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Add 128-bit operations to bigint

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This commit is contained in:
Victor Zverovich
2022-04-02 07:40:52 -07:00
parent ef54f9aa38
commit b4dc7a1d34
3 changed files with 113 additions and 83 deletions
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67
include/fmt/format-inl.h
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@@ -368,23 +368,36 @@ class bigint {
if (carry != 0) bigits_.push_back(carry);
}
FMT_CONSTEXPR20 void multiply(uint64_t value) {
const bigit mask = ~bigit(0);
const double_bigit lower = value & mask;
const double_bigit upper = value >> bigit_bits;
double_bigit carry = 0;
template <typename UInt, FMT_ENABLE_IF(std::is_same<UInt, uint64_t>::value ||
std::is_same<UInt, uint128_t>::value)>
FMT_CONSTEXPR20 void multiply(UInt value) {
const UInt lower = static_cast<bigit>(value);
const UInt upper = value >> bigit_bits;
UInt carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
double_bigit result = bigits_[i] * lower + (carry & mask);
UInt result = lower * bigits_[i] + static_cast<bigit>(carry);
carry =
bigits_[i] * upper + (result >> bigit_bits) + (carry >> bigit_bits);
upper * bigits_[i] + (result >> bigit_bits) + (carry >> bigit_bits);
bigits_[i] = static_cast<bigit>(result);
}
while (carry != 0) {
bigits_.push_back(carry & mask);
bigits_.push_back(static_cast<bigit>(carry));
carry >>= bigit_bits;
}
}
template <typename UInt, FMT_ENABLE_IF(std::is_same<UInt, uint64_t>::value ||
std::is_same<UInt, uint128_t>::value)>
FMT_CONSTEXPR20 void assign(UInt n) {
size_t num_bigits = 0;
do {
bigits_[num_bigits++] = static_cast<bigit>(n);
n >>= bigit_bits;
} while (n != 0);
bigits_.resize(num_bigits);
exp_ = 0;
}
public:
FMT_CONSTEXPR20 bigint() : exp_(0) {}
explicit bigint(uint64_t n) { assign(n); }
@@ -400,14 +413,9 @@ class bigint {
exp_ = other.exp_;
}
FMT_CONSTEXPR20 void assign(uint64_t n) {
size_t num_bigits = 0;
do {
bigits_[num_bigits++] = n & ~bigit(0);
n >>= bigit_bits;
} while (n != 0);
bigits_.resize(num_bigits);
exp_ = 0;
template <typename Int> FMT_CONSTEXPR20 void operator=(Int n) {
FMT_ASSERT(n > 0, "");
assign(uint64_or_128_t<Int>(n));
}
FMT_CONSTEXPR20 int num_bigits() const {
@@ -478,14 +486,14 @@ class bigint {
// Assigns pow(10, exp) to this bigint.
FMT_CONSTEXPR20 void assign_pow10(int exp) {
FMT_ASSERT(exp >= 0, "");
if (exp == 0) return assign(1);
if (exp == 0) return *this = 1;
// Find the top bit.
int bitmask = 1;
while (exp >= bitmask) bitmask <<= 1;
bitmask >>= 1;
// pow(10, exp) = pow(5, exp) * pow(2, exp). First compute pow(5, exp) by
// repeated squaring and multiplication.
assign(5);
*this = 5;
bitmask >>= 1;
while (bitmask != 0) {
square();
@@ -2061,12 +2069,12 @@ FMT_CONSTEXPR20 inline void format_dragon(fp value, unsigned flags,
bool is_predecessor_closer = (flags & dragon::predecessor_closer) != 0;
int shift = is_predecessor_closer ? 2 : 1;
if (value.e >= 0) {
numerator.assign(value.f);
numerator = value.f;
numerator <<= value.e + shift;
lower.assign(1);
lower = 1;
lower <<= value.e;
if (is_predecessor_closer) {
upper_store.assign(1);
upper_store = 1;
upper_store <<= value.e + 1;
upper = &upper_store;
}
@@ -2082,16 +2090,16 @@ FMT_CONSTEXPR20 inline void format_dragon(fp value, unsigned flags,
}
numerator *= value.f;
numerator <<= shift;
denominator.assign(1);
denominator = 1;
denominator <<= shift - value.e;
} else {
numerator.assign(value.f);
numerator = value.f;
numerator <<= shift;
denominator.assign_pow10(exp10);
denominator <<= shift - value.e;
lower.assign(1);
lower = 1;
if (is_predecessor_closer) {
upper_store.assign(1ULL << 1);
upper_store = 1ULL << 1;
upper = &upper_store;
}
}
@@ -2278,13 +2286,14 @@ FMT_HEADER_ONLY_CONSTEXPR20 int format_float(Float value, int precision,
} // namespace detail
template <> struct formatter<detail::bigint> {
FMT_CONSTEXPR format_parse_context::iterator parse(
format_parse_context& ctx) {
FMT_CONSTEXPR auto parse(format_parse_context& ctx)
-> format_parse_context::iterator {
return ctx.begin();
}
format_context::iterator format(const detail::bigint& n,
format_context& ctx) {
template <typename FormatContext>
auto format(const detail::bigint& n, FormatContext& ctx) const ->
typename FormatContext::iterator {
auto out = ctx.out();
bool first = true;
for (auto i = n.bigits_.size(); i > 0; --i) {