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 /*

  * Copyright 2013 Google Inc.

  *

  * Use of this source code is governed by a BSD-style license that can be

  * found in the LICENSE file.

  */

 #ifndef SkTFitsIn_DEFINED

 #define SkTFitsIn_DEFINED

 #include "SkTypes.h"

 #include "SkTLogic.h"

 #include <limits>

 namespace sktfitsin {

 namespace Private {

 /** SkTHasMoreDigits::type = (digits(A) >= digits(B)) ? SkTrue : SkFalse. */

 template<typename A, typename B> struct SkTHasMoreDigits {

     typedef SkTBool<std::numeric_limits<A>::digits >= std::numeric_limits<B>::digits> type;

 };

 /** A high or low side predicate which is used when it is statically known

  *  that source values are in the range of the Destination.

  */

 template <typename S> struct SkTOutOfRange_False {

     typedef SkFalse can_be_true;

     typedef S source_type;

     static bool apply(S s) {

         return false;

     }

 };

 /** A low side predicate which tests if the source value < Min(D).

  *  Assumes that Min(S) <= Min(D).

  */

 template <typename D, typename S> struct SkTOutOfRange_LT_MinD {

     typedef SkTrue can_be_true;

     typedef S source_type;

     static bool apply(S s) {

         typedef typename SkTHasMoreDigits<S, D>::type precondition;

         SK_COMPILE_ASSERT(precondition::value, SkTOutOfRange_LT_MinD__minS_gt_minD);

         return s < static_cast<S>((std::numeric_limits<D>::min)());

     }

 };

 /** A low side predicate which tests if the source value is less than 0. */

 template <typename D, typename S> struct SkTOutOfRange_LT_Zero {

     typedef SkTrue can_be_true;

     typedef S source_type;

     static bool apply(S s) {

         return s < static_cast<S>(0);

     }

 };

 /** A high side predicate which tests if the source value > Max(D).

  *  Assumes that Max(S) >= Max(D).

  */

 template <typename D, typename S> struct SkTOutOfRange_GT_MaxD {

     typedef SkTrue can_be_true;

     typedef S source_type;

     static bool apply(S s) {

         typedef typename SkTHasMoreDigits<S, D>::type precondition;

         SK_COMPILE_ASSERT(precondition::value, SkTOutOfRange_GT_MaxD__maxS_lt_maxD);

         return s > static_cast<S>((std::numeric_limits<D>::max)());

     }

 };

 /** Composes two SkTOutOfRange predicates.

  *  First checks OutOfRange_Low then, if in range, OutOfRange_High.

  */

 template<class OutOfRange_Low, class OutOfRange_High> struct SkTOutOfRange_Either {

     typedef SkTrue can_be_true;

     typedef typename OutOfRange_Low::source_type source_type;

     static bool apply(source_type s) {

         bool outOfRange = OutOfRange_Low::apply(s);

         if (!outOfRange) {

             outOfRange = OutOfRange_High::apply(s);

         }

         return outOfRange;

     }

 };

 /** SkTCombineOutOfRange::type is an SkTOutOfRange_XXX type which is the

  *  optimal combination of OutOfRange_Low and OutOfRange_High.

  */

 template<class OutOfRange_Low, class OutOfRange_High> struct SkTCombineOutOfRange {

     typedef SkTOutOfRange_Either<OutOfRange_Low, OutOfRange_High> Both;

     typedef SkTOutOfRange_False<typename OutOfRange_Low::source_type> Neither;

     typedef typename OutOfRange_Low::can_be_true apply_low;

     typedef typename OutOfRange_High::can_be_true apply_high;

     typedef typename SkTMux<apply_low, apply_high,

                             Both, OutOfRange_Low, OutOfRange_High, Neither>::type type;

 };

 template<typename D, typename S, class OutOfRange_Low, class OutOfRange_High>

 struct SkTRangeChecker {

     /** This is the method which is called at runtime to do the range check. */

     static bool OutOfRange(S s) {

         typedef typename SkTCombineOutOfRange<OutOfRange_Low, OutOfRange_High>::type Combined;

         return Combined::apply(s);

     }

 };

 /** SkTFitsIn_Unsigned2Unsiged::type is an SkTRangeChecker with an OutOfRange(S s) method

  *  the implementation of which is tailored for the source and destination types.

  *  Assumes that S and D are unsigned integer types.

  */

 template<typename D, typename S> struct SkTFitsIn_Unsigned2Unsiged {

     typedef SkTOutOfRange_False<S> OutOfRange_Low;

     typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;

     typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyCheck;

     typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck;

     // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, nothing to check.

     // This also protects the precondition of SkTOutOfRange_GT_MaxD.

     typedef typename SkTHasMoreDigits<D, S>::type sourceFitsInDesitination;

     typedef typename SkTIf<sourceFitsInDesitination, NoCheck, HighSideOnlyCheck>::type type;

 };

 /** SkTFitsIn_Signed2Signed::type is an SkTRangeChecker with an OutOfRange(S s) method

  *  the implementation of which is tailored for the source and destination types.

  *  Assumes that S and D are signed integer types.

  */

 template<typename D, typename S> struct SkTFitsIn_Signed2Signed {

     typedef SkTOutOfRange_LT_MinD<D, S> OutOfRange_Low;

     typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;

     typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck;

     typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck;

     // If std::numeric_limits<D>::digits >= std::numeric_limits<S>::digits, nothing to check.

     // This also protects the precondition of SkTOutOfRange_LT_MinD and SkTOutOfRange_GT_MaxD.

     typedef typename SkTHasMoreDigits<D, S>::type sourceFitsInDesitination;

     typedef typename SkTIf<sourceFitsInDesitination, NoCheck, FullCheck>::type type;

 };

 /** SkTFitsIn_Signed2Unsigned::type is an SkTRangeChecker with an OutOfRange(S s) method

  *  the implementation of which is tailored for the source and destination types.

  *  Assumes that S is a signed integer type and D is an unsigned integer type.

  */

 template<typename D, typename S> struct SkTFitsIn_Signed2Unsigned {

     typedef SkTOutOfRange_LT_Zero<D, S> OutOfRange_Low;

     typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;

     typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> FullCheck;

     typedef SkTRangeChecker<D, S, OutOfRange_Low, SkTOutOfRange_False<S> > LowSideOnlyCheck;

     // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(),

     // no need to check the high side. (Until C++11, assume more digits means greater max.)

     // This also protects the precondition of SkTOutOfRange_GT_MaxD.

     typedef typename SkTHasMoreDigits<D, S>::type sourceCannotExceedDesitination;

     typedef typename SkTIf<sourceCannotExceedDesitination, LowSideOnlyCheck, FullCheck>::type type;

 };

 /** SkTFitsIn_Unsigned2Signed::type is an SkTRangeChecker with an OutOfRange(S s) method

  *  the implementation of which is tailored for the source and destination types.

  *  Assumes that S is an usigned integer type and D is a signed integer type.

  */

 template<typename D, typename S> struct SkTFitsIn_Unsigned2Signed {

     typedef SkTOutOfRange_False<S> OutOfRange_Low;

     typedef SkTOutOfRange_GT_MaxD<D, S> OutOfRange_High;

     typedef SkTRangeChecker<D, S, OutOfRange_Low, OutOfRange_High> HighSideOnlyCheck;

     typedef SkTRangeChecker<D, S, SkTOutOfRange_False<S>, SkTOutOfRange_False<S> > NoCheck;

     // If std::numeric_limits<D>::max() >= std::numeric_limits<S>::max(), nothing to check.

     // (Until C++11, assume more digits means greater max.)

     // This also protects the precondition of SkTOutOfRange_GT_MaxD.

     typedef typename SkTHasMoreDigits<D, S>::type sourceCannotExceedDesitination;

     typedef typename SkTIf<sourceCannotExceedDesitination, NoCheck, HighSideOnlyCheck>::type type;

 };

 /** SkTFitsIn::type is an SkTRangeChecker with an OutOfRange(S s) method

  *  the implementation of which is tailored for the source and destination types.

  *  Assumes that S and D are integer types.

  */

 template<typename D, typename S> struct SkTFitsIn {

     // One of the following will be the 'selector' type.

     typedef SkTFitsIn_Signed2Signed<D, S> S2S;

     typedef SkTFitsIn_Signed2Unsigned<D, S> S2U;

     typedef SkTFitsIn_Unsigned2Signed<D, S> U2S;

     typedef SkTFitsIn_Unsigned2Unsiged<D, S> U2U;

     typedef SkTBool<std::numeric_limits<S>::is_signed> S_is_signed;

     typedef SkTBool<std::numeric_limits<D>::is_signed> D_is_signed;

     typedef typename SkTMux<S_is_signed, D_is_signed, S2S, S2U, U2S, U2U>::type selector;

     // This type is an SkTRangeChecker.

     typedef typename selector::type type;

 };

 } // namespace Private

 } // namespace sktfitsin

 /** Returns true if the integer source value 's' will fit in the integer destination type 'D'. */

 template <typename D, typename S> inline bool SkTFitsIn(S s) {

     SK_COMPILE_ASSERT(std::numeric_limits<S>::is_integer, SkTFitsIn_source_must_be_integer);

     SK_COMPILE_ASSERT(std::numeric_limits<D>::is_integer, SkTFitsIn_destination_must_be_integer);

     return !sktfitsin::Private::SkTFitsIn<D, S>::type::OutOfRange(s);

 }

 #endif