| /* |

| * 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_ |