1 files changed, 129 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/VorbisBitArray.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/VorbisBitArray.java
new file mode 100644
index 0000000000..4ea27c0149
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/VorbisBitArray.java
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2016 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 org.mozilla.thirdparty.com.google.android.exoplayer2.extractor;
+
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Assertions;
+
+/**
+ * Wraps a byte array, providing methods that allow it to be read as a Vorbis bitstream.
+ *
+ * @see <a href="https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-360002">Vorbis bitpacking
+ *     specification</a>
+ */
+public final class VorbisBitArray {
+
+  private final byte[] data;
+  private final int byteLimit;
+
+  private int byteOffset;
+  private int bitOffset;
+
+  /**
+   * Creates a new instance that wraps an existing array.
+   *
+   * @param data the array to wrap.
+   */
+  public VorbisBitArray(byte[] data) {
+    this.data = data;
+    byteLimit = data.length;
+  }
+
+  /**
+   * Resets the reading position to zero.
+   */
+  public void reset() {
+    byteOffset = 0;
+    bitOffset = 0;
+  }
+
+  /**
+   * Reads a single bit.
+   *
+   * @return {@code true} if the bit is set, {@code false} otherwise.
+   */
+  public boolean readBit() {
+    boolean returnValue = (((data[byteOffset] & 0xFF) >> bitOffset) & 0x01) == 1;
+    skipBits(1);
+    return returnValue;
+  }
+
+  /**
+   * Reads up to 32 bits.
+   *
+   * @param numBits The number of bits to read.
+   * @return An integer whose bottom {@code numBits} bits hold the read data.
+   */
+  public int readBits(int numBits) {
+    int tempByteOffset = byteOffset;
+    int bitsRead = Math.min(numBits, 8 - bitOffset);
+    int returnValue = ((data[tempByteOffset++] & 0xFF) >> bitOffset) & (0xFF >> (8 - bitsRead));
+    while (bitsRead < numBits) {
+      returnValue |= (data[tempByteOffset++] & 0xFF) << bitsRead;
+      bitsRead += 8;
+    }
+    returnValue &= 0xFFFFFFFF >>> (32 - numBits);
+    skipBits(numBits);
+    return returnValue;
+  }
+
+  /**
+   * Skips {@code numberOfBits} bits.
+   *
+   * @param numBits The number of bits to skip.
+   */
+  public void skipBits(int numBits) {
+    int numBytes = numBits / 8;
+    byteOffset += numBytes;
+    bitOffset += numBits - (numBytes * 8);
+    if (bitOffset > 7) {
+      byteOffset++;
+      bitOffset -= 8;
+    }
+    assertValidOffset();
+  }
+
+  /**
+   * Returns the reading position in bits.
+   */
+  public int getPosition() {
+    return byteOffset * 8 + bitOffset;
+  }
+
+  /**
+   * Sets the reading position in bits.
+   *
+   * @param position The new reading position in bits.
+   */
+  public void setPosition(int position) {
+    byteOffset = position / 8;
+    bitOffset = position - (byteOffset * 8);
+    assertValidOffset();
+  }
+
+  /**
+   * Returns the number of remaining bits.
+   */
+  public int bitsLeft() {
+    return (byteLimit - byteOffset) * 8 - bitOffset;
+  }
+
+  private void assertValidOffset() {
+    // It is fine for position to be at the end of the array, but no further.
+    Assertions.checkState(byteOffset >= 0
+        && (byteOffset < byteLimit || (byteOffset == byteLimit && bitOffset == 0)));
+  }
+
+}