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Refactor float formatting
This commit is contained in:
Victor Zverovich
Victor Zverovich
parent
712abe40f2
commit
b4b64b9cce
@ -1204,157 +1204,6 @@ template <typename Char> struct basic_format_specs {
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using format_specs = basic_format_specs<char>;
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namespace detail {
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// A floating-point presentation format.
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enum class float_format : unsigned char {
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general, // General: exponent notation or fixed point based on magnitude.
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exp, // Exponent notation with the default precision of 6, e.g. 1.2e-3.
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fixed, // Fixed point with the default precision of 6, e.g. 0.0012.
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hex
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};
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struct float_specs {
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int precision;
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float_format format : 8;
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sign_t sign : 8;
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bool upper : 1;
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bool locale : 1;
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bool binary32 : 1;
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bool use_grisu : 1;
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bool showpoint : 1;
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};
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// Writes the exponent exp in the form "[+-]d{2,3}" to buffer.
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template <typename Char, typename It> It write_exponent(int exp, It it) {
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FMT_ASSERT(-10000 < exp && exp < 10000, "exponent out of range");
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if (exp < 0) {
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*it++ = static_cast<Char>('-');
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exp = -exp;
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} else {
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*it++ = static_cast<Char>('+');
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}
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if (exp >= 100) {
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const char* top = data::digits[exp / 100];
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if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
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*it++ = static_cast<Char>(top[1]);
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exp %= 100;
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}
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const char* d = data::digits[exp];
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*it++ = static_cast<Char>(d[0]);
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*it++ = static_cast<Char>(d[1]);
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return it;
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}
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template <typename Char> class float_writer {
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private:
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// The number is given as v = digits_ * pow(10, exp_).
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const char* digits_;
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int num_digits_;
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int exp_;
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size_t size_;
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float_specs specs_;
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Char decimal_point_;
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template <typename It> It prettify(It it) const {
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// pow(10, full_exp - 1) <= v <= pow(10, full_exp).
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int full_exp = num_digits_ + exp_;
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if (specs_.format == float_format::exp) {
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// Insert a decimal point after the first digit and add an exponent.
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*it++ = static_cast<Char>(*digits_);
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int num_zeros = specs_.precision - num_digits_;
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if (num_digits_ > 1 || specs_.showpoint) *it++ = decimal_point_;
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it = copy_str<Char>(digits_ + 1, digits_ + num_digits_, it);
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if (num_zeros > 0 && specs_.showpoint)
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it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
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*it++ = static_cast<Char>(specs_.upper ? 'E' : 'e');
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return write_exponent<Char>(full_exp - 1, it);
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}
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if (num_digits_ <= full_exp) {
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// 1234e7 -> 12340000000[.0+]
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it = copy_str<Char>(digits_, digits_ + num_digits_, it);
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it = std::fill_n(it, full_exp - num_digits_, static_cast<Char>('0'));
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if (specs_.showpoint) {
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*it++ = decimal_point_;
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int num_zeros = specs_.precision - full_exp;
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if (num_zeros <= 0) {
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if (specs_.format != float_format::fixed)
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*it++ = static_cast<Char>('0');
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return it;
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}
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#ifdef FMT_FUZZ
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if (num_zeros > 5000)
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throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
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#endif
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it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
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}
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} else if (full_exp > 0) {
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// 1234e-2 -> 12.34[0+]
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it = copy_str<Char>(digits_, digits_ + full_exp, it);
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if (!specs_.showpoint) {
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if (num_digits_ != full_exp) *it++ = decimal_point_;
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return copy_str<Char>(digits_ + full_exp, digits_ + num_digits_, it);
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}
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*it++ = decimal_point_;
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it = copy_str<Char>(digits_ + full_exp, digits_ + num_digits_, it);
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if (specs_.precision > num_digits_) {
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// Add trailing zeros.
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int num_zeros = specs_.precision - num_digits_;
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it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
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}
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} else {
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// 1234e-6 -> 0.001234
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*it++ = static_cast<Char>('0');
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int num_zeros = -full_exp;
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if (num_digits_ == 0 && specs_.precision >= 0 &&
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specs_.precision < num_zeros) {
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num_zeros = specs_.precision;
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}
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if (num_zeros != 0 || num_digits_ != 0 || specs_.showpoint) {
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*it++ = decimal_point_;
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it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
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it = copy_str<Char>(digits_, digits_ + num_digits_, it);
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}
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}
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return it;
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}
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public:
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float_writer(const char* digits, int num_digits, int exp, float_specs specs,
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Char decimal_point)
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: digits_(digits),
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num_digits_(num_digits),
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exp_(exp),
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specs_(specs),
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decimal_point_(decimal_point) {
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int full_exp = num_digits + exp - 1;
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int precision = specs.precision > 0 ? specs.precision : 16;
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if (specs_.format == float_format::general &&
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!(full_exp >= -4 && full_exp < precision)) {
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specs_.format = float_format::exp;
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}
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size_ = prettify(counting_iterator()).count();
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size_ += specs.sign ? 1 : 0;
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}
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size_t size() const { return size_; }
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template <typename It> It operator()(It it) const {
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if (specs_.sign) *it++ = static_cast<Char>(data::signs[specs_.sign]);
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return prettify(it);
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}
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};
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template <typename T>
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int format_float(T value, int precision, float_specs specs, buffer<char>& buf);
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// Formats a floating-point number with snprintf.
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template <typename T>
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int snprintf_float(T value, int precision, float_specs specs,
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buffer<char>& buf);
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template <typename T> T promote_float(T value) { return value; }
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inline double promote_float(float value) { return static_cast<double>(value); }
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namespace dragonbox {
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// Type-specific information that Dragonbox uses.
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@ -1421,6 +1270,160 @@ template <typename T> struct decimal_fp {
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template <typename T> decimal_fp<T> to_decimal(T x) FMT_NOEXCEPT;
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} // namespace dragonbox
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// A floating-point presentation format.
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enum class float_format : unsigned char {
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general, // General: exponent notation or fixed point based on magnitude.
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exp, // Exponent notation with the default precision of 6, e.g. 1.2e-3.
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fixed, // Fixed point with the default precision of 6, e.g. 0.0012.
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hex
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};
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struct float_specs {
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int precision;
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float_format format : 8;
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sign_t sign : 8;
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bool upper : 1;
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bool locale : 1;
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bool binary32 : 1;
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bool use_grisu : 1;
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bool showpoint : 1;
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};
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// Writes the exponent exp in the form "[+-]d{2,3}" to buffer.
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template <typename Char, typename It> It write_exponent(int exp, It it) {
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FMT_ASSERT(-10000 < exp && exp < 10000, "exponent out of range");
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if (exp < 0) {
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*it++ = static_cast<Char>('-');
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exp = -exp;
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} else {
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*it++ = static_cast<Char>('+');
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}
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if (exp >= 100) {
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const char* top = data::digits[exp / 100];
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if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
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*it++ = static_cast<Char>(top[1]);
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exp %= 100;
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}
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const char* d = data::digits[exp];
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*it++ = static_cast<Char>(d[0]);
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*it++ = static_cast<Char>(d[1]);
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return it;
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}
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template <typename OutputIt, typename Char>
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OutputIt write_float(OutputIt it, const buffer<char>& significand, int exp,
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float_specs specs, Char decimal_point) {
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const char* digits = significand.data();
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int num_digits = static_cast<int>(significand.size());
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int full_exp = exp + num_digits;
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auto format = specs.format;
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if (format == float_format::general &&
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!(full_exp >= -3 &&
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full_exp < (specs.precision > 0 ? specs.precision : 16) + 1)) {
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format = float_format::exp;
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}
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const Char zero = static_cast<Char>('0');
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if (format == float_format::exp) {
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// Insert a decimal point after the first digit and add an exponent.
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*it++ = static_cast<Char>(*digits);
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int num_zeros = specs.precision - num_digits;
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if (num_digits > 1 || specs.showpoint) *it++ = decimal_point;
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it = copy_str<Char>(digits + 1, digits + num_digits, it);
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if (num_zeros > 0 && specs.showpoint) it = std::fill_n(it, num_zeros, zero);
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*it++ = static_cast<Char>(specs.upper ? 'E' : 'e');
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return write_exponent<Char>(full_exp - 1, it);
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}
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if (num_digits <= full_exp) {
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// 1234e7 -> 12340000000[.0+]
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it = copy_str<Char>(digits, digits + num_digits, it);
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it = std::fill_n(it, full_exp - num_digits, zero);
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if (specs.showpoint) {
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*it++ = decimal_point;
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int num_zeros = specs.precision - full_exp;
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if (num_zeros <= 0) {
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if (format != float_format::fixed) *it++ = zero;
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return it;
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}
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#ifdef FMT_FUZZ
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if (num_zeros > 5000)
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throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
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#endif
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it = std::fill_n(it, num_zeros, zero);
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}
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} else if (full_exp > 0) {
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// 1234e-2 -> 12.34[0+]
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it = copy_str<Char>(digits, digits + full_exp, it);
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if (!specs.showpoint) {
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if (num_digits != full_exp) *it++ = decimal_point;
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return copy_str<Char>(digits + full_exp, digits + num_digits, it);
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}
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*it++ = decimal_point;
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it = copy_str<Char>(digits + full_exp, digits + num_digits, it);
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if (specs.precision > num_digits) {
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// Add trailing zeros.
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int num_zeros = specs.precision - num_digits;
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it = std::fill_n(it, num_zeros, zero);
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}
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} else {
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// 1234e-6 -> 0.001234
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*it++ = zero;
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int num_zeros = -full_exp;
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if (num_digits == 0 && specs.precision >= 0 &&
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specs.precision < num_zeros) {
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num_zeros = specs.precision;
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}
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if (num_zeros != 0 || num_digits != 0 || specs.showpoint) {
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*it++ = decimal_point;
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it = std::fill_n(it, num_zeros, zero);
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it = copy_str<Char>(digits, digits + num_digits, it);
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}
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}
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return it;
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}
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template <typename Char> class float_writer {
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private:
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// The number is given as v = significand_ * pow(10, exp_).
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const buffer<char>& significand_;
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int exp_;
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size_t size_;
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float_specs specs_;
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Char decimal_point_;
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template <typename It> It prettify(It it) const {
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return write_float(it, significand_, exp_, specs_, decimal_point_);
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}
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public:
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float_writer(const buffer<char>& significand, int exp, float_specs specs,
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Char decimal_point)
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: significand_(significand),
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exp_(exp),
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specs_(specs),
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decimal_point_(decimal_point) {
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size_ = prettify(counting_iterator()).count();
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size_ += specs.sign ? 1 : 0;
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}
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size_t size() const { return size_; }
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template <typename It> It operator()(It it) const {
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if (specs_.sign) *it++ = static_cast<Char>(data::signs[specs_.sign]);
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return prettify(it);
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}
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};
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template <typename T>
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int format_float(T value, int precision, float_specs specs, buffer<char>& buf);
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// Formats a floating-point number with snprintf.
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template <typename T>
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int snprintf_float(T value, int precision, float_specs specs,
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buffer<char>& buf);
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template <typename T> T promote_float(T value) { return value; }
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inline double promote_float(float value) { return static_cast<double>(value); }
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template <typename Handler>
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FMT_CONSTEXPR void handle_int_type_spec(char spec, Handler&& handler) {
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switch (spec) {
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@ -1868,8 +1871,7 @@ OutputIt write(OutputIt out, T value, basic_format_specs<Char> specs,
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fspecs.precision = precision;
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Char point =
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fspecs.locale ? decimal_point<Char>(loc) : static_cast<Char>('.');
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float_writer<Char> w(buffer.data(), static_cast<int>(buffer.size()), exp,
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fspecs, point);
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float_writer<Char> w(buffer, exp, fspecs, point);
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return write_padded<align::right>(out, specs, w.size(), w);
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}
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@ -1892,8 +1894,7 @@ OutputIt write(OutputIt out, T value) {
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auto dec = dragonbox::to_decimal(static_cast<type>(value));
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memory_buffer buf;
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write<char>(buffer_appender<char>(buf), dec.significand);
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float_writer<Char> w(buf.data(), static_cast<int>(buf.size()), dec.exponent,
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fspecs, static_cast<Char>('.'));
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float_writer<Char> w(buf, dec.exponent, fspecs, static_cast<Char>('.'));
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return base_iterator(out, w(reserve(out, w.size())));
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}
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