llvm/libc/src/stdio/printf_core/float_dec_converter.h

//===-- Decimal Float Converter for printf ----------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FLOAT_DEC_CONVERTER_H
#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FLOAT_DEC_CONVERTER_H

#include "src/__support/CPP/string_view.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/rounding_mode.h"
#include "src/__support/big_int.h" // is_big_int_v
#include "src/__support/float_to_string.h"
#include "src/__support/integer_to_string.h"
#include "src/__support/libc_assert.h"
#include "src/__support/macros/config.h"
#include "src/stdio/printf_core/converter_utils.h"
#include "src/stdio/printf_core/core_structs.h"
#include "src/stdio/printf_core/float_inf_nan_converter.h"
#include "src/stdio/printf_core/writer.h"

#include <inttypes.h>
#include <stddef.h>

namespace LIBC_NAMESPACE_DECL {
namespace printf_core {

StorageType;
DecimalString;
ExponentString;

// Returns true if value is divisible by 2^p.
template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_integral_v<T> || is_big_int_v<T>,
                                       bool>
multiple_of_power_of_2(T value, uint32_t p) { … }

constexpr size_t BLOCK_SIZE = …;
constexpr uint32_t MAX_BLOCK = …;

// constexpr size_t BLOCK_SIZE = 18;
// constexpr uint32_t MAX_BLOCK = 999999999999999999;
constexpr char DECIMAL_POINT = …;

LIBC_INLINE RoundDirection get_round_direction(int last_digit, bool truncated,
                                               Sign sign) { … }

template <typename T>
LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_integral_v<T> || is_big_int_v<T>,
                                       bool>
zero_after_digits(int32_t base_2_exp, int32_t digits_after_point, T mantissa,
                  const int32_t mant_width) { … }

class PaddingWriter { … };

/*
  We only need to round a given segment if all of the segments below it are
  the max (or this is the last segment). This means that we don't have to
  write those initially, we can just keep the most recent non-maximal
  segment and a counter of the number of maximal segments. When we reach a
  non-maximal segment, we write the stored segment as well as as many 9s as
  are necessary. Alternately, if we reach the end and have to round up, then
  we round the stored segment, and write zeroes following it. If this
  crosses the decimal point, then we have to shift it one space to the
  right.
  This FloatWriter class does the buffering and counting, and writes to the
  output when necessary.
*/
class FloatWriter { … };

// This implementation is based on the Ryu Printf algorithm by Ulf Adams:
// Ulf Adams. 2019. Ryū revisited: printf floating point conversion.
// Proc. ACM Program. Lang. 3, OOPSLA, Article 169 (October 2019), 23 pages.
// https://doi.org/10.1145/3360595
template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE int convert_float_decimal_typed(Writer *writer,
                                            const FormatSection &to_conv,
                                            fputil::FPBits<T> float_bits) { … }

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE int convert_float_dec_exp_typed(Writer *writer,
                                            const FormatSection &to_conv,
                                            fputil::FPBits<T> float_bits) { … }

template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
LIBC_INLINE int convert_float_dec_auto_typed(Writer *writer,
                                             const FormatSection &to_conv,
                                             fputil::FPBits<T> float_bits) { … }

// TODO: unify the float converters to remove the duplicated checks for inf/nan.
LIBC_INLINE int convert_float_decimal(Writer *writer,
                                      const FormatSection &to_conv) { … }

LIBC_INLINE int convert_float_dec_exp(Writer *writer,
                                      const FormatSection &to_conv) { … }

LIBC_INLINE int convert_float_dec_auto(Writer *writer,
                                       const FormatSection &to_conv) { … }

} // namespace printf_core
} // namespace LIBC_NAMESPACE_DECL

#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FLOAT_DEC_CONVERTER_H