protected override IEnumerable <Concatenation> ReadImpl(ITextScanner scanner, ITextContext context)
{
var success = false;
foreach (var concatenation in Branch(scanner, context, new List <Element>(lexers.Count)))
{
success = true;
yield return(concatenation);
}
if (!success)
{
scanner.Seek(context.Offset);
}
}
protected override IEnumerable <Alternation> ReadImpl(ITextScanner scanner, ITextContext context)
{
for (var i = 0; i < lexers.Length; i++)
{
scanner.Seek(context.Offset);
var lexer = lexers[i];
Debug.Assert(lexer != null, "lexer != null");
var element = lexer.Read(scanner);
if (element != null)
{
yield return(new Alternation(element.Text, element, context, i + 1));
}
}
}
protected override IEnumerable <Repetition> ReadImpl(ITextScanner scanner, ITextContext context)
{
var success = false;
foreach (var repetition in Branch(scanner, context, new List <Element>(LowerBound)))
{
success = true;
yield return(repetition);
}
if (!success)
{
scanner.Seek(context.Offset);
}
}
public bool MoveNext()
{
if (!initialized)
{
start = scanner.Offset;
scanner.StartRecording();
inner = lexer.ReadImpl(scanner, context).GetEnumerator();
initialized = true;
}
if (scanner.Offset != context.Offset)
{
scanner.Seek(context.Offset);
}
if (!inner.MoveNext())
{
if (scanner.Offset != context.Offset)
{
scanner.Seek(context.Offset);
}
return(false);
}
Current = inner.Current;
return(true);
}
public static TElement Read <TElement>([NotNull] this ILexer <TElement> instance, [NotNull] ITextScanner scanner) where TElement : Element
{
if (instance == null)
{
throw new ArgumentNullException(nameof(instance));
}
if (scanner == null)
{
throw new ArgumentNullException(nameof(scanner));
}
var offset = scanner.Offset;
scanner.StartRecording();
TElement candidate = null;
try
{
var context = scanner.GetContext();
foreach (var element in instance.Read(scanner, context))
{
if (candidate == null)
{
candidate = element;
}
else if (element.Text.Length > candidate.Text.Length)
{
candidate = element;
}
}
if (candidate == null)
{
return(null);
}
scanner.Seek(offset + candidate.Text.Length);
}
finally
{
scanner.StopRecording();
}
return(candidate);
}