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// 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_
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