1 /* 2 * Copyright 2011 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkConstexprMath_DEFINED 9 #define SkConstexprMath_DEFINED 10 11 #include "SkTypes.h" 12 #include <limits.h> 13 14 template <uintmax_t N, uintmax_t B> 15 struct SK_LOG { 16 //! Compile-time constant ceiling(logB(N)). 17 static const uintmax_t value = 1 + SK_LOG<N/B, B>::value; 18 }; 19 template <uintmax_t B> 20 struct SK_LOG<1, B> { 21 static const uintmax_t value = 0; 22 }; 23 template <uintmax_t B> 24 struct SK_LOG<0, B> { 25 static const uintmax_t value = 0; 26 }; 27 28 template<uintmax_t N> 29 struct SK_2N1 { 30 //! Compile-time constant (2^N)-1. 31 static const uintmax_t value = (SK_2N1<N-1>::value << 1) + 1; 32 }; 33 template<> 34 struct SK_2N1<1> { 35 static const uintmax_t value = 1; 36 }; 37 38 /** Compile-time constant number of base n digits in type t 39 if the bits of type t are considered as unsigned base two. 40 */ 41 #define SK_BASE_N_DIGITS_IN(n, t) (\ 42 SK_LOG<SK_2N1<(sizeof(t) * CHAR_BIT)>::value, n>::value\ 43 ) 44 /** Compile-time constant number of base 10 digits in type t 45 if the bits of type t are considered as unsigned base two. 46 */ 47 #define SK_DIGITS_IN(t) SK_BASE_N_DIGITS_IN(10, (t)) 48 49 // Compile-time constant maximum value of two unsigned values. 50 template <uintmax_t a, uintmax_t b> struct SkTUMax { 51 static const uintmax_t value = (b < a) ? a : b; 52 }; 53 54 #endif 55