/**
* Finds the look-ahead set for a production pattern element. The
* maximum look-ahead length must be specified. This method does
* NOT take the element repeat into consideration when creating
* the look-ahead set. It is also possible to specify a look-ahead
* set filter, which will make sure that unnecessary token
* sequences will be avoided.
*
* @param elem the production pattern element
* @param length the maximum look-ahead length
* @param dummy a parameter to distinguish the method
* @param stack the call stack used for loop detection
* @param filter the look-ahead set filter
*
* @return the look-ahead set for the pattern element
*
* @throws ParserCreationException if an infinite loop was found
* in the grammar
*/
private LookAheadSet FindLookAhead(ProductionPatternElement elem,
int length,
int dummy,
CallStack stack,
LookAheadSet filter)
{
LookAheadSet result;
ProductionPattern pattern;
if (elem.IsToken())
{
result = new LookAheadSet(length);
result.Add(elem.Id);
}
else
{
pattern = GetPattern(elem.Id);
result = FindLookAhead(pattern, length, stack, filter);
if (stack.Contains(pattern.Name))
{
result = result.CreateRepetitive();
}
}
return(result);
}
/**
* Checks a production pattern element for completeness. If
* the element references a production pattern not added to
* this parser, a parser creation exception will be thrown.
*
* @param name the name of the pattern being checked
* @param elem the production pattern element to check
*
* @throws ParserCreationException if the element referenced a
* pattern not added to this parser
*/
private void CheckElement(string name,
ProductionPatternElement elem)
{
if (elem.IsProduction() && GetPattern(elem.Id) == null)
{
throw new ParserCreationException(
ParserCreationException.ErrorType.INVALID_PRODUCTION,
name,
"an undefined production pattern id (" + elem.Id +
") is referenced");
}
}
/**
* Adds a production pattern element to this alternative. The
* multiplicity values in the element will be overridden with
* the specified values. The element is appended to the end of
* the element list.
*
* @param elem the production pattern element
* @param min the minimum number of occurancies
* @param max the maximum number of occurancies, or
* -1 for infinite
*/
public void AddElement(ProductionPatternElement elem,
int min,
int max)
{
if (elem.IsToken())
{
AddToken(elem.Id, min, max);
}
else
{
AddProduction(elem.Id, min, max);
}
}
/**
* Finds the look-ahead set for a production pattern element. The
* maximum look-ahead length must be specified. This method takes
* the element repeats into consideration when creating the
* look-ahead set, but does NOT include an empty sequence even if
* the minimum count is zero (0). It is also possible to specify a
* look-ahead set filter, which will make sure that unnecessary
* token sequences will be avoided.
*
* @param elem the production pattern element
* @param length the maximum look-ahead length
* @param stack the call stack used for loop detection
* @param filter the look-ahead set filter
*
* @return the look-ahead set for the pattern element
*
* @throws ParserCreationException if an infinite loop was found
* in the grammar
*/
private LookAheadSet FindLookAhead(ProductionPatternElement elem,
int length,
CallStack stack,
LookAheadSet filter)
{
LookAheadSet result;
LookAheadSet first;
LookAheadSet follow;
int max;
// Find initial element look-ahead
first = FindLookAhead(elem, length, 0, stack, filter);
result = new LookAheadSet(length);
result.AddAll(first);
if (filter == null || !filter.IsOverlap(result))
{
return(result);
}
// Handle element repetitions
if (elem.MaxCount == Int32.MaxValue)
{
first = first.CreateRepetitive();
}
max = elem.MaxCount;
if (length < max)
{
max = length;
}
for (int i = 1; i < max; i++)
{
first = first.CreateOverlaps(filter);
if (first.Size() <= 0 || first.GetMinLength() >= length)
{
break;
}
follow = FindLookAhead(elem,
length,
0,
stack,
filter.CreateFilter(first));
first = first.CreateCombination(follow);
result.AddAll(first);
}
return(result);
}
/**
* Checks if the next tokens match a production pattern
* element. If the element has a look-ahead set it will be
* used, otherwise the look-ahead set of the referenced
* production or token will be used.
*
* @param elem the pattern element to check
*
* @return true if the next tokens match, or
* false otherwise
*/
private bool IsNext(ProductionPatternElement elem)
{
LookAheadSet set = elem.LookAhead;
if (set != null)
{
return(set.IsNext(this));
}
else if (elem.IsToken())
{
return(elem.IsMatch(PeekToken(0)));
}
else
{
return(IsNext(GetPattern(elem.Id)));
}
}
/**
* Parses a production pattern element. All nodes parsed may
* or may not be added to the parse tree node specified,
* depending on the analyzer callbacks.
*
* @param node the production parse tree node
* @param elem the production pattern element to parse
*
* @throws ParseException if the input couldn't be parsed
* correctly
*/
private void ParseElement(Production node,
ProductionPatternElement elem)
{
Node child;
for (int i = 0; i < elem.MaxCount; i++)
{
string pr = Enum.GetName(typeof(SyntaxConstants), elem.GetId());
if (i < elem.MinCount || IsNext(elem))
{
if (elem.IsToken())
{
child = NextToken(elem.Id);
EnterNode(child);
AddNode(node, ExitNode(child));
if (ExitNode(child) != null)
{
production.AddRecursiveProduction("Enter: " + pr + "\n");
}
production.AddProductionCode(elem.GetId());
production.AddProductionState("Enter: " + pr + "\n");
}
else
{
pr = pr.Substring(5);
production.AddRecursiveProduction("Enter: <" + pr + ">\n");
production.AddProductionCode(elem.GetId());
production.AddProductionState("Enter: <" + pr + ">\n");
child = ParsePattern(GetPattern(elem.Id));
AddNode(node, child);
}
}
else
{
pr = pr.Substring(5);
production.AddRecursiveProduction("Enter: NULL <" + pr + ">\n");
production.AddProductionState("NULL");
production.AddProductionCode(elem.GetId());
break;
}
}
}
/**
* Returns a string representation of a production pattern
* element.
*
* @param elem the production pattern element
*
* @return a detailed string representation of the element
*/
private string ToString(ProductionPatternElement elem)
{
StringBuilder buffer = new StringBuilder();
int min = elem.MinCount;
int max = elem.MaxCount;
if (min == 0 && max == 1)
{
buffer.Append("[");
}
if (elem.IsToken())
{
buffer.Append(GetTokenDescription(elem.Id));
}
else
{
buffer.Append(GetPattern(elem.Id).Name);
}
if (min == 0 && max == 1)
{
buffer.Append("]");
}
else if (min == 0 && max == Int32.MaxValue)
{
buffer.Append("*");
}
else if (min == 1 && max == Int32.MaxValue)
{
buffer.Append("+");
}
else if (min != 1 || max != 1)
{
buffer.Append("{");
buffer.Append(min);
buffer.Append(",");
buffer.Append(max);
buffer.Append("}");
}
return(buffer.ToString());
}
/**
* Adds a production pattern element to this alternative. The
* element is appended to the end of the element list.
*
* @param elem the production pattern element
*/
public void AddElement(ProductionPatternElement elem)
{
elements.Add(elem);
}
