michael@0: /*
michael@0:  * Copyright 2011 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #ifndef SkConstexprMath_DEFINED
michael@0: #define SkConstexprMath_DEFINED
michael@0: 
michael@0: #include "SkTypes.h"
michael@0: #include <limits.h>
michael@0: 
michael@0: template <uintmax_t N, uintmax_t B>
michael@0: struct SK_LOG {
michael@0:     //! Compile-time constant ceiling(logB(N)).
michael@0:     static const uintmax_t value = 1 + SK_LOG<N/B, B>::value;
michael@0: };
michael@0: template <uintmax_t B>
michael@0: struct SK_LOG<1, B> {
michael@0:     static const uintmax_t value = 0;
michael@0: };
michael@0: template <uintmax_t B>
michael@0: struct SK_LOG<0, B> {
michael@0:     static const uintmax_t value = 0;
michael@0: };
michael@0: 
michael@0: template<uintmax_t N>
michael@0: struct SK_2N1 {
michael@0:     //! Compile-time constant (2^N)-1.
michael@0:     static const uintmax_t value = (SK_2N1<N-1>::value << 1) + 1;
michael@0: };
michael@0: template<>
michael@0: struct SK_2N1<1> {
michael@0:     static const uintmax_t value = 1;
michael@0: };
michael@0: 
michael@0: /** Compile-time constant number of base n digits in type t
michael@0:     if the bits of type t are considered as unsigned base two.
michael@0: */
michael@0: #define SK_BASE_N_DIGITS_IN(n, t) (\
michael@0:     SK_LOG<SK_2N1<(sizeof(t) * CHAR_BIT)>::value, n>::value\
michael@0: )
michael@0: /** Compile-time constant number of base 10 digits in type t
michael@0:     if the bits of type t are considered as unsigned base two.
michael@0: */
michael@0: #define SK_DIGITS_IN(t) SK_BASE_N_DIGITS_IN(10, (t))
michael@0: 
michael@0: // Compile-time constant maximum value of two unsigned values.
michael@0: template <uintmax_t a, uintmax_t b> struct SkTUMax {
michael@0:     static const uintmax_t value = (b < a) ? a : b;
michael@0: };
michael@0: 
michael@0: #endif