More cleanup for v1.

NTwain/Data/ValueExtensions.cs

@@ -0,0 +1,111 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+
+namespace NTwain.Data
+{
+    /// <summary>
+    /// Utility on converting (possibly bad) integer values to enum values.
+    /// </summary>
+    public static class ValueExtensions
+    {
+        /// <summary>
+        /// Casts a list of objects to a list of specified enum.
+        /// </summary>
+        /// <typeparam name="TEnum">The type of the enum.</typeparam>
+        /// <param name="list">The list.</param>
+        /// <returns></returns>
+        public static IList<TEnum> CastToEnum<TEnum>(this IEnumerable<object> list) where TEnum : struct,IConvertible
+        {
+            return list.CastToEnum<TEnum>(true);
+        }
+        /// <summary>
+        /// Casts a list of objects to a list of specified enum.
+        /// </summary>
+        /// <typeparam name="TEnum">The type of the enum.</typeparam>
+        /// <param name="list">The list.</param>
+        /// <param name="tryUpperWord">set to <c>true</c> for working with bad values.</param>
+        /// <returns></returns>
+        public static IList<TEnum> CastToEnum<TEnum>(this IEnumerable<object> list, bool tryUpperWord) where TEnum : struct,IConvertible
+        {
+            return list.Select(o => o.ConvertToEnum<TEnum>(tryUpperWord)).ToList();
+        }
+
+        /// <summary>
+        /// Casts an objects to the specified enum.
+        /// </summary>
+        /// <typeparam name="TEnum">The type of the enum.</typeparam>
+        /// <param name="value">The value.</param>
+        /// <returns></returns>
+        public static TEnum ConvertToEnum<TEnum>(this object value) where TEnum : struct,IConvertible
+        {
+            return ConvertToEnum<TEnum>(value, true);
+        }
+        /// <summary>
+        /// Casts an objects to the specified enum.
+        /// </summary>
+        /// <typeparam name="TEnum">The type of the enum.</typeparam>
+        /// <param name="value">The value.</param>
+        /// <param name="tryUpperWord">if set to <c>true</c> [try upper word].</param>
+        /// <returns></returns>
+        public static TEnum ConvertToEnum<TEnum>(this object value, bool tryUpperWord) where TEnum : struct,IConvertible
+        {
+            var returnType = typeof(TEnum);
+
+            // standard int values
+            if (returnType.IsEnum)
+            {
+                if (tryUpperWord)
+                {
+                    // small routine to work with bad sources that may put
+                    // 16bit value in the upper word instead of lower word (as per the twain spec).
+                    var rawType = Enum.GetUnderlyingType(returnType);
+                    if (typeof(ushort).IsAssignableFrom(rawType))
+                    {
+                        var intVal = Convert.ToUInt32(value, CultureInfo.InvariantCulture);
+                        var enumVal = GetLowerWord(intVal);
+                        if (!Enum.IsDefined(returnType, enumVal))
+                        {
+                            return (TEnum)Enum.ToObject(returnType, GetUpperWord(intVal));
+                        }
+                    }
+                }
+                // this may work better?
+                return (TEnum)Enum.ToObject(returnType, value);
+                //// cast to underlying type first then to the enum
+                //return (T)Convert.ChangeType(value, rawType);
+            }
+            else if (typeof(IConvertible).IsAssignableFrom(returnType))
+            {
+                // for regular integers and whatnot
+                return (TEnum)Convert.ChangeType(value, returnType, CultureInfo.InvariantCulture);
+            }
+            // return as-is from cap. if caller made a mistake then there should be exceptions
+            return (TEnum)value;
+        }
+
+        static ushort GetLowerWord(uint value)
+        {
+            return (ushort)(value & 0xffff);
+        }
+        static uint GetUpperWord(uint value)
+        {
+            return (ushort)(value >> 16);
+        }
+
+        /// <summary>
+        /// Tries to convert to a value to <see cref="TWFix32"/> if possible.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        /// <returns></returns>
+        public static TWFix32 ConvertToFix32(this object value)
+        {
+            if (value is TWFix32)
+            {
+                return (TWFix32)value;
+            }
+            return (TWFix32)Convert.ToSingle(value, CultureInfo.InvariantCulture);
+        }
+    }
+}