1 files changed, 49 insertions, 0 deletions
diff --git a/dom/media/BitWriter.h b/dom/media/BitWriter.h
new file mode 100644
index 0000000000..6abf7bcde3
--- /dev/null
+++ b/dom/media/BitWriter.h
@@ -0,0 +1,49 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef BIT_WRITER_H_
+#define BIT_WRITER_H_
+
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+
+class MediaByteBuffer;
+
+class BitWriter {
+ public:
+  explicit BitWriter(MediaByteBuffer* aBuffer);
+  virtual ~BitWriter();
+  void WriteBits(uint64_t aValue, size_t aBits);
+  void WriteBit(bool aValue) { WriteBits(aValue, 1); }
+  void WriteU8(uint8_t aValue) { WriteBits(aValue, 8); }
+  void WriteU32(uint32_t aValue) { WriteBits(aValue, 32); }
+  void WriteU64(uint64_t aValue) { WriteBits(aValue, 64); }
+
+  // Write unsigned integer into Exp-Golomb-coded. 2^32-2 at most
+  void WriteUE(uint32_t aValue);
+  // Write unsigned integer Little Endian Base 128 coded.
+  void WriteULEB128(uint64_t aValue);
+
+  // Write RBSP trailing bits.
+  void CloseWithRbspTrailing();
+
+  // Advance position forward without modifying buffer, which is usually used
+  // along with the case when directly appending a byte array to the
+  // MediaByteBuffer for the efficiency, instead of writing bits one by one.
+  // So this can only be called when the bit index is zero.
+  void AdvanceBytes(uint32_t aByteOffset);
+
+  // Return the number of bits written so far;
+  size_t BitCount() const { return mPosition * 8 + mBitIndex; }
+
+ private:
+  RefPtr<MediaByteBuffer> mBuffer;
+  size_t mPosition = 0;
+  uint8_t mBitIndex = 0;
+};
+
+}  // namespace mozilla
+
+#endif  // BIT_WRITER_H_