Android example source code file (RandomBlock.java)

This example Android source code file (RandomBlock.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, block_size, closeable, debug, eofexception, fileinputstream, io, ioexception, randomaccessfile, randomblock, string, tag, util, utilities, utils

The RandomBlock.java Android example source code

/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed 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 com.android.server;

import android.util.Slog;

import java.io.Closeable;
import java.io.DataOutput;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;

/**
 * A 4k block of random {@code byte}s.
 */
class RandomBlock {

    private static final String TAG = "RandomBlock";
    private static final boolean DEBUG = false;
    private static final int BLOCK_SIZE = 4096;
    private byte[] block = new byte[BLOCK_SIZE];

    private RandomBlock() { }

    static RandomBlock fromFile(String filename) throws IOException {
        if (DEBUG) Slog.v(TAG, "reading from file " + filename);
        InputStream stream = null;
        try {
            stream = new FileInputStream(filename);
            return fromStream(stream);
        } finally {
            close(stream);
        }
    }

    private static RandomBlock fromStream(InputStream in) throws IOException {
        RandomBlock retval = new RandomBlock();
        int total = 0;
        while(total < BLOCK_SIZE) {
            int result = in.read(retval.block, total, BLOCK_SIZE - total);
            if (result == -1) {
                throw new EOFException();
            }
            total += result;
        }
        return retval;
    }

    void toFile(String filename) throws IOException {
        if (DEBUG) Slog.v(TAG, "writing to file " + filename);
        RandomAccessFile out = null;
        try {
            out = new RandomAccessFile(filename, "rws");
            toDataOut(out);
            truncateIfPossible(out);
        } finally {
            close(out);
        }
    }

    private static void truncateIfPossible(RandomAccessFile f) {
        try {
            f.setLength(BLOCK_SIZE);
        } catch (IOException e) {
            // ignore this exception.  Sometimes, the file we're trying to
            // write is a character device, such as /dev/urandom, and
            // these character devices do not support setting the length.
        }
    }

    private void toDataOut(DataOutput out) throws IOException {
        out.write(block);
    }

    private static void close(Closeable c) {
        try {
            if (c == null) {
                return;
            }
            c.close();
        } catch (IOException e) {
            Slog.w(TAG, "IOException thrown while closing Closeable", e);
        }
    }
}