filename)