public static IEnumerable <Partition <TResult> > Split <TSource, TResult>(this IEnumerable <TSource> source, int maxSize, Func <TSource, TResult> selector, Func <TSource, bool> predicate = default)
{
if (source is null)
{
throw new ArgumentNullException(paramName: nameof(source));
}
else if (maxSize < 1)
{
throw new ArgumentOutOfRangeException(paramName: nameof(maxSize), message: FormatXResource(locator: typeof(ArgumentOutOfRangeException), subpath: "CanNotLessThanOne"));
}
else if (selector is null)
{
throw new ArgumentNullException(paramName: nameof(selector));
}
//
TResult[] portion;
var partitionUpperBound = maxSize - 1;
var buffer = new List <TResult>();
var bufferTailIndex = -1;
var partitionIndex = -1;
foreach (var item in source)
{
if (bufferTailIndex == partitionUpperBound)
{
portion = new TResult[maxSize];
buffer.CopyTo(index: 0, array: portion, arrayIndex: 0, count: maxSize);
bufferTailIndex = -1;
yield return(new Partition <TResult>(elements: ListReadOnlyWrap <TResult> .WrapOrEmpty(list: portion), index: checked (++partitionIndex)));
}
if (predicate?.Invoke(item) ?? true)
{
if (buffer.Count > ++bufferTailIndex)
{
buffer[bufferTailIndex] = selector(item);
}
else
{
buffer.Add(selector(item));
}
}
}
if (bufferTailIndex > -1)
{
portion = new TResult[bufferTailIndex + 1];
buffer.CopyTo(index: 0, array: portion, arrayIndex: 0, count: bufferTailIndex + 1);
buffer.Clear();
yield return(new Partition <TResult>(elements: ListReadOnlyWrap <TResult> .WrapOrEmpty(list: portion), index: checked (++partitionIndex)));
}
else
{
buffer.Clear();
}
}
internal Partition(ListReadOnlyWrap <T> elements, int index)
{
if (index < 0)
{
throw new ArgumentOutOfRangeException(paramName: nameof(index));
}
else if (elements is null)
{
throw new ArgumentNullException(paramName: nameof(elements));
}
//
Index = index;
Elements = elements;
}
