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diff --git a/media/libstagefright/webm/EbmlUtil.h b/media/libstagefright/webm/EbmlUtil.h
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+++ b/media/libstagefright/webm/EbmlUtil.h
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+/*
+ * Copyright (C) 2014 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.
+ */
+
+#ifndef EBMLUTIL_H_
+#define EBMLUTIL_H_
+
+#include <stdint.h>
+
+namespace webm {
+
+// Encode the id and/or size of an EBML element bytes by setting a leading length descriptor bit:
+//
+//   1xxxxxxx                                                                - 1-byte values
+//   01xxxxxx xxxxxxxx                                                       -
+//   001xxxxx xxxxxxxx xxxxxxxx                                              -
+//   0001xxxx xxxxxxxx xxxxxxxx xxxxxxxx                                     - ...
+//   00001xxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx                            -
+//   000001xx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx                   -
+//   0000001x xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx          -
+//   00000001 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx - 8-byte values
+//
+// This function uses the least the number of bytes possible.
+uint64_t encodeUnsigned(uint64_t u);
+
+// Like above but pads the input value with leading zeros up to the specified width. The length
+// descriptor is calculated based on width.
+uint64_t encodeUnsigned(uint64_t u, int width);
+
+// Serialize an EBML coded id or size in big-endian order.
+int serializeCodedUnsigned(uint64_t u, uint8_t* bary);
+
+// Calculate the length of an EBML coded id or size from its length descriptor.
+int sizeOf(uint64_t u);
+
+}
+
+#endif /* EBMLUTIL_H_ */