/**自定义实现简单的文件加密解密工具* Created by zhangshuo on 2016/6/28.*/
public class CustomFileCipherUtil {/*** 加密后的文件的后缀*/public static final String CIPHER_TEXT_SUFFIX = ".cipher";/*** 加解密时以32K个字节为单位进行加解密计算*/private static final int CIPHER_BUFFER_LENGHT = 32 * 1024;/*** 加密，这里主要是演示加密的原理，没有用什么实际的加密算法** @param filePath 明文文件绝对路径* @return*/public static boolean encrypt(String filePath, CipherListener listener) {try {long startTime = System.currentTimeMillis();File f = new File(filePath);RandomAccessFile raf = new RandomAccessFile(f, "rw");long totalLenght = raf.length();FileChannel channel = raf.getChannel();long multiples = totalLenght / CIPHER_BUFFER_LENGHT;long remainder = totalLenght % CIPHER_BUFFER_LENGHT;MappedByteBuffer buffer = null;byte tmp;byte rawByte;//先对整除部分加密for(int i = 0; i < multiples; i++){buffer = channel.map(FileChannel.MapMode.READ_WRITE, i * CIPHER_BUFFER_LENGHT, (i + 1) * CIPHER_BUFFER_LENGHT);//此处的加密方法很简单，只是简单的异或计算for (int j = 0; j < CIPHER_BUFFER_LENGHT; ++j) {rawByte = buffer.get(j);tmp = (byte) (rawByte ^ j);buffer.put(j, tmp);if(null != listener){listener.onProgress(i * CIPHER_BUFFER_LENGHT + j, totalLenght);}}buffer.force();buffer.clear();}//对余数部分加密buffer = channel.map(FileChannel.MapMode.READ_WRITE, multiples * CIPHER_BUFFER_LENGHT, multiples * CIPHER_BUFFER_LENGHT + remainder);for (int j = 0; j < remainder; ++j) {rawByte = buffer.get(j);tmp = (byte) (rawByte ^ j);buffer.put(j, tmp);if(null != listener){listener.onProgress(multiples * CIPHER_BUFFER_LENGHT + j, totalLenght);}}buffer.force();buffer.clear();channel.close();raf.close();//对加密后的文件重命名，增加.cipher后缀
//            f.renameTo(new File(f.getPath() + CIPHER_TEXT_SUFFIX));Log.d("加密用时：", (System.currentTimeMillis() - startTime) /1000 + "s");return true;} catch (Exception e) {e.printStackTrace();return false;}}/*** 解密，这里主要是演示加密的原理，没有用什么实际的加密算法** @param filePath 密文文件绝对路径，文件需要以.cipher结尾才会认为其实可解密密文* @return*/public static boolean decrypt(String filePath, CipherListener listener) {try {long startTime = System.currentTimeMillis();File f = new File(filePath);
//            if(!f.getPath().toLowerCase().endsWith(CIPHER_TEXT_SUFFIX)){
//                //后缀不同，认为是不可解密的密文
//                return false;
//            }RandomAccessFile raf = new RandomAccessFile(f, "rw");long totalLenght = raf.length();FileChannel channel = raf.getChannel();long multiples = totalLenght / CIPHER_BUFFER_LENGHT;long remainder = totalLenght % CIPHER_BUFFER_LENGHT;MappedByteBuffer buffer = null;byte tmp;byte rawByte;//先对整除部分解密for(int i = 0; i < multiples; i++){buffer = channel.map(FileChannel.MapMode.READ_WRITE, i * CIPHER_BUFFER_LENGHT, (i + 1) * CIPHER_BUFFER_LENGHT);//此处的解密方法很简单，只是简单的异或计算for (int j = 0; j < CIPHER_BUFFER_LENGHT; ++j) {rawByte = buffer.get(j);tmp = (byte) (rawByte ^ j);buffer.put(j, tmp);if(null != listener){listener.onProgress(i * CIPHER_BUFFER_LENGHT + j, totalLenght);}}buffer.force();buffer.clear();}//对余数部分解密buffer = channel.map(FileChannel.MapMode.READ_WRITE, multiples * CIPHER_BUFFER_LENGHT, multiples * CIPHER_BUFFER_LENGHT + remainder);for (int j = 0; j < remainder; ++j) {rawByte = buffer.get(j);tmp = (byte) (rawByte ^ j);buffer.put(j, tmp);if(null != listener){listener.onProgress(multiples * CIPHER_BUFFER_LENGHT + j, totalLenght);}}buffer.force();buffer.clear();channel.close();raf.close();//对加密后的文件重命名，增加.cipher后缀
//            f.renameTo(new File(f.getPath().substring(f.getPath().toLowerCase().indexOf(CIPHER_TEXT_SUFFIX))));Log.d("解密用时：", (System.currentTimeMillis() - startTime) / 1000 + "s");return true;} catch (Exception e) {e.printStackTrace();return false;}}/*** 用于加解密进度的监听器*/public interface CipherListener{void onProgress(long current, long total);}
}