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| 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 #include <type_traits> |
| 15 |
| 16 namespace sktfitsin { |
| 17 namespace Private { |
| 18 |
| 19 /** SkTMux::type = (a && b) ? Both : (a) ? A : (b) ? B : Neither; */ |
| 20 template <bool a, bool b, typename Both, typename A, typename B, typename Neithe
r> |
| 21 struct SkTMux { |
| 22 using type = skstd::conditional_t<a, skstd::conditional_t<b, Both, A>, |
| 23 skstd::conditional_t<b, B, Neither>>; |
| 24 }; |
| 25 |
| 26 /** SkTHasMoreDigits = (digits(A) >= digits(B)) ? true_type : false_type. */ |
| 27 template<typename A, typename B> struct SkTHasMoreDigits |
| 28 : skstd::bool_constant<std::numeric_limits<A>::digits >= std::numeric_limits
<B>::digits> |
| 29 { }; |
| 30 |
| 31 /** A high or low side predicate which is used when it is statically known |
| 32 * that source values are in the range of the Destination. |
| 33 */ |
| 34 template <typename S> struct SkTOutOfRange_False { |
| 35 typedef std::false_type can_be_true; |
| 36 typedef S source_type; |
| 37 static bool apply(S s) { |
| 38 return false; |
| 39 } |
| 40 }; |
| 41 |
| 42 /** A low side predicate which tests if the source value < Min(D). |
| 43 * Assumes that Min(S) <= Min(D). |
| 44 */ |
| 45 template <typename D, typename S> struct SkTOutOfRange_LT_MinD { |
| 46 typedef std::true_type can_be_true; |
| 47 typedef S source_type; |
| 48 static bool apply(S s) { |
| 49 typedef SkTHasMoreDigits<S, D> precondition; |
| 50 static_assert(precondition::value, "SkTOutOfRange_LT_MinD__minS_gt_minD"
); |
| 51 |
| 52 return s < static_cast<S>((std::numeric_limits<D>::min)()); |
| 53 } |
| 54 }; |
| 55 |
| 56 /** A low side predicate which tests if the source value is less than 0. */ |
| 57 template <typename D, typename S> struct SkTOutOfRange_LT_Zero { |
| 58 typedef std::true_type can_be_true; |
| 59 typedef S source_type; |
| 60 static bool apply(S s) { |
| 61 return s < static_cast<S>(0); |
| 62 } |
| 63 }; |
| 64 |
| 65 /** A high side predicate which tests if the source value > Max(D). |
| 66 * Assumes that Max(S) >= Max(D). |
| 67 */ |
| 68 template <typename D, typename S> struct SkTOutOfRange_GT_MaxD { |
| 69 typedef std::true_type can_be_true; |
| 70 typedef S source_type; |
| 71 static bool apply(S s) { |
| 72 typedef SkTHasMoreDigits<S, D> precondition; |
| 73 static_assert(precondition::value, "SkTOutOfRange_GT_MaxD__maxS_lt_maxD"
); |
| 74 |
| 75 return s > static_cast<S>((std::numeric_limits<D>::max)()); |
| 76 } |
| 77 }; |
| 78 |
| 79 /** Composes two SkTOutOfRange predicates. |
| 80 * First checks OutOfRange_Low then, if in range, OutOfRange_High. |
| 81 */ |
| 82 template<class OutOfRange_Low, class OutOfRange_High> struct SkTOutOfRange_Eithe
r { |
| 83 typedef std::true_type can_be_true; |
| 84 typedef typename OutOfRange_Low::source_type source_type; |
| 85 static bool apply(source_type s) { |
| 86 bool outOfRange = OutOfRange_Low::apply(s); |
| 87 if (!outOfRange) { |
| 88 outOfRange = OutOfRange_High::apply(s); |
| 89 } |
| 90 return outOfRange; |
| 91 } |
| 92 }; |
| 93 |
| 94 /** SkTCombineOutOfRange::type is an SkTOutOfRange_XXX type which is the |
| 95 * optimal combination of OutOfRange_Low and OutOfRange_High. |
| 96 */ |
| 97 template<class OutOfRange_Low, class OutOfRange_High> struct SkTCombineOutOfRang
e { |
| 98 typedef SkTOutOfRange_Either<OutOfRange_Low, OutOfRange_High> Both; |
| 99 typedef SkTOutOfRange_False<typename OutOfRange_Low::source_type> Neither; |
| 100 |
| 101 typedef typename OutOfRange_Low::can_be_true apply_low; |
| 102 typedef typename OutOfRange_High::can_be_true apply_high; |
| 103 |
| 104 typedef typename SkTMux<apply_low::value, apply_high::value, |
| 105 Both, OutOfRange_Low, OutOfRange_High, Neither>::typ
e type; |
| 106 }; |
| 107 |
| 108 template<typename D, typename S, class OutOfRange_Low, class OutOfRange_High> |
| 109 struct SkTRangeChecker { |
| 110 /** This is the method which is called at runtime to do the range check. */ |
| 111 static bool OutOfRange(S s) { |
| 112 typedef typename SkTCombineOutOfRange<OutOfRange_Low, OutOfRange_High>::
type Combined; |
| 113 return Combined::apply(s); |
| 114 } |
| 115 }; |
| 116 |
| 117 /** SkTFitsIn_Unsigned2Unsiged::type is an SkTRangeChecker with an OutOfRange(S
s) method |
| 118 * the implementation of which is tailored for the source and destination types
. |
| 119 * Assumes that S and D are unsigned integer types. |
| 120 */ |
| 121 template<typename D, typename S> struct SkTFitsIn_Unsigned2Unsiged { |
| 122 typedef SkTOutOfRange_False<S> OutOfRange_Low; |
| 123 typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 124 |
| 125 typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyC
heck; |
| 126 typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S>
> NoCheck; |
| 127 |
| 128 // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, noth
ing to check. |
| 129 // This also protects the precondition of SkTOutOfRange_GT_MaxD. |
| 130 typedef SkTHasMoreDigits<D, S> sourceFitsInDesitination; |
| 131 typedef skstd::conditional_t<sourceFitsInDesitination::value, NoCheck, HighS
ideOnlyCheck> type; |
| 132 }; |
| 133 |
| 134 /** SkTFitsIn_Signed2Signed::type is an SkTRangeChecker with an OutOfRange(S s)
method |
| 135 * the implementation of which is tailored for the source and destination types
. |
| 136 * Assumes that S and D are signed integer types. |
| 137 */ |
| 138 template<typename D, typename S> struct SkTFitsIn_Signed2Signed { |
| 139 typedef SkTOutOfRange_LT_MinD<D, S> OutOfRange_Low; |
| 140 typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 141 |
| 142 typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck; |
| 143 typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S>
> NoCheck; |
| 144 |
| 145 // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, noth
ing to check. |
| 146 // This also protects the precondition of SkTOutOfRange_LT_MinD and SkTOutOf
Range_GT_MaxD. |
| 147 typedef SkTHasMoreDigits<D, S> sourceFitsInDesitination; |
| 148 typedef skstd::conditional_t<sourceFitsInDesitination::value, NoCheck, FullC
heck> type; |
| 149 }; |
| 150 |
| 151 /** SkTFitsIn_Signed2Unsigned::type is an SkTRangeChecker with an OutOfRange(S s
) method |
| 152 * the implementation of which is tailored for the source and destination types
. |
| 153 * Assumes that S is a signed integer type and D is an unsigned integer type. |
| 154 */ |
| 155 template<typename D, typename S> struct SkTFitsIn_Signed2Unsigned { |
| 156 typedef SkTOutOfRange_LT_Zero<D, S> OutOfRange_Low; |
| 157 typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 158 |
| 159 typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck; |
| 160 typedef SkTRangeChecker<D, S, OutOfRange_Low, SkTOutOfRange_False<S> > LowSi
deOnlyCheck; |
| 161 |
| 162 // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(), |
| 163 // no need to check the high side. (Until C++11, assume more digits means gr
eater max.) |
| 164 // This also protects the precondition of SkTOutOfRange_GT_MaxD. |
| 165 typedef SkTHasMoreDigits<D, S> sourceCannotExceedDest; |
| 166 typedef skstd::conditional_t<sourceCannotExceedDest::value, LowSideOnlyCheck
, FullCheck> type; |
| 167 }; |
| 168 |
| 169 /** SkTFitsIn_Unsigned2Signed::type is an SkTRangeChecker with an OutOfRange(S s
) method |
| 170 * the implementation of which is tailored for the source and destination types
. |
| 171 * Assumes that S is an usigned integer type and D is a signed integer type. |
| 172 */ |
| 173 template<typename D, typename S> struct SkTFitsIn_Unsigned2Signed { |
| 174 typedef SkTOutOfRange_False<S> OutOfRange_Low; |
| 175 typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High; |
| 176 |
| 177 typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyC
heck; |
| 178 typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S>
> NoCheck; |
| 179 |
| 180 // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(), nothin
g to check. |
| 181 // (Until C++11, assume more digits means greater max.) |
| 182 // This also protects the precondition of SkTOutOfRange_GT_MaxD. |
| 183 typedef SkTHasMoreDigits<D, S> sourceCannotExceedDest; |
| 184 typedef skstd::conditional_t<sourceCannotExceedDest::value, NoCheck, HighSid
eOnlyCheck> type; |
| 185 }; |
| 186 |
| 187 /** SkTFitsIn::type is an SkTRangeChecker with an OutOfRange(S s) method |
| 188 * the implementation of which is tailored for the source and destination types
. |
| 189 * Assumes that S and D are integer types. |
| 190 */ |
| 191 template<typename D, typename S> struct SkTFitsIn { |
| 192 // One of the following will be the 'selector' type. |
| 193 typedef SkTFitsIn_Signed2Signed<D, S> S2S; |
| 194 typedef SkTFitsIn_Signed2Unsigned<D, S> S2U; |
| 195 typedef SkTFitsIn_Unsigned2Signed<D, S> U2S; |
| 196 typedef SkTFitsIn_Unsigned2Unsiged<D, S> U2U; |
| 197 |
| 198 typedef skstd::bool_constant<std::numeric_limits<S>::is_signed> S_is_signed; |
| 199 typedef skstd::bool_constant<std::numeric_limits<D>::is_signed> D_is_signed; |
| 200 |
| 201 typedef typename SkTMux<S_is_signed::value, D_is_signed::value, |
| 202 S2S, S2U, U2S, U2U>::type selector; |
| 203 // This type is an SkTRangeChecker. |
| 204 typedef typename selector::type type; |
| 205 }; |
| 206 |
| 207 } // namespace Private |
| 208 } // namespace sktfitsin |
| 209 |
| 210 /** Returns true if the integer source value 's' will fit in the integer destina
tion type 'D'. */ |
| 211 template <typename D, typename S> inline bool SkTFitsIn(S s) { |
| 212 static_assert(std::numeric_limits<S>::is_integer, "SkTFitsIn_source_must_be_
integer"); |
| 213 static_assert(std::numeric_limits<D>::is_integer, "SkTFitsIn_destination_mus
t_be_integer"); |
| 214 |
| 215 return !sktfitsin::Private::SkTFitsIn<D, S>::type::OutOfRange(s); |
| 216 } |
| 217 |
| 218 #endif |
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