1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/skia/trunk/src/utils/SkTFitsIn.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,209 @@
1.4 +/*
1.5 + * Copyright 2013 Google Inc.
1.6 + *
1.7 + * Use of this source code is governed by a BSD-style license that can be
1.8 + * found in the LICENSE file.
1.9 + */
1.10 +
1.11 +#ifndef SkTFitsIn_DEFINED
1.12 +#define SkTFitsIn_DEFINED
1.13 +
1.14 +#include "SkTypes.h"
1.15 +#include "SkTLogic.h"
1.16 +#include <limits>
1.17 +
1.18 +namespace sktfitsin {
1.19 +namespace Private {
1.20 +
1.21 +/** SkTHasMoreDigits::type = (digits(A) >= digits(B)) ? SkTrue : SkFalse. */
1.22 +template<typename A, typename B> struct SkTHasMoreDigits {
1.23 + typedef SkTBool<std::numeric_limits<A>::digits >= std::numeric_limits<B>::digits> type;
1.24 +};
1.25 +
1.26 +/** A high or low side predicate which is used when it is statically known
1.27 + * that source values are in the range of the Destination.
1.28 + */
1.29 +template <typename S> struct SkTOutOfRange_False {
1.30 + typedef SkFalse can_be_true;
1.31 + typedef S source_type;
1.32 + static bool apply(S s) {
1.33 + return false;
1.34 + }
1.35 +};
1.36 +
1.37 +/** A low side predicate which tests if the source value < Min(D).
1.38 + * Assumes that Min(S) <= Min(D).
1.39 + */
1.40 +template <typename D, typename S> struct SkTOutOfRange_LT_MinD {
1.41 + typedef SkTrue can_be_true;
1.42 + typedef S source_type;
1.43 + static bool apply(S s) {
1.44 + typedef typename SkTHasMoreDigits<S, D>::type precondition;
1.45 + SK_COMPILE_ASSERT(precondition::value, SkTOutOfRange_LT_MinD__minS_gt_minD);
1.46 +
1.47 + return s < static_cast<S>((std::numeric_limits<D>::min)());
1.48 + }
1.49 +};
1.50 +
1.51 +/** A low side predicate which tests if the source value is less than 0. */
1.52 +template <typename D, typename S> struct SkTOutOfRange_LT_Zero {
1.53 + typedef SkTrue can_be_true;
1.54 + typedef S source_type;
1.55 + static bool apply(S s) {
1.56 + return s < static_cast<S>(0);
1.57 + }
1.58 +};
1.59 +
1.60 +/** A high side predicate which tests if the source value > Max(D).
1.61 + * Assumes that Max(S) >= Max(D).
1.62 + */
1.63 +template <typename D, typename S> struct SkTOutOfRange_GT_MaxD {
1.64 + typedef SkTrue can_be_true;
1.65 + typedef S source_type;
1.66 + static bool apply(S s) {
1.67 + typedef typename SkTHasMoreDigits<S, D>::type precondition;
1.68 + SK_COMPILE_ASSERT(precondition::value, SkTOutOfRange_GT_MaxD__maxS_lt_maxD);
1.69 +
1.70 + return s > static_cast<S>((std::numeric_limits<D>::max)());
1.71 + }
1.72 +};
1.73 +
1.74 +/** Composes two SkTOutOfRange predicates.
1.75 + * First checks OutOfRange_Low then, if in range, OutOfRange_High.
1.76 + */
1.77 +template<class OutOfRange_Low, class OutOfRange_High> struct SkTOutOfRange_Either {
1.78 + typedef SkTrue can_be_true;
1.79 + typedef typename OutOfRange_Low::source_type source_type;
1.80 + static bool apply(source_type s) {
1.81 + bool outOfRange = OutOfRange_Low::apply(s);
1.82 + if (!outOfRange) {
1.83 + outOfRange = OutOfRange_High::apply(s);
1.84 + }
1.85 + return outOfRange;
1.86 + }
1.87 +};
1.88 +
1.89 +/** SkTCombineOutOfRange::type is an SkTOutOfRange_XXX type which is the
1.90 + * optimal combination of OutOfRange_Low and OutOfRange_High.
1.91 + */
1.92 +template<class OutOfRange_Low, class OutOfRange_High> struct SkTCombineOutOfRange {
1.93 + typedef SkTOutOfRange_Either<OutOfRange_Low, OutOfRange_High> Both;
1.94 + typedef SkTOutOfRange_False<typename OutOfRange_Low::source_type> Neither;
1.95 +
1.96 + typedef typename OutOfRange_Low::can_be_true apply_low;
1.97 + typedef typename OutOfRange_High::can_be_true apply_high;
1.98 +
1.99 + typedef typename SkTMux<apply_low, apply_high,
1.100 + Both, OutOfRange_Low, OutOfRange_High, Neither>::type type;
1.101 +};
1.102 +
1.103 +template<typename D, typename S, class OutOfRange_Low, class OutOfRange_High>
1.104 +struct SkTRangeChecker {
1.105 + /** This is the method which is called at runtime to do the range check. */
1.106 + static bool OutOfRange(S s) {
1.107 + typedef typename SkTCombineOutOfRange<OutOfRange_Low, OutOfRange_High>::type Combined;
1.108 + return Combined::apply(s);
1.109 + }
1.110 +};
1.111 +
1.112 +/** SkTFitsIn_Unsigned2Unsiged::type is an SkTRangeChecker with an OutOfRange(S s) method
1.113 + * the implementation of which is tailored for the source and destination types.
1.114 + * Assumes that S and D are unsigned integer types.
1.115 + */
1.116 +template<typename D, typename S> struct SkTFitsIn_Unsigned2Unsiged {
1.117 + typedef SkTOutOfRange_False<S> OutOfRange_Low;
1.118 + typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;
1.119 +
1.120 + typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyCheck;
1.121 + typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck;
1.122 +
1.123 + // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, nothing to check.
1.124 + // This also protects the precondition of SkTOutOfRange_GT_MaxD.
1.125 + typedef typename SkTHasMoreDigits<D, S>::type sourceFitsInDesitination;
1.126 + typedef typename SkTIf<sourceFitsInDesitination, NoCheck, HighSideOnlyCheck>::type type;
1.127 +};
1.128 +
1.129 +/** SkTFitsIn_Signed2Signed::type is an SkTRangeChecker with an OutOfRange(S s) method
1.130 + * the implementation of which is tailored for the source and destination types.
1.131 + * Assumes that S and D are signed integer types.
1.132 + */
1.133 +template<typename D, typename S> struct SkTFitsIn_Signed2Signed {
1.134 + typedef SkTOutOfRange_LT_MinD<D, S> OutOfRange_Low;
1.135 + typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;
1.136 +
1.137 + typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck;
1.138 + typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck;
1.139 +
1.140 + // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, nothing to check.
1.141 + // This also protects the precondition of SkTOutOfRange_LT_MinD and SkTOutOfRange_GT_MaxD.
1.142 + typedef typename SkTHasMoreDigits<D, S>::type sourceFitsInDesitination;
1.143 + typedef typename SkTIf<sourceFitsInDesitination, NoCheck, FullCheck>::type type;
1.144 +};
1.145 +
1.146 +/** SkTFitsIn_Signed2Unsigned::type is an SkTRangeChecker with an OutOfRange(S s) method
1.147 + * the implementation of which is tailored for the source and destination types.
1.148 + * Assumes that S is a signed integer type and D is an unsigned integer type.
1.149 + */
1.150 +template<typename D, typename S> struct SkTFitsIn_Signed2Unsigned {
1.151 + typedef SkTOutOfRange_LT_Zero<D, S> OutOfRange_Low;
1.152 + typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;
1.153 +
1.154 + typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck;
1.155 + typedef SkTRangeChecker<D, S, OutOfRange_Low, SkTOutOfRange_False<S> > LowSideOnlyCheck;
1.156 +
1.157 + // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(),
1.158 + // no need to check the high side. (Until C++11, assume more digits means greater max.)
1.159 + // This also protects the precondition of SkTOutOfRange_GT_MaxD.
1.160 + typedef typename SkTHasMoreDigits<D, S>::type sourceCannotExceedDesitination;
1.161 + typedef typename SkTIf<sourceCannotExceedDesitination, LowSideOnlyCheck, FullCheck>::type type;
1.162 +};
1.163 +
1.164 +/** SkTFitsIn_Unsigned2Signed::type is an SkTRangeChecker with an OutOfRange(S s) method
1.165 + * the implementation of which is tailored for the source and destination types.
1.166 + * Assumes that S is an usigned integer type and D is a signed integer type.
1.167 + */
1.168 +template<typename D, typename S> struct SkTFitsIn_Unsigned2Signed {
1.169 + typedef SkTOutOfRange_False<S> OutOfRange_Low;
1.170 + typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;
1.171 +
1.172 + typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyCheck;
1.173 + typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck;
1.174 +
1.175 + // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(), nothing to check.
1.176 + // (Until C++11, assume more digits means greater max.)
1.177 + // This also protects the precondition of SkTOutOfRange_GT_MaxD.
1.178 + typedef typename SkTHasMoreDigits<D, S>::type sourceCannotExceedDesitination;
1.179 + typedef typename SkTIf<sourceCannotExceedDesitination, NoCheck, HighSideOnlyCheck>::type type;
1.180 +};
1.181 +
1.182 +/** SkTFitsIn::type is an SkTRangeChecker with an OutOfRange(S s) method
1.183 + * the implementation of which is tailored for the source and destination types.
1.184 + * Assumes that S and D are integer types.
1.185 + */
1.186 +template<typename D, typename S> struct SkTFitsIn {
1.187 + // One of the following will be the 'selector' type.
1.188 + typedef SkTFitsIn_Signed2Signed<D, S> S2S;
1.189 + typedef SkTFitsIn_Signed2Unsigned<D, S> S2U;
1.190 + typedef SkTFitsIn_Unsigned2Signed<D, S> U2S;
1.191 + typedef SkTFitsIn_Unsigned2Unsiged<D, S> U2U;
1.192 +
1.193 + typedef SkTBool<std::numeric_limits<S>::is_signed> S_is_signed;
1.194 + typedef SkTBool<std::numeric_limits<D>::is_signed> D_is_signed;
1.195 +
1.196 + typedef typename SkTMux<S_is_signed, D_is_signed, S2S, S2U, U2S, U2U>::type selector;
1.197 + // This type is an SkTRangeChecker.
1.198 + typedef typename selector::type type;
1.199 +};
1.200 +
1.201 +} // namespace Private
1.202 +} // namespace sktfitsin
1.203 +
1.204 +/** Returns true if the integer source value 's' will fit in the integer destination type 'D'. */
1.205 +template <typename D, typename S> inline bool SkTFitsIn(S s) {
1.206 + SK_COMPILE_ASSERT(std::numeric_limits<S>::is_integer, SkTFitsIn_source_must_be_integer);
1.207 + SK_COMPILE_ASSERT(std::numeric_limits<D>::is_integer, SkTFitsIn_destination_must_be_integer);
1.208 +
1.209 + return !sktfitsin::Private::SkTFitsIn<D, S>::type::OutOfRange(s);
1.210 +}
1.211 +
1.212 +#endif
