Repo created

TMessagesProj/jni/voip/webrtc/common_video/h265/h265_inline.h

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+/*
+ *  Copyright (c) 2023 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+// This header file includes the inline functions in H265 parser.
+
+#ifndef COMMON_VIDEO_H265_H265_INLINE_H_
+#define COMMON_VIDEO_H265_H265_INLINE_H_
+
+#include <stdint.h>
+
+#include "rtc_base/compile_assert_c.h"
+
+extern const int8_t kWebRtcVideo_CountLeadingZeros32_Table[64];
+
+static __inline int WebRtcVideo_CountLeadingZeros32_NotBuiltin(uint32_t n) {
+  // Normalize n by rounding up to the nearest number that is a sequence of 0
+  // bits followed by a sequence of 1 bits. This number has the same number of
+  // leading zeros as the original n. There are exactly 33 such values.
+  n |= n >> 1;
+  n |= n >> 2;
+  n |= n >> 4;
+  n |= n >> 8;
+  n |= n >> 16;
+
+  // Multiply the modified n with a constant selected (by exhaustive search)
+  // such that each of the 33 possible values of n give a product whose 6 most
+  // significant bits are unique. Then look up the answer in the table.
+  return kWebRtcVideo_CountLeadingZeros32_Table[(n * 0x8c0b2891) >> 26];
+}
+
+// Returns the number of leading zero bits in the argument.
+static __inline int WebRtcVideo_CountLeadingZeros32(uint32_t n) {
+#ifdef __GNUC__
+  RTC_COMPILE_ASSERT(sizeof(unsigned int) == sizeof(uint32_t));
+  return n == 0 ? 32 : __builtin_clz(n);
+#else
+  return WebRtcVideo_CountLeadingZeros32_NotBuiltin(n);
+#endif
+}
+#endif  // COMMON_VIDEO_H265_H265_INLINE_H_