public static bool StartsWith(this LexingContext context, string start)
{
if (start == null)
{
throw new ArgumentNullException(nameof(start));
}
var remaining = context.GetRemainingCharCount();
if (remaining < start.Length)
{
return(false);
}
var text = context.Text;
var initialIndex = context.Index;
for (var i = 0; i < start.Length; i++)
{
var c1 = text[initialIndex + i];
var c2 = start[i];
if (c1 != c2)
{
return(false);
}
}
return(true);
}
public static void AdvanceByChar(this LexingContext context)
{
context.Index++;
context.Column++;
context.IncreaseVersion();
}
public static void Advance(this LexingContext context, int indexShift, int lineShift, int column)
{
context.Index += indexShift;
context.Line += lineShift;
context.Column = column;
context.IncreaseVersion();
}
public IList <IToken> Lexize(string input)
{
var context = new LexingContext(input);
var tokens = new List <IToken>();
foreach (var producer in this.Producers)
{
producer.Context = context;
}
var length = input.Length;
while (context.Index < length)
{
var indexBeforeProducing = context.Index;
foreach (var producer in this.Producers)
{
var oldVersion = context.Version;
var oldIndex = context.Index;
var oldLine = context.Line;
var token = producer.Produce();
if (token != null)
{
if (context.Version <= oldVersion)
{
throw new LexingException(
$"Producer '{producer.GetType().FullName}' has produced a token of type '{token.GetType().FullName}' ('{token}'), but context version has not increased.",
new Position(context.Length, context.Column));
}
if (context.Index <= oldIndex)
{
throw new LexingException(
$"Producer '{producer.GetType().FullName}' has produced a token of type '{token.GetType().FullName}' ('{token}'), but context index has not increased.",
new Position(context.Length, context.Column));
}
if (context.Line < oldLine)
{
throw new LexingException(
$"Producer '{producer.GetType().FullName}' has produced a token of type '{token.GetType().FullName}' ('{token}'), but context line has decreased.",
new Position(context.Length, context.Column));
}
if (token is IEmptyToken && this.IgnoreEmptyTokens)
{
// do nothing
}
else
{
tokens.Add(token);
}
break;
}
if (context.Version > oldVersion)
{
break;
}
}
if (context.Index == indexBeforeProducing)
{
var position = new Position(context.Line, context.Column);
var c = input[context.Index];
throw new LexingException($"Could not lexize starting from char '{c}'. See '{nameof(LexingException.Position)}' property to get more information.", position);
}
}
return(tokens);
}
public static int GetRemainingCharCount(this LexingContext context)
{
return(context.Length - context.Index);
}
