libcxx/test/support/hexfloat.h

   1 //===----------------------------------------------------------------------===//
   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 // Define a hexfloat literal emulator since we can't depend on being able to
  10 //   for hexfloat literals
  11
  12 // 0x10.F5p-10 == hexfloat<double>(0x10, 0xF5, -10)
  13
  14 #ifndef HEXFLOAT_H
  15 #define HEXFLOAT_H
  16
  17 #include <cmath>
  18 #include <climits>
  19
  20 template <class T>
  21 class hexfloat
  22 {
  23     T value_;
  24
  25     static int CountLeadingZeros(unsigned long long n) {
  26         const std::size_t Digits = sizeof(unsigned long long) * CHAR_BIT;
  27         const unsigned long long TopBit = 1ull << (Digits - 1);
  28         if (n == 0) return Digits;
  29         int LeadingZeros = 0;
  30         while ((n & TopBit) == 0) {
  31             ++LeadingZeros;
  32             n <<= 1;
  33         }
  34         return LeadingZeros;
  35     }
  36
  37 public:
  38     hexfloat(long long m1, unsigned long long m0, int exp)
  39     {
  40         const std::size_t Digits = sizeof(unsigned long long) * CHAR_BIT;
  41         int s = m1 < 0 ? -1 : 1;
  42         int exp2 = -static_cast<int>(Digits - CountLeadingZeros(m0)/4*4);
  43         value_ = std::ldexp(m1 + s * std::ldexp(T(m0), exp2), exp);
  44     }
  45
  46     operator T() const {return value_;}
  47 };
  48
  49 #endif