From fd80d48f5085032839aa5ddabe32eb4e7c06a1c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominik=20Sch=C3=BCrmann?= <dominik@dominikschuermann.de>
Date: Thu, 24 Sep 2015 14:11:20 +0200
Subject: phrase confirmation

---
 .../keychain/experimental/BitInputStream.java      | 125 +++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/BitInputStream.java

(limited to 'OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/BitInputStream.java')

diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/BitInputStream.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/BitInputStream.java
new file mode 100644
index 000000000..b6ec7234e
--- /dev/null
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/experimental/BitInputStream.java
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) Andreas Jakl
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.sufficientlysecure.keychain.experimental;
+
+import java.io.EOFException;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * The BitInputStream allows reading individual bits from a
+ * general Java InputStream.
+ * Like the various Stream-classes from Java, the BitInputStream
+ * has to be created based on another Input stream. It provides
+ * a function to read the next bit from the sream, as well as to read multiple
+ * bits at once and write the resulting data into an integer value.
+ * <p/>
+ * source: http://developer.nokia.com/Community/Wiki/Bit_Input/Output_Stream_utility_classes_for_efficient_data_transfer
+ */
+public class BitInputStream {
+    /**
+     * The Java InputStream this class is working on.
+     */
+    private InputStream iIs;
+
+    /**
+     * The buffer containing the currently processed
+     * byte of the input stream.
+     */
+    private int iBuffer;
+
+    /**
+     * Next bit of the current byte value that the user will
+     * get. If it's 8, the next bit will be read from the
+     * next byte of the InputStream.
+     */
+    private int iNextBit = 8;
+
+    /**
+     * Create a new bit input stream based on an existing Java InputStream.
+     *
+     * @param aIs the input stream this class should read the bits from.
+     */
+    public BitInputStream(InputStream aIs) {
+        iIs = aIs;
+    }
+
+    /**
+     * Read a specified number of bits and return them combined as
+     * an integer value. The bits are written to the integer
+     * starting at the highest bit ( << aNumberOfBits ), going down
+     * to the lowest bit ( << 0 )
+     *
+     * @param aNumberOfBits defines how many bits to read from the stream.
+     * @return integer value containing the bits read from the stream.
+     * @throws IOException
+     */
+    synchronized public int readBits(final int aNumberOfBits)
+            throws IOException {
+        int value = 0;
+        for (int i = aNumberOfBits - 1; i >= 0; i--) {
+            value |= (readBit() << i);
+        }
+        return value;
+    }
+
+    synchronized public int available() {
+        try {
+            return (8 - iNextBit) + iIs.available() * 8; // bytestream to bitstream available
+        } catch (Exception e) {
+            return 0;
+        }
+    }
+
+    /**
+     * Read the next bit from the stream.
+     *
+     * @return 0 if the bit is 0, 1 if the bit is 1.
+     * @throws IOException
+     */
+    synchronized public int readBit() throws IOException {
+        if (iIs == null)
+            throw new IOException("Already closed");
+
+        if (iNextBit == 8) {
+            iBuffer = iIs.read();
+
+            if (iBuffer == -1)
+                throw new EOFException();
+
+            iNextBit = 0;
+        }
+
+        int bit = iBuffer & (1 << iNextBit);
+        iNextBit++;
+
+        bit = (bit == 0) ? 0 : 1;
+
+        return bit;
+    }
+
+    /**
+     * Close the underlying input stream.
+     *
+     * @throws IOException
+     */
+    public void close() throws IOException {
+        iIs.close();
+        iIs = null;
+    }
+}
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