diff options
Diffstat (limited to 'mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/VorbisBitArray.java')
-rw-r--r-- | mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/VorbisBitArray.java | 129 |
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))); + } + +} |