1 files changed, 155 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/mkv/VarintReader.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/mkv/VarintReader.java
new file mode 100644
index 0000000000..8a8d572ea5
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/mkv/VarintReader.java
@@ -0,0 +1,155 @@
+/*
+ * 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.mkv;
+
+import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorInput;
+import java.io.EOFException;
+import java.io.IOException;
+
+/**
+ * Reads EBML variable-length integers (varints) from an {@link ExtractorInput}.
+ */
+/* package */ final class VarintReader {
+
+  private static final int STATE_BEGIN_READING = 0;
+  private static final int STATE_READ_CONTENTS = 1;
+
+  /**
+   * The first byte of a variable-length integer (varint) will have one of these bit masks
+   * indicating the total length in bytes.
+   *
+   * <p>{@code 0x80} is a one-byte integer, {@code 0x40} is two bytes, and so on up to eight bytes.
+   */
+  private static final long[] VARINT_LENGTH_MASKS = new long[] {
+    0x80L, 0x40L, 0x20L, 0x10L, 0x08L, 0x04L, 0x02L, 0x01L
+  };
+
+  private final byte[] scratch;
+
+  private int state;
+  private int length;
+
+  public VarintReader() {
+    scratch = new byte[8];
+  }
+
+  /**
+   * Resets the reader to start reading a new variable-length integer.
+   */
+  public void reset() {
+    state = STATE_BEGIN_READING;
+    length = 0;
+  }
+
+  /**
+   * Reads an EBML variable-length integer (varint) from an {@link ExtractorInput} such that
+   * reading can be resumed later if an error occurs having read only some of it.
+   * <p>
+   * If an value is successfully read, then the reader will automatically reset itself ready to
+   * read another value.
+   * <p>
+   * If an {@link IOException} or {@link InterruptedException} is throw, the read can be resumed
+   * later by calling this method again, passing an {@link ExtractorInput} providing data starting
+   * where the previous one left off.
+   *
+   * @param input The {@link ExtractorInput} from which the integer should be read.
+   * @param allowEndOfInput True if encountering the end of the input having read no data is
+   *     allowed, and should result in {@link C#RESULT_END_OF_INPUT} being returned. False if it
+   *     should be considered an error, causing an {@link EOFException} to be thrown.
+   * @param removeLengthMask Removes the variable-length integer length mask from the value.
+   * @param maximumAllowedLength Maximum allowed length of the variable integer to be read.
+   * @return The read value, or {@link C#RESULT_END_OF_INPUT} if {@code allowEndOfStream} is true
+   *     and the end of the input was encountered, or {@link C#RESULT_MAX_LENGTH_EXCEEDED} if the
+   *     length of the varint exceeded maximumAllowedLength.
+   * @throws IOException If an error occurs reading from the input.
+   * @throws InterruptedException If the thread is interrupted.
+   */
+  public long readUnsignedVarint(ExtractorInput input, boolean allowEndOfInput,
+      boolean removeLengthMask, int maximumAllowedLength) throws IOException, InterruptedException {
+    if (state == STATE_BEGIN_READING) {
+      // Read the first byte to establish the length.
+      if (!input.readFully(scratch, 0, 1, allowEndOfInput)) {
+        return C.RESULT_END_OF_INPUT;
+      }
+      int firstByte = scratch[0] & 0xFF;
+      length = parseUnsignedVarintLength(firstByte);
+      if (length == C.LENGTH_UNSET) {
+        throw new IllegalStateException("No valid varint length mask found");
+      }
+      state = STATE_READ_CONTENTS;
+    }
+
+    if (length > maximumAllowedLength) {
+      state = STATE_BEGIN_READING;
+      return C.RESULT_MAX_LENGTH_EXCEEDED;
+    }
+
+    if (length != 1) {
+      // Read the remaining bytes.
+      input.readFully(scratch, 1, length - 1);
+    }
+
+    state = STATE_BEGIN_READING;
+    return assembleVarint(scratch, length, removeLengthMask);
+  }
+
+  /**
+   * Returns the number of bytes occupied by the most recently parsed varint.
+   */
+  public int getLastLength() {
+    return length;
+  }
+
+  /**
+   * Parses and the length of the varint given the first byte.
+   *
+   * @param firstByte First byte of the varint.
+   * @return Length of the varint beginning with the given byte if it was valid,
+   *     {@link C#LENGTH_UNSET} otherwise.
+   */
+  public static int parseUnsignedVarintLength(int firstByte) {
+    int varIntLength = C.LENGTH_UNSET;
+    for (int i = 0; i < VARINT_LENGTH_MASKS.length; i++) {
+      if ((VARINT_LENGTH_MASKS[i] & firstByte) != 0) {
+        varIntLength = i + 1;
+        break;
+      }
+    }
+    return varIntLength;
+  }
+
+  /**
+   * Assemble a varint from the given byte array.
+   *
+   * @param varintBytes Bytes that make up the varint.
+   * @param varintLength Length of the varint to assemble.
+   * @param removeLengthMask Removes the variable-length integer length mask from the value.
+   * @return Parsed and assembled varint.
+   */
+  public static long assembleVarint(byte[] varintBytes, int varintLength,
+      boolean removeLengthMask) {
+    long varint = varintBytes[0] & 0xFFL;
+    if (removeLengthMask) {
+      varint &= ~VARINT_LENGTH_MASKS[varintLength - 1];
+    }
+    for (int i = 1; i < varintLength; i++) {
+      varint = (varint << 8) | (varintBytes[i] & 0xFFL);
+    }
+    return varint;
+  }
+
+}