Android example source code file (FileUtils.java)

This example Android source code file (FileUtils.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

bytearrayoutputstream, fileinputstream, fileoutputstream, filestatus, fileutils, io, ioexception, pattern, regex, s_iroth, s_irusr, s_irwxo, s_irwxu, s_iwusr, s_ixusr, string

The FileUtils.java Android example source code

/*
 * Copyright (C) 2006 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 android.os;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.regex.Pattern;


/**
 * Tools for managing files.  Not for public consumption.
 * @hide
 */
public class FileUtils
{
    public static final int S_IRWXU = 00700;
    public static final int S_IRUSR = 00400;
    public static final int S_IWUSR = 00200;
    public static final int S_IXUSR = 00100;

    public static final int S_IRWXG = 00070;
    public static final int S_IRGRP = 00040;
    public static final int S_IWGRP = 00020;
    public static final int S_IXGRP = 00010;

    public static final int S_IRWXO = 00007;
    public static final int S_IROTH = 00004;
    public static final int S_IWOTH = 00002;
    public static final int S_IXOTH = 00001;
    
    
    /**
     * File status information. This class maps directly to the POSIX stat structure.
     * @hide
     */
    public static final class FileStatus {
        public int dev;
        public int ino;
        public int mode;
        public int nlink;
        public int uid;
        public int gid;
        public int rdev;
        public long size;
        public int blksize;
        public long blocks;
        public long atime;
        public long mtime;
        public long ctime;
    }
    
    /**
     * Get the status for the given path. This is equivalent to the POSIX stat(2) system call. 
     * @param path The path of the file to be stat'd.
     * @param status Optional argument to fill in. It will only fill in the status if the file
     * exists. 
     * @return true if the file exists and false if it does not exist. If you do not have 
     * permission to stat the file, then this method will return false.
     */
    public static native boolean getFileStatus(String path, FileStatus status);

    /** Regular expression for safe filenames: no spaces or metacharacters */
    private static final Pattern SAFE_FILENAME_PATTERN = Pattern.compile("[\\w%+,./=_-]+");

    public static native int setPermissions(String file, int mode, int uid, int gid);

    public static native int getPermissions(String file, int[] outPermissions);

    /** returns the FAT file system volume ID for the volume mounted 
     * at the given mount point, or -1 for failure
     * @param mount point for FAT volume
     * @return volume ID or -1
     */
    public static native int getFatVolumeId(String mountPoint);
        
    // copy a file from srcFile to destFile, return true if succeed, return
    // false if fail
    public static boolean copyFile(File srcFile, File destFile) {
        boolean result = false;
        try {
            InputStream in = new FileInputStream(srcFile);
            try {
                result = copyToFile(in, destFile);
            } finally  {
                in.close();
            }
        } catch (IOException e) {
            result = false;
        }
        return result;
    }
    
    /**
     * Copy data from a source stream to destFile.
     * Return true if succeed, return false if failed.
     */
    public static boolean copyToFile(InputStream inputStream, File destFile) {
        try {
            if (destFile.exists()) {
                destFile.delete();
            }
            OutputStream out = new FileOutputStream(destFile);
            try {
                byte[] buffer = new byte[4096];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) >= 0) {
                    out.write(buffer, 0, bytesRead);
                }
            } finally {
                out.close();
            }
            return true;
        } catch (IOException e) {
            return false;
        }
    }

    /**
     * Check if a filename is "safe" (no metacharacters or spaces).
     * @param file  The file to check
     */
    public static boolean isFilenameSafe(File file) {
        // Note, we check whether it matches what's known to be safe,
        // rather than what's known to be unsafe.  Non-ASCII, control
        // characters, etc. are all unsafe by default.
        return SAFE_FILENAME_PATTERN.matcher(file.getPath()).matches();
    }

    /**
     * Read a text file into a String, optionally limiting the length.
     * @param file to read (will not seek, so things like /proc files are OK)
     * @param max length (positive for head, negative of tail, 0 for no limit)
     * @param ellipsis to add of the file was truncated (can be null)
     * @return the contents of the file, possibly truncated
     * @throws IOException if something goes wrong reading the file
     */
    public static String readTextFile(File file, int max, String ellipsis) throws IOException {
        InputStream input = new FileInputStream(file);
        try {
            long size = file.length();
            if (max > 0 || (size > 0 && max == 0)) {  // "head" mode: read the first N bytes
                if (size > 0 && (max == 0 || size < max)) max = (int) size;
                byte[] data = new byte[max + 1];
                int length = input.read(data);
                if (length <= 0) return "";
                if (length <= max) return new String(data, 0, length);
                if (ellipsis == null) return new String(data, 0, max);
                return new String(data, 0, max) + ellipsis;
            } else if (max < 0) {  // "tail" mode: keep the last N
                int len;
                boolean rolled = false;
                byte[] last = null, data = null;
                do {
                    if (last != null) rolled = true;
                    byte[] tmp = last; last = data; data = tmp;
                    if (data == null) data = new byte[-max];
                    len = input.read(data);
                } while (len == data.length);

                if (last == null && len <= 0) return "";
                if (last == null) return new String(data, 0, len);
                if (len > 0) {
                    rolled = true;
                    System.arraycopy(last, len, last, 0, last.length - len);
                    System.arraycopy(data, 0, last, last.length - len, len);
                }
                if (ellipsis == null || !rolled) return new String(last);
                return ellipsis + new String(last);
            } else {  // "cat" mode: size unknown, read it all in streaming fashion
                ByteArrayOutputStream contents = new ByteArrayOutputStream();
                int len;
                byte[] data = new byte[1024];
                do {
                    len = input.read(data);
                    if (len > 0) contents.write(data, 0, len);
                } while (len == data.length);
                return contents.toString();
            }
        } finally {
            input.close();
        }
    }
}