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Diffstat (limited to 'include/rapidjson/internal/biginteger.h')
| -rw-r--r-- | include/rapidjson/internal/biginteger.h | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/include/rapidjson/internal/biginteger.h b/include/rapidjson/internal/biginteger.h new file mode 100644 index 0000000..a31c8a8 --- /dev/null +++ b/include/rapidjson/internal/biginteger.h @@ -0,0 +1,290 @@ +// 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 RAPIDJSON_BIGINTEGER_H_ +#define RAPIDJSON_BIGINTEGER_H_ + +#include "../rapidjson.h" + +#if defined(_MSC_VER) && !__INTEL_COMPILER && defined(_M_AMD64) +#include <intrin.h> // for _umul128 +#pragma intrinsic(_umul128) +#endif + +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) { + 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; + RAPIDJSON_ASSERT(count_ + offset <= kCapacity); + + if (interShift == 0) { + std::memmove(digits_ + offset, digits_, 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 *= 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); + 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 { 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) { + 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) { + 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 +RAPIDJSON_NAMESPACE_END + +#endif // RAPIDJSON_BIGINTEGER_H_ |