internal static IReadOnlyCollection <T> ReifyCollection <T>(IEnumerable <T> source)
{
if (source is IReadOnlyCollection <T> result)
{
return(result);
}
if (source is ICollection <T> collection)
{
return(new CollectionWrapper <T>(collection));
}
if (source is ICollection nongenericCollection)
{
return(new NongenericCollectionWrapper <T>(nongenericCollection));
}
var builder = new LargeArrayBuilder <T>(initialize: true);
builder.AddRange(source);
return(builder.ToArray());
}
/// <summary>Converts an enumerable to an array.</summary>
/// <param name="source">The enumerable to convert.</param>
/// <returns>The resulting array.</returns>
internal static T[] ToArray <T>(IEnumerable <T> source)
{
Debug.Assert(source != null);
if (source is ICollection <T> collection)
{
int count = collection.Count;
if (0u >= (uint)count)
{
return(EmptyArray <T> .Instance); // Array.Empty<T>();
}
var result = new T[count];
collection.CopyTo(result, arrayIndex: 0);
return(result);
}
var builder = new LargeArrayBuilder <T>(initialize: true);
builder.AddRange(source);
return(builder.ToArray());
}