draft for encryption

library/src/main/java/com/danikula/videocache/Config.java

@@ -1,5 +1,6 @@
 package com.danikula.videocache;
 
+import com.danikula.videocache.encrypt.Cipher;
 import com.danikula.videocache.file.DiskUsage;
 import com.danikula.videocache.file.FileNameGenerator;
 import com.danikula.videocache.headers.HeaderInjector;
@@ -19,13 +20,16 @@ class Config {
     public final DiskUsage diskUsage;
     public final SourceInfoStorage sourceInfoStorage;
     public final HeaderInjector headerInjector;
+    public final Cipher cipher;
 
-    Config(File cacheRoot, FileNameGenerator fileNameGenerator, DiskUsage diskUsage, SourceInfoStorage sourceInfoStorage, HeaderInjector headerInjector) {
+    Config(File cacheRoot, FileNameGenerator fileNameGenerator, DiskUsage diskUsage, SourceInfoStorage sourceInfoStorage,
+           HeaderInjector headerInjector, Cipher cipher) {
         this.cacheRoot = cacheRoot;
         this.fileNameGenerator = fileNameGenerator;
         this.diskUsage = diskUsage;
         this.sourceInfoStorage = sourceInfoStorage;
         this.headerInjector = headerInjector;
+        this.cipher = cipher;
     }
 
     File generateCacheFile(String url) {

library/src/main/java/com/danikula/videocache/HttpProxyCacheServer.java

@@ -3,6 +3,8 @@ package com.danikula.videocache;
 import android.content.Context;
 import android.net.Uri;
 
+import com.danikula.videocache.encrypt.Cipher;
+import com.danikula.videocache.encrypt.NoCipher;
 import com.danikula.videocache.file.DiskUsage;
 import com.danikula.videocache.file.FileNameGenerator;
 import com.danikula.videocache.file.Md5FileNameGenerator;
@@ -353,6 +355,7 @@ public class HttpProxyCacheServer {
         private DiskUsage diskUsage;
         private SourceInfoStorage sourceInfoStorage;
         private HeaderInjector headerInjector;
+        private Cipher cipher;
 
         public Builder(Context context) {
             this.sourceInfoStorage = SourceInfoStorageFactory.newSourceInfoStorage(context);
@@ -360,6 +363,7 @@ public class HttpProxyCacheServer {
             this.diskUsage = new TotalSizeLruDiskUsage(DEFAULT_MAX_SIZE);
             this.fileNameGenerator = new Md5FileNameGenerator();
             this.headerInjector = new EmptyHeadersInjector();
+            this.cipher = new NoCipher();
         }
 
         /**
@@ -390,6 +394,17 @@ public class HttpProxyCacheServer {
             return this;
         }
 
+        /**
+         * Overrides default cipher for cached files.
+         *
+         * @param cipher a new cipher, can't be {@code null}.
+         * @return a builder.
+         */
+        public Builder cipher(Cipher cipher) {
+            this.cipher = checkNotNull(cipher);
+            return this;
+        }
+
         /**
          * Sets max cache size in bytes.
          * <p>
@@ -452,8 +467,7 @@ public class HttpProxyCacheServer {
         }
 
         private Config buildConfig() {
-            return new Config(cacheRoot, fileNameGenerator, diskUsage, sourceInfoStorage, headerInjector);
+            return new Config(cacheRoot, fileNameGenerator, diskUsage, sourceInfoStorage, headerInjector, cipher);
         }
-
     }
 }

library/src/main/java/com/danikula/videocache/encrypt/Cipher.java

@@ -0,0 +1,26 @@
+package com.danikula.videocache.encrypt;
+
+/**
+ * Defines a encryption/decryption for cached data.
+ *
+ * @author Alexey Danilov (danikula@gmail.com).
+ */
+public interface Cipher {
+
+    /**
+     * Encrypts piece of data. Resulting byte[] array must have <b>same size<b/>.
+     *
+     * @param data   an input data to be encrypted.
+     * @param length an length of data to be encrypted.
+     */
+    void encrypt(byte[] data, long length);
+
+    /**
+     * Decrypts piece of data. Resulting byte[] array must have <b>same size<b/>.
+     *
+     * @param data   an input data to be decrypted.
+     * @param offset an offset of data to be decrypted.
+     * @param length a length of data to be decrypted.
+     */
+    void decrypt(byte[] data, long offset, int length);
+}

library/src/main/java/com/danikula/videocache/encrypt/CipherAwareCacheWrapper.java

@@ -0,0 +1,55 @@
+package com.danikula.videocache.encrypt;
+
+import com.danikula.videocache.Cache;
+import com.danikula.videocache.ProxyCacheException;
+
+import static com.danikula.videocache.Preconditions.checkNotNull;
+
+/**
+ * {@link Cache} that take into account encryption/decryption.
+ *
+ * @author Alexey Danilov (danikula@gmail.com).
+ */
+public class CipherAwareCacheWrapper implements Cache {
+
+    private final Cache cache;
+    private final Cipher cipher;
+
+    public CipherAwareCacheWrapper(Cache cache, Cipher cipher) {
+        this.cache = checkNotNull(cache);
+        this.cipher = checkNotNull(cipher);
+    }
+
+    @Override
+    public int read(byte[] buffer, long offset, int length) throws ProxyCacheException {
+        cache.read(buffer, offset, length);
+        cipher.decrypt(buffer, offset, length);
+        return 0;
+    }
+
+    @Override
+    public void append(byte[] data, int length) throws ProxyCacheException {
+        cipher.encrypt(data, length);
+        cache.append(data, length);
+    }
+
+    @Override
+    public long available() throws ProxyCacheException {
+        return cache.available();
+    }
+
+    @Override
+    public void close() throws ProxyCacheException {
+        cache.close();
+    }
+
+    @Override
+    public void complete() throws ProxyCacheException {
+        cache.complete();
+    }
+
+    @Override
+    public boolean isCompleted() {
+        return cache.isCompleted();
+    }
+}

library/src/main/java/com/danikula/videocache/encrypt/NoCipher.java

@@ -0,0 +1,17 @@
+package com.danikula.videocache.encrypt;
+
+/**
+ * {@link Cipher} that does not perform any encryption/decryption.
+ *
+ * @author Alexey Danilov (danikula@gmail.com).
+ */
+public class NoCipher implements Cipher {
+
+    @Override
+    public void encrypt(byte[] data, long length) {
+    }
+
+    @Override
+    public void decrypt(byte[] data, long offset, int length) {
+    }
+}