libc/src/__support/FPUtil/fpbits_str.h

   1 //===------ Pretty print function for FPBits --------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_FPBITS_STR_H
  10 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_FPBITS_STR_H
  11
  12 #include "src/__support/CPP/string.h"
  13 #include "src/__support/CPP/type_traits.h"
  14 #include "src/__support/FPUtil/FPBits.h"
  15 #include "src/__support/integer_to_string.h"
  16 #include "src/__support/macros/attributes.h"
  17 #include "src/__support/macros/config.h"
  18
  19 namespace LIBC_NAMESPACE_DECL {
  20
  21 namespace details {
  22
  23 // Format T as uppercase hexadecimal number with leading zeros.
  24 template <typename T>
  25 using ZeroPaddedHexFmt = IntegerToString<
  26     T, typename radix::Hex::WithWidth<(sizeof(T) * 2)>::WithPrefix::Uppercase>;
  27
  28 } // namespace details
  29
  30 // Converts the bits to a string in the following format:
  31 //    "0x<NNN...N> = S: N, E: 0xNNNN, M:0xNNN...N"
  32 // 1. N is a hexadecimal digit.
  33 // 2. The hexadecimal number on the LHS is the raw numerical representation
  34 //    of the bits.
  35 // 3. The exponent is always 16 bits wide irrespective of the type of the
  36 //    floating encoding.
  37 template <typename T> LIBC_INLINE cpp::string str(fputil::FPBits<T> x) {
  38   using StorageType = typename fputil::FPBits<T>::StorageType;
  39
  40   if (x.is_nan())
  41     return "(NaN)";
  42   if (x.is_inf())
  43     return x.is_neg() ? "(-Infinity)" : "(+Infinity)";
  44
  45   const auto sign_char = [](Sign sign) -> char {
  46     return sign.is_neg() ? '1' : '0';
  47   };
  48
  49   cpp::string s;
  50
  51   const details::ZeroPaddedHexFmt<StorageType> bits(x.uintval());
  52   s += bits.view();
  53
  54   s += " = (S: ";
  55   s += sign_char(x.sign());
  56
  57   s += ", E: ";
  58   const details::ZeroPaddedHexFmt<uint16_t> exponent(x.get_biased_exponent());
  59   s += exponent.view();
  60
  61   if constexpr (fputil::get_fp_type<T>() == fputil::FPType::X86_Binary80) {
  62     s += ", I: ";
  63     s += sign_char(x.get_implicit_bit() ? Sign::NEG : Sign::POS);
  64   }
  65
  66   s += ", M: ";
  67   const details::ZeroPaddedHexFmt<StorageType> mantissa(x.get_mantissa());
  68   s += mantissa.view();
  69
  70   s += ')';
  71   return s;
  72 }
  73
  74 } // namespace LIBC_NAMESPACE_DECL
  75
  76 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_FPBITS_STR_H