service/java/com/android/server/wifi/util/FileUtils.java

/*
 * Copyright (C) 2019 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.wifi.util;

import android.system.ErrnoException;
import android.system.Os;
import android.util.Log;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

/**
 * Utility methods useful for working with files.
 *
 * Note: @hide methods copied from android.os.FileUtils
 */
public final class FileUtils {
    private static final String TAG = "FileUtils";

    /**
     * Change the mode of a file.
     *
     * @param path path of the file
     * @param mode to apply through {@code chmod}
     * @return 0 on success, otherwise errno.
     */
    public static int chmod(String path, int mode) {
        try {
            Os.chmod(path, mode);
            return 0;
        } catch (ErrnoException e) {
            Log.w(TAG, "Failed to chmod(" + path + ", " + mode + "): ", e);
            return e.errno;
        }
    }

    public static void rename(File source, File target) {
        if (target.isDirectory()) {
            if (!target.delete()) {
                Log.e(TAG, "Failed to delete file which is a directory " + target);
            }
        }
        if (!source.renameTo(target)) {
            Log.e(TAG, "Failed to rename " + source + " to " + target);
        }
    }

    /**
     * Writes the bytes given in {@code content} to the file whose absolute path
     * is {@code filename}.
     */
    public static void bytesToFile(String filename, byte[] content) throws IOException {
        try (FileOutputStream fos = new FileOutputStream(filename)) {
            fos.write(content);
        }
    }

    /**
     * Writes string to file. Basically same as "echo -n $string > $filename"
     *
     * @param filename
     * @param string
     * @throws IOException
     */
    public static void stringToFile(String filename, String string) throws IOException {
        bytesToFile(filename, string.getBytes(StandardCharsets.UTF_8));
    }
}