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bitUtils.h
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1 //
2 // Copyright 2016 Pixar
3 //
4 // Licensed under the Apache License, Version 2.0 (the "Apache License")
5 // with the following modification; you may not use this file except in
6 // compliance with the Apache License and the following modification to it:
7 // Section 6. Trademarks. is deleted and replaced with:
8 //
9 // 6. Trademarks. This License does not grant permission to use the trade
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11 // and its affiliates, except as required to comply with Section 4(c) of
12 // the License and to reproduce the content of the NOTICE file.
13 //
14 // You may obtain a copy of the Apache License at
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16 // http://www.apache.org/licenses/LICENSE-2.0
17 //
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19 // distributed under the Apache License with the above modification is
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24 #ifndef TF_BIT_UTILS_H
25 #define TF_BIT_UTILS_H
26 
29 
30 #include "pxr/pxr.h"
31 
32 #include <cstddef>
33 #include <type_traits>
34 
35 PXR_NAMESPACE_OPEN_SCOPE
36 
44 #define TF_BITS_FOR_VALUES(n) \
45  Tf_NumBits<n-1>::type::value
46 
47 template <size_t N, size_t SUM=0, size_t BIT=sizeof(N)*8/2>
48 struct Tf_NumBits
49 {
50  // The result is computed by divide and conquer; for a given word N the
51  // bit at position BIT divides the word in an upper and a lower half.
52  // If the upper half contain any ones, then the result is SUM plus BIT
53  // plus the result for the upper half. If not, the result is SUM plus
54  // the result for the lower half.
55  typedef typename std::conditional<N >= (1ULL<<BIT),
56  Tf_NumBits<(N>>BIT), SUM+BIT, BIT/2>,
57  Tf_NumBits<N, SUM, BIT/2> >::type _func;
58  typedef typename _func::type type;
59 };
60 
61 template <size_t N, size_t SUM>
62 struct Tf_NumBits<N, SUM, 0>
63 {
64  typedef std::integral_constant<size_t, SUM+1> type;
65 };
66 
77 #define TF_BITS_FOR_ENUM_VALUES(n) \
78  (TF_BITS_FOR_VALUES(n) + 1)
79 
80 PXR_NAMESPACE_CLOSE_SCOPE
81 
82 #endif /* TF_BIT_UTILS_H */