blame: source/code/Libs/include/cereal/external/rapidjson/internal/biginteger.h

// Tencent is pleased to support the open source community by making RapidJSON available.

// 

// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.

//

// Licensed under the MIT License (the "License"); you may not use this file except

// in compliance with the License. You may obtain a copy of the License at

//

// http://opensource.org/licenses/MIT

//

// Unless required by applicable law or agreed to in writing, software distributed 

// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 

// CONDITIONS OF ANY KIND, either express or implied. See the License for the 

// specific language governing permissions and limitations under the License.

#ifndef CEREAL_RAPIDJSON_BIGINTEGER_H_

#define CEREAL_RAPIDJSON_BIGINTEGER_H_

#include "../rapidjson.h"

#if defined(_MSC_VER) && defined(_M_AMD64)

#include <intrin.h> // for _umul128

#pragma intrinsic(_umul128)

#endif

CEREAL_RAPIDJSON_NAMESPACE_BEGIN

namespace internal {

class BigInteger {

public:

    typedef uint64_t Type;

    BigInteger(const BigInteger& rhs) : count_(rhs.count_) {

        std::memcpy(digits_, rhs.digits_, count_ * sizeof(Type));

    }

    explicit BigInteger(uint64_t u) : count_(1) {

        digits_[0] = u;

    }

    BigInteger(const char* decimals, size_t length) : count_(1) {

        CEREAL_RAPIDJSON_ASSERT(length > 0);

        digits_[0] = 0;

        size_t i = 0;

        const size_t kMaxDigitPerIteration = 19;  // 2^64 = 18446744073709551616 > 10^19

        while (length >= kMaxDigitPerIteration) {

            AppendDecimal64(decimals + i, decimals + i + kMaxDigitPerIteration);

            length -= kMaxDigitPerIteration;

            i += kMaxDigitPerIteration;

        }

        if (length > 0)

            AppendDecimal64(decimals + i, decimals + i + length);

    }

    BigInteger& operator=(const BigInteger &rhs)

    {

        if (this != &rhs) {

            count_ = rhs.count_;

            std::memcpy(digits_, rhs.digits_, count_ * sizeof(Type));

        }

        return *this;

    }

    BigInteger& operator=(uint64_t u) {

        digits_[0] = u;            

        count_ = 1;

        return *this;

    }

    BigInteger& operator+=(uint64_t u) {

        Type backup = digits_[0];

        digits_[0] += u;

        for (size_t i = 0; i < count_ - 1; i++) {

            if (digits_[i] >= backup)

                return *this; // no carry

            backup = digits_[i + 1];

            digits_[i + 1] += 1;

        }

        // Last carry

        if (digits_[count_ - 1] < backup)

            PushBack(1);

        return *this;

    }

    BigInteger& operator*=(uint64_t u) {

        if (u == 0) return *this = 0;

        if (u == 1) return *this;

        if (*this == 1) return *this = u;

        uint64_t k = 0;

        for (size_t i = 0; i < count_; i++) {

            uint64_t hi;

            digits_[i] = MulAdd64(digits_[i], u, k, &hi);

            k = hi;

        }

        if (k > 0)

            PushBack(k);

        return *this;

    }

    BigInteger& operator*=(uint32_t u) {

        if (u == 0) return *this = 0;

        if (u == 1) return *this;

        if (*this == 1) return *this = u;

        uint64_t k = 0;

        for (size_t i = 0; i < count_; i++) {

            const uint64_t c = digits_[i] >> 32;

            const uint64_t d = digits_[i] & 0xFFFFFFFF;

            const uint64_t uc = u * c;

            const uint64_t ud = u * d;

            const uint64_t p0 = ud + k;

            const uint64_t p1 = uc + (p0 >> 32);

            digits_[i] = (p0 & 0xFFFFFFFF) | (p1 << 32);

            k = p1 >> 32;

        }

        if (k > 0)

            PushBack(k);

        return *this;

    }

    BigInteger& operator<<=(size_t shift) {

        if (IsZero() || shift == 0) return *this;

        size_t offset = shift / kTypeBit;

        size_t interShift = shift % kTypeBit;

        CEREAL_RAPIDJSON_ASSERT(count_ + offset <= kCapacity);

        if (interShift == 0) {

            std::memmove(&digits_[count_ - 1 + offset], &digits_[count_ - 1], count_ * sizeof(Type));

            count_ += offset;

        }

        else {

            digits_[count_] = 0;

            for (size_t i = count_; i > 0; i--)

                digits_[i + offset] = (digits_[i] << interShift) | (digits_[i - 1] >> (kTypeBit - interShift));

            digits_[offset] = digits_[0] << interShift;

            count_ += offset;

            if (digits_[count_])

                count_++;

        }

        std::memset(digits_, 0, offset * sizeof(Type));

        return *this;

    }

    bool operator==(const BigInteger& rhs) const {

        return count_ == rhs.count_ && std::memcmp(digits_, rhs.digits_, count_ * sizeof(Type)) == 0;

    }

    bool operator==(const Type rhs) const {

        return count_ == 1 && digits_[0] == rhs;

    }

    BigInteger& MultiplyPow5(unsigned exp) {

        static const uint32_t kPow5[12] = {

            5,

            5 * 5,

            5 * 5 * 5,

            5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,

            5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5

        };

        if (exp == 0) return *this;

        for (; exp >= 27; exp -= 27) *this *= CEREAL_RAPIDJSON_UINT64_C2(0X6765C793, 0XFA10079D); // 5^27

        for (; exp >= 13; exp -= 13) *this *= static_cast<uint32_t>(1220703125u); // 5^13

        if (exp > 0)                 *this *= kPow5[exp - 1];

        return *this;

    }

    // Compute absolute difference of this and rhs.

    // Assume this != rhs

    bool Difference(const BigInteger& rhs, BigInteger* out) const {

        int cmp = Compare(rhs);

        CEREAL_RAPIDJSON_ASSERT(cmp != 0);

        const BigInteger *a, *b;  // Makes a > b

        bool ret;

        if (cmp < 0) { a = &rhs; b = this; ret = true; }

        else         { a = this; b = &rhs; ret = false; }

        Type borrow = 0;

        for (size_t i = 0; i < a->count_; i++) {

            Type d = a->digits_[i] - borrow;

            if (i < b->count_)

                d -= b->digits_[i];

            borrow = (d > a->digits_[i]) ? 1 : 0;

            out->digits_[i] = d;

            if (d != 0)

                out->count_ = i + 1;

        }

        return ret;

    }

    int Compare(const BigInteger& rhs) const {

        if (count_ != rhs.count_)

            return count_ < rhs.count_ ? -1 : 1;

        for (size_t i = count_; i-- > 0;)

            if (digits_[i] != rhs.digits_[i])

                return digits_[i] < rhs.digits_[i] ? -1 : 1;

        return 0;

    }

    size_t GetCount() const { return count_; }

    Type GetDigit(size_t index) const { CEREAL_RAPIDJSON_ASSERT(index < count_); return digits_[index]; }

    bool IsZero() const { return count_ == 1 && digits_[0] == 0; }

private:

    void AppendDecimal64(const char* begin, const char* end) {

        uint64_t u = ParseUint64(begin, end);

        if (IsZero())

            *this = u;

        else {

            unsigned exp = static_cast<unsigned>(end - begin);

            (MultiplyPow5(exp) <<= exp) += u;   // *this = *this * 10^exp + u

        }

    }

    void PushBack(Type digit) {

        CEREAL_RAPIDJSON_ASSERT(count_ < kCapacity);

        digits_[count_++] = digit;

    }

    static uint64_t ParseUint64(const char* begin, const char* end) {

        uint64_t r = 0;

        for (const char* p = begin; p != end; ++p) {

            CEREAL_RAPIDJSON_ASSERT(*p >= '0' && *p <= '9');

            r = r * 10u + static_cast<unsigned>(*p - '0');

        }

        return r;

    }

    // Assume a * b + k < 2^128

    static uint64_t MulAdd64(uint64_t a, uint64_t b, uint64_t k, uint64_t* outHigh) {

#if defined(_MSC_VER) && defined(_M_AMD64)

        uint64_t low = _umul128(a, b, outHigh) + k;

        if (low < k)

            (*outHigh)++;

        return low;

#elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)

        __extension__ typedef unsigned __int128 uint128;

        uint128 p = static_cast<uint128>(a) * static_cast<uint128>(b);

        p += k;

        *outHigh = static_cast<uint64_t>(p >> 64);

        return static_cast<uint64_t>(p);

#else

        const uint64_t a0 = a & 0xFFFFFFFF, a1 = a >> 32, b0 = b & 0xFFFFFFFF, b1 = b >> 32;

        uint64_t x0 = a0 * b0, x1 = a0 * b1, x2 = a1 * b0, x3 = a1 * b1;

        x1 += (x0 >> 32); // can't give carry

        x1 += x2;

        if (x1 < x2)

            x3 += (static_cast<uint64_t>(1) << 32);

        uint64_t lo = (x1 << 32) + (x0 & 0xFFFFFFFF);

        uint64_t hi = x3 + (x1 >> 32);

        lo += k;

        if (lo < k)

            hi++;

        *outHigh = hi;

        return lo;

#endif

    }

    static const size_t kBitCount = 3328;  // 64bit * 54 > 10^1000

    static const size_t kCapacity = kBitCount / sizeof(Type);

    static const size_t kTypeBit = sizeof(Type) * 8;

    Type digits_[kCapacity];

    size_t count_;

};

} // namespace internal

CEREAL_RAPIDJSON_NAMESPACE_END

#endif // CEREAL_RAPIDJSON_BIGINTEGER_H_