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Move format_float to format.h for __float128

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This commit is contained in:
Victor Zverovich
2022-05-29 09:55:42 -07:00
parent 2b9037a190
commit c2fcdc54e2
2 changed files with 819 additions and 823 deletions
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783
include/fmt/format-inl.h
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@ -128,567 +128,16 @@ FMT_FUNC std::system_error vsystem_error(int error_code, string_view format_str,
namespace detail { namespace detail {
template <typename T = void> struct basic_impl_data {
// Normalized 64-bit significands of pow(10, k), for k = -348, -340, ..., 340.
// These are generated by support/compute-powers.py.
static constexpr uint64_t pow10_significands[87] = {
0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76, 0x8b16fb203055ac76,
0xcf42894a5dce35ea, 0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f, 0xbe5691ef416bd60c,
0x8dd01fad907ffc3c, 0xd3515c2831559a83, 0x9d71ac8fada6c9b5,
0xea9c227723ee8bcb, 0xaecc49914078536d, 0x823c12795db6ce57,
0xc21094364dfb5637, 0x9096ea6f3848984f, 0xd77485cb25823ac7,
0xa086cfcd97bf97f4, 0xef340a98172aace5, 0xb23867fb2a35b28e,
0x84c8d4dfd2c63f3b, 0xc5dd44271ad3cdba, 0x936b9fcebb25c996,
0xdbac6c247d62a584, 0xa3ab66580d5fdaf6, 0xf3e2f893dec3f126,
0xb5b5ada8aaff80b8, 0x87625f056c7c4a8b, 0xc9bcff6034c13053,
0x964e858c91ba2655, 0xdff9772470297ebd, 0xa6dfbd9fb8e5b88f,
0xf8a95fcf88747d94, 0xb94470938fa89bcf, 0x8a08f0f8bf0f156b,
0xcdb02555653131b6, 0x993fe2c6d07b7fac, 0xe45c10c42a2b3b06,
0xaa242499697392d3, 0xfd87b5f28300ca0e, 0xbce5086492111aeb,
0x8cbccc096f5088cc, 0xd1b71758e219652c, 0x9c40000000000000,
0xe8d4a51000000000, 0xad78ebc5ac620000, 0x813f3978f8940984,
0xc097ce7bc90715b3, 0x8f7e32ce7bea5c70, 0xd5d238a4abe98068,
0x9f4f2726179a2245, 0xed63a231d4c4fb27, 0xb0de65388cc8ada8,
0x83c7088e1aab65db, 0xc45d1df942711d9a, 0x924d692ca61be758,
0xda01ee641a708dea, 0xa26da3999aef774a, 0xf209787bb47d6b85,
0xb454e4a179dd1877, 0x865b86925b9bc5c2, 0xc83553c5c8965d3d,
0x952ab45cfa97a0b3, 0xde469fbd99a05fe3, 0xa59bc234db398c25,
0xf6c69a72a3989f5c, 0xb7dcbf5354e9bece, 0x88fcf317f22241e2,
0xcc20ce9bd35c78a5, 0x98165af37b2153df, 0xe2a0b5dc971f303a,
0xa8d9d1535ce3b396, 0xfb9b7cd9a4a7443c, 0xbb764c4ca7a44410,
0x8bab8eefb6409c1a, 0xd01fef10a657842c, 0x9b10a4e5e9913129,
0xe7109bfba19c0c9d, 0xac2820d9623bf429, 0x80444b5e7aa7cf85,
0xbf21e44003acdd2d, 0x8e679c2f5e44ff8f, 0xd433179d9c8cb841,
0x9e19db92b4e31ba9, 0xeb96bf6ebadf77d9, 0xaf87023b9bf0ee6b,
};
#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wnarrowing"
#endif
// Binary exponents of pow(10, k), for k = -348, -340, ..., 340, corresponding
// to significands above.
static constexpr int16_t pow10_exponents[87] = {
-1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980, -954,
-927, -901, -874, -847, -821, -794, -768, -741, -715, -688, -661,
-635, -608, -582, -555, -529, -502, -475, -449, -422, -396, -369,
-343, -316, -289, -263, -236, -210, -183, -157, -130, -103, -77,
-50, -24, 3, 30, 56, 83, 109, 136, 162, 189, 216,
242, 269, 295, 322, 348, 375, 402, 428, 455, 481, 508,
534, 561, 588, 614, 641, 667, 694, 720, 747, 774, 800,
827, 853, 880, 907, 933, 960, 986, 1013, 1039, 1066};
#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
# pragma GCC diagnostic pop
#endif
static constexpr uint64_t power_of_10_64[20] = {
1, FMT_POWERS_OF_10(1ULL), FMT_POWERS_OF_10(1000000000ULL),
10000000000000000000ULL};
};
// This is a struct rather than an alias to avoid shadowing warnings in gcc.
struct impl_data : basic_impl_data<> {};
#if __cplusplus < 201703L #if __cplusplus < 201703L
template <typename T> template <typename T> constexpr uint64_t basic_data<T>::pow10_significands[];
constexpr uint64_t basic_impl_data<T>::pow10_significands[]; template <typename T> constexpr int16_t basic_data<T>::pow10_exponents[];
template <typename T> constexpr int16_t basic_impl_data<T>::pow10_exponents[]; template <typename T> constexpr uint64_t basic_data<T>::power_of_10_64[];
template <typename T> constexpr uint64_t basic_impl_data<T>::power_of_10_64[];
#endif #endif
// Normalizes the value converted from double and multiplied by (1 << SHIFT).
template <int SHIFT = 0, typename F>
FMT_CONSTEXPR basic_fp<F> normalize(basic_fp<F> value) {
// Handle subnormals.
const auto implicit_bit = F(1) << num_significand_bits<double>();
const auto shifted_implicit_bit = implicit_bit << SHIFT;
while ((value.f & shifted_implicit_bit) == 0) {
value.f <<= 1;
--value.e;
}
// Subtract 1 to account for hidden bit.
const auto offset = basic_fp<F>::num_significand_bits -
num_significand_bits<double>() - SHIFT - 1;
value.f <<= offset;
value.e -= offset;
return value;
}
template <typename F> inline bool operator==(basic_fp<F> x, basic_fp<F> y) { template <typename F> inline bool operator==(basic_fp<F> x, basic_fp<F> y) {
return x.f == y.f && x.e == y.e; return x.f == y.f && x.e == y.e;
} }
// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
FMT_CONSTEXPR inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
#if FMT_USE_INT128
auto product = static_cast<__uint128_t>(lhs) * rhs;
auto f = static_cast<uint64_t>(product >> 64);
return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
#else
// Multiply 32-bit parts of significands.
uint64_t mask = (1ULL << 32) - 1;
uint64_t a = lhs >> 32, b = lhs & mask;
uint64_t c = rhs >> 32, d = rhs & mask;
uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
// Compute mid 64-bit of result and round.
uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
#endif
}
using fp = basic_fp<unsigned long long>;
FMT_CONSTEXPR inline fp operator*(fp x, fp y) {
return {multiply(x.f, y.f), x.e + y.e + 64};
}
// Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
// (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
FMT_CONSTEXPR inline fp get_cached_power(int min_exponent,
int& pow10_exponent) {
const int shift = 32;
// log10(2) = 0x0.4d104d427de7fbcc...
const int64_t significand = 0x4d104d427de7fbcc;
int index = static_cast<int>(
((min_exponent + fp::num_significand_bits - 1) * (significand >> shift) +
((int64_t(1) << shift) - 1)) // ceil
>> 32 // arithmetic shift
);
// Decimal exponent of the first (smallest) cached power of 10.
const int first_dec_exp = -348;
// Difference between 2 consecutive decimal exponents in cached powers of 10.
const int dec_exp_step = 8;
index = (index - first_dec_exp - 1) / dec_exp_step + 1;
pow10_exponent = first_dec_exp + index * dec_exp_step;
return {impl_data::pow10_significands[index],
impl_data::pow10_exponents[index]};
}
class bigint {
private:
// A bigint is stored as an array of bigits (big digits), with bigit at index
// 0 being the least significant one.
using bigit = uint32_t;
using double_bigit = uint64_t;
enum { bigits_capacity = 32 };
basic_memory_buffer<bigit, bigits_capacity> bigits_;
int exp_;
FMT_CONSTEXPR20 bigit operator[](int index) const {
return bigits_[to_unsigned(index)];
}
FMT_CONSTEXPR20 bigit& operator[](int index) {
return bigits_[to_unsigned(index)];
}
static FMT_CONSTEXPR_DECL const int bigit_bits = num_bits<bigit>();
friend struct formatter<bigint>;
FMT_CONSTEXPR20 void subtract_bigits(int index, bigit other, bigit& borrow) {
auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
(*this)[index] = static_cast<bigit>(result);
borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
}
FMT_CONSTEXPR20 void remove_leading_zeros() {
int num_bigits = static_cast<int>(bigits_.size()) - 1;
while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
bigits_.resize(to_unsigned(num_bigits + 1));
}
// Computes *this -= other assuming aligned bigints and *this >= other.
FMT_CONSTEXPR20 void subtract_aligned(const bigint& other) {
FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
FMT_ASSERT(compare(*this, other) >= 0, "");
bigit borrow = 0;
int i = other.exp_ - exp_;
for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j)
subtract_bigits(i, other.bigits_[j], borrow);
while (borrow > 0) subtract_bigits(i, 0, borrow);
remove_leading_zeros();
}
FMT_CONSTEXPR20 void multiply(uint32_t value) {
const double_bigit wide_value = value;
bigit carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
double_bigit result = bigits_[i] * wide_value + carry;
bigits_[i] = static_cast<bigit>(result);
carry = static_cast<bigit>(result >> bigit_bits);
}
if (carry != 0) bigits_.push_back(carry);
}
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) {
using half_uint =
conditional_t<std::is_same<UInt, uint128_t>::value, uint64_t, uint32_t>;
const int shift = num_bits<half_uint>() - bigit_bits;
const UInt lower = static_cast<half_uint>(value);
const UInt upper = value >> num_bits<half_uint>();
UInt carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
UInt result = lower * bigits_[i] + static_cast<bigit>(carry);
carry = (upper * bigits_[i] << shift) + (result >> bigit_bits) +
(carry >> bigit_bits);
bigits_[i] = static_cast<bigit>(result);
}
while (carry != 0) {
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); }
bigint(const bigint&) = delete;
void operator=(const bigint&) = delete;
FMT_CONSTEXPR20 void assign(const bigint& other) {
auto size = other.bigits_.size();
bigits_.resize(size);
auto data = other.bigits_.data();
std::copy(data, data + size, make_checked(bigits_.data(), size));
exp_ = other.exp_;
}
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 {
return static_cast<int>(bigits_.size()) + exp_;
}
FMT_NOINLINE FMT_CONSTEXPR20 bigint& operator<<=(int shift) {
FMT_ASSERT(shift >= 0, "");
exp_ += shift / bigit_bits;
shift %= bigit_bits;
if (shift == 0) return *this;
bigit carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
bigit c = bigits_[i] >> (bigit_bits - shift);
bigits_[i] = (bigits_[i] << shift) + carry;
carry = c;
}
if (carry != 0) bigits_.push_back(carry);
return *this;
}
template <typename Int> FMT_CONSTEXPR20 bigint& operator*=(Int value) {
FMT_ASSERT(value > 0, "");
multiply(uint32_or_64_or_128_t<Int>(value));
return *this;
}
friend FMT_CONSTEXPR20 int compare(const bigint& lhs, const bigint& rhs) {
int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
if (num_lhs_bigits != num_rhs_bigits)
return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
int i = static_cast<int>(lhs.bigits_.size()) - 1;
int j = static_cast<int>(rhs.bigits_.size()) - 1;
int end = i - j;
if (end < 0) end = 0;
for (; i >= end; --i, --j) {
bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
}
if (i != j) return i > j ? 1 : -1;
return 0;
}
// Returns compare(lhs1 + lhs2, rhs).
friend FMT_CONSTEXPR20 int add_compare(const bigint& lhs1, const bigint& lhs2,
const bigint& rhs) {
int max_lhs_bigits = (std::max)(lhs1.num_bigits(), lhs2.num_bigits());
int num_rhs_bigits = rhs.num_bigits();
if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
if (max_lhs_bigits > num_rhs_bigits) return 1;
auto get_bigit = [](const bigint& n, int i) -> bigit {
return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
};
double_bigit borrow = 0;
int min_exp = (std::min)((std::min)(lhs1.exp_, lhs2.exp_), rhs.exp_);
for (int i = num_rhs_bigits - 1; i >= min_exp; --i) {
double_bigit sum =
static_cast<double_bigit>(get_bigit(lhs1, i)) + get_bigit(lhs2, i);
bigit rhs_bigit = get_bigit(rhs, i);
if (sum > rhs_bigit + borrow) return 1;
borrow = rhs_bigit + borrow - sum;
if (borrow > 1) return -1;
borrow <<= bigit_bits;
}
return borrow != 0 ? -1 : 0;
}
// Assigns pow(10, exp) to this bigint.
FMT_CONSTEXPR20 void assign_pow10(int exp) {
FMT_ASSERT(exp >= 0, "");
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.
*this = 5;
bitmask >>= 1;
while (bitmask != 0) {
square();
if ((exp & bitmask) != 0) *this *= 5;
bitmask >>= 1;
}
*this <<= exp; // Multiply by pow(2, exp) by shifting.
}
FMT_CONSTEXPR20 void square() {
int num_bigits = static_cast<int>(bigits_.size());
int num_result_bigits = 2 * num_bigits;
basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
bigits_.resize(to_unsigned(num_result_bigits));
auto sum = uint128_t();
for (int bigit_index = 0; bigit_index < num_bigits; ++bigit_index) {
// Compute bigit at position bigit_index of the result by adding
// cross-product terms n[i] * n[j] such that i + j == bigit_index.
for (int i = 0, j = bigit_index; j >= 0; ++i, --j) {
// Most terms are multiplied twice which can be optimized in the future.
sum += static_cast<double_bigit>(n[i]) * n[j];
}
(*this)[bigit_index] = static_cast<bigit>(sum);
sum >>= num_bits<bigit>(); // Compute the carry.
}
// Do the same for the top half.
for (int bigit_index = num_bigits; bigit_index < num_result_bigits;
++bigit_index) {
for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
sum += static_cast<double_bigit>(n[i++]) * n[j--];
(*this)[bigit_index] = static_cast<bigit>(sum);
sum >>= num_bits<bigit>();
}
remove_leading_zeros();
exp_ *= 2;
}
// If this bigint has a bigger exponent than other, adds trailing zero to make
// exponents equal. This simplifies some operations such as subtraction.
FMT_CONSTEXPR20 void align(const bigint& other) {
int exp_difference = exp_ - other.exp_;
if (exp_difference <= 0) return;
int num_bigits = static_cast<int>(bigits_.size());
bigits_.resize(to_unsigned(num_bigits + exp_difference));
for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
bigits_[j] = bigits_[i];
std::uninitialized_fill_n(bigits_.data(), exp_difference, 0);
exp_ -= exp_difference;
}
// Divides this bignum by divisor, assigning the remainder to this and
// returning the quotient.
FMT_CONSTEXPR20 int divmod_assign(const bigint& divisor) {
FMT_ASSERT(this != &divisor, "");
if (compare(*this, divisor) < 0) return 0;
FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
align(divisor);
int quotient = 0;
do {
subtract_aligned(divisor);
++quotient;
} while (compare(*this, divisor) >= 0);
return quotient;
}
};
enum class round_direction { unknown, up, down };
// Given the divisor (normally a power of 10), the remainder = v % divisor for
// some number v and the error, returns whether v should be rounded up, down, or
// whether the rounding direction can't be determined due to error.
// error should be less than divisor / 2.
FMT_CONSTEXPR inline round_direction get_round_direction(uint64_t divisor,
uint64_t remainder,
uint64_t error) {
FMT_ASSERT(remainder < divisor, ""); // divisor - remainder won't overflow.
FMT_ASSERT(error < divisor, ""); // divisor - error won't overflow.
FMT_ASSERT(error < divisor - error, ""); // error * 2 won't overflow.
// Round down if (remainder + error) * 2 <= divisor.
if (remainder <= divisor - remainder && error * 2 <= divisor - remainder * 2)
return round_direction::down;
// Round up if (remainder - error) * 2 >= divisor.
if (remainder >= error &&
remainder - error >= divisor - (remainder - error)) {
return round_direction::up;
}
return round_direction::unknown;
}
namespace digits {
enum result {
more, // Generate more digits.
done, // Done generating digits.
error // Digit generation cancelled due to an error.
};
}
struct gen_digits_handler {
char* buf;
int size;
int precision;
int exp10;
bool fixed;
FMT_CONSTEXPR digits::result on_digit(char digit, uint64_t divisor,
uint64_t remainder, uint64_t error,
bool integral) {
FMT_ASSERT(remainder < divisor, "");
buf[size++] = digit;
if (!integral && error >= remainder) return digits::error;
if (size < precision) return digits::more;
if (!integral) {
// Check if error * 2 < divisor with overflow prevention.
// The check is not needed for the integral part because error = 1
// and divisor > (1 << 32) there.
if (error >= divisor || error >= divisor - error) return digits::error;
} else {
FMT_ASSERT(error == 1 && divisor > 2, "");
}
auto dir = get_round_direction(divisor, remainder, error);
if (dir != round_direction::up)
return dir == round_direction::down ? digits::done : digits::error;
++buf[size - 1];
for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
buf[i] = '0';
++buf[i - 1];
}
if (buf[0] > '9') {
buf[0] = '1';
if (fixed)
buf[size++] = '0';
else
++exp10;
}
return digits::done;
}
};
inline FMT_CONSTEXPR20 void adjust_precision(int& precision, int exp10) {
// Adjust fixed precision by exponent because it is relative to decimal
// point.
if (exp10 > 0 && precision > max_value<int>() - exp10)
FMT_THROW(format_error("number is too big"));
precision += exp10;
}
// Generates output using the Grisu digit-gen algorithm.
// error: the size of the region (lower, upper) outside of which numbers
// definitely do not round to value (Delta in Grisu3).
FMT_INLINE FMT_CONSTEXPR20 digits::result grisu_gen_digits(
fp value, uint64_t error, int& exp, gen_digits_handler& handler) {
const fp one(1ULL << -value.e, value.e);
// The integral part of scaled value (p1 in Grisu) = value / one. It cannot be
// zero because it contains a product of two 64-bit numbers with MSB set (due
// to normalization) - 1, shifted right by at most 60 bits.
auto integral = static_cast<uint32_t>(value.f >> -one.e);
FMT_ASSERT(integral != 0, "");
FMT_ASSERT(integral == value.f >> -one.e, "");
// The fractional part of scaled value (p2 in Grisu) c = value % one.
uint64_t fractional = value.f & (one.f - 1);
exp = count_digits(integral); // kappa in Grisu.
// Non-fixed formats require at least one digit and no precision adjustment.
if (handler.fixed) {
adjust_precision(handler.precision, exp + handler.exp10);
// Check if precision is satisfied just by leading zeros, e.g.
// format("{:.2f}", 0.001) gives "0.00" without generating any digits.
if (handler.precision <= 0) {
if (handler.precision < 0) return digits::done;
// Divide by 10 to prevent overflow.
uint64_t divisor = impl_data::power_of_10_64[exp - 1] << -one.e;
auto dir = get_round_direction(divisor, value.f / 10, error * 10);
if (dir == round_direction::unknown) return digits::error;
handler.buf[handler.size++] = dir == round_direction::up ? '1' : '0';
return digits::done;
}
}
// Generate digits for the integral part. This can produce up to 10 digits.
do {
uint32_t digit = 0;
auto divmod_integral = [&](uint32_t divisor) {
digit = integral / divisor;
integral %= divisor;
};
// This optimization by Milo Yip reduces the number of integer divisions by
// one per iteration.
switch (exp) {
case 10:
divmod_integral(1000000000);
break;
case 9:
divmod_integral(100000000);
break;
case 8:
divmod_integral(10000000);
break;
case 7:
divmod_integral(1000000);
break;
case 6:
divmod_integral(100000);
break;
case 5:
divmod_integral(10000);
break;
case 4:
divmod_integral(1000);
break;
case 3:
divmod_integral(100);
break;
case 2:
divmod_integral(10);
break;
case 1:
digit = integral;
integral = 0;
break;
default:
FMT_ASSERT(false, "invalid number of digits");
}
--exp;
auto remainder = (static_cast<uint64_t>(integral) << -one.e) + fractional;
auto result = handler.on_digit(static_cast<char>('0' + digit),
impl_data::power_of_10_64[exp] << -one.e,
remainder, error, true);
if (result != digits::more) return result;
} while (exp > 0);
// Generate digits for the fractional part.
for (;;) {
fractional *= 10;
error *= 10;
char digit = static_cast<char>('0' + (fractional >> -one.e));
fractional &= one.f - 1;
--exp;
auto result = handler.on_digit(digit, one.f, fractional, error, false);
if (result != digits::more) return result;
}
}
inline FMT_CONSTEXPR20 uint128_fallback& uint128_fallback::operator+=( inline FMT_CONSTEXPR20 uint128_fallback& uint128_fallback::operator+=(
uint64_t n) noexcept { uint64_t n) noexcept {
if (is_constant_evaluated()) { if (is_constant_evaluated()) {
@ -1992,143 +1441,6 @@ small_divisor_case_label:
} }
} // namespace dragonbox } // namespace dragonbox
// format_dragon flags.
enum dragon {
predecessor_closer = 1,
fixup = 2, // Run fixup to correct exp10 which can be off by one.
fixed = 4,
};
// Formats a floating-point number using a variation of the Fixed-Precision
// Positive Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
// https://fmt.dev/papers/p372-steele.pdf.
FMT_CONSTEXPR20 inline void format_dragon(basic_fp<uint128_t> value,
unsigned flags, int num_digits,
buffer<char>& buf, int& exp10) {
bigint numerator; // 2 * R in (FPP)^2.
bigint denominator; // 2 * S in (FPP)^2.
// lower and upper are differences between value and corresponding boundaries.
bigint lower; // (M^- in (FPP)^2).
bigint upper_store; // upper's value if different from lower.
bigint* upper = nullptr; // (M^+ in (FPP)^2).
// Shift numerator and denominator by an extra bit or two (if lower boundary
// is closer) to make lower and upper integers. This eliminates multiplication
// by 2 during later computations.
bool is_predecessor_closer = (flags & dragon::predecessor_closer) != 0;
int shift = is_predecessor_closer ? 2 : 1;
if (value.e >= 0) {
numerator = value.f;
numerator <<= value.e + shift;
lower = 1;
lower <<= value.e;
if (is_predecessor_closer) {
upper_store = 1;
upper_store <<= value.e + 1;
upper = &upper_store;
}
denominator.assign_pow10(exp10);
denominator <<= shift;
} else if (exp10 < 0) {
numerator.assign_pow10(-exp10);
lower.assign(numerator);
if (is_predecessor_closer) {
upper_store.assign(numerator);
upper_store <<= 1;
upper = &upper_store;
}
numerator *= value.f;
numerator <<= shift;
denominator = 1;
denominator <<= shift - value.e;
} else {
numerator = value.f;
numerator <<= shift;
denominator.assign_pow10(exp10);
denominator <<= shift - value.e;
lower = 1;
if (is_predecessor_closer) {
upper_store = 1ULL << 1;
upper = &upper_store;
}
}
bool even = (value.f & 1) == 0;
if (!upper) upper = &lower;
if ((flags & dragon::fixup) != 0) {
if (add_compare(numerator, *upper, denominator) + even <= 0) {
--exp10;
numerator *= 10;
if (num_digits < 0) {
lower *= 10;
if (upper != &lower) *upper *= 10;
}
}
if ((flags & dragon::fixed) != 0) adjust_precision(num_digits, exp10 + 1);
}
// Invariant: value == (numerator / denominator) * pow(10, exp10).
if (num_digits < 0) {
// Generate the shortest representation.
num_digits = 0;
char* data = buf.data();
for (;;) {
int digit = numerator.divmod_assign(denominator);
bool low = compare(numerator, lower) - even < 0; // numerator <[=] lower.
// numerator + upper >[=] pow10:
bool high = add_compare(numerator, *upper, denominator) + even > 0;
data[num_digits++] = static_cast<char>('0' + digit);
if (low || high) {
if (!low) {
++data[num_digits - 1];
} else if (high) {
int result = add_compare(numerator, numerator, denominator);
// Round half to even.
if (result > 0 || (result == 0 && (digit % 2) != 0))
++data[num_digits - 1];
}
buf.try_resize(to_unsigned(num_digits));
exp10 -= num_digits - 1;
return;
}
numerator *= 10;
lower *= 10;
if (upper != &lower) *upper *= 10;
}
}
// Generate the given number of digits.
exp10 -= num_digits - 1;
if (num_digits == 0) {
denominator *= 10;
auto digit = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
buf.push_back(digit);
return;
}
buf.try_resize(to_unsigned(num_digits));
for (int i = 0; i < num_digits - 1; ++i) {
int digit = numerator.divmod_assign(denominator);
buf[i] = static_cast<char>('0' + digit);
numerator *= 10;
}
int digit = numerator.divmod_assign(denominator);
auto result = add_compare(numerator, numerator, denominator);
if (result > 0 || (result == 0 && (digit % 2) != 0)) {
if (digit == 9) {
const auto overflow = '0' + 10;
buf[num_digits - 1] = overflow;
// Propagate the carry.
for (int i = num_digits - 1; i > 0 && buf[i] == overflow; --i) {
buf[i] = '0';
++buf[i - 1];
}
if (buf[0] == overflow) {
buf[0] = '1';
++exp10;
}
return;
}
++digit;
}
buf[num_digits - 1] = static_cast<char>('0' + digit);
}
#ifdef _MSC_VER #ifdef _MSC_VER
FMT_FUNC auto fmt_snprintf(char* buf, size_t size, const char* fmt, ...) FMT_FUNC auto fmt_snprintf(char* buf, size_t size, const char* fmt, ...)
-> int { -> int {
@ -2139,95 +1451,6 @@ FMT_FUNC auto fmt_snprintf(char* buf, size_t size, const char* fmt, ...)
return result; return result;
} }
#endif #endif
template <typename Float>
FMT_HEADER_ONLY_CONSTEXPR20 int format_float(Float value, int precision,
float_specs specs,
buffer<char>& buf) {
// float is passed as double to reduce the number of instantiations.
static_assert(!std::is_same<Float, float>::value, "");
FMT_ASSERT(value >= 0, "value is negative");
auto converted_value = convert_float(value);
const bool fixed = specs.format == float_format::fixed;
if (value <= 0) { // <= instead of == to silence a warning.
if (precision <= 0 || !fixed) {
buf.push_back('0');
return 0;
}
buf.try_resize(to_unsigned(precision));
fill_n(buf.data(), precision, '0');
return -precision;
}
int exp = 0;
bool use_dragon = true;
unsigned dragon_flags = 0;
if (!is_fast_float<Float>()) {
const auto inv_log2_10 = 0.3010299956639812; // 1 / log2(10)
using info = dragonbox::float_info<decltype(converted_value)>;
const auto f = basic_fp<typename info::carrier_uint>(converted_value);
// Compute exp, an approximate power of 10, such that
// 10^(exp - 1) <= value < 10^exp or 10^exp <= value < 10^(exp + 1).
// This is based on log10(value) == log2(value) / log2(10) and approximation
// of log2(value) by e + num_fraction_bits idea from double-conversion.
exp = static_cast<int>(
std::ceil((f.e + count_digits<1>(f.f) - 1) * inv_log2_10 - 1e-10));
dragon_flags = dragon::fixup;
} else if (!is_constant_evaluated() && precision < 0) {
// Use Dragonbox for the shortest format.
if (specs.binary32) {
auto dec = dragonbox::to_decimal(static_cast<float>(value));
write<char>(buffer_appender<char>(buf), dec.significand);
return dec.exponent;
}
auto dec = dragonbox::to_decimal(static_cast<double>(value));
write<char>(buffer_appender<char>(buf), dec.significand);
return dec.exponent;
} else {
// Use Grisu + Dragon4 for the given precision:
// https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf.
const int min_exp = -60; // alpha in Grisu.
int cached_exp10 = 0; // K in Grisu.
fp normalized = normalize(fp(converted_value));
const auto cached_pow = get_cached_power(
min_exp - (normalized.e + fp::num_significand_bits), cached_exp10);
normalized = normalized * cached_pow;
gen_digits_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
if (grisu_gen_digits(normalized, 1, exp, handler) != digits::error &&
!is_constant_evaluated()) {
exp += handler.exp10;
buf.try_resize(to_unsigned(handler.size));
use_dragon = false;
} else {
exp += handler.size - cached_exp10 - 1;
precision = handler.precision;
}
}
if (use_dragon) {
auto f = basic_fp<uint128_t>();
bool is_predecessor_closer = specs.binary32
? f.assign(static_cast<float>(value))
: f.assign(converted_value);
if (is_predecessor_closer) dragon_flags |= dragon::predecessor_closer;
if (fixed) dragon_flags |= dragon::fixed;
// Limit precision to the maximum possible number of significant digits in
// an IEEE754 double because we don't need to generate zeros.
const int max_double_digits = 767;
if (precision > max_double_digits) precision = max_double_digits;
format_dragon(f, dragon_flags, precision, buf, exp);
}
if (!fixed && !specs.showpoint) {
// Remove trailing zeros.
auto num_digits = buf.size();
while (num_digits > 0 && buf[num_digits - 1] == '0') {
--num_digits;
++exp;
}
buf.try_resize(num_digits);
}
return exp;
}
} // namespace detail } // namespace detail
template <> struct formatter<detail::bigint> { template <> struct formatter<detail::bigint> {

859
include/fmt/format.h
View File

@ -1410,10 +1410,130 @@ template <typename F> struct basic_fp {
} }
}; };
template <typename T> using fp = basic_fp<unsigned long long>;
FMT_HEADER_ONLY_CONSTEXPR20 auto format_float(T value, int precision,
float_specs specs, // Normalizes the value converted from double and multiplied by (1 << SHIFT).
buffer<char>& buf) -> int; template <int SHIFT = 0, typename F>
FMT_CONSTEXPR basic_fp<F> normalize(basic_fp<F> value) {
// Handle subnormals.
const auto implicit_bit = F(1) << num_significand_bits<double>();
const auto shifted_implicit_bit = implicit_bit << SHIFT;
while ((value.f & shifted_implicit_bit) == 0) {
value.f <<= 1;
--value.e;
}
// Subtract 1 to account for hidden bit.
const auto offset = basic_fp<F>::num_significand_bits -
num_significand_bits<double>() - SHIFT - 1;
value.f <<= offset;
value.e -= offset;
return value;
}
// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
FMT_CONSTEXPR inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
#if FMT_USE_INT128
auto product = static_cast<__uint128_t>(lhs) * rhs;
auto f = static_cast<uint64_t>(product >> 64);
return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
#else
// Multiply 32-bit parts of significands.
uint64_t mask = (1ULL << 32) - 1;
uint64_t a = lhs >> 32, b = lhs & mask;
uint64_t c = rhs >> 32, d = rhs & mask;
uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
// Compute mid 64-bit of result and round.
uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
#endif
}
FMT_CONSTEXPR inline fp operator*(fp x, fp y) {
return {multiply(x.f, y.f), x.e + y.e + 64};
}
template <typename T = void> struct basic_data {
// Normalized 64-bit significands of pow(10, k), for k = -348, -340, ..., 340.
// These are generated by support/compute-powers.py.
static constexpr uint64_t pow10_significands[87] = {
0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76, 0x8b16fb203055ac76,
0xcf42894a5dce35ea, 0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f, 0xbe5691ef416bd60c,
0x8dd01fad907ffc3c, 0xd3515c2831559a83, 0x9d71ac8fada6c9b5,
0xea9c227723ee8bcb, 0xaecc49914078536d, 0x823c12795db6ce57,
0xc21094364dfb5637, 0x9096ea6f3848984f, 0xd77485cb25823ac7,
0xa086cfcd97bf97f4, 0xef340a98172aace5, 0xb23867fb2a35b28e,
0x84c8d4dfd2c63f3b, 0xc5dd44271ad3cdba, 0x936b9fcebb25c996,
0xdbac6c247d62a584, 0xa3ab66580d5fdaf6, 0xf3e2f893dec3f126,
0xb5b5ada8aaff80b8, 0x87625f056c7c4a8b, 0xc9bcff6034c13053,
0x964e858c91ba2655, 0xdff9772470297ebd, 0xa6dfbd9fb8e5b88f,
0xf8a95fcf88747d94, 0xb94470938fa89bcf, 0x8a08f0f8bf0f156b,
0xcdb02555653131b6, 0x993fe2c6d07b7fac, 0xe45c10c42a2b3b06,
0xaa242499697392d3, 0xfd87b5f28300ca0e, 0xbce5086492111aeb,
0x8cbccc096f5088cc, 0xd1b71758e219652c, 0x9c40000000000000,
0xe8d4a51000000000, 0xad78ebc5ac620000, 0x813f3978f8940984,
0xc097ce7bc90715b3, 0x8f7e32ce7bea5c70, 0xd5d238a4abe98068,
0x9f4f2726179a2245, 0xed63a231d4c4fb27, 0xb0de65388cc8ada8,
0x83c7088e1aab65db, 0xc45d1df942711d9a, 0x924d692ca61be758,
0xda01ee641a708dea, 0xa26da3999aef774a, 0xf209787bb47d6b85,
0xb454e4a179dd1877, 0x865b86925b9bc5c2, 0xc83553c5c8965d3d,
0x952ab45cfa97a0b3, 0xde469fbd99a05fe3, 0xa59bc234db398c25,
0xf6c69a72a3989f5c, 0xb7dcbf5354e9bece, 0x88fcf317f22241e2,
0xcc20ce9bd35c78a5, 0x98165af37b2153df, 0xe2a0b5dc971f303a,
0xa8d9d1535ce3b396, 0xfb9b7cd9a4a7443c, 0xbb764c4ca7a44410,
0x8bab8eefb6409c1a, 0xd01fef10a657842c, 0x9b10a4e5e9913129,
0xe7109bfba19c0c9d, 0xac2820d9623bf429, 0x80444b5e7aa7cf85,
0xbf21e44003acdd2d, 0x8e679c2f5e44ff8f, 0xd433179d9c8cb841,
0x9e19db92b4e31ba9, 0xeb96bf6ebadf77d9, 0xaf87023b9bf0ee6b,
};
#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wnarrowing"
#endif
// Binary exponents of pow(10, k), for k = -348, -340, ..., 340, corresponding
// to significands above.
static constexpr int16_t pow10_exponents[87] = {
-1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980, -954,
-927, -901, -874, -847, -821, -794, -768, -741, -715, -688, -661,
-635, -608, -582, -555, -529, -502, -475, -449, -422, -396, -369,
-343, -316, -289, -263, -236, -210, -183, -157, -130, -103, -77,
-50, -24, 3, 30, 56, 83, 109, 136, 162, 189, 216,
242, 269, 295, 322, 348, 375, 402, 428, 455, 481, 508,
534, 561, 588, 614, 641, 667, 694, 720, 747, 774, 800,
827, 853, 880, 907, 933, 960, 986, 1013, 1039, 1066};
#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
# pragma GCC diagnostic pop
#endif
static constexpr uint64_t power_of_10_64[20] = {
1, FMT_POWERS_OF_10(1ULL), FMT_POWERS_OF_10(1000000000ULL),
10000000000000000000ULL};
};
// This is a struct rather than an alias to avoid shadowing warnings in gcc.
struct data : basic_data<> {};
// Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
// (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
FMT_CONSTEXPR inline fp get_cached_power(int min_exponent,
int& pow10_exponent) {
const int shift = 32;
// log10(2) = 0x0.4d104d427de7fbcc...
const int64_t significand = 0x4d104d427de7fbcc;
int index = static_cast<int>(
((min_exponent + fp::num_significand_bits - 1) * (significand >> shift) +
((int64_t(1) << shift) - 1)) // ceil
>> 32 // arithmetic shift
);
// Decimal exponent of the first (smallest) cached power of 10.
const int first_dec_exp = -348;
// Difference between 2 consecutive decimal exponents in cached powers of 10.
const int dec_exp_step = 8;
index = (index - first_dec_exp - 1) / dec_exp_step + 1;
pow10_exponent = first_dec_exp + index * dec_exp_step;
return {data::pow10_significands[index], data::pow10_exponents[index]};
}
#ifndef _MSC_VER #ifndef _MSC_VER
# define FMT_SNPRINTF snprintf # define FMT_SNPRINTF snprintf
@ -2055,6 +2175,28 @@ FMT_CONSTEXPR auto write(OutputIt out, const Char* s,
: write_ptr<Char>(out, bit_cast<uintptr_t>(s), &specs); : write_ptr<Char>(out, bit_cast<uintptr_t>(s), &specs);
} }
template <typename Char, typename OutputIt, typename T,
FMT_ENABLE_IF(is_integral<T>::value &&
!std::is_same<T, bool>::value &&
!std::is_same<T, Char>::value)>
FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
bool negative = is_negative(value);
// Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
if (negative) abs_value = ~abs_value + 1;
int num_digits = count_digits(abs_value);
auto size = (negative ? 1 : 0) + static_cast<size_t>(num_digits);
auto it = reserve(out, size);
if (auto ptr = to_pointer<Char>(it, size)) {
if (negative) *ptr++ = static_cast<Char>('-');
format_decimal<Char>(ptr, abs_value, num_digits);
return out;
}
if (negative) *it++ = static_cast<Char>('-');
it = format_decimal<Char>(it, abs_value, num_digits).end;
return base_iterator(out, it);
}
template <typename Char, typename OutputIt> template <typename Char, typename OutputIt>
FMT_CONSTEXPR20 auto write_nonfinite(OutputIt out, bool isnan, FMT_CONSTEXPR20 auto write_nonfinite(OutputIt out, bool isnan,
basic_format_specs<Char> specs, basic_format_specs<Char> specs,
@ -2081,12 +2223,12 @@ struct big_decimal_fp {
int exponent; int exponent;
}; };
constexpr auto get_significand_size(const big_decimal_fp& fp) -> int { constexpr auto get_significand_size(const big_decimal_fp& f) -> int {
return fp.significand_size; return f.significand_size;
} }
template <typename T> template <typename T>
inline auto get_significand_size(const dragonbox::decimal_fp<T>& fp) -> int { inline auto get_significand_size(const dragonbox::decimal_fp<T>& f) -> int {
return count_digits(fp.significand); return count_digits(f.significand);
} }
template <typename Char, typename OutputIt> template <typename Char, typename OutputIt>
@ -2180,12 +2322,12 @@ FMT_CONSTEXPR20 auto write_significand(OutputIt out, T significand,
template <typename OutputIt, typename DecimalFP, typename Char, template <typename OutputIt, typename DecimalFP, typename Char,
typename Grouping = digit_grouping<Char>> typename Grouping = digit_grouping<Char>>
FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& fp, FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& f,
const basic_format_specs<Char>& specs, const basic_format_specs<Char>& specs,
float_specs fspecs, locale_ref loc) float_specs fspecs, locale_ref loc)
-> OutputIt { -> OutputIt {
auto significand = fp.significand; auto significand = f.significand;
int significand_size = get_significand_size(fp); int significand_size = get_significand_size(f);
const Char zero = static_cast<Char>('0'); const Char zero = static_cast<Char>('0');
auto sign = fspecs.sign; auto sign = fspecs.sign;
size_t size = to_unsigned(significand_size) + (sign ? 1 : 0); size_t size = to_unsigned(significand_size) + (sign ? 1 : 0);
@ -2194,7 +2336,7 @@ FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& fp,
Char decimal_point = Char decimal_point =
fspecs.locale ? detail::decimal_point<Char>(loc) : static_cast<Char>('.'); fspecs.locale ? detail::decimal_point<Char>(loc) : static_cast<Char>('.');
int output_exp = fp.exponent + significand_size - 1; int output_exp = f.exponent + significand_size - 1;
auto use_exp_format = [=]() { auto use_exp_format = [=]() {
if (fspecs.format == float_format::exp) return true; if (fspecs.format == float_format::exp) return true;
if (fspecs.format != float_format::general) return false; if (fspecs.format != float_format::general) return false;
@ -2232,10 +2374,10 @@ FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& fp,
: base_iterator(out, write(reserve(out, size))); : base_iterator(out, write(reserve(out, size)));
} }
int exp = fp.exponent + significand_size; int exp = f.exponent + significand_size;
if (fp.exponent >= 0) { if (f.exponent >= 0) {
// 1234e5 -> 123400000[.0+] // 1234e5 -> 123400000[.0+]
size += to_unsigned(fp.exponent); size += to_unsigned(f.exponent);
int num_zeros = fspecs.precision - exp; int num_zeros = fspecs.precision - exp;
abort_fuzzing_if(num_zeros > 5000); abort_fuzzing_if(num_zeros > 5000);
if (fspecs.showpoint) { if (fspecs.showpoint) {
@ -2248,7 +2390,7 @@ FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& fp,
return write_padded<align::right>(out, specs, size, [&](iterator it) { return write_padded<align::right>(out, specs, size, [&](iterator it) {
if (sign) *it++ = detail::sign<Char>(sign); if (sign) *it++ = detail::sign<Char>(sign);
it = write_significand<Char>(it, significand, significand_size, it = write_significand<Char>(it, significand, significand_size,
fp.exponent, grouping); f.exponent, grouping);
if (!fspecs.showpoint) return it; if (!fspecs.showpoint) return it;
*it++ = decimal_point; *it++ = decimal_point;
return num_zeros > 0 ? detail::fill_n(it, num_zeros, zero) : it; return num_zeros > 0 ? detail::fill_n(it, num_zeros, zero) : it;
@ -2299,16 +2441,16 @@ template <typename Char> class fallback_digit_grouping {
}; };
template <typename OutputIt, typename DecimalFP, typename Char> template <typename OutputIt, typename DecimalFP, typename Char>
FMT_CONSTEXPR20 auto write_float(OutputIt out, const DecimalFP& fp, FMT_CONSTEXPR20 auto write_float(OutputIt out, const DecimalFP& f,
const basic_format_specs<Char>& specs, const basic_format_specs<Char>& specs,
float_specs fspecs, locale_ref loc) float_specs fspecs, locale_ref loc)
-> OutputIt { -> OutputIt {
if (is_constant_evaluated()) { if (is_constant_evaluated()) {
return do_write_float<OutputIt, DecimalFP, Char, return do_write_float<OutputIt, DecimalFP, Char,
fallback_digit_grouping<Char>>(out, fp, specs, fspecs, fallback_digit_grouping<Char>>(out, f, specs, fspecs,
loc); loc);
} else { } else {
return do_write_float(out, fp, specs, fspecs, loc); return do_write_float(out, f, specs, fspecs, loc);
} }
} }
@ -2351,6 +2493,659 @@ FMT_INLINE FMT_CONSTEXPR bool signbit(T value) {
return std::signbit(static_cast<double>(value)); return std::signbit(static_cast<double>(value));
} }
enum class round_direction { unknown, up, down };
// Given the divisor (normally a power of 10), the remainder = v % divisor for
// some number v and the error, returns whether v should be rounded up, down, or
// whether the rounding direction can't be determined due to error.
// error should be less than divisor / 2.
FMT_CONSTEXPR inline round_direction get_round_direction(uint64_t divisor,
uint64_t remainder,
uint64_t error) {
FMT_ASSERT(remainder < divisor, ""); // divisor - remainder won't overflow.
FMT_ASSERT(error < divisor, ""); // divisor - error won't overflow.
FMT_ASSERT(error < divisor - error, ""); // error * 2 won't overflow.
// Round down if (remainder + error) * 2 <= divisor.
if (remainder <= divisor - remainder && error * 2 <= divisor - remainder * 2)
return round_direction::down;
// Round up if (remainder - error) * 2 >= divisor.
if (remainder >= error &&
remainder - error >= divisor - (remainder - error)) {
return round_direction::up;
}
return round_direction::unknown;
}
namespace digits {
enum result {
more, // Generate more digits.
done, // Done generating digits.
error // Digit generation cancelled due to an error.
};
}
struct gen_digits_handler {
char* buf;
int size;
int precision;
int exp10;
bool fixed;
FMT_CONSTEXPR digits::result on_digit(char digit, uint64_t divisor,
uint64_t remainder, uint64_t error,
bool integral) {
FMT_ASSERT(remainder < divisor, "");
buf[size++] = digit;
if (!integral && error >= remainder) return digits::error;
if (size < precision) return digits::more;
if (!integral) {
// Check if error * 2 < divisor with overflow prevention.
// The check is not needed for the integral part because error = 1
// and divisor > (1 << 32) there.
if (error >= divisor || error >= divisor - error) return digits::error;
} else {
FMT_ASSERT(error == 1 && divisor > 2, "");
}
auto dir = get_round_direction(divisor, remainder, error);
if (dir != round_direction::up)
return dir == round_direction::down ? digits::done : digits::error;
++buf[size - 1];
for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
buf[i] = '0';
++buf[i - 1];
}
if (buf[0] > '9') {
buf[0] = '1';
if (fixed)
buf[size++] = '0';
else
++exp10;
}
return digits::done;
}
};
inline FMT_CONSTEXPR20 void adjust_precision(int& precision, int exp10) {
// Adjust fixed precision by exponent because it is relative to decimal
// point.
if (exp10 > 0 && precision > max_value<int>() - exp10)
FMT_THROW(format_error("number is too big"));
precision += exp10;
}
// Generates output using the Grisu digit-gen algorithm.
// error: the size of the region (lower, upper) outside of which numbers
// definitely do not round to value (Delta in Grisu3).
FMT_INLINE FMT_CONSTEXPR20 auto grisu_gen_digits(fp value, uint64_t error,
int& exp,
gen_digits_handler& handler)
-> digits::result {
const fp one(1ULL << -value.e, value.e);
// The integral part of scaled value (p1 in Grisu) = value / one. It cannot be
// zero because it contains a product of two 64-bit numbers with MSB set (due
// to normalization) - 1, shifted right by at most 60 bits.
auto integral = static_cast<uint32_t>(value.f >> -one.e);
FMT_ASSERT(integral != 0, "");
FMT_ASSERT(integral == value.f >> -one.e, "");
// The fractional part of scaled value (p2 in Grisu) c = value % one.
uint64_t fractional = value.f & (one.f - 1);
exp = count_digits(integral); // kappa in Grisu.
// Non-fixed formats require at least one digit and no precision adjustment.
if (handler.fixed) {
adjust_precision(handler.precision, exp + handler.exp10);
// Check if precision is satisfied just by leading zeros, e.g.
// format("{:.2f}", 0.001) gives "0.00" without generating any digits.
if (handler.precision <= 0) {
if (handler.precision < 0) return digits::done;
// Divide by 10 to prevent overflow.
uint64_t divisor = data::power_of_10_64[exp - 1] << -one.e;
auto dir = get_round_direction(divisor, value.f / 10, error * 10);
if (dir == round_direction::unknown) return digits::error;
handler.buf[handler.size++] = dir == round_direction::up ? '1' : '0';
return digits::done;
}
}
// Generate digits for the integral part. This can produce up to 10 digits.
do {
uint32_t digit = 0;
auto divmod_integral = [&](uint32_t divisor) {
digit = integral / divisor;
integral %= divisor;
};
// This optimization by Milo Yip reduces the number of integer divisions by
// one per iteration.
switch (exp) {
case 10:
divmod_integral(1000000000);
break;
case 9:
divmod_integral(100000000);
break;
case 8:
divmod_integral(10000000);
break;
case 7:
divmod_integral(1000000);
break;
case 6:
divmod_integral(100000);
break;
case 5:
divmod_integral(10000);
break;
case 4:
divmod_integral(1000);
break;
case 3:
divmod_integral(100);
break;
case 2:
divmod_integral(10);
break;
case 1:
digit = integral;
integral = 0;
break;
default:
FMT_ASSERT(false, "invalid number of digits");
}
--exp;
auto remainder = (static_cast<uint64_t>(integral) << -one.e) + fractional;
auto result = handler.on_digit(static_cast<char>('0' + digit),
data::power_of_10_64[exp] << -one.e,
remainder, error, true);
if (result != digits::more) return result;
} while (exp > 0);
// Generate digits for the fractional part.
for (;;) {
fractional *= 10;
error *= 10;
char digit = static_cast<char>('0' + (fractional >> -one.e));
fractional &= one.f - 1;
--exp;
auto result = handler.on_digit(digit, one.f, fractional, error, false);
if (result != digits::more) return result;
}
}
class bigint {
private:
// A bigint is stored as an array of bigits (big digits), with bigit at index
// 0 being the least significant one.
using bigit = uint32_t;
using double_bigit = uint64_t;
enum { bigits_capacity = 32 };
basic_memory_buffer<bigit, bigits_capacity> bigits_;
int exp_;
FMT_CONSTEXPR20 bigit operator[](int index) const {
return bigits_[to_unsigned(index)];
}
FMT_CONSTEXPR20 bigit& operator[](int index) {
return bigits_[to_unsigned(index)];
}
static FMT_CONSTEXPR_DECL const int bigit_bits = num_bits<bigit>();
friend struct formatter<bigint>;
FMT_CONSTEXPR20 void subtract_bigits(int index, bigit other, bigit& borrow) {
auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
(*this)[index] = static_cast<bigit>(result);
borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
}
FMT_CONSTEXPR20 void remove_leading_zeros() {
int num_bigits = static_cast<int>(bigits_.size()) - 1;
while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
bigits_.resize(to_unsigned(num_bigits + 1));
}
// Computes *this -= other assuming aligned bigints and *this >= other.
FMT_CONSTEXPR20 void subtract_aligned(const bigint& other) {
FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
FMT_ASSERT(compare(*this, other) >= 0, "");
bigit borrow = 0;
int i = other.exp_ - exp_;
for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j)
subtract_bigits(i, other.bigits_[j], borrow);
while (borrow > 0) subtract_bigits(i, 0, borrow);
remove_leading_zeros();
}
FMT_CONSTEXPR20 void multiply(uint32_t value) {
const double_bigit wide_value = value;
bigit carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
double_bigit result = bigits_[i] * wide_value + carry;
bigits_[i] = static_cast<bigit>(result);
carry = static_cast<bigit>(result >> bigit_bits);
}
if (carry != 0) bigits_.push_back(carry);
}
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) {
using half_uint =
conditional_t<std::is_same<UInt, uint128_t>::value, uint64_t, uint32_t>;
const int shift = num_bits<half_uint>() - bigit_bits;
const UInt lower = static_cast<half_uint>(value);
const UInt upper = value >> num_bits<half_uint>();
UInt carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
UInt result = lower * bigits_[i] + static_cast<bigit>(carry);
carry = (upper * bigits_[i] << shift) + (result >> bigit_bits) +
(carry >> bigit_bits);
bigits_[i] = static_cast<bigit>(result);
}
while (carry != 0) {
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); }
bigint(const bigint&) = delete;
void operator=(const bigint&) = delete;
FMT_CONSTEXPR20 void assign(const bigint& other) {
auto size = other.bigits_.size();
bigits_.resize(size);
auto data = other.bigits_.data();
std::copy(data, data + size, make_checked(bigits_.data(), size));
exp_ = other.exp_;
}
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 {
return static_cast<int>(bigits_.size()) + exp_;
}
FMT_NOINLINE FMT_CONSTEXPR20 bigint& operator<<=(int shift) {
FMT_ASSERT(shift >= 0, "");
exp_ += shift / bigit_bits;
shift %= bigit_bits;
if (shift == 0) return *this;
bigit carry = 0;
for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
bigit c = bigits_[i] >> (bigit_bits - shift);
bigits_[i] = (bigits_[i] << shift) + carry;
carry = c;
}
if (carry != 0) bigits_.push_back(carry);
return *this;
}
template <typename Int> FMT_CONSTEXPR20 bigint& operator*=(Int value) {
FMT_ASSERT(value > 0, "");
multiply(uint32_or_64_or_128_t<Int>(value));
return *this;
}
friend FMT_CONSTEXPR20 int compare(const bigint& lhs, const bigint& rhs) {
int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
if (num_lhs_bigits != num_rhs_bigits)
return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
int i = static_cast<int>(lhs.bigits_.size()) - 1;
int j = static_cast<int>(rhs.bigits_.size()) - 1;
int end = i - j;
if (end < 0) end = 0;
for (; i >= end; --i, --j) {
bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
}
if (i != j) return i > j ? 1 : -1;
return 0;
}
// Returns compare(lhs1 + lhs2, rhs).
friend FMT_CONSTEXPR20 int add_compare(const bigint& lhs1, const bigint& lhs2,
const bigint& rhs) {
auto minimum = [](int a, int b) { return a < b ? a : b; };
auto maximum = [](int a, int b) { return a > b ? a : b; };
int max_lhs_bigits = maximum(lhs1.num_bigits(), lhs2.num_bigits());
int num_rhs_bigits = rhs.num_bigits();
if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
if (max_lhs_bigits > num_rhs_bigits) return 1;
auto get_bigit = [](const bigint& n, int i) -> bigit {
return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
};
double_bigit borrow = 0;
int min_exp = minimum(minimum(lhs1.exp_, lhs2.exp_), rhs.exp_);
for (int i = num_rhs_bigits - 1; i >= min_exp; --i) {
double_bigit sum =
static_cast<double_bigit>(get_bigit(lhs1, i)) + get_bigit(lhs2, i);
bigit rhs_bigit = get_bigit(rhs, i);
if (sum > rhs_bigit + borrow) return 1;
borrow = rhs_bigit + borrow - sum;
if (borrow > 1) return -1;
borrow <<= bigit_bits;
}
return borrow != 0 ? -1 : 0;
}
// Assigns pow(10, exp) to this bigint.
FMT_CONSTEXPR20 void assign_pow10(int exp) {
FMT_ASSERT(exp >= 0, "");
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.
*this = 5;
bitmask >>= 1;
while (bitmask != 0) {
square();
if ((exp & bitmask) != 0) *this *= 5;
bitmask >>= 1;
}
*this <<= exp; // Multiply by pow(2, exp) by shifting.
}
FMT_CONSTEXPR20 void square() {
int num_bigits = static_cast<int>(bigits_.size());
int num_result_bigits = 2 * num_bigits;
basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
bigits_.resize(to_unsigned(num_result_bigits));
auto sum = uint128_t();
for (int bigit_index = 0; bigit_index < num_bigits; ++bigit_index) {
// Compute bigit at position bigit_index of the result by adding
// cross-product terms n[i] * n[j] such that i + j == bigit_index.
for (int i = 0, j = bigit_index; j >= 0; ++i, --j) {
// Most terms are multiplied twice which can be optimized in the future.
sum += static_cast<double_bigit>(n[i]) * n[j];
}
(*this)[bigit_index] = static_cast<bigit>(sum);
sum >>= num_bits<bigit>(); // Compute the carry.
}
// Do the same for the top half.
for (int bigit_index = num_bigits; bigit_index < num_result_bigits;
++bigit_index) {
for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
sum += static_cast<double_bigit>(n[i++]) * n[j--];
(*this)[bigit_index] = static_cast<bigit>(sum);
sum >>= num_bits<bigit>();
}
remove_leading_zeros();
exp_ *= 2;
}
// If this bigint has a bigger exponent than other, adds trailing zero to make
// exponents equal. This simplifies some operations such as subtraction.
FMT_CONSTEXPR20 void align(const bigint& other) {
int exp_difference = exp_ - other.exp_;
if (exp_difference <= 0) return;
int num_bigits = static_cast<int>(bigits_.size());
bigits_.resize(to_unsigned(num_bigits + exp_difference));
for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
bigits_[j] = bigits_[i];
std::uninitialized_fill_n(bigits_.data(), exp_difference, 0);
exp_ -= exp_difference;
}
// Divides this bignum by divisor, assigning the remainder to this and
// returning the quotient.
FMT_CONSTEXPR20 int divmod_assign(const bigint& divisor) {
FMT_ASSERT(this != &divisor, "");
if (compare(*this, divisor) < 0) return 0;
FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
align(divisor);
int quotient = 0;
do {
subtract_aligned(divisor);
++quotient;
} while (compare(*this, divisor) >= 0);
return quotient;
}
};
// format_dragon flags.
enum dragon {
predecessor_closer = 1,
fixup = 2, // Run fixup to correct exp10 which can be off by one.
fixed = 4,
};
// Formats a floating-point number using a variation of the Fixed-Precision
// Positive Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
// https://fmt.dev/papers/p372-steele.pdf.
FMT_CONSTEXPR20 inline void format_dragon(basic_fp<uint128_t> value,
unsigned flags, int num_digits,
buffer<char>& buf, int& exp10) {
bigint numerator; // 2 * R in (FPP)^2.
bigint denominator; // 2 * S in (FPP)^2.
// lower and upper are differences between value and corresponding boundaries.
bigint lower; // (M^- in (FPP)^2).
bigint upper_store; // upper's value if different from lower.
bigint* upper = nullptr; // (M^+ in (FPP)^2).
// Shift numerator and denominator by an extra bit or two (if lower boundary
// is closer) to make lower and upper integers. This eliminates multiplication
// by 2 during later computations.
bool is_predecessor_closer = (flags & dragon::predecessor_closer) != 0;
int shift = is_predecessor_closer ? 2 : 1;
if (value.e >= 0) {
numerator = value.f;
numerator <<= value.e + shift;
lower = 1;
lower <<= value.e;
if (is_predecessor_closer) {
upper_store = 1;
upper_store <<= value.e + 1;
upper = &upper_store;
}
denominator.assign_pow10(exp10);
denominator <<= shift;
} else if (exp10 < 0) {
numerator.assign_pow10(-exp10);
lower.assign(numerator);
if (is_predecessor_closer) {
upper_store.assign(numerator);
upper_store <<= 1;
upper = &upper_store;
}
numerator *= value.f;
numerator <<= shift;
denominator = 1;
denominator <<= shift - value.e;
} else {
numerator = value.f;
numerator <<= shift;
denominator.assign_pow10(exp10);
denominator <<= shift - value.e;
lower = 1;
if (is_predecessor_closer) {
upper_store = 1ULL << 1;
upper = &upper_store;
}
}
bool even = (value.f & 1) == 0;
if (!upper) upper = &lower;
if ((flags & dragon::fixup) != 0) {
if (add_compare(numerator, *upper, denominator) + even <= 0) {
--exp10;
numerator *= 10;
if (num_digits < 0) {
lower *= 10;
if (upper != &lower) *upper *= 10;
}
}
if ((flags & dragon::fixed) != 0) adjust_precision(num_digits, exp10 + 1);
}
// Invariant: value == (numerator / denominator) * pow(10, exp10).
if (num_digits < 0) {
// Generate the shortest representation.
num_digits = 0;
char* data = buf.data();
for (;;) {
int digit = numerator.divmod_assign(denominator);
bool low = compare(numerator, lower) - even < 0; // numerator <[=] lower.
// numerator + upper >[=] pow10:
bool high = add_compare(numerator, *upper, denominator) + even > 0;
data[num_digits++] = static_cast<char>('0' + digit);
if (low || high) {
if (!low) {
++data[num_digits - 1];
} else if (high) {
int result = add_compare(numerator, numerator, denominator);
// Round half to even.
if (result > 0 || (result == 0 && (digit % 2) != 0))
++data[num_digits - 1];
}
buf.try_resize(to_unsigned(num_digits));
exp10 -= num_digits - 1;
return;
}
numerator *= 10;
lower *= 10;
if (upper != &lower) *upper *= 10;
}
}
// Generate the given number of digits.
exp10 -= num_digits - 1;
if (num_digits == 0) {
denominator *= 10;
auto digit = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
buf.push_back(digit);
return;
}
buf.try_resize(to_unsigned(num_digits));
for (int i = 0; i < num_digits - 1; ++i) {
int digit = numerator.divmod_assign(denominator);
buf[i] = static_cast<char>('0' + digit);
numerator *= 10;
}
int digit = numerator.divmod_assign(denominator);
auto result = add_compare(numerator, numerator, denominator);
if (result > 0 || (result == 0 && (digit % 2) != 0)) {
if (digit == 9) {
const auto overflow = '0' + 10;
buf[num_digits - 1] = overflow;
// Propagate the carry.
for (int i = num_digits - 1; i > 0 && buf[i] == overflow; --i) {
buf[i] = '0';
++buf[i - 1];
}
if (buf[0] == overflow) {
buf[0] = '1';
++exp10;
}
return;
}
++digit;
}
buf[num_digits - 1] = static_cast<char>('0' + digit);
}
template <typename Float>
FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
buffer<char>& buf) -> int {
// float is passed as double to reduce the number of instantiations.
static_assert(!std::is_same<Float, float>::value, "");
FMT_ASSERT(value >= 0, "value is negative");
auto converted_value = convert_float(value);
const bool fixed = specs.format == float_format::fixed;
if (value <= 0) { // <= instead of == to silence a warning.
if (precision <= 0 || !fixed) {
buf.push_back('0');
return 0;
}
buf.try_resize(to_unsigned(precision));
fill_n(buf.data(), precision, '0');
return -precision;
}
int exp = 0;
bool use_dragon = true;
unsigned dragon_flags = 0;
if (!is_fast_float<Float>()) {
const auto inv_log2_10 = 0.3010299956639812; // 1 / log2(10)
using info = dragonbox::float_info<decltype(converted_value)>;
const auto f = basic_fp<typename info::carrier_uint>(converted_value);
// Compute exp, an approximate power of 10, such that
// 10^(exp - 1) <= value < 10^exp or 10^exp <= value < 10^(exp + 1).
// This is based on log10(value) == log2(value) / log2(10) and approximation
// of log2(value) by e + num_fraction_bits idea from double-conversion.
exp = static_cast<int>(
std::ceil((f.e + count_digits<1>(f.f) - 1) * inv_log2_10 - 1e-10));
dragon_flags = dragon::fixup;
} else if (!is_constant_evaluated() && precision < 0) {
// Use Dragonbox for the shortest format.
if (specs.binary32) {
auto dec = dragonbox::to_decimal(static_cast<float>(value));
write<char>(buffer_appender<char>(buf), dec.significand);
return dec.exponent;
}
auto dec = dragonbox::to_decimal(static_cast<double>(value));
write<char>(buffer_appender<char>(buf), dec.significand);
return dec.exponent;
} else {
// Use Grisu + Dragon4 for the given precision:
// https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf.
const int min_exp = -60; // alpha in Grisu.
int cached_exp10 = 0; // K in Grisu.
fp normalized = normalize(fp(converted_value));
const auto cached_pow = get_cached_power(
min_exp - (normalized.e + fp::num_significand_bits), cached_exp10);
normalized = normalized * cached_pow;
gen_digits_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
if (grisu_gen_digits(normalized, 1, exp, handler) != digits::error &&
!is_constant_evaluated()) {
exp += handler.exp10;
buf.try_resize(to_unsigned(handler.size));
use_dragon = false;
} else {
exp += handler.size - cached_exp10 - 1;
precision = handler.precision;
}
}
if (use_dragon) {
auto f = basic_fp<uint128_t>();
bool is_predecessor_closer = specs.binary32
? f.assign(static_cast<float>(value))
: f.assign(converted_value);
if (is_predecessor_closer) dragon_flags |= dragon::predecessor_closer;
if (fixed) dragon_flags |= dragon::fixed;
// Limit precision to the maximum possible number of significant digits in
// an IEEE754 double because we don't need to generate zeros.
const int max_double_digits = 767;
if (precision > max_double_digits) precision = max_double_digits;
format_dragon(f, dragon_flags, precision, buf, exp);
}
if (!fixed && !specs.showpoint) {
// Remove trailing zeros.
auto num_digits = buf.size();
while (num_digits > 0 && buf[num_digits - 1] == '0') {
--num_digits;
++exp;
}
buf.try_resize(num_digits);
}
return exp;
}
template <typename Char, typename OutputIt, typename T, template <typename Char, typename OutputIt, typename T,
FMT_ENABLE_IF(is_floating_point<T>::value)> FMT_ENABLE_IF(is_floating_point<T>::value)>
FMT_CONSTEXPR20 auto write(OutputIt out, T value, FMT_CONSTEXPR20 auto write(OutputIt out, T value,
@ -2398,8 +3193,8 @@ FMT_CONSTEXPR20 auto write(OutputIt out, T value,
if (const_check(std::is_same<T, float>())) fspecs.binary32 = true; if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
int exp = format_float(convert_float(value), precision, fspecs, buffer); int exp = format_float(convert_float(value), precision, fspecs, buffer);
fspecs.precision = precision; fspecs.precision = precision;
auto fp = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp}; auto f = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp};
return write_float(out, fp, specs, fspecs, loc); return write_float(out, f, specs, fspecs, loc);
} }
template <typename Char, typename OutputIt, typename T, template <typename Char, typename OutputIt, typename T,
@ -2454,28 +3249,6 @@ constexpr auto write(OutputIt out, const T& value) -> OutputIt {
return write<Char>(out, to_string_view(value)); return write<Char>(out, to_string_view(value));
} }
template <typename Char, typename OutputIt, typename T,
FMT_ENABLE_IF(is_integral<T>::value &&
!std::is_same<T, bool>::value &&
!std::is_same<T, Char>::value)>
FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
bool negative = is_negative(value);
// Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
if (negative) abs_value = ~abs_value + 1;
int num_digits = count_digits(abs_value);
auto size = (negative ? 1 : 0) + static_cast<size_t>(num_digits);
auto it = reserve(out, size);
if (auto ptr = to_pointer<Char>(it, size)) {
if (negative) *ptr++ = static_cast<Char>('-');
format_decimal<Char>(ptr, abs_value, num_digits);
return out;
}
if (negative) *it++ = static_cast<Char>('-');
it = format_decimal<Char>(it, abs_value, num_digits).end;
return base_iterator(out, it);
}
// FMT_ENABLE_IF() condition separated to workaround an MSVC bug. // FMT_ENABLE_IF() condition separated to workaround an MSVC bug.
template < template <
typename Char, typename OutputIt, typename T, typename Char, typename OutputIt, typename T,