CSHARP-4909: Add serialization support for new Numeric types (#1449)

Author: papafe

src/MongoDB.Bson/IO/JsonConvert.cs

@@ -90,6 +90,18 @@ public static double ToDouble(string value)
             return double.Parse(value, NumberFormatInfo.InvariantInfo);
         }
 
+#if NET5_0_OR_GREATER
+        /// <summary>
+        /// Converts a string to a Half.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        /// <returns>A Half.</returns>
+        public static Half ToHalf(string value)
+        {
+            return Half.Parse(value, NumberFormatInfo.InvariantInfo);
+        }
+#endif
+
         /// <summary>
         /// Converts a string to an Int16.
         /// </summary>
@@ -200,6 +212,18 @@ public static string ToString(float value)
             return value.ToString("R", NumberFormatInfo.InvariantInfo);
         }
 
+#if NET5_0_OR_GREATER
+        /// <summary>
+        /// Converts a Half to a string.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        /// <returns>A string.</returns>
+        public static string ToString(Half value)
+        {
+            return value.ToString("G5", NumberFormatInfo.InvariantInfo);
+        }
+#endif
+
         /// <summary>
         /// Converts an Int32 to a string.
         /// </summary>

src/MongoDB.Bson/ObjectModel/Decimal128.cs

@@ -259,6 +259,20 @@ public static explicit operator Decimal128(float value)
             return new Decimal128(value);
         }
 
+#if NET5_0_OR_GREATER
+        /// <summary>
+        /// Performs an explicit conversion from <see cref="Half"/> to <see cref="Decimal128"/>.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        /// <returns>
+        /// The result of the conversion.
+        /// </returns>
+        public static explicit operator Decimal128(Half value)
+        {
+            return new Decimal128(value);
+        }
+#endif
+
         /// <summary>
         /// Performs an implicit conversion from <see cref="System.Int32"/> to <see cref="Decimal128"/>.
         /// </summary>
@@ -371,6 +385,20 @@ public static explicit operator float(Decimal128 value)
             return Decimal128.ToSingle(value);
         }
 
+#if NET5_0_OR_GREATER
+        /// <summary>
+        /// Performs an explicit conversion from <see cref="Decimal128"/> to <see cref="Half"/>.
+        /// </summary>
+        /// <param name="value">The value to convert.</param>
+        /// <returns>
+        /// The result of the conversion.
+        /// </returns>
+        public static explicit operator Half(Decimal128 value)
+        {
+            return Decimal128.ToHalf(value);
+        }
+#endif
+
         /// <summary>
         /// Performs an explicit conversion from <see cref="Decimal128"/> to <see cref="System.Int32"/>.
         /// </summary>
@@ -962,6 +990,40 @@ public static float ToSingle(Decimal128 d)
             }
         }
 
+#if NET5_0_OR_GREATER
+        /// <summary>
+        /// Converts the value of the specified <see cref="Decimal128"/> to the equivalent <see cref="Half"/>.
+        /// </summary>
+        /// <param name="d">The number to convert.</param>
+        /// <returns>A <see cref="Half"/> equivalent to <paramref name="d" />.</returns>
+        public static Half ToHalf(Decimal128 d)
+        {
+            if (Flags.IsFirstForm(d._highBits))
+            {
+                // TODO: implement this more efficiently
+                var stringValue = d.ToString();
+                return Half.Parse(stringValue, CultureInfo.InvariantCulture);
+            }
+
+            if (Flags.IsSecondForm(d._highBits))
+            {
+                return (Half)0.0;
+            }
+
+            if (Flags.IsPositiveInfinity(d._highBits))
+            {
+                return Half.PositiveInfinity;
+            }
+
+            if (Flags.IsNegativeInfinity(d._highBits))
+            {
+                return Half.NegativeInfinity;
+            }
+
+            return Half.NaN;
+        }
+#endif
+
         /// <summary>
         /// Converts the value of the specified <see cref="Decimal128"/> to the equivalent 16-bit unsigned integer.
         /// </summary>
@@ -1441,6 +1503,21 @@ public Decimal128(float value)
             _lowBits = decimal128Value.GetIEEELowBits();
         }
 
+#if NET5_0_OR_GREATER
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Decimal128"/> struct.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        public Decimal128(Half value)
+        {
+            // TODO: implement this more efficiently
+            var stringValue = JsonConvert.ToString(value);
+            var decimal128Value = Decimal128.Parse(stringValue);
+            _highBits = MapIEEEHighBitsToDecimal128HighBits(decimal128Value.GetIEEEHighBits());
+            _lowBits = decimal128Value.GetIEEELowBits();
+        }
+#endif
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Decimal128"/> struct.
         /// </summary>