/// <summary>
/// Constructs a new SourceText from this text with the specified changes.
/// </summary>
public virtual SourceText WithChanges(IEnumerable <TextChange> changes)
{
if (changes == null)
{
throw new ArgumentNullException(nameof(changes));
}
if (!changes.Any())
{
return(this);
}
var segments = ArrayBuilder <SourceText> .GetInstance();
var changeRanges = ArrayBuilder <TextChangeRange> .GetInstance();
int position = 0;
foreach (var change in changes)
{
// there can be no overlapping changes
if (change.Span.Start < position)
{
throw new ArgumentException(CodeAnalysisResources.ChangesMustBeOrderedAndNotOverlapping, nameof(changes));
}
var newTextLength = change.NewText?.Length ?? 0;
// ignore changes that don't change anything
if (change.Span.Length == 0 && newTextLength == 0)
{
continue;
}
// if we've skipped a range, add
if (change.Span.Start > position)
{
var subText = this.GetSubText(new TextSpan(position, change.Span.Start - position));
CompositeText.AddSegments(segments, subText);
}
if (newTextLength > 0)
{
var segment = SourceText.From(change.NewText, this.Encoding, this.ChecksumAlgorithm);
CompositeText.AddSegments(segments, segment);
}
position = change.Span.End;
changeRanges.Add(new TextChangeRange(change.Span, newTextLength));
}
// no changes actually happend?
if (position == 0 && segments.Count == 0)
{
changeRanges.Free();
return(this);
}
if (position < this.Length)
{
var subText = this.GetSubText(new TextSpan(position, this.Length - position));
CompositeText.AddSegments(segments, subText);
}
var newText = CompositeText.ToSourceTextAndFree(segments, this, adjustSegments: true);
if (newText != this)
{
return(new ChangedText(this, newText, changeRanges.ToImmutableAndFree()));
}
else
{
return(this);
}
}
