Java ByteBuffer Read readFrom(File file, ByteBuffer buffer)

Description

read From

License

Open Source License

Declaration

public static void readFrom(File file, ByteBuffer buffer) throws IOException 

Method Source Code

//package com.java2s;
//  are made available under the terms of the Eclipse Public License v1.0

import java.io.File;

import java.io.IOException;
import java.io.InputStream;

import java.io.RandomAccessFile;

import java.nio.ByteBuffer;

import java.nio.channels.FileChannel;

public class Main {
    public static void readFrom(File file, ByteBuffer buffer) throws IOException {
        try (RandomAccessFile raf = new RandomAccessFile(file, "r")) {
            FileChannel channel = raf.getChannel();
            long needed = raf.length();

            while (needed > 0 && buffer.hasRemaining())
                needed = needed - channel.read(buffer);
        }/*from   w w  w  . jav a 2 s.co  m*/
    }

    public static void readFrom(InputStream is, int needed, ByteBuffer buffer) throws IOException {
        ByteBuffer tmp = allocate(8192);

        while (needed > 0 && buffer.hasRemaining()) {
            int l = is.read(tmp.array(), 0, 8192);
            if (l < 0)
                break;
            tmp.position(0);
            tmp.limit(l);
            buffer.put(tmp);
        }
    }

    /** Get remaining from null checked buffer
     * @param buffer The buffer to get the remaining from, in flush mode.
     * @return 0 if the buffer is null, else the bytes remaining in the buffer.
     */
    public static int length(ByteBuffer buffer) {
        return buffer == null ? 0 : buffer.remaining();
    }

    /** Allocate ByteBuffer in flush mode.
     * The position and limit will both be zero, indicating that the buffer is
     * empty and must be flipped before any data is put to it.
     * @param capacity capacity of the allocated ByteBuffer
     * @return Buffer
     */
    public static ByteBuffer allocate(int capacity) {
        ByteBuffer buf = ByteBuffer.allocate(capacity);
        buf.limit(0);
        return buf;
    }

    /**
     * Put data from one buffer into another, avoiding over/under flows
     * @param from Buffer to take bytes from in flush mode
     * @param to   Buffer to put bytes to in fill mode.
     * @return number of bytes moved
     */
    public static int put(ByteBuffer from, ByteBuffer to) {
        int put;
        int remaining = from.remaining();
        if (remaining > 0) {
            if (remaining <= to.remaining()) {
                to.put(from);
                put = remaining;
                from.position(from.limit());
            } else if (from.hasArray()) {
                put = to.remaining();
                to.put(from.array(), from.arrayOffset() + from.position(), put);
                from.position(from.position() + put);
            } else {
                put = to.remaining();
                ByteBuffer slice = from.slice();
                slice.limit(put);
                to.put(slice);
                from.position(from.position() + put);
            }
        } else
            put = 0;

        return put;
    }
}

Related

1. readFileToByteBuffer(File file)
2. readFixedLengthString(ByteBuffer buf, int length)
3. readFixedLengthString(ByteBuffer byteBuffer, int size)
4. readFixedPoint88(ByteBuffer bb)
5. readFourByteInt(ByteBuffer buffer, int start)
6. readFully(final FileChannel src, final ByteBuffer dst, final long position)
7. readHealthFloat16(ByteBuffer data)
8. readHexString(ByteBuffer buffer, int nrBytes)
9. readIso639(ByteBuffer bb)