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diff --git a/mozglue/misc/decimal/Decimal.h b/mozglue/misc/decimal/Decimal.h
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+/*
+ * Copyright (C) 2012 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * Imported from:
+ * https://chromium.googlesource.com/chromium/src.git/+/master/third_party/WebKit/Source/platform/Decimal.h
+ * Check UPSTREAM-GIT-SHA for the commit ID of the last update from Blink core.
+ */
+
+#ifndef Decimal_h
+#define Decimal_h
+
+#include "mozilla/Assertions.h"
+#include <stdint.h>
+#include "mozilla/Types.h"
+
+#include <string>
+
+#ifndef ASSERT
+#define DEFINED_ASSERT_FOR_DECIMAL_H 1
+#define ASSERT MOZ_ASSERT
+#endif
+
+#define PLATFORM_EXPORT
+
+// To use USING_FAST_MALLOC we'd need:
+// https://chromium.googlesource.com/chromium/src.git/+/master/third_party/WebKit/Source/wtf/Allocator.h
+// Since we don't allocate Decimal objects, no need.
+#define USING_FAST_MALLOC(type) \
+  void ignore_this_dummy_method() = delete
+
+#define DISALLOW_NEW()                                          \
+    private:                                                    \
+        void* operator new(size_t) = delete;                    \
+        void* operator new(size_t, void*) = delete;             \
+    public:
+
+namespace blink {
+
+namespace DecimalPrivate {
+constexpr int ExponentMax = 1023;
+constexpr int ExponentMin = -1023;
+constexpr int Precision = 18;
+
+static const uint64_t MaxCoefficient = UINT64_C(0xDE0B6B3A763FFFF);  // 999999999999999999 == 18 9's
+class SpecialValueHandler;
+}
+
+struct DecimalLiteral {
+  int32_t value;
+  friend constexpr DecimalLiteral operator*(int32_t lhs, DecimalLiteral rhs) {
+    return {lhs * rhs.value};
+  }
+  constexpr DecimalLiteral operator-() {
+    return {-value};
+  }
+};
+
+constexpr DecimalLiteral operator""_d(unsigned long long value) {
+  return {static_cast<int32_t>(value)};
+}
+
+// This class represents decimal base floating point number.
+//
+// FIXME: Once all C++ compiler support decimal type, we should replace this
+// class to compiler supported one. See below URI for current status of decimal
+// type for C++: // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1977.html
+class PLATFORM_EXPORT Decimal {
+    USING_FAST_MALLOC(Decimal);
+public:
+    enum Sign {
+        Positive,
+        Negative,
+    };
+
+    // You should not use EncodedData other than unit testing.
+    class EncodedData {
+        DISALLOW_NEW();
+        // For accessing FormatClass.
+        friend class Decimal;
+        friend class DecimalPrivate::SpecialValueHandler;
+    public:
+     constexpr EncodedData(Sign sign, int exponent, uint64_t coefficient)
+         : m_coefficient(0),
+           m_exponent(0),
+           m_formatClass(coefficient ? ClassNormal : ClassZero),
+           m_sign(sign) {
+       if (exponent >= DecimalPrivate::ExponentMin &&
+           exponent <= DecimalPrivate::ExponentMax) {
+         while (coefficient > DecimalPrivate::MaxCoefficient) {
+           coefficient /= 10;
+           ++exponent;
+         }
+       }
+
+       if (exponent > DecimalPrivate::ExponentMax) {
+         m_formatClass = ClassInfinity;
+         return;
+       }
+
+       if (exponent < DecimalPrivate::ExponentMin) {
+         m_formatClass = ClassZero;
+         return;
+       }
+
+       m_coefficient = coefficient;
+       m_exponent = static_cast<int16_t>(exponent);
+     }
+
+        bool operator==(const EncodedData&) const;
+        bool operator!=(const EncodedData& another) const { return !operator==(another); }
+
+        uint64_t coefficient() const { return m_coefficient; }
+        int countDigits() const;
+        int exponent() const { return m_exponent; }
+        bool isFinite() const { return !isSpecial(); }
+        bool isInfinity() const { return m_formatClass == ClassInfinity; }
+        bool isNaN() const { return m_formatClass == ClassNaN; }
+        bool isSpecial() const { return m_formatClass == ClassInfinity || m_formatClass == ClassNaN; }
+        bool isZero() const { return m_formatClass == ClassZero; }
+        Sign sign() const { return m_sign; }
+        void setSign(Sign sign) { m_sign = sign; }
+
+    private:
+        enum FormatClass {
+            ClassInfinity,
+            ClassNormal,
+            ClassNaN,
+            ClassZero,
+        };
+
+        constexpr EncodedData(Sign sign, FormatClass formatClass)
+            : m_coefficient(0),
+              m_exponent(0),
+              m_formatClass(formatClass),
+              m_sign(sign) {}
+
+        FormatClass formatClass() const { return m_formatClass; }
+
+        uint64_t m_coefficient;
+        int16_t m_exponent;
+        FormatClass m_formatClass;
+        Sign m_sign;
+    };
+
+    constexpr explicit Decimal(DecimalLiteral i32)
+    : m_data(i32.value < 0 ? Negative : Positive, 0,
+             i32.value < 0 ? static_cast<uint64_t>(-static_cast<int64_t>(i32.value))
+                     : static_cast<uint64_t>(i32.value)) {}
+
+    MFBT_API explicit Decimal(int32_t i32 = 0);
+    MFBT_API Decimal(Sign sign, int exponent, uint64_t coefficient);
+    MFBT_API Decimal(const Decimal&);
+
+    MFBT_API Decimal& operator=(const Decimal&);
+    MFBT_API Decimal& operator+=(const Decimal&);
+    MFBT_API Decimal& operator-=(const Decimal&);
+    MFBT_API Decimal& operator*=(const Decimal&);
+    MFBT_API Decimal& operator/=(const Decimal&);
+
+    MFBT_API Decimal operator-() const;
+
+    MFBT_API bool operator==(const Decimal&) const;
+    MFBT_API bool operator!=(const Decimal&) const;
+    MFBT_API bool operator<(const Decimal&) const;
+    MFBT_API bool operator<=(const Decimal&) const;
+    MFBT_API bool operator>(const Decimal&) const;
+    MFBT_API bool operator>=(const Decimal&) const;
+
+    MFBT_API Decimal operator+(const Decimal&) const;
+    MFBT_API Decimal operator-(const Decimal&) const;
+    MFBT_API Decimal operator*(const Decimal&) const;
+    MFBT_API Decimal operator/(const Decimal&) const;
+
+    int exponent() const
+    {
+        ASSERT(isFinite());
+        return m_data.exponent();
+    }
+
+    bool isFinite() const { return m_data.isFinite(); }
+    bool isInfinity() const { return m_data.isInfinity(); }
+    bool isNaN() const { return m_data.isNaN(); }
+    bool isNegative() const { return sign() == Negative; }
+    bool isPositive() const { return sign() == Positive; }
+    bool isSpecial() const { return m_data.isSpecial(); }
+    bool isZero() const { return m_data.isZero(); }
+
+    MFBT_API Decimal abs() const;
+    MFBT_API Decimal ceil() const;
+    MFBT_API Decimal floor() const;
+    MFBT_API Decimal remainder(const Decimal&) const;
+    MFBT_API Decimal round() const;
+
+    MFBT_API double toDouble() const;
+    // Note: toString method supports infinity and nan but fromString not.
+    MFBT_API std::string toString() const;
+    MFBT_API bool toString(char* strBuf, size_t bufLength) const;
+
+    static MFBT_API Decimal fromDouble(double);
+    // fromString supports following syntax EBNF:
+    //  number ::= sign? digit+ ('.' digit*) (exponent-marker sign? digit+)?
+    //          | sign? '.' digit+ (exponent-marker sign? digit+)?
+    //  sign ::= '+' | '-'
+    //  exponent-marker ::= 'e' | 'E'
+    //  digit ::= '0' | '1' | ... | '9'
+    // Note: fromString doesn't support "infinity" and "nan".
+    static MFBT_API Decimal fromString(const std::string& aValue);
+    static MFBT_API Decimal infinity(Sign);
+    static MFBT_API Decimal nan();
+    static MFBT_API Decimal zero(Sign);
+
+    // You should not use below methods. We expose them for unit testing.
+    MFBT_API explicit Decimal(const EncodedData&);
+    const EncodedData& value() const { return m_data; }
+
+private:
+    struct AlignedOperands {
+        uint64_t lhsCoefficient;
+        uint64_t rhsCoefficient;
+        int exponent;
+    };
+
+    MFBT_API explicit Decimal(double);
+    MFBT_API Decimal compareTo(const Decimal&) const;
+
+    static MFBT_API AlignedOperands alignOperands(const Decimal& lhs, const Decimal& rhs);
+    static inline Sign invertSign(Sign sign) { return sign == Negative ? Positive : Negative; }
+
+    Sign sign() const { return m_data.sign(); }
+
+    EncodedData m_data;
+};
+
+} // namespace blink
+
+namespace mozilla {
+typedef blink::Decimal Decimal;
+using blink::operator""_d;
+} // namespace mozilla
+
+#undef USING_FAST_MALLOC
+
+#ifdef DEFINED_ASSERT_FOR_DECIMAL_H
+#undef DEFINED_ASSERT_FOR_DECIMAL_H
+#undef ASSERT
+#endif
+
+#endif // Decimal_h