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 <climits>
  18 #include <cmath>
  19 #include <cstddef>
  20
  21 template <class T>
  22 class hexfloat
  23 {
  24     T value_;
  25
  26     static int CountLeadingZeros(unsigned long long n) {
  27         const std::size_t Digits = sizeof(unsigned long long) * CHAR_BIT;
  28         const unsigned long long TopBit = 1ull << (Digits - 1);
  29         if (n == 0) return Digits;
  30         int LeadingZeros = 0;
  31         while ((n & TopBit) == 0) {
  32             ++LeadingZeros;
  33             n <<= 1;
  34         }
  35         return LeadingZeros;
  36     }
  37
  38 public:
  39     hexfloat(long long m1, unsigned long long m0, int exp)
  40     {
  41         const std::size_t Digits = sizeof(unsigned long long) * CHAR_BIT;
  42         int s = m1 < 0 ? -1 : 1;
  43         int exp2 = -static_cast<int>(Digits - CountLeadingZeros(m0)/4*4);
  44         value_ = std::ldexp(m1 + s * std::ldexp(T(m0), exp2), exp);
  45     }
  46
  47     operator T() const {return value_;}
  48 };
  49
  50 #endif