Java tutorial
/* * Copyright 2012-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://aws.amazon.com/apache2.0 * * or in the "license" file accompanying this file. This file 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.amazonaws.util; import java.io.File; import java.io.FileOutputStream; import java.io.FileWriter; import java.io.IOException; import java.io.OutputStream; import java.util.Random; import org.apache.commons.io.IOUtils; /** * Helper class that helps in creating and writing data to temporary files. * */ public class FileUtils { static final int ASCII_LOW = 33; // '!', skipping space for readability static final int ASCII_HIGH = 126; // include a line break character static final int modulo = ASCII_HIGH - ASCII_LOW + 2; private static final Random rand = new Random(); /** * Returns a reference to the file created with the given file name in the * System's temporary directory. * * @param fileName * @return a reference to the file * @throws IOException */ public static File createTempFileForTesting(String fileName) throws IOException { return File.createTempFile(String.valueOf(System.currentTimeMillis()), fileName); } /** * Creates a file with the given name in the System's temporary directory. * Adds the data to the given file and returns the reference to the file. * * @param fileName * @param data * @return reference to the file. * @throws IOException */ public static File createTempFileForTesting(String fileName, String data) throws IOException { return appendDataToTempFile(File.createTempFile(String.valueOf(System.currentTimeMillis()), fileName), data); } /** * Appends the given data to the file specified in the input and returns the * reference to the file. * * @param file * @param dataToAppend * @return reference to the file. * @throws IOException */ public static File appendDataToTempFile(File file, String dataToAppend) throws IOException { FileWriter outputWriter = new FileWriter(file); try { outputWriter.append(dataToAppend); } finally { outputWriter.close(); } return file; } /** * Generate a random ASCII file of the specified number of bytes. The ASCII * characters ranges over all printable ASCII from 33 to 126 inclusive and * LF '\n', intentionally skipping space for readability. */ public static File generateRandomAsciiFile(long byteSize) throws IOException { return generateRandomAsciiFile(byteSize, true); } public static File generateRandomAsciiFile(long byteSize, boolean deleteOnExit) throws IOException { File file = File.createTempFile("CryptoTestUtils", ".txt"); System.out.println("Generating random ASCII file with size: " + byteSize + " at " + file); if (deleteOnExit) file.deleteOnExit(); OutputStream out = new FileOutputStream(file); int BUFSIZE = 1024 * 8; byte[] buf = new byte[1024 * 8]; long counts = byteSize / BUFSIZE; try { while (counts-- > 0) { IOUtils.write(fillRandomAscii(buf), out); } int remainder = (int) byteSize % BUFSIZE; if (remainder > 0) { buf = new byte[remainder]; IOUtils.write(fillRandomAscii(buf), out); } } finally { out.close(); } return file; } private static byte[] fillRandomAscii(byte[] bytes) { rand.nextBytes(bytes); for (int i = 0; i < bytes.length; i++) { byte b = bytes[i]; if (b < ASCII_LOW || b > ASCII_HIGH) { byte c = (byte) (b % modulo); if (c < 0) c = (byte) (c + modulo); bytes[i] = (byte) (c + ASCII_LOW); if (bytes[i] > ASCII_HIGH) bytes[i] = (byte) '\n'; } } return bytes; } }