- preparation for http range requests: cryptor supports partial decryption now

main/crypto-api/src/main/java/org/cryptomator/crypto/Cryptor.java

@@ -79,6 +79,13 @@ public interface Cryptor extends SensitiveDataSwipeListener {
 	 */
 	Long decryptedFile(SeekableByteChannel encryptedFile, OutputStream plaintextFile) throws IOException;
 
+	/**
+	 * @param pos First byte (inclusive)
+	 * @param length Number of requested bytes beginning at pos.
+	 * @return Number of decrypted bytes. This might not be equal to the number of bytes requested due to potential overheads.
+	 */
+	Long decryptRange(SeekableByteChannel encryptedFile, OutputStream plaintextFile, long pos, long length) throws IOException;
+
 	/**
 	 * @return Number of encrypted bytes. This might not be equal to the encrypted file size due to optional metadata written to it.
 	 */

main/crypto-api/src/main/java/org/cryptomator/crypto/SamplingDecorator.java

@@ -87,6 +87,12 @@ public class SamplingDecorator implements Cryptor, CryptorIOSampling {
 		return cryptor.decryptedFile(encryptedFile, countingInputStream);
 	}
 
+	@Override
+	public Long decryptRange(SeekableByteChannel encryptedFile, OutputStream plaintextFile, long pos, long length) throws IOException {
+		final OutputStream countingInputStream = new CountingOutputStream(decryptedBytes, plaintextFile);
+		return cryptor.decryptRange(encryptedFile, countingInputStream, pos, length);
+	}
+
 	@Override
 	public Long encryptFile(InputStream plaintextFile, SeekableByteChannel encryptedFile) throws IOException {
 		final InputStream countingInputStream = new CountingInputStream(encryptedBytes, plaintextFile);