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Diffstat (limited to 'src/base/math_utils.h')
-rw-r--r-- | src/base/math_utils.h | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/base/math_utils.h b/src/base/math_utils.h new file mode 100644 index 0000000..48f1a24 --- /dev/null +++ b/src/base/math_utils.h @@ -0,0 +1,80 @@ +// Copyright 2018 Google LLC +// +// 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 +// +// https://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 ASTC_CODEC_BASE_MATH_UTILS_H_ +#define ASTC_CODEC_BASE_MATH_UTILS_H_ + +#include "src/base/uint128.h" + +#include <cassert> +#include <cstdint> +#include <type_traits> + +namespace astc_codec { +namespace base { + +inline int Log2Floor(uint32_t n) { + if (n == 0) { + return -1; + } + + int log = 0; + uint32_t value = n; + for (int i = 4; i >= 0; --i) { + int shift = (1 << i); + uint32_t x = value >> shift; + if (x != 0) { + value = x; + log += shift; + } + } + assert(value == 1); + return log; +} + +inline int CountOnes(uint32_t n) { + n -= ((n >> 1) & 0x55555555); + n = ((n >> 2) & 0x33333333) + (n & 0x33333333); + return static_cast<int>((((n + (n >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24); +} + +template<typename T> +inline T ReverseBits(T value) { + uint32_t s = sizeof(value) * 8; + T mask = ~T(0); + while ((s >>= 1) > 0) { + mask ^= (mask << s); + value = ((value >> s) & mask) | ((value << s) & ~mask); + } + + return value; +} + +template<typename T> +inline T GetBits(T source, uint32_t offset, uint32_t count) { + static_assert(std::is_same<T, UInt128>::value || std::is_unsigned<T>::value, + "T must be unsigned."); + + const uint32_t total_bits = sizeof(T) * 8; + assert(count > 0); + assert(offset + count <= total_bits); + + const T mask = count == total_bits ? ~T(0) : ~T(0) >> (total_bits - count); + return (source >> offset) & mask; +} + +} // namespace base +} // namespace astc_codec + +#endif // ASTC_CODEC_BASE_MATH_UTILS_H_ |