Revision: 21883
Author: [email protected]
Date: Wed Jun 18 11:01:54 2014 UTC
Log: Add safe numerics classes, imported from Chromium.
Not used for anything yet.
[email protected]
Review URL: https://codereview.chromium.org/336183003
http://code.google.com/p/v8/source/detail?r=21883
Added:
/branches/bleeding_edge/src/base/safe_conversions.h
/branches/bleeding_edge/src/base/safe_conversions_impl.h
/branches/bleeding_edge/src/base/safe_math.h
/branches/bleeding_edge/src/base/safe_math_impl.h
Modified:
/branches/bleeding_edge/BUILD.gn
/branches/bleeding_edge/tools/gyp/v8.gyp
=======================================
--- /dev/null
+++ /branches/bleeding_edge/src/base/safe_conversions.h Wed Jun 18 11:01:54
2014 UTC
@@ -0,0 +1,67 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Slightly adapted for inclusion in V8.
+// Copyright 2014 the V8 project authors. All rights reserved.
+
+#ifndef V8_BASE_SAFE_CONVERSIONS_H_
+#define V8_BASE_SAFE_CONVERSIONS_H_
+
+#include <limits>
+
+#include "src/base/safe_conversions_impl.h"
+
+namespace v8 {
+namespace base {
+
+// Convenience function that returns true if the supplied value is in range
+// for the destination type.
+template <typename Dst, typename Src>
+inline bool IsValueInRangeForNumericType(Src value) {
+ return internal::DstRangeRelationToSrcRange<Dst>(value) ==
+ internal::RANGE_VALID;
+}
+
+// checked_cast<> is analogous to static_cast<> for numeric types,
+// except that it CHECKs that the specified numeric conversion will not
+// overflow or underflow. NaN source will always trigger a CHECK.
+template <typename Dst, typename Src>
+inline Dst checked_cast(Src value) {
+ CHECK(IsValueInRangeForNumericType<Dst>(value));
+ return static_cast<Dst>(value);
+}
+
+// saturated_cast<> is analogous to static_cast<> for numeric types, except
+// that the specified numeric conversion will saturate rather than
overflow or
+// underflow. NaN assignment to an integral will trigger a CHECK condition.
+template <typename Dst, typename Src>
+inline Dst saturated_cast(Src value) {
+ // Optimization for floating point values, which already saturate.
+ if (std::numeric_limits<Dst>::is_iec559)
+ return static_cast<Dst>(value);
+
+ switch (internal::DstRangeRelationToSrcRange<Dst>(value)) {
+ case internal::RANGE_VALID:
+ return static_cast<Dst>(value);
+
+ case internal::RANGE_UNDERFLOW:
+ return std::numeric_limits<Dst>::min();
+
+ case internal::RANGE_OVERFLOW:
+ return std::numeric_limits<Dst>::max();
+
+ // Should fail only on attempting to assign NaN to a saturated integer.
+ case internal::RANGE_INVALID:
+ CHECK(false);
+ return std::numeric_limits<Dst>::max();
+ }
+
+ UNREACHABLE();
+ return static_cast<Dst>(value);
+}
+
+} // namespace base
+} // namespace v8
+
+#endif // V8_BASE_SAFE_CONVERSIONS_H_
=======================================
--- /dev/null
+++ /branches/bleeding_edge/src/base/safe_conversions_impl.h Wed Jun 18
11:01:54 2014 UTC
@@ -0,0 +1,220 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Slightly adapted for inclusion in V8.
+// Copyright 2014 the V8 project authors. All rights reserved.
+
+#ifndef V8_BASE_SAFE_CONVERSIONS_IMPL_H_
+#define V8_BASE_SAFE_CONVERSIONS_IMPL_H_
+
+#include <limits>
+
+#include "src/base/macros.h"
+
+namespace v8 {
+namespace base {
+namespace internal {
+
+// The std library doesn't provide a binary max_exponent for integers,
however
+// we can compute one by adding one to the number of non-sign bits. This
allows
+// for accurate range comparisons between floating point and integer types.
+template <typename NumericType>
+struct MaxExponent {
+ static const int value = std::numeric_limits<NumericType>::is_iec559
+ ?
std::numeric_limits<NumericType>::max_exponent
+ : (sizeof(NumericType) * 8 + 1 -
+
std::numeric_limits<NumericType>::is_signed);
+};
+
+enum IntegerRepresentation {
+ INTEGER_REPRESENTATION_UNSIGNED,
+ INTEGER_REPRESENTATION_SIGNED
+};
+
+// A range for a given nunmeric Src type is contained for a given numeric
Dst
+// type if both numeric_limits<Src>::max() <= numeric_limits<Dst>::max()
and
+// numeric_limits<Src>::min() >= numeric_limits<Dst>::min() are true.
+// We implement this as template specializations rather than simple static
+// comparisons to ensure type correctness in our comparisons.
+enum NumericRangeRepresentation {
+ NUMERIC_RANGE_NOT_CONTAINED,
+ NUMERIC_RANGE_CONTAINED
+};
+
+// Helper templates to statically determine if our destination type can
contain
+// maximum and minimum values represented by the source type.
+
+template <
+ typename Dst,
+ typename Src,
+ IntegerRepresentation DstSign = std::numeric_limits<Dst>::is_signed
+ ? INTEGER_REPRESENTATION_SIGNED
+ :
INTEGER_REPRESENTATION_UNSIGNED,
+ IntegerRepresentation SrcSign =
+ std::numeric_limits<Src>::is_signed
+ ? INTEGER_REPRESENTATION_SIGNED
+ : INTEGER_REPRESENTATION_UNSIGNED >
+struct StaticDstRangeRelationToSrcRange;
+
+// Same sign: Dst is guaranteed to contain Src only if its range is equal
or
+// larger.
+template <typename Dst, typename Src, IntegerRepresentation Sign>
+struct StaticDstRangeRelationToSrcRange<Dst, Src, Sign, Sign> {
+ static const NumericRangeRepresentation value =
+ MaxExponent<Dst>::value >= MaxExponent<Src>::value
+ ? NUMERIC_RANGE_CONTAINED
+ : NUMERIC_RANGE_NOT_CONTAINED;
+};
+
+// Unsigned to signed: Dst is guaranteed to contain source only if its
range is
+// larger.
+template <typename Dst, typename Src>
+struct StaticDstRangeRelationToSrcRange<Dst,
+ Src,
+ INTEGER_REPRESENTATION_SIGNED,
+ INTEGER_REPRESENTATION_UNSIGNED> {
+ static const NumericRangeRepresentation value =
+ MaxExponent<Dst>::value > MaxExponent<Src>::value
+ ? NUMERIC_RANGE_CONTAINED
+ : NUMERIC_RANGE_NOT_CONTAINED;
+};
+
+// Signed to unsigned: Dst cannot be statically determined to contain Src.
+template <typename Dst, typename Src>
+struct StaticDstRangeRelationToSrcRange<Dst,
+ Src,
+ INTEGER_REPRESENTATION_UNSIGNED,
+ INTEGER_REPRESENTATION_SIGNED> {
+ static const NumericRangeRepresentation value =
NUMERIC_RANGE_NOT_CONTAINED;
+};
+
+enum RangeConstraint {
+ RANGE_VALID = 0x0, // Value can be represented by the destination type.
+ RANGE_UNDERFLOW = 0x1, // Value would overflow.
+ RANGE_OVERFLOW = 0x2, // Value would underflow.
+ RANGE_INVALID = RANGE_UNDERFLOW | RANGE_OVERFLOW // Invalid (i.e. NaN).
+};
+
+// Helper function for coercing an int back to a RangeContraint.
+inline RangeConstraint GetRangeConstraint(int integer_range_constraint) {
+ // TODO(jochen/jkummerow): Re-enable this when checks.h is available in
base.
+ // ASSERT(integer_range_constraint >= RANGE_VALID &&
+ // integer_range_constraint <= RANGE_INVALID);
+ return static_cast<RangeConstraint>(integer_range_constraint);
+}
+
+// This function creates a RangeConstraint from an upper and lower bound
+// check by taking advantage of the fact that only NaN can be out of range
in
+// both directions at once.
+inline RangeConstraint GetRangeConstraint(bool is_in_upper_bound,
+ bool is_in_lower_bound) {
+ return GetRangeConstraint((is_in_upper_bound ? 0 : RANGE_OVERFLOW) |
+ (is_in_lower_bound ? 0 : RANGE_UNDERFLOW));
+}
+
+template <
+ typename Dst,
+ typename Src,
+ IntegerRepresentation DstSign = std::numeric_limits<Dst>::is_signed
+ ? INTEGER_REPRESENTATION_SIGNED
+ :
INTEGER_REPRESENTATION_UNSIGNED,
+ IntegerRepresentation SrcSign = std::numeric_limits<Src>::is_signed
+ ? INTEGER_REPRESENTATION_SIGNED
+ :
INTEGER_REPRESENTATION_UNSIGNED,
+ NumericRangeRepresentation DstRange =
+ StaticDstRangeRelationToSrcRange<Dst, Src>::value >
+struct DstRangeRelationToSrcRangeImpl;
+
+// The following templates are for ranges that must be verified at
runtime. We
+// split it into checks based on signedness to avoid confusing casts and
+// compiler warnings on signed an unsigned comparisons.
+
+// Dst range is statically determined to contain Src: Nothing to check.
+template <typename Dst,
+ typename Src,
+ IntegerRepresentation DstSign,
+ IntegerRepresentation SrcSign>
+struct DstRangeRelationToSrcRangeImpl<Dst,
+ Src,
+ DstSign,
+ SrcSign,
+ NUMERIC_RANGE_CONTAINED> {
+ static RangeConstraint Check(Src value) { return RANGE_VALID; }
+};
+
+// Signed to signed narrowing: Both the upper and lower boundaries may be
+// exceeded.
+template <typename Dst, typename Src>
+struct DstRangeRelationToSrcRangeImpl<Dst,
+ Src,
+ INTEGER_REPRESENTATION_SIGNED,
+ INTEGER_REPRESENTATION_SIGNED,
+ NUMERIC_RANGE_NOT_CONTAINED> {
+ static RangeConstraint Check(Src value) {
+ return std::numeric_limits<Dst>::is_iec559
+ ? GetRangeConstraint(value <=
std::numeric_limits<Dst>::max(),
+ value >=
-std::numeric_limits<Dst>::max())
+ : GetRangeConstraint(value <=
std::numeric_limits<Dst>::max(),
+ value >=
std::numeric_limits<Dst>::min());
+ }
+};
+
+// Unsigned to unsigned narrowing: Only the upper boundary can be exceeded.
+template <typename Dst, typename Src>
+struct DstRangeRelationToSrcRangeImpl<Dst,
+ Src,
+ INTEGER_REPRESENTATION_UNSIGNED,
+ INTEGER_REPRESENTATION_UNSIGNED,
+ NUMERIC_RANGE_NOT_CONTAINED> {
+ static RangeConstraint Check(Src value) {
+ return GetRangeConstraint(value <= std::numeric_limits<Dst>::max(),
true);
+ }
+};
+
+// Unsigned to signed: The upper boundary may be exceeded.
+template <typename Dst, typename Src>
+struct DstRangeRelationToSrcRangeImpl<Dst,
+ Src,
+ INTEGER_REPRESENTATION_SIGNED,
+ INTEGER_REPRESENTATION_UNSIGNED,
+ NUMERIC_RANGE_NOT_CONTAINED> {
+ static RangeConstraint Check(Src value) {
+ return sizeof(Dst) > sizeof(Src)
+ ? RANGE_VALID
+ : GetRangeConstraint(
+ value <=
static_cast<Src>(std::numeric_limits<Dst>::max()),
+ true);
+ }
+};
+
+// Signed to unsigned: The upper boundary may be exceeded for a narrower
Dst,
+// and any negative value exceeds the lower boundary.
+template <typename Dst, typename Src>
+struct DstRangeRelationToSrcRangeImpl<Dst,
+ Src,
+ INTEGER_REPRESENTATION_UNSIGNED,
+ INTEGER_REPRESENTATION_SIGNED,
+ NUMERIC_RANGE_NOT_CONTAINED> {
+ static RangeConstraint Check(Src value) {
+ return (MaxExponent<Dst>::value >= MaxExponent<Src>::value)
+ ? GetRangeConstraint(true, value >= static_cast<Src>(0))
+ : GetRangeConstraint(
+ value <=
static_cast<Src>(std::numeric_limits<Dst>::max()),
+ value >= static_cast<Src>(0));
+ }
+};
+
+template <typename Dst, typename Src>
+inline RangeConstraint DstRangeRelationToSrcRange(Src value) {
+ // Both source and destination must be numeric.
+ STATIC_ASSERT(std::numeric_limits<Src>::is_specialized);
+ STATIC_ASSERT(std::numeric_limits<Dst>::is_specialized);
+ return DstRangeRelationToSrcRangeImpl<Dst, Src>::Check(value);
+}
+
+} // namespace internal
+} // namespace base
+} // namespace v8
+
+#endif // V8_BASE_SAFE_CONVERSIONS_IMPL_H_
=======================================
--- /dev/null
+++ /branches/bleeding_edge/src/base/safe_math.h Wed Jun 18 11:01:54 2014
UTC
@@ -0,0 +1,276 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Slightly adapted for inclusion in V8.
+// Copyright 2014 the V8 project authors. All rights reserved.
+
+#ifndef V8_BASE_SAFE_MATH_H_
+#define V8_BASE_SAFE_MATH_H_
+
+#include "src/base/safe_math_impl.h"
+
+namespace v8 {
+namespace base {
+namespace internal {
+
+// CheckedNumeric implements all the logic and operators for detecting
integer
+// boundary conditions such as overflow, underflow, and invalid
conversions.
+// The CheckedNumeric type implicitly converts from floating point and
integer
+// data types, and contains overloads for basic arithmetic operations
(i.e.: +,
+// -, *, /, %).
+//
+// The following methods convert from CheckedNumeric to standard numeric
values:
+// IsValid() - Returns true if the underlying numeric value is valid (i.e.
has
+// has not wrapped and is not the result of an invalid
conversion).
+// ValueOrDie() - Returns the underlying value. If the state is not valid
this
+// call will crash on a CHECK.
+// ValueOrDefault() - Returns the current value, or the supplied default
if the
+// state is not valid.
+// ValueFloating() - Returns the underlying floating point value (valid
only
+// only for floating point CheckedNumeric types).
+//
+// Bitwise operations are explicitly not supported, because correct
+// handling of some cases (e.g. sign manipulation) is ambiguous. Comparison
+// operations are explicitly not supported because they could result in a
crash
+// on a CHECK condition. You should use patterns like the following for
these
+// operations:
+// Bitwise operation:
+// CheckedNumeric<int> checked_int = untrusted_input_value;
+// int x = checked_int.ValueOrDefault(0) | kFlagValues;
+// Comparison:
+// CheckedNumeric<size_t> checked_size;
+// CheckedNumeric<int> checked_size = untrusted_input_value;
+// checked_size = checked_size + HEADER LENGTH;
+// if (checked_size.IsValid() && checked_size.ValueOrDie() < buffer_size)
+// Do stuff...
+template <typename T>
+class CheckedNumeric {
+ public:
+ typedef T type;
+
+ CheckedNumeric() {}
+
+ // Copy constructor.
+ template <typename Src>
+ CheckedNumeric(const CheckedNumeric<Src>& rhs)
+ : state_(rhs.ValueUnsafe(), rhs.validity()) {}
+
+ template <typename Src>
+ CheckedNumeric(Src value, RangeConstraint validity)
+ : state_(value, validity) {}
+
+ // This is not an explicit constructor because we implicitly upgrade
regular
+ // numerics to CheckedNumerics to make them easier to use.
+ template <typename Src>
+ CheckedNumeric(Src value) // NOLINT
+ : state_(value) {
+ // Argument must be numeric.
+ STATIC_ASSERT(std::numeric_limits<Src>::is_specialized);
+ }
+
+ // IsValid() is the public API to test if a CheckedNumeric is currently
valid.
+ bool IsValid() const { return validity() == RANGE_VALID; }
+
+ // ValueOrDie() The primary accessor for the underlying value. If the
current
+ // state is not valid it will CHECK and crash.
+ T ValueOrDie() const {
+ CHECK(IsValid());
+ return state_.value();
+ }
+
+ // ValueOrDefault(T default_value) A convenience method that returns the
+ // current value if the state is valid, and the supplied default_value
for
+ // any other state.
+ T ValueOrDefault(T default_value) const {
+ return IsValid() ? state_.value() : default_value;
+ }
+
+ // ValueFloating() - Since floating point values include their validity
state,
+ // we provide an easy method for extracting them directly, without a
risk of
+ // crashing on a CHECK.
+ T ValueFloating() const {
+ // Argument must be a floating-point value.
+ STATIC_ASSERT(std::numeric_limits<T>::is_iec559);
+ return CheckedNumeric<T>::cast(*this).ValueUnsafe();
+ }
+
+ // validity() - DO NOT USE THIS IN EXTERNAL CODE - It is public right
now for
+ // tests and to avoid a big matrix of friend operator overloads. But the
+ // values it returns are likely to change in the future.
+ // Returns: current validity state (i.e. valid, overflow, underflow,
nan).
+ // TODO(jschuh): crbug.com/332611 Figure out and implement semantics for
+ // saturation/wrapping so we can expose this state consistently and
implement
+ // saturated arithmetic.
+ RangeConstraint validity() const { return state_.validity(); }
+
+ // ValueUnsafe() - DO NOT USE THIS IN EXTERNAL CODE - It is public right
now
+ // for tests and to avoid a big matrix of friend operator overloads. But
the
+ // values it returns are likely to change in the future.
+ // Returns: the raw numeric value, regardless of the current state.
+ // TODO(jschuh): crbug.com/332611 Figure out and implement semantics for
+ // saturation/wrapping so we can expose this state consistently and
implement
+ // saturated arithmetic.
+ T ValueUnsafe() const { return state_.value(); }
+
+ // Prototypes for the supported arithmetic operator overloads.
+ template <typename Src> CheckedNumeric& operator+=(Src rhs);
+ template <typename Src> CheckedNumeric& operator-=(Src rhs);
+ template <typename Src> CheckedNumeric& operator*=(Src rhs);
+ template <typename Src> CheckedNumeric& operator/=(Src rhs);
+ template <typename Src> CheckedNumeric& operator%=(Src rhs);
+
+ CheckedNumeric operator-() const {
+ RangeConstraint validity;
+ T value = CheckedNeg(state_.value(), &validity);
+ // Negation is always valid for floating point.
+ if (std::numeric_limits<T>::is_iec559)
+ return CheckedNumeric<T>(value);
+
+ validity = GetRangeConstraint(state_.validity() | validity);
+ return CheckedNumeric<T>(value, validity);
+ }
+
+ CheckedNumeric Abs() const {
+ RangeConstraint validity;
+ T value = CheckedAbs(state_.value(), &validity);
+ // Absolute value is always valid for floating point.
+ if (std::numeric_limits<T>::is_iec559)
+ return CheckedNumeric<T>(value);
+
+ validity = GetRangeConstraint(state_.validity() | validity);
+ return CheckedNumeric<T>(value, validity);
+ }
+
+ CheckedNumeric& operator++() {
+ *this += 1;
+ return *this;
+ }
+
+ CheckedNumeric operator++(int) {
+ CheckedNumeric value = *this;
+ *this += 1;
+ return value;
+ }
+
+ CheckedNumeric& operator--() {
+ *this -= 1;
+ return *this;
+ }
+
+ CheckedNumeric operator--(int) {
+ CheckedNumeric value = *this;
+ *this -= 1;
+ return value;
+ }
+
+ // These static methods behave like a convenience cast operator targeting
+ // the desired CheckedNumeric type. As an optimization, a reference is
+ // returned when Src is the same type as T.
+ template <typename Src>
+ static CheckedNumeric<T> cast(
+ Src u,
+ typename enable_if<std::numeric_limits<Src>::is_specialized,
int>::type =
+ 0) {
+ return u;
+ }
+
+ template <typename Src>
+ static CheckedNumeric<T> cast(
+ const CheckedNumeric<Src>& u,
+ typename enable_if<!is_same<Src, T>::value, int>::type = 0) {
+ return u;
+ }
+
+ static const CheckedNumeric<T>& cast(const CheckedNumeric<T>& u) {
return u; }
+
+ private:
+ CheckedNumericState<T> state_;
+};
+
+// This is the boilerplate for the standard arithmetic operator overloads.
A
+// macro isn't the prettiest solution, but it beats rewriting these five
times.
+// Some details worth noting are:
+// * We apply the standard arithmetic promotions.
+// * We skip range checks for floating points.
+// * We skip range checks for destination integers with sufficient range.
+// TODO(jschuh): extract these out into templates.
+#define BASE_NUMERIC_ARITHMETIC_OPERATORS(NAME, OP,
COMPOUND_OP) \
+ /* Binary arithmetic operator for CheckedNumerics of the same type.
*/ \
+ template <typename
T> \
+ CheckedNumeric<typename ArithmeticPromotion<T>::type> operator
OP( \
+ const CheckedNumeric<T>& lhs, const CheckedNumeric<T>& rhs)
{ \
+ typedef typename ArithmeticPromotion<T>::type
Promotion; \
+ /* Floating point always takes the fast path
*/ \
+ if
(std::numeric_limits<T>::is_iec559) \
+ return CheckedNumeric<T>(lhs.ValueUnsafe() OP
rhs.ValueUnsafe()); \
+ if (IsIntegerArithmeticSafe<Promotion, T,
T>::value) \
+ return
CheckedNumeric<Promotion>( \
+ lhs.ValueUnsafe() OP
rhs.ValueUnsafe(), \
+ GetRangeConstraint(rhs.validity() |
lhs.validity())); \
+ RangeConstraint validity =
RANGE_VALID; \
+ T result =
Checked##NAME(static_cast<Promotion>(lhs.ValueUnsafe()), \
+
static_cast<Promotion>(rhs.ValueUnsafe()), \
+
&validity); \
+ return
CheckedNumeric<Promotion>( \
+
result, \
+ GetRangeConstraint(validity | lhs.validity() |
rhs.validity())); \
+
}
\
+ /* Assignment arithmetic operator implementation from CheckedNumeric.
*/ \
+ template <typename
T> \
+ template <typename
Src> \
+ CheckedNumeric<T>& CheckedNumeric<T>::operator COMPOUND_OP(Src rhs)
{ \
+ *this = CheckedNumeric<T>::cast(*this) OP
CheckedNumeric<Src>::cast(rhs); \
+ return
*this; \
+
}
\
+ /* Binary arithmetic operator for CheckedNumeric of different type.
*/ \
+ template <typename T, typename
Src> \
+ CheckedNumeric<typename ArithmeticPromotion<T, Src>::type> operator
OP( \
+ const CheckedNumeric<Src>& lhs, const CheckedNumeric<T>& rhs)
{ \
+ typedef typename ArithmeticPromotion<T, Src>::type
Promotion; \
+ if (IsIntegerArithmeticSafe<Promotion, T,
Src>::value) \
+ return
CheckedNumeric<Promotion>( \
+ lhs.ValueUnsafe() OP
rhs.ValueUnsafe(), \
+ GetRangeConstraint(rhs.validity() |
lhs.validity())); \
+ return
CheckedNumeric<Promotion>::cast(lhs) \
+ OP
CheckedNumeric<Promotion>::cast(rhs); \
+
}
\
+ /* Binary arithmetic operator for left CheckedNumeric and right numeric.
*/ \
+ template <typename T, typename
Src> \
+ CheckedNumeric<typename ArithmeticPromotion<T, Src>::type> operator
OP( \
+ const CheckedNumeric<T>& lhs, Src rhs)
{ \
+ typedef typename ArithmeticPromotion<T, Src>::type
Promotion; \
+ if (IsIntegerArithmeticSafe<Promotion, T,
Src>::value) \
+ return CheckedNumeric<Promotion>(lhs.ValueUnsafe() OP
rhs, \
+
lhs.validity()); \
+ return
CheckedNumeric<Promotion>::cast(lhs) \
+ OP
CheckedNumeric<Promotion>::cast(rhs); \
+
}
\
+ /* Binary arithmetic operator for right numeric and left CheckedNumeric.
*/ \
+ template <typename T, typename
Src> \
+ CheckedNumeric<typename ArithmeticPromotion<T, Src>::type> operator
OP( \
+ Src lhs, const CheckedNumeric<T>& rhs)
{ \
+ typedef typename ArithmeticPromotion<T, Src>::type
Promotion; \
+ if (IsIntegerArithmeticSafe<Promotion, T,
Src>::value) \
+ return CheckedNumeric<Promotion>(lhs OP
rhs.ValueUnsafe(), \
+
rhs.validity()); \
+ return
CheckedNumeric<Promotion>::cast(lhs) \
+ OP
CheckedNumeric<Promotion>::cast(rhs); \
+ }
+
+BASE_NUMERIC_ARITHMETIC_OPERATORS(Add, +, += )
+BASE_NUMERIC_ARITHMETIC_OPERATORS(Sub, -, -= )
+BASE_NUMERIC_ARITHMETIC_OPERATORS(Mul, *, *= )
+BASE_NUMERIC_ARITHMETIC_OPERATORS(Div, /, /= )
+BASE_NUMERIC_ARITHMETIC_OPERATORS(Mod, %, %= )
+
+#undef BASE_NUMERIC_ARITHMETIC_OPERATORS
+
+} // namespace internal
+
+using internal::CheckedNumeric;
+
+} // namespace base
+} // namespace v8
+
+#endif // V8_BASE_SAFE_MATH_H_
=======================================
--- /dev/null
+++ /branches/bleeding_edge/src/base/safe_math_impl.h Wed Jun 18 11:01:54
2014 UTC
@@ -0,0 +1,531 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Slightly adapted for inclusion in V8.
+// Copyright 2014 the V8 project authors. All rights reserved.
+
+#ifndef V8_BASE_SAFE_MATH_IMPL_H_
+#define V8_BASE_SAFE_MATH_IMPL_H_
+
+#include <stdint.h>
+
+#include <cmath>
+#include <cstdlib>
+#include <limits>
+
+#include "src/base/macros.h"
+#include "src/base/safe_conversions.h"
+
+namespace v8 {
+namespace base {
+namespace internal {
+
+
+// From Chromium's base/template_util.h:
+
+template<class T, T v>
+struct integral_constant {
+ static const T value = v;
+ typedef T value_type;
+ typedef integral_constant<T, v> type;
+};
+
+template <class T, T v> const T integral_constant<T, v>::value;
+
+typedef integral_constant<bool, true> true_type;
+typedef integral_constant<bool, false> false_type;
+
+template <class T, class U> struct is_same : public false_type {};
+template <class T> struct is_same<T, T> : true_type {};
+
+template<bool B, class T = void>
+struct enable_if {};
+
+template<class T>
+struct enable_if<true, T> { typedef T type; };
+
+// </template_util.h>
+
+
+// Everything from here up to the floating point operations is portable
C++,
+// but it may not be fast. This code could be split based on
+// platform/architecture and replaced with potentially faster
implementations.
+
+// Integer promotion templates used by the portable checked integer
arithmetic.
+template <size_t Size, bool IsSigned>
+struct IntegerForSizeAndSign;
+template <>
+struct IntegerForSizeAndSign<1, true> {
+ typedef int8_t type;
+};
+template <>
+struct IntegerForSizeAndSign<1, false> {
+ typedef uint8_t type;
+};
+template <>
+struct IntegerForSizeAndSign<2, true> {
+ typedef int16_t type;
+};
+template <>
+struct IntegerForSizeAndSign<2, false> {
+ typedef uint16_t type;
+};
+template <>
+struct IntegerForSizeAndSign<4, true> {
+ typedef int32_t type;
+};
+template <>
+struct IntegerForSizeAndSign<4, false> {
+ typedef uint32_t type;
+};
+template <>
+struct IntegerForSizeAndSign<8, true> {
+ typedef int64_t type;
+};
+template <>
+struct IntegerForSizeAndSign<8, false> {
+ typedef uint64_t type;
+};
+
+// WARNING: We have no IntegerForSizeAndSign<16, *>. If we ever add one to
+// support 128-bit math, then the ArithmeticPromotion template below will
need
+// to be updated (or more likely replaced with a decltype expression).
+
+template <typename Integer>
+struct UnsignedIntegerForSize {
+ typedef typename enable_if<
+ std::numeric_limits<Integer>::is_integer,
+ typename IntegerForSizeAndSign<sizeof(Integer), false>::type>::type
type;
+};
+
+template <typename Integer>
+struct SignedIntegerForSize {
+ typedef typename enable_if<
+ std::numeric_limits<Integer>::is_integer,
+ typename IntegerForSizeAndSign<sizeof(Integer), true>::type>::type
type;
+};
+
+template <typename Integer>
+struct TwiceWiderInteger {
+ typedef typename enable_if<
+ std::numeric_limits<Integer>::is_integer,
+ typename IntegerForSizeAndSign<
+ sizeof(Integer) * 2,
+ std::numeric_limits<Integer>::is_signed>::type>::type type;
+};
+
+template <typename Integer>
+struct PositionOfSignBit {
+ static const typename enable_if<std::numeric_limits<Integer>::is_integer,
+ size_t>::type value = 8 *
sizeof(Integer) - 1;
+};
+
+// Helper templates for integer manipulations.
+
+template <typename T>
+bool HasSignBit(T x) {
+ // Cast to unsigned since right shift on signed is undefined.
+ return !!(static_cast<typename UnsignedIntegerForSize<T>::type>(x) >>
+ PositionOfSignBit<T>::value);
+}
+
+// This wrapper undoes the standard integer promotions.
+template <typename T>
+T BinaryComplement(T x) {
+ return ~x;
+}
+
+// Here are the actual portable checked integer math implementations.
+// TODO(jschuh): Break this code out from the enable_if pattern and find a
clean
+// way to coalesce things into the CheckedNumericState specializations
below.
+
+template <typename T>
+typename enable_if<std::numeric_limits<T>::is_integer, T>::type
+CheckedAdd(T x, T y, RangeConstraint* validity) {
+ // Since the value of x+y is undefined if we have a signed type, we
compute
+ // it using the unsigned type of the same size.
+ typedef typename UnsignedIntegerForSize<T>::type UnsignedDst;
+ UnsignedDst ux = static_cast<UnsignedDst>(x);
+ UnsignedDst uy = static_cast<UnsignedDst>(y);
+ UnsignedDst uresult = ux + uy;
+ // Addition is valid if the sign of (x + y) is equal to either that of x
or
+ // that of y.
+ if (std::numeric_limits<T>::is_signed) {
+ if (HasSignBit(BinaryComplement((uresult ^ ux) & (uresult ^ uy))))
+ *validity = RANGE_VALID;
+ else // Direction of wrap is inverse of result sign.
+ *validity = HasSignBit(uresult) ? RANGE_OVERFLOW : RANGE_UNDERFLOW;
+
+ } else { // Unsigned is either valid or overflow.
+ *validity = BinaryComplement(x) >= y ? RANGE_VALID : RANGE_OVERFLOW;
+ }
+ return static_cast<T>(uresult);
+}
+
+template <typename T>
+typename enable_if<std::numeric_limits<T>::is_integer, T>::type
+CheckedSub(T x, T y, RangeConstraint* validity) {
+ // Since the value of x+y is undefined if we have a signed type, we
compute
+ // it using the unsigned type of the same size.
+ typedef typename UnsignedIntegerForSize<T>::type UnsignedDst;
+ UnsignedDst ux = static_cast<UnsignedDst>(x);
+ UnsignedDst uy = static_cast<UnsignedDst>(y);
+ UnsignedDst uresult = ux - uy;
+ // Subtraction is valid if either x and y have same sign, or (x-y) and x
have
+ // the same sign.
+ if (std::numeric_limits<T>::is_signed) {
+ if (HasSignBit(BinaryComplement((uresult ^ ux) & (ux ^ uy))))
+ *validity = RANGE_VALID;
+ else // Direction of wrap is inverse of result sign.
+ *validity = HasSignBit(uresult) ? RANGE_OVERFLOW : RANGE_UNDERFLOW;
+
+ } else { // Unsigned is either valid or underflow.
+ *validity = x >= y ? RANGE_VALID : RANGE_UNDERFLOW;
+ }
+ return static_cast<T>(uresult);
+}
+
+// Integer multiplication is a bit complicated. In the fast case we just
+// we just promote to a twice wider type, and range check the result. In
the
+// slow case we need to manually check that the result won't be truncated
by
+// checking with division against the appropriate bound.
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer && sizeof(T) * 2 <=
sizeof(uintmax_t),
+ T>::type
+CheckedMul(T x, T y, RangeConstraint* validity) {
+ typedef typename TwiceWiderInteger<T>::type IntermediateType;
+ IntermediateType tmp =
+ static_cast<IntermediateType>(x) * static_cast<IntermediateType>(y);
+ *validity = DstRangeRelationToSrcRange<T>(tmp);
+ return static_cast<T>(tmp);
+}
+
+template <typename T>
+typename enable_if<std::numeric_limits<T>::is_integer &&
+ std::numeric_limits<T>::is_signed &&
+ (sizeof(T) * 2 > sizeof(uintmax_t)),
+ T>::type
+CheckedMul(T x, T y, RangeConstraint* validity) {
+ // if either side is zero then the result will be zero.
+ if (!(x || y)) {
+ return RANGE_VALID;
+
+ } else if (x > 0) {
+ if (y > 0)
+ *validity =
+ x <= std::numeric_limits<T>::max() / y ? RANGE_VALID :
RANGE_OVERFLOW;
+ else
+ *validity = y >= std::numeric_limits<T>::min() / x ? RANGE_VALID
+ : RANGE_UNDERFLOW;
+
+ } else {
+ if (y > 0)
+ *validity = x >= std::numeric_limits<T>::min() / y ? RANGE_VALID
+ : RANGE_UNDERFLOW;
+ else
+ *validity =
+ y >= std::numeric_limits<T>::max() / x ? RANGE_VALID :
RANGE_OVERFLOW;
+ }
+
+ return x * y;
+}
+
+template <typename T>
+typename enable_if<std::numeric_limits<T>::is_integer &&
+ !std::numeric_limits<T>::is_signed &&
+ (sizeof(T) * 2 > sizeof(uintmax_t)),
+ T>::type
+CheckedMul(T x, T y, RangeConstraint* validity) {
+ *validity = (y == 0 || x <= std::numeric_limits<T>::max() / y)
+ ? RANGE_VALID
+ : RANGE_OVERFLOW;
+ return x * y;
+}
+
+// Division just requires a check for an invalid negation on signed min/-1.
+template <typename T>
+T CheckedDiv(
+ T x,
+ T y,
+ RangeConstraint* validity,
+ typename enable_if<std::numeric_limits<T>::is_integer, int>::type = 0)
{
+ if (std::numeric_limits<T>::is_signed && x ==
std::numeric_limits<T>::min() &&
+ y == static_cast<T>(-1)) {
+ *validity = RANGE_OVERFLOW;
+ return std::numeric_limits<T>::min();
+ }
+
+ *validity = RANGE_VALID;
+ return x / y;
+}
+
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed,
+ T>::type
+CheckedMod(T x, T y, RangeConstraint* validity) {
+ *validity = y > 0 ? RANGE_VALID : RANGE_INVALID;
+ return x % y;
+}
+
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer
&& !std::numeric_limits<T>::is_signed,
+ T>::type
+CheckedMod(T x, T y, RangeConstraint* validity) {
+ *validity = RANGE_VALID;
+ return x % y;
+}
+
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed,
+ T>::type
+CheckedNeg(T value, RangeConstraint* validity) {
+ *validity =
+ value != std::numeric_limits<T>::min() ? RANGE_VALID :
RANGE_OVERFLOW;
+ // The negation of signed min is min, so catch that one.
+ return -value;
+}
+
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer
&& !std::numeric_limits<T>::is_signed,
+ T>::type
+CheckedNeg(T value, RangeConstraint* validity) {
+ // The only legal unsigned negation is zero.
+ *validity = value ? RANGE_UNDERFLOW : RANGE_VALID;
+ return static_cast<T>(
+ -static_cast<typename SignedIntegerForSize<T>::type>(value));
+}
+
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed,
+ T>::type
+CheckedAbs(T value, RangeConstraint* validity) {
+ *validity =
+ value != std::numeric_limits<T>::min() ? RANGE_VALID :
RANGE_OVERFLOW;
+ return std::abs(value);
+}
+
+template <typename T>
+typename enable_if<
+ std::numeric_limits<T>::is_integer
&& !std::numeric_limits<T>::is_signed,
+ T>::type
+CheckedAbs(T value, RangeConstraint* validity) {
+ // Absolute value of a positive is just its identiy.
+ *validity = RANGE_VALID;
+ return value;
+}
+
+// These are the floating point stubs that the compiler needs to see. Only
the
+// negation operation is ever called.
+#define BASE_FLOAT_ARITHMETIC_STUBS(NAME) \
+ template <typename T> \
+ typename enable_if<std::numeric_limits<T>::is_iec559, T>::type \
+ Checked##NAME(T, T, RangeConstraint*) { \
+ UNREACHABLE(); \
+ return 0; \
+ }
+
+BASE_FLOAT_ARITHMETIC_STUBS(Add)
+BASE_FLOAT_ARITHMETIC_STUBS(Sub)
+BASE_FLOAT_ARITHMETIC_STUBS(Mul)
+BASE_FLOAT_ARITHMETIC_STUBS(Div)
+BASE_FLOAT_ARITHMETIC_STUBS(Mod)
+
+#undef BASE_FLOAT_ARITHMETIC_STUBS
+
+template <typename T>
+typename enable_if<std::numeric_limits<T>::is_iec559, T>::type CheckedNeg(
+ T value,
+ RangeConstraint*) {
+ return -value;
+}
+
+template <typename T>
+typename enable_if<std::numeric_limits<T>::is_iec559, T>::type CheckedAbs(
+ T value,
+ RangeConstraint*) {
+ return std::abs(value);
+}
+
+// Floats carry around their validity state with them, but integers do
not. So,
+// we wrap the underlying value in a specialization in order to hide that
detail
+// and expose an interface via accessors.
+enum NumericRepresentation {
+ NUMERIC_INTEGER,
+ NUMERIC_FLOATING,
+ NUMERIC_UNKNOWN
+};
+
+template <typename NumericType>
+struct GetNumericRepresentation {
+ static const NumericRepresentation value =
+ std::numeric_limits<NumericType>::is_integer
+ ? NUMERIC_INTEGER
+ : (std::numeric_limits<NumericType>::is_iec559 ? NUMERIC_FLOATING
+ :
NUMERIC_UNKNOWN);
+};
+
+template <typename T, NumericRepresentation type =
+ GetNumericRepresentation<T>::value>
+class CheckedNumericState {};
+
+// Integrals require quite a bit of additional housekeeping to manage
state.
+template <typename T>
+class CheckedNumericState<T, NUMERIC_INTEGER> {
+ private:
+ T value_;
+ RangeConstraint validity_;
+
+ public:
+ template <typename Src, NumericRepresentation type>
+ friend class CheckedNumericState;
+
+ CheckedNumericState() : value_(0), validity_(RANGE_VALID) {}
+
+ template <typename Src>
+ CheckedNumericState(Src value, RangeConstraint validity)
+ : value_(value),
+ validity_(GetRangeConstraint(validity |
+
DstRangeRelationToSrcRange<T>(value))) {
+ // Argument must be numeric.
+ STATIC_ASSERT(std::numeric_limits<Src>::is_specialized);
+ }
+
+ // Copy constructor.
+ template <typename Src>
+ CheckedNumericState(const CheckedNumericState<Src>& rhs)
+ : value_(static_cast<T>(rhs.value())),
+ validity_(GetRangeConstraint(
+ rhs.validity() | DstRangeRelationToSrcRange<T>(rhs.value())))
{}
+
+ template <typename Src>
+ explicit CheckedNumericState(
+ Src value,
+ typename enable_if<std::numeric_limits<Src>::is_specialized,
int>::type =
+ 0)
+ : value_(static_cast<T>(value)),
+ validity_(DstRangeRelationToSrcRange<T>(value)) {}
+
+ RangeConstraint validity() const { return validity_; }
+ T value() const { return value_; }
+};
+
+// Floating points maintain their own validity, but need translation
wrappers.
+template <typename T>
+class CheckedNumericState<T, NUMERIC_FLOATING> {
+ private:
+ T value_;
+
+ public:
+ template <typename Src, NumericRepresentation type>
+ friend class CheckedNumericState;
+
+ CheckedNumericState() : value_(0.0) {}
+
+ template <typename Src>
+ CheckedNumericState(
+ Src value,
+ RangeConstraint validity,
+ typename enable_if<std::numeric_limits<Src>::is_integer, int>::type
= 0) {
+ switch (DstRangeRelationToSrcRange<T>(value)) {
+ case RANGE_VALID:
+ value_ = static_cast<T>(value);
+ break;
+
+ case RANGE_UNDERFLOW:
+ value_ = -std::numeric_limits<T>::infinity();
+ break;
+
+ case RANGE_OVERFLOW:
+ value_ = std::numeric_limits<T>::infinity();
+ break;
+
+ case RANGE_INVALID:
+ value_ = std::numeric_limits<T>::quiet_NaN();
+ break;
+ }
+ }
+
+ template <typename Src>
+ explicit CheckedNumericState(
+ Src value,
+ typename enable_if<std::numeric_limits<Src>::is_specialized,
int>::type =
+ 0)
+ : value_(static_cast<T>(value)) {}
+
+ // Copy constructor.
+ template <typename Src>
+ CheckedNumericState(const CheckedNumericState<Src>& rhs)
+ : value_(static_cast<T>(rhs.value())) {}
+
+ RangeConstraint validity() const {
+ return GetRangeConstraint(value_ <= std::numeric_limits<T>::max(),
+ value_ >= -std::numeric_limits<T>::max());
+ }
+ T value() const { return value_; }
+};
+
+// For integers less than 128-bit and floats 32-bit or larger, we can
distil
+// C/C++ arithmetic promotions down to two simple rules:
+// 1. The type with the larger maximum exponent always takes precedence.
+// 2. The resulting type must be promoted to at least an int.
+// The following template specializations implement that promotion logic.
+enum ArithmeticPromotionCategory {
+ LEFT_PROMOTION,
+ RIGHT_PROMOTION,
+ DEFAULT_PROMOTION
+};
+
+template <typename Lhs,
+ typename Rhs = Lhs,
+ ArithmeticPromotionCategory Promotion =
+ (MaxExponent<Lhs>::value > MaxExponent<Rhs>::value)
+ ? (MaxExponent<Lhs>::value > MaxExponent<int>::value
+ ? LEFT_PROMOTION
+ : DEFAULT_PROMOTION)
+ : (MaxExponent<Rhs>::value > MaxExponent<int>::value
+ ? RIGHT_PROMOTION
+ : DEFAULT_PROMOTION) >
+struct ArithmeticPromotion;
+
+template <typename Lhs, typename Rhs>
+struct ArithmeticPromotion<Lhs, Rhs, LEFT_PROMOTION> {
+ typedef Lhs type;
+};
+
+template <typename Lhs, typename Rhs>
+struct ArithmeticPromotion<Lhs, Rhs, RIGHT_PROMOTION> {
+ typedef Rhs type;
+};
+
+template <typename Lhs, typename Rhs>
+struct ArithmeticPromotion<Lhs, Rhs, DEFAULT_PROMOTION> {
+ typedef int type;
+};
+
+// We can statically check if operations on the provided types can wrap,
so we
+// can skip the checked operations if they're not needed. So, for an
integer we
+// care if the destination type preserves the sign and is twice the width
of
+// the source.
+template <typename T, typename Lhs, typename Rhs>
+struct IsIntegerArithmeticSafe {
+ static const bool value = !std::numeric_limits<T>::is_iec559 &&
+ StaticDstRangeRelationToSrcRange<T,
Lhs>::value ==
+ NUMERIC_RANGE_CONTAINED &&
+ sizeof(T) >= (2 * sizeof(Lhs)) &&
+ StaticDstRangeRelationToSrcRange<T,
Rhs>::value !=
+ NUMERIC_RANGE_CONTAINED &&
+ sizeof(T) >= (2 * sizeof(Rhs));
+};
+
+} // namespace internal
+} // namespace base
+} // namespace v8
+
+#endif // V8_BASE_SAFE_MATH_IMPL_H_
=======================================
--- /branches/bleeding_edge/BUILD.gn Wed Jun 18 07:30:56 2014 UTC
+++ /branches/bleeding_edge/BUILD.gn Wed Jun 18 11:01:54 2014 UTC
@@ -974,6 +974,10 @@
"src/base/macros.h",
"src/base/once.cc",
"src/base/once.h",
+ "src/base/safe_conversions.h",
+ "src/base/safe_conversions_impl.h",
+ "src/base/safe_math.h",
+ "src/base/safe_math_impl.h",
"src/base/win32-headers.h",
]
=======================================
--- /branches/bleeding_edge/tools/gyp/v8.gyp Wed Jun 18 07:30:56 2014 UTC
+++ /branches/bleeding_edge/tools/gyp/v8.gyp Wed Jun 18 11:01:54 2014 UTC
@@ -1080,6 +1080,10 @@
'../../src/base/macros.h',
'../../src/base/once.cc',
'../../src/base/once.h',
+ '../../src/base/safe_conversions.h',
+ '../../src/base/safe_conversions_impl.h',
+ '../../src/base/safe_math.h',
+ '../../src/base/safe_math_impl.h',
'../../src/base/win32-headers.h',
],
'conditions': [
--
--
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