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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>
#include <type_traits>
namespace sktfitsin {
namespace Private {
/** SkTMux::type = (a && b) ? Both : (a) ? A : (b) ? B : Neither; */
template <bool a, bool b, typename Both, typename A, typename B, typename Neither>
struct SkTMux {
using type = skstd::conditional_t<a, skstd::conditional_t<b, Both, A>,
skstd::conditional_t<b, B, Neither>>;
};
/** SkTHasMoreDigits = (digits(A) >= digits(B)) ? true_type : false_type. */
template<typename A, typename B> struct SkTHasMoreDigits
: skstd::bool_constant<std::numeric_limits<A>::digits >= std::numeric_limits<B>::digits>
{ };
/** 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 std::false_type 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 std::true_type can_be_true;
typedef S source_type;
static bool apply(S s) {
typedef SkTHasMoreDigits<S, D> precondition;
static_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 std::true_type 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 std::true_type can_be_true;
typedef S source_type;
static bool apply(S s) {
typedef SkTHasMoreDigits<S, D> precondition;
static_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 std::true_type 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::value, apply_high::value,
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 SkTHasMoreDigits<D, S> sourceFitsInDesitination;
typedef skstd::conditional_t<sourceFitsInDesitination::value, NoCheck, HighSideOnlyCheck> 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 SkTHasMoreDigits<D, S> sourceFitsInDesitination;
typedef skstd::conditional_t<sourceFitsInDesitination::value, NoCheck, FullCheck> 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 SkTHasMoreDigits<D, S> sourceCannotExceedDest;
typedef skstd::conditional_t<sourceCannotExceedDest::value, LowSideOnlyCheck, FullCheck> 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 SkTHasMoreDigits<D, S> sourceCannotExceedDest;
typedef skstd::conditional_t<sourceCannotExceedDest::value, NoCheck, HighSideOnlyCheck> 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 skstd::bool_constant<std::numeric_limits<S>::is_signed> S_is_signed;
typedef skstd::bool_constant<std::numeric_limits<D>::is_signed> D_is_signed;
typedef typename SkTMux<S_is_signed::value, D_is_signed::value,
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) {
static_assert(std::numeric_limits<S>::is_integer, "SkTFitsIn_source_must_be_integer");
static_assert(std::numeric_limits<D>::is_integer, "SkTFitsIn_destination_must_be_integer");
return !sktfitsin::Private::SkTFitsIn<D, S>::type::OutOfRange(s);
}
#endif
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