Maps a portion of a file to memory and returns the mapped read-only byte buffer using the given offset and length. - Java java.nio

Java examples for java.nio:ByteBuffer Read

  1. HOME
  2. Java
  3. java.nio
  4. ByteBuffer Read

Description

Maps a portion of a file to memory and returns the mapped read-only byte buffer using the given offset and length.

Demo Code


//package com.java2s;
import java.io.IOException;

import java.nio.MappedByteBuffer;

import java.nio.channels.FileChannel;
import static java.nio.channels.FileChannel.MapMode.*;
import java.nio.file.Path;
import static java.nio.file.StandardOpenOption.*;

public class Main {
    /**//from   w w w.ja va  2 s .  c o m
     * Maps a portion of a file to memory and returns the mapped read-only byte
     * buffer using the given offset and length.
     * 
     * @param path
     * @param offset
     * @param length
     * @return
     * @throws IOException 
     */
    public static MappedByteBuffer openReadOnly(Path path, int offset,
            int length) throws IOException {
        try (FileChannel fc = FileChannel.open(path, READ)) {
            return fc.map(READ_ONLY, offset, truncateLength(fc, length));
        }
    }

    /**
     * Maps the whole file to memory and returns the mapped read-only byte buffer.
     * If the file is larger than {@link java.lang.Integer#MAX_VALUE}, then all
     * bytes beyond that limit are omitted.
     * 
     * @param path
     * @return
     * @throws IOException 
     */
    public static MappedByteBuffer openReadOnly(Path path)
            throws IOException {
        return openReadOnly(path, 0, -1);
    }

    private static int truncateLength(FileChannel fc, int length)
            throws IOException {
        return (int) Math.min(length > 0 ? length : fc.size(),
                Integer.MAX_VALUE);
    }
}

Related Tutorials