make it build

include/fast_float/digit_comparison.h

@@ -72,7 +72,7 @@ to_extended(T value) noexcept {
                  binary_format<T>::minimum_exponent();
   equiv_uint bits;
 #if FASTFLOAT_HAS_BIT_CAST
-  bits = std::bit_cast<equiv_uint>(value);
+  bits = bit_cast<equiv_uint>(value);
 #else
   ::memcpy(&bits, &value, sizeof(T));
 #endif

include/fast_float/float_common.h

@@ -260,6 +260,88 @@ struct is_supported_char_type
                              > {
 };
 
+union float_union {
+  float f;
+  uint32_t bits;
+};
+
+union double_union {
+  double f;
+  uint64_t bits;
+};
+
+template <typename T, typename U> constexpr T bit_cast(const U &u);
+
+template <>
+fastfloat_really_inline constexpr float bit_cast(const uint32_t &u) {
+  float_union fu;
+  fu.bits = u;
+  return fu.f;
+}
+
+template <>
+fastfloat_really_inline constexpr double bit_cast(const uint64_t &u) {
+  double_union fu;
+  fu.bits = u;
+  return fu.f;
+}
+
+template <>
+fastfloat_really_inline constexpr uint32_t bit_cast(const float &u) {
+  float_union fu;
+  fu.f = u;
+  return fu.bits;
+}
+
+template <>
+fastfloat_really_inline constexpr uint64_t bit_cast(const double &u) {
+  double_union fu;
+  fu.f = u;
+  return fu.bits;
+}
+
+#ifdef __STDCPP_FLOAT16_T__
+union float16_union {
+  std::float16_t f;
+  uint16_t bits;
+};
+
+template <>
+fastfloat_really_inline constexpr uint16_t bit_cast(const std::float16_t &u) {
+  float16_union fu;
+  fu.f = u;
+  return fu.bits;
+}
+
+template <>
+fastfloat_really_inline constexpr std::float16_t bit_cast(const uint16_t &u) {
+  float16_union fu;
+  fu.bits = u;
+  return fu.f;
+}
+#endif // __STDCPP_FLOAT16_T__
+
+#ifdef __STDCPP_BFLOAT16_T__
+union bfloat16_union {
+  std::bfloat16_t f;
+  uint16_t bits;
+};
+
+template <>
+fastfloat_really_inline constexpr uint16_t bit_cast(const std::bfloat16_t &u) {
+  bfloat16_union fu;
+  fu.f = u;
+  return fu.bits;
+}
+
+template <>
+fastfloat_really_inline constexpr std::bfloat16_t bit_cast(const uint16_t &u) {
+  bfloat16_union fu;
+  fu.bits = u;
+  return fu.f;
+}
+#endif // __STDCPP_BFLOAT16_T__
+
 // Compares two ASCII strings in a case insensitive manner.
 template <typename UC>
 inline FASTFLOAT_CONSTEXPR14 bool
@@ -630,12 +712,13 @@ inline constexpr uint64_t binary_format<double>::max_mantissa_fast_path() {
 
 // credit: Jakub Jelínek
 #ifdef __STDCPP_FLOAT16_T__
-
 template <typename U> struct binary_format_lookup_tables<std::float16_t, U> {
-  static constexpr std::float16_t powers_of_ten[] = {};
+  static constexpr std::float16_t powers_of_ten[] = {1}; // todo: fix this
-  static constexpr uint64_t max_mantissa[] = {};
+  static constexpr uint64_t max_mantissa[] = {1};        // todo: fix this
 };
 
+#if FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE
+
 template <typename U>
 constexpr std::float16_t
     binary_format_lookup_tables<std::float16_t, U>::powers_of_ten[];
@@ -644,6 +727,33 @@ template <typename U>
 constexpr uint64_t
     binary_format_lookup_tables<std::float16_t, U>::max_mantissa[];
 
+#endif
+
+template <>
+inline constexpr std::float16_t
+binary_format<std::float16_t>::exact_power_of_ten(int64_t power) {
+  // Work around clang bug https://godbolt.org/z/zedh7rrhc
+  return (void)powers_of_ten[0], powers_of_ten[power];
+}
+
+template <>
+inline constexpr binary_format<std::float16_t>::equiv_uint
+binary_format<std::float16_t>::exponent_mask() {
+  return 0x7C00;
+}
+
+template <>
+inline constexpr binary_format<std::float16_t>::equiv_uint
+binary_format<std::float16_t>::mantissa_mask() {
+  return 0x03FF;
+}
+
+template <>
+inline constexpr binary_format<std::float16_t>::equiv_uint
+binary_format<std::float16_t>::hidden_bit_mask() {
+  return 0x0400;
+}
+
 template <>
 inline constexpr int binary_format<std::float16_t>::max_exponent_fast_path() {
   return 0;
@@ -655,6 +765,13 @@ binary_format<std::float16_t>::max_mantissa_fast_path() {
   return 0;
 }
 
+template <>
+inline constexpr uint64_t
+binary_format<std::float16_t>::max_mantissa_fast_path(int64_t power) {
+  // Work around clang bug https://godbolt.org/z/zedh7rrhc
+  return (void)max_mantissa[0], max_mantissa[power];
+}
+
 template <>
 inline constexpr int binary_format<std::float16_t>::min_exponent_fast_path() {
   return 0;
@@ -705,13 +822,13 @@ template <> constexpr size_t binary_format<std::float16_t>::max_digits() {
 
 // credit: Jakub Jelínek
 #ifdef __STDCPP_BFLOAT16_T__
-
 template <typename U> struct binary_format_lookup_tables<std::bfloat16_t, U> {
-  static constexpr std::bfloat16_t powers_of_ten[] = {};
+  static constexpr std::bfloat16_t powers_of_ten[] = {1}; // todo: fix this
-
+  static constexpr uint64_t max_mantissa[] = {1};         // todo: fix this
-  static constexpr uint64_t max_mantissa[] = {};
 };
 
+#if FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE
+
 template <typename U>
 constexpr std::bfloat16_t
     binary_format_lookup_tables<std::bfloat16_t, U>::powers_of_ten[];
@@ -720,17 +837,51 @@ template <typename U>
 constexpr uint64_t
     binary_format_lookup_tables<std::bfloat16_t, U>::max_mantissa[];
 
+#endif
+
+template <>
+inline constexpr std::bfloat16_t
+binary_format<std::bfloat16_t>::exact_power_of_ten(int64_t power) {
+  // Work around clang bug https://godbolt.org/z/zedh7rrhc
+  return (void)powers_of_ten[0], powers_of_ten[power];
+}
+
 template <>
 inline constexpr int binary_format<std::bfloat16_t>::max_exponent_fast_path() {
   return 0;
 }
 
+template <>
+inline constexpr binary_format<std::bfloat16_t>::equiv_uint
+binary_format<std::bfloat16_t>::exponent_mask() {
+  return 0x7F80;
+}
+
+template <>
+inline constexpr binary_format<std::bfloat16_t>::equiv_uint
+binary_format<std::bfloat16_t>::mantissa_mask() {
+  return 0x007F;
+}
+
+template <>
+inline constexpr binary_format<std::bfloat16_t>::equiv_uint
+binary_format<std::bfloat16_t>::hidden_bit_mask() {
+  return 0x0080;
+}
+
 template <>
 inline constexpr uint64_t
 binary_format<std::bfloat16_t>::max_mantissa_fast_path() {
   return 0;
 }
 
+template <>
+inline constexpr uint64_t
+binary_format<std::bfloat16_t>::max_mantissa_fast_path(int64_t power) {
+  // Work around clang bug https://godbolt.org/z/zedh7rrhc
+  return (void)max_mantissa[0], max_mantissa[power];
+}
+
 template <>
 inline constexpr int binary_format<std::bfloat16_t>::min_exponent_fast_path() {
   return 0;
@@ -892,6 +1043,34 @@ to_float(bool negative, adjusted_mantissa am, T &value) {
 #endif
 }
 
+#ifdef __STDCPP_FLOAT16_T__
+template <>
+fastfloat_really_inline void to_float<std::float16_t>(bool negative,
+                                                      adjusted_mantissa am,
+                                                      std::float16_t &value) {
+  constexpr int mantissa_bits =
+      binary_format<std::float16_t>::mantissa_explicit_bits();
+  value = bit_cast<std::float16_t>(
+      uint16_t(am.mantissa | (uint16_t(am.power2) << mantissa_bits) |
+               (negative ? 0x8000 : 0)));
+}
+
+#endif // __STDCPP_FLOAT16_T__
+
+#ifdef __STDCPP_BFLOAT16_T__
+template <>
+fastfloat_really_inline void to_float<std::bfloat16_t>(bool negative,
+                                                       adjusted_mantissa am,
+                                                       std::bfloat16_t &value) {
+  constexpr int mantissa_bits =
+      binary_format<std::bfloat16_t>::mantissa_explicit_bits();
+  value = bit_cast<std::bfloat16_t>(
+      uint16_t(am.mantissa | (uint16_t(am.power2) << mantissa_bits) |
+               (negative ? 0x8000 : 0)));
+}
+
+#endif // __STDCPP_BFLOAT16_T__
+
 template <typename = void> struct space_lut {
   static constexpr bool value[] = {
       0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
@@ -944,10 +1123,12 @@ template <> constexpr char16_t const *str_const_nan<char16_t>() {
 template <> constexpr char32_t const *str_const_nan<char32_t>() {
   return U"nan";
 }
+
 #ifdef __cpp_char8_t
 template <> constexpr char8_t const *str_const_nan<char8_t>() {
   return u8"nan";
 }
+
 #endif
 
 template <typename UC> constexpr UC const *str_const_inf();
@@ -965,10 +1146,12 @@ template <> constexpr char16_t const *str_const_inf<char16_t>() {
 template <> constexpr char32_t const *str_const_inf<char32_t>() {
   return U"infinity";
 }
+
 #ifdef __cpp_char8_t
 template <> constexpr char8_t const *str_const_inf<char8_t>() {
   return u8"infinity";
 }
+
 #endif
 
 template <typename = void> struct int_luts {
@@ -1038,6 +1221,7 @@ fastfloat_really_inline constexpr uint64_t min_safe_u64(int base) {
 
 static_assert(std::is_same<equiv_uint_t<double>, uint64_t>::value,
               "equiv_uint should be uint64_t for double");
+
 static_assert(std::is_same<equiv_uint_t<float>, uint32_t>::value,
               "equiv_uint should be uint32_t for float");
 
@@ -1051,6 +1235,18 @@ static_assert(std::is_same<equiv_uint_t<std::float32_t>, uint32_t>::value,
               "equiv_uint should be uint32_t for std::float32_t");
 #endif
 
+#ifdef __STDCPP_FLOAT16_T__
+static_assert(
+    std::is_same<binary_format<std::float16_t>::equiv_uint, uint16_t>::value,
+    "equiv_uint should be uint16_t for std::float16_t");
+#endif
+
+#ifdef __STDCPP_BFLOAT16_T__
+static_assert(
+    std::is_same<binary_format<std::bfloat16_t>::equiv_uint, uint16_t>::value,
+    "equiv_uint should be uint16_t for std::bfloat16_t");
+#endif
+
 constexpr chars_format operator~(chars_format rhs) noexcept {
   using int_type = std::underlying_type<chars_format>::type;
   return static_cast<chars_format>(~static_cast<int_type>(rhs));

tests/example_test.cpp

@@ -122,6 +122,7 @@ int main() {
   }
   std::cout << "parsed the number " << result << std::endl;
 #ifdef __STDCPP_FLOAT16_T__
+  printf("16-bit float\n");
   // Parse as 16-bit float
   std::float16_t parsed_16{};
   input = "10000e-1452";