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_FP_BITS_STR_H
  10 #define LLVM_LIBC_SRC_SUPPORT_FPUTIL_FP_BITS_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/FPUtil/FloatProperties.h"
  16 #include "src/__support/integer_to_string.h"
  17 #include "src/__support/macros/attributes.h"
  18
  19 namespace __llvm_libc {
  20
  21 // Converts the bits to a string in the following format:
  22 //    "0x<NNN...N> = S: N, E: 0xNNNN, M:0xNNN...N"
  23 // 1. N is a hexadecimal digit.
  24 // 2. The hexadecimal number on the LHS is the raw numerical representation
  25 //    of the bits.
  26 // 3. The exponent is always 16 bits wide irrespective of the type of the
  27 //    floating encoding.
  28 template <typename T> LIBC_INLINE cpp::string str(fputil::FPBits<T> x) {
  29   using UIntType = typename fputil::FPBits<T>::UIntType;
  30
  31   if (x.is_nan())
  32     return "(NaN)";
  33   if (x.is_inf())
  34     return x.get_sign() ? "(-Infinity)" : "(+Infinity)";
  35
  36   auto zerofill = [](char *arr, size_t n) {
  37     for (size_t i = 0; i < n; ++i)
  38       arr[i] = '0';
  39   };
  40
  41   cpp::string s("0x");
  42   char bitsbuf[IntegerToString::hex_bufsize<UIntType>()];
  43   zerofill(bitsbuf, sizeof(bitsbuf));
  44   IntegerToString::hex(x.bits, bitsbuf, false);
  45   s += cpp::string(bitsbuf, sizeof(bitsbuf));
  46
  47   s += " = (";
  48   s += cpp::string("S: ") + (x.get_sign() ? "1" : "0");
  49
  50   char expbuf[IntegerToString::hex_bufsize<uint16_t>()];
  51   zerofill(expbuf, sizeof(expbuf));
  52   IntegerToString::hex(x.get_unbiased_exponent(), expbuf, false);
  53   s += cpp::string(", E: 0x") + cpp::string(expbuf, sizeof(expbuf));
  54
  55   if constexpr (cpp::is_same_v<T, long double> &&
  56                 fputil::FloatProperties<long double>::MANTISSA_WIDTH == 63) {
  57     s += cpp::string(", I: ") + (x.get_implicit_bit() ? "1" : "0");
  58   }
  59
  60   char mantbuf[IntegerToString::hex_bufsize<UIntType>()] = {'0'};
  61   zerofill(mantbuf, sizeof(mantbuf));
  62   IntegerToString::hex(x.get_mantissa(), mantbuf, false);
  63   s += cpp::string(", M: 0x") + cpp::string(mantbuf, sizeof(mantbuf));
  64
  65   s += ")";
  66   return s;
  67 }
  68
  69 } // namespace __llvm_libc
  70
  71 #endif // LLVM_LIBC_SRC_SUPPORT_FPUTIL_FP_BITS_STR_H