| /* |
| * Copyright 2016 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| * |
| */ |
| |
| #include "util.h" |
| |
| // |
| // |
| // |
| |
| #include <intrin.h> |
| |
| // |
| // |
| // |
| |
| skc_bool |
| skc_is_pow2_uint(skc_uint n) |
| { |
| return (n & (n-1)) == 0; |
| } |
| |
| // |
| // ASSUMES NON-ZERO |
| // |
| |
| skc_uint |
| skc_msb_idx_uint(skc_uint n) |
| { |
| |
| #ifdef _MSC_VER |
| |
| skc_uint index; |
| |
| _BitScanReverse(&index,n); |
| |
| return index; |
| |
| #elif defined(__GNUC__) |
| |
| #error "BUSTED msb_index()" |
| return 31 - __builtin_clz(mask); |
| |
| #else |
| |
| #error "No msb_index()" |
| |
| #endif |
| |
| } |
| |
| // |
| // |
| // |
| |
| skc_uint |
| skc_pow2_rd_uint(skc_uint n) |
| { |
| return 1u << skc_msb_idx_uint(n); |
| } |
| |
| // |
| // |
| // |
| |
| skc_uint |
| skc_pow2_ru_uint(skc_uint n) |
| { |
| n--; |
| n |= n >> 1; |
| n |= n >> 2; |
| n |= n >> 4; |
| n |= n >> 8; |
| n |= n >> 16; |
| n++; |
| |
| return n; |
| } |
| |
| // |
| // |
| // |
