bungeman@google.com | f5cc5b1 | 2013-07-12 18:22:49 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2013 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 SkTFitsIn_DEFINED |
| 9 | #define SkTFitsIn_DEFINED |
| 10 | |
| 11 | #include "SkTypes.h" |
| 12 | #include "SkTLogic.h" |
| 13 | #include <limits> |
| 14 | |
| 15 | namespace sktfitsin { |
| 16 | namespace Private { |
| 17 | |
| 18 | /** SkTHasMoreDigits::type = (digits(A) >= digits(B)) ? SkTrue : SkFalse. */ |
| 19 | template<typename A, typename B> struct SkTHasMoreDigits { |
| 20 | typedef SkTBool<std::numeric_limits<A>::digits >= std::numeric_limits<B>::digits> type; |
| 21 | }; |
| 22 | |
| 23 | /** A high or low side predicate which is used when it is statically known |
| 24 | * that source values are in the range of the Destination. |
| 25 | */ |
| 26 | template <typename S> struct SkTOutOfRange_False { |
| 27 | typedef SkFalse can_be_true; |
| 28 | typedef S source_type; |
| 29 | static bool apply(S s) { |
| 30 | return false; |
| 31 | } |
| 32 | }; |
| 33 | |
| 34 | /** A low side predicate which tests if the source value < Min(D). |
| 35 | * Assumes that Min(S) <= Min(D). |
| 36 | */ |
| 37 | template <typename D, typename S> struct SkTOutOfRange_LT_MinD { |
| 38 | typedef SkTrue can_be_true; |
| 39 | typedef S source_type; |
| 40 | static bool apply(S s) { |
| 41 | typedef typename SkTHasMoreDigits<S, D>::type precondition; |
| 42 | SK_COMPILE_ASSERT(precondition::value, SkTOutOfRange_LT_MinD__minS_gt_minD); |
| 43 | |
| 44 | return s < static_cast<S>((std::numeric_limits<D>::min)()); |
| 45 | } |
| 46 | }; |
| 47 | |
| 48 | /** A low side predicate which tests if the source value is less than 0. */ |
| 49 | template <typename D, typename S> struct SkTOutOfRange_LT_Zero { |
| 50 | typedef SkTrue can_be_true; |
| 51 | typedef S source_type; |
| 52 | static bool apply(S s) { |
| 53 | return s < static_cast<S>(0); |
| 54 | } |
| 55 | }; |
| 56 | |
| 57 | /** A high side predicate which tests if the source value > Max(D). |
| 58 | * Assumes that Max(S) >= Max(D). |
| 59 | */ |
| 60 | template <typename D, typename S> struct SkTOutOfRange_GT_MaxD { |
| 61 | typedef SkTrue can_be_true; |
| 62 | typedef S source_type; |
| 63 | static bool apply(S s) { |
| 64 | typedef typename SkTHasMoreDigits<S, D>::type precondition; |
| 65 | SK_COMPILE_ASSERT(precondition::value, SkTOutOfRange_GT_MaxD__maxS_lt_maxD); |
| 66 | |
| 67 | return s > static_cast<S>((std::numeric_limits<D>::max)()); |
| 68 | } |
| 69 | }; |
| 70 | |
| 71 | /** Composes two SkTOutOfRange predicates. |
| 72 | * First checks OutOfRange_Low then, if in range, OutOfRange_High. |
| 73 | */ |
| 74 | template<class OutOfRange_Low, class OutOfRange_High> struct SkTOutOfRange_Either { |
| 75 | typedef SkTrue can_be_true; |
| 76 | typedef typename OutOfRange_Low::source_type source_type; |
| 77 | static bool apply(source_type s) { |
| 78 | bool outOfRange = OutOfRange_Low::apply(s); |
| 79 | if (!outOfRange) { |
| 80 | outOfRange = OutOfRange_High::apply(s); |
| 81 | } |
| 82 | return outOfRange; |
| 83 | } |
| 84 | }; |
| 85 | |
| 86 | /** SkTCombineOutOfRange::type is an SkTOutOfRange_XXX type which is the |
| 87 | * optimal combination of OutOfRange_Low and OutOfRange_High. |
| 88 | */ |
| 89 | template<class OutOfRange_Low, class OutOfRange_High> struct SkTCombineOutOfRange { |
| 90 | typedef SkTOutOfRange_Either<OutOfRange_Low, OutOfRange_High> Both; |
| 91 | typedef SkTOutOfRange_False<typename OutOfRange_Low::source_type> Neither; |
| 92 | |
| 93 | typedef typename OutOfRange_Low::can_be_true apply_low; |
| 94 | typedef typename OutOfRange_High::can_be_true apply_high; |
| 95 | |
| 96 | typedef typename SkTMux<apply_low, apply_high, |
| 97 | Both, OutOfRange_Low, OutOfRange_High, Neither>::type type; |
| 98 | }; |
| 99 | |
| 100 | template<typename D, typename S, class OutOfRange_Low, class OutOfRange_High> |
| 101 | struct SkTRangeChecker { |
| 102 | /** This is the method which is called at runtime to do the range check. */ |
| 103 | static bool OutOfRange(S s) { |
| 104 | typedef typename SkTCombineOutOfRange<OutOfRange_Low, OutOfRange_High>::type Combined; |
| 105 | return Combined::apply(s); |
| 106 | } |
| 107 | }; |
| 108 | |
| 109 | /** SkTFitsIn_Unsigned2Unsiged::type is an SkTRangeChecker with an OutOfRange(S s) method |
| 110 | * the implementation of which is tailored for the source and destination types. |
| 111 | * Assumes that S and D are unsigned integer types. |
| 112 | */ |
| 113 | template<typename D, typename S> struct SkTFitsIn_Unsigned2Unsiged { |
| 114 | typedef SkTOutOfRange_False<S> OutOfRange_Low; |
| 115 | typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 116 | |
| 117 | typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyCheck; |
| 118 | typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck; |
| 119 | |
| 120 | // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, nothing to check. |
| 121 | // This also protects the precondition of SkTOutOfRange_GT_MaxD. |
| 122 | typedef typename SkTHasMoreDigits<D, S>::type sourceFitsInDesitination; |
| 123 | typedef typename SkTIf<sourceFitsInDesitination, NoCheck, HighSideOnlyCheck>::type type; |
| 124 | }; |
| 125 | |
| 126 | /** SkTFitsIn_Signed2Signed::type is an SkTRangeChecker with an OutOfRange(S s) method |
| 127 | * the implementation of which is tailored for the source and destination types. |
| 128 | * Assumes that S and D are signed integer types. |
| 129 | */ |
| 130 | template<typename D, typename S> struct SkTFitsIn_Signed2Signed { |
| 131 | typedef SkTOutOfRange_LT_MinD<D, S> OutOfRange_Low; |
| 132 | typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 133 | |
| 134 | typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck; |
| 135 | typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck; |
| 136 | |
| 137 | // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, nothing to check. |
| 138 | // This also protects the precondition of SkTOutOfRange_LT_MinD and SkTOutOfRange_GT_MaxD. |
| 139 | typedef typename SkTHasMoreDigits<D, S>::type sourceFitsInDesitination; |
| 140 | typedef typename SkTIf<sourceFitsInDesitination, NoCheck, FullCheck>::type type; |
| 141 | }; |
| 142 | |
| 143 | /** SkTFitsIn_Signed2Unsigned::type is an SkTRangeChecker with an OutOfRange(S s) method |
| 144 | * the implementation of which is tailored for the source and destination types. |
| 145 | * Assumes that S is a signed integer type and D is an unsigned integer type. |
| 146 | */ |
| 147 | template<typename D, typename S> struct SkTFitsIn_Signed2Unsigned { |
| 148 | typedef SkTOutOfRange_LT_Zero<D, S> OutOfRange_Low; |
| 149 | typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 150 | |
| 151 | typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck; |
| 152 | typedef SkTRangeChecker<D, S, OutOfRange_Low, SkTOutOfRange_False<S> > LowSideOnlyCheck; |
| 153 | |
| 154 | // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(), |
| 155 | // no need to check the high side. (Until C++11, assume more digits means greater max.) |
| 156 | // This also protects the precondition of SkTOutOfRange_GT_MaxD. |
| 157 | typedef typename SkTHasMoreDigits<D, S>::type sourceCannotExceedDesitination; |
| 158 | typedef typename SkTIf<sourceCannotExceedDesitination, LowSideOnlyCheck, FullCheck>::type type; |
| 159 | }; |
| 160 | |
| 161 | /** SkTFitsIn_Unsigned2Signed::type is an SkTRangeChecker with an OutOfRange(S s) method |
| 162 | * the implementation of which is tailored for the source and destination types. |
| 163 | * Assumes that S is an usigned integer type and D is a signed integer type. |
| 164 | */ |
| 165 | template<typename D, typename S> struct SkTFitsIn_Unsigned2Signed { |
| 166 | typedef SkTOutOfRange_False<S> OutOfRange_Low; |
| 167 | typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 168 | |
| 169 | typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyCheck; |
| 170 | typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck; |
| 171 | |
| 172 | // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(), nothing to check. |
| 173 | // (Until C++11, assume more digits means greater max.) |
| 174 | // This also protects the precondition of SkTOutOfRange_GT_MaxD. |
| 175 | typedef typename SkTHasMoreDigits<D, S>::type sourceCannotExceedDesitination; |
| 176 | typedef typename SkTIf<sourceCannotExceedDesitination, NoCheck, HighSideOnlyCheck>::type type; |
| 177 | }; |
| 178 | |
| 179 | /** SkTFitsIn::type is an SkTRangeChecker with an OutOfRange(S s) method |
| 180 | * the implementation of which is tailored for the source and destination types. |
| 181 | * Assumes that S and D are integer types. |
| 182 | */ |
| 183 | template<typename D, typename S> struct SkTFitsIn { |
| 184 | // One of the following will be the 'selector' type. |
| 185 | typedef SkTFitsIn_Signed2Signed<D, S> S2S; |
| 186 | typedef SkTFitsIn_Signed2Unsigned<D, S> S2U; |
| 187 | typedef SkTFitsIn_Unsigned2Signed<D, S> U2S; |
| 188 | typedef SkTFitsIn_Unsigned2Unsiged<D, S> U2U; |
| 189 | |
| 190 | typedef SkTBool<std::numeric_limits<S>::is_signed> S_is_signed; |
| 191 | typedef SkTBool<std::numeric_limits<D>::is_signed> D_is_signed; |
| 192 | |
| 193 | typedef typename SkTMux<S_is_signed, D_is_signed, S2S, S2U, U2S, U2U>::type selector; |
| 194 | // This type is an SkTRangeChecker. |
| 195 | typedef typename selector::type type; |
| 196 | }; |
| 197 | |
| 198 | } // namespace Private |
| 199 | } // namespace sktfitsin |
| 200 | |
| 201 | /** Returns true if the integer source value 's' will fit in the integer destination type 'D'. */ |
| 202 | template <typename D, typename S> inline bool SkTFitsIn(S s) { |
| 203 | SK_COMPILE_ASSERT(std::numeric_limits<S>::is_integer, SkTFitsIn_source_must_be_integer); |
| 204 | SK_COMPILE_ASSERT(std::numeric_limits<D>::is_integer, SkTFitsIn_destination_must_be_integer); |
| 205 | |
| 206 | return !sktfitsin::Private::SkTFitsIn<D, S>::type::OutOfRange(s); |
| 207 | } |
| 208 | |
| 209 | #endif |