chromium/third_party/fast_float/src/include/fast_float/decimal_to_binary.h

#ifndef FASTFLOAT_DECIMAL_TO_BINARY_H
#define FASTFLOAT_DECIMAL_TO_BINARY_H

#include "float_common.h"
#include "fast_table.h"
#include <cfloat>
#include <cinttypes>
#include <cmath>
#include <cstdint>
#include <cstdlib>
#include <cstring>

namespace fast_float {

// This will compute or rather approximate w * 5**q and return a pair of 64-bit
// words approximating the result, with the "high" part corresponding to the
// most significant bits and the low part corresponding to the least significant
// bits.
//
template <int bit_precision>
fastfloat_really_inline FASTFLOAT_CONSTEXPR20 value128
compute_product_approximation(int64_t q, uint64_t w) { … }

namespace detail {
/**
 * For q in (0,350), we have that
 *  f = (((152170 + 65536) * q ) >> 16);
 * is equal to
 *   floor(p) + q
 * where
 *   p = log(5**q)/log(2) = q * log(5)/log(2)
 *
 * For negative values of q in (-400,0), we have that
 *  f = (((152170 + 65536) * q ) >> 16);
 * is equal to
 *   -ceil(p) + q
 * where
 *   p = log(5**-q)/log(2) = -q * log(5)/log(2)
 */
constexpr fastfloat_really_inline int32_t power(int32_t q) noexcept { … }
} // namespace detail

// create an adjusted mantissa, biased by the invalid power2
// for significant digits already multiplied by 10 ** q.
template <typename binary>
fastfloat_really_inline FASTFLOAT_CONSTEXPR14 adjusted_mantissa
compute_error_scaled(int64_t q, uint64_t w, int lz) noexcept { … }

// w * 10 ** q, without rounding the representation up.
// the power2 in the exponent will be adjusted by invalid_am_bias.
template <typename binary>
fastfloat_really_inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa
compute_error(int64_t q, uint64_t w) noexcept { … }

// w * 10 ** q
// The returned value should be a valid ieee64 number that simply need to be
// packed. However, in some very rare cases, the computation will fail. In such
// cases, we return an adjusted_mantissa with a negative power of 2: the caller
// should recompute in such cases.
template <typename binary>
fastfloat_really_inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa
compute_float(int64_t q, uint64_t w) noexcept { … }

} // namespace fast_float

#endif