Float16

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

@@ -10,6 +10,7 @@
 #ifdef __has_include
 #if __has_include(<stdfloat>) && (__cplusplus > 202002L || _MSVC_LANG > 202002L)
 #include <stdfloat>
+
 #endif
 #endif
 #include "constexpr_feature_detect.h"
@@ -202,9 +203,98 @@ fastfloat_really_inline constexpr bool is_supported_float_type() {
 #if __STDCPP_FLOAT64_T__
          || std::is_same<T, std::float64_t>::value
 #endif
+#ifdef __STDCPP_FLOAT16_T__
+         || std::is_same<T, std::float16_t>::value
+#endif // __STDCPP_FLOAT16_T__
+#ifdef _STDCPP_BFLOAT16
+         || std::is_same<T, std::bfloat16_t>::value
+#endif // _STDCPP_BFLOAT16
       ;
 }
 
+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__
+
+
 template <typename UC>
 fastfloat_really_inline constexpr bool is_supported_char_type() {
   return std::is_same<UC, char>::value || std::is_same<UC, wchar_t>::value ||
@@ -377,7 +467,7 @@ template <typename T, typename U = void> struct binary_format_lookup_tables;
 
 template <typename T> struct binary_format : binary_format_lookup_tables<T> {
   using equiv_uint =
-      typename std::conditional<sizeof(T) == 4, uint32_t, uint64_t>::type;
+      typename std::conditional<sizeof(T) == 2, uint16_t, typename std::conditional<sizeof(T) == 4, uint32_t, uint64_t>::type>::type;
 
   static inline constexpr int mantissa_explicit_bits();
   static inline constexpr int minimum_exponent();
@@ -556,6 +646,215 @@ template <>
 inline constexpr uint64_t binary_format<double>::max_mantissa_fast_path() {
   return uint64_t(2) << mantissa_explicit_bits();
 }
+
+// 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[] = {1};// todo: fix this
+  static constexpr uint64_t max_mantissa[] = {1};// todo: fix this
+};
+
+template <typename U>
+constexpr std::float16_t
+    binary_format_lookup_tables<std::float16_t, U>::powers_of_ten[];
+
+template <typename U>
+constexpr uint64_t
+    binary_format_lookup_tables<std::float16_t, U>::max_mantissa[];
+
+template <>
+inline constexpr std::float16_t
+binary_format<std::float16_t>::exact_power_of_ten(int64_t power) {
+  return 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;
+}
+
+template <>
+inline constexpr uint64_t
+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) {
+  return max_mantissa[power];
+}
+
+template <>
+inline constexpr int binary_format<std::float16_t>::min_exponent_fast_path() {
+  return 0;
+}
+template <>
+constexpr int binary_format<std::float16_t>::mantissa_explicit_bits() {
+  return 10;
+}
+
+template <>
+constexpr int binary_format<std::float16_t>::max_exponent_round_to_even() {
+  return 5;
+}
+
+template <>
+constexpr int binary_format<std::float16_t>::min_exponent_round_to_even() {
+  return -22;
+}
+
+template <> constexpr int binary_format<std::float16_t>::minimum_exponent() {
+  return -15;
+}
+
+template <> constexpr int binary_format<std::float16_t>::infinite_power() {
+  return 0x1F;
+}
+
+template <> constexpr int binary_format<std::float16_t>::sign_index() {
+  return 15;
+}
+
+template <>
+constexpr int binary_format<std::float16_t>::largest_power_of_ten() {
+  return 4;
+}
+
+template <>
+constexpr int binary_format<std::float16_t>::smallest_power_of_ten() {
+  return -27;
+}
+
+template <> constexpr size_t binary_format<std::float16_t>::max_digits() {
+  return 22;
+}
+
+#endif
+
+// 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[] = {1};// todo: fix this
+
+  static constexpr uint64_t max_mantissa[] = {1};// todo: fix this
+};
+
+template <typename U>
+constexpr std::bfloat16_t
+    binary_format_lookup_tables<std::bfloat16_t, U>::powers_of_ten[];
+
+template <typename U>
+constexpr uint64_t
+    binary_format_lookup_tables<std::bfloat16_t, U>::max_mantissa[];
+
+template <>
+inline constexpr std::bfloat16_t
+binary_format<std::bfloat16_t>::exact_power_of_ten(int64_t power) {
+  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) {
+  return max_mantissa[power];
+}
+
+template <>
+inline constexpr int binary_format<std::bfloat16_t>::min_exponent_fast_path() {
+  return 0;
+}
+
+template <>
+constexpr int binary_format<std::bfloat16_t>::mantissa_explicit_bits() {
+  return 7;
+}
+
+template <>
+constexpr int binary_format<std::bfloat16_t>::max_exponent_round_to_even() {
+  return 3;
+}
+
+template <>
+constexpr int binary_format<std::bfloat16_t>::min_exponent_round_to_even() {
+  return -24;
+}
+
+template <> constexpr int binary_format<std::bfloat16_t>::minimum_exponent() {
+  return -127;
+}
+
+template <> constexpr int binary_format<std::bfloat16_t>::infinite_power() {
+  return 0xFF;
+}
+
+template <> constexpr int binary_format<std::bfloat16_t>::sign_index() {
+  return 15;
+}
+
+template <>
+constexpr int binary_format<std::bfloat16_t>::largest_power_of_ten() {
+  return 38;
+}
+
+template <>
+constexpr int binary_format<std::bfloat16_t>::smallest_power_of_ten() {
+  return -60;
+}
+
+template <> constexpr size_t binary_format<std::bfloat16_t>::max_digits() {
+  return 98;
+}
+
+#endif
+
 template <>
 inline constexpr uint64_t
 binary_format<double>::max_mantissa_fast_path(int64_t power) {
@@ -660,6 +959,32 @@ to_float(bool negative, adjusted_mantissa am, T &value) {
   ::memcpy(&value, &word, sizeof(T));
 #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__
 
 #ifdef FASTFLOAT_SKIP_WHITE_SPACE // disabled by default
 template <typename = void> struct space_lut {
@@ -780,6 +1105,21 @@ fastfloat_really_inline constexpr uint64_t min_safe_u64(int base) {
   return int_luts<>::min_safe_u64[base - 2];
 }
 
+
+
+static_assert(std::is_same<binary_format<double>::equiv_uint, uint64_t>::value,
+              "equiv_uint should be uint64_t for double");
+static_assert(std::is_same<binary_format<float>::equiv_uint, uint32_t>::value,
+              "equiv_uint should be uint32_t for float");
+#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 // __STDCPP_FLOAT16_T__
+#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 // __STDCPP_BFLOAT16_T__
+
 } // namespace fast_float
 
 #endif