/*
 * Copyright (C) 2007 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.dexgen.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

/**
 * File I/O utilities.
 */
public final class FileUtils {
    /**
     * This class is uninstantiable.
     */
    private FileUtils() {
        // This space intentionally left blank.
    }

    /**
     * Reads the named file, translating {@link IOException} to a
     * {@link RuntimeException} of some sort.
     *
     * @param fileName {@code non-null;} name of the file to read
     * @return {@code non-null;} contents of the file
     */
    public static byte[] readFile(String fileName) {
        File file = new File(fileName);
        return readFile(file);
    }

    /**
     * Reads the given file, translating {@link IOException} to a
     * {@link RuntimeException} of some sort.
     *
     * @param file {@code non-null;} the file to read
     * @return {@code non-null;} contents of the file
     */
    public static byte[] readFile(File file) {
        if (!file.exists()) {
            throw new RuntimeException(file + ": file not found");
        }

        if (!file.isFile()) {
            throw new RuntimeException(file + ": not a file");
        }

        if (!file.canRead()) {
            throw new RuntimeException(file + ": file not readable");
        }

        long longLength = file.length();
        int length = (int) longLength;
        if (length != longLength) {
            throw new RuntimeException(file + ": file too long");
        }

        byte[] result = new byte[length];

        try {
            // convert to try-with-resources once dexgen uses an Android API 19+ which supports it
            FileInputStream in = new FileInputStream(file);
            try {
                int at = 0;
                while (length > 0) {
                    int amt = in.read(result, at, length);
                    if (amt == -1) {
                        throw new RuntimeException(file + ": unexpected EOF");
                    }
                    at += amt;
                    length -= amt;
                }
            } finally {
                in.close();
            }
        } catch (IOException ex) {
            throw new RuntimeException(file + ": trouble reading", ex);
        }

        return result;
    }
}
