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// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "util.h"
#include <assert.h>
//
//
//
#if defined(_MSC_VER) && !defined(__clang__)
#include <intrin.h>
#endif
//
//
//
bool
is_pow2_u32(uint32_t n)
{
return n && !(n & (n - 1));
}
//
//
//
uint32_t
pow2_ru_u32(uint32_t n)
{
assert(n <= 0x80000000U);
n--;
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
n++;
return n;
}
//
//
//
uint32_t
pow2_rd_u32(uint32_t n)
{
assert(n > 0);
return 1u << msb_idx_u32(n);
}
//
// ASSUMES NON-ZERO
//
uint32_t
msb_idx_u32(uint32_t n)
{
assert(n > 0);
#if defined(_MSC_VER) && !defined(__clang__)
uint32_t index;
_BitScanReverse((unsigned long *)&index, n);
return index;
#elif defined(__GNUC__)
return __builtin_clz(n) ^ 31;
#else
#error "No msb_index()"
#endif
}
//
//
//
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