public bool ExecuteNext()
{
if (_statement == null)
{
return(false);
}
if (_statement.Type != ASTNodeType.STATEMENT)
{
throw new RunTimeError(_statement, "Invalid script");
}
var node = _statement.FirstChild();
if (node == null)
{
throw new RunTimeError(_statement, "Invalid statement");
}
int depth = 0;
switch (node.Type)
{
case ASTNodeType.IF:
{
PushScope(node);
var expr = node.FirstChild();
var result = EvaluateExpression(ref expr);
// Advance to next statement
_statement = _statement.Next();
// Evaluated true. Jump right into execution.
if (result)
{
break;
}
// The expression evaluated false, so keep advancing until
// we hit an elseif, else, or endif statement that matches
// and try again.
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.IF)
{
depth++;
}
else if (node.Type == ASTNodeType.ELSEIF)
{
if (depth == 0)
{
expr = node.FirstChild();
result = EvaluateExpression(ref expr);
// Evaluated true. Jump right into execution
if (result)
{
_statement = _statement.Next();
break;
}
}
}
else if (node.Type == ASTNodeType.ELSE)
{
if (depth == 0)
{
// Jump into the else clause
_statement = _statement.Next();
break;
}
}
else if (node.Type == ASTNodeType.ENDIF)
{
if (depth == 0)
{
break;
}
depth--;
}
_statement = _statement.Next();
}
if (_statement == null)
{
throw new RunTimeError(node, "If with no matching endif");
}
break;
}
case ASTNodeType.ELSEIF:
// If we hit the elseif statement during normal advancing, skip over it. The only way
// to execute an elseif clause is to jump directly in from an if statement.
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.IF)
{
depth++;
}
else if (node.Type == ASTNodeType.ENDIF)
{
if (depth == 0)
{
break;
}
depth--;
}
_statement = _statement.Next();
}
if (_statement == null)
{
throw new RunTimeError(node, "If with no matching endif");
}
break;
case ASTNodeType.ENDIF:
PopScope();
_statement = _statement.Next();
break;
case ASTNodeType.ELSE:
// If we hit the else statement during normal advancing, skip over it. The only way
// to execute an else clause is to jump directly in from an if statement.
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.IF)
{
depth++;
}
else if (node.Type == ASTNodeType.ENDIF)
{
if (depth == 0)
{
break;
}
depth--;
}
_statement = _statement.Next();
}
if (_statement == null)
{
throw new RunTimeError(node, "If with no matching endif");
}
break;
case ASTNodeType.WHILE:
{
// When we first enter the loop, push a new scope
if (_scope.StartNode != node)
{
PushScope(node);
}
var expr = node.FirstChild();
var result = EvaluateExpression(ref expr);
// Advance to next statement
_statement = _statement.Next();
// The expression evaluated false, so keep advancing until
// we hit an endwhile statement.
if (!result)
{
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.WHILE)
{
depth++;
}
else if (node.Type == ASTNodeType.ENDWHILE)
{
if (depth == 0)
{
PopScope();
// Go one past the endwhile so the loop doesn't repeat
_statement = _statement.Next();
break;
}
depth--;
}
_statement = _statement.Next();
}
}
break;
}
case ASTNodeType.ENDWHILE:
// Walk backward to the while statement
_statement = _statement.Prev();
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.ENDWHILE)
{
depth++;
}
else if (node.Type == ASTNodeType.WHILE)
{
if (depth == 0)
{
break;
}
depth--;
}
_statement = _statement.Prev();
}
if (_statement == null)
{
throw new RunTimeError(node, "Unexpected endwhile");
}
break;
case ASTNodeType.FOR:
{
// The iterator variable's name is the hash code of the for loop's ASTNode.
var iterName = node.GetHashCode().ToString();
// When we first enter the loop, push a new scope
if (_scope.StartNode != node)
{
PushScope(node);
// Grab the arguments
var max = node.FirstChild();
if (max.Type != ASTNodeType.INTEGER)
{
throw new RunTimeError(max, "Invalid for loop syntax");
}
// Create a dummy argument that acts as our loop variable
var iter = new ASTNode(ASTNodeType.INTEGER, "0", node, 0);
_scope.SetVar(iterName, new Argument(this, iter));
}
else
{
// Increment the iterator argument
var arg = _scope.GetVar(iterName);
var iter = new ASTNode(ASTNodeType.INTEGER, (arg.AsUInt() + 1).ToString(), node, 0);
_scope.SetVar(iterName, new Argument(this, iter));
}
// Check loop condition
var i = _scope.GetVar(iterName);
// Grab the max value to iterate to
node = node.FirstChild();
var end = new Argument(this, node);
if (i.AsUInt() < end.AsUInt())
{
// enter the loop
_statement = _statement.Next();
}
else
{
// Walk until the end of the loop
_statement = _statement.Next();
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.FOR ||
node.Type == ASTNodeType.FOREACH)
{
depth++;
}
else if (node.Type == ASTNodeType.ENDFOR)
{
if (depth == 0)
{
PopScope();
// Go one past the end so the loop doesn't repeat
_statement = _statement.Next();
break;
}
depth--;
}
_statement = _statement.Next();
}
}
}
break;
case ASTNodeType.FOREACH:
{
// foreach VAR in LIST
// The iterator's name is the hash code of the for loop's ASTNode.
var varName = node.FirstChild().Lexeme;
var listName = node.FirstChild().Next().Lexeme;
var iterName = node.GetHashCode().ToString();
// When we first enter the loop, push a new scope
if (_scope.StartNode != node)
{
PushScope(node);
// Create a dummy argument that acts as our iterator object
var iter = new ASTNode(ASTNodeType.INTEGER, "0", node, 0);
_scope.SetVar(iterName, new Argument(this, iter));
// Make the user-chosen variable have the value for the front of the list
var arg = Interpreter.GetListValue(listName, 0);
if (arg != null)
{
_scope.SetVar(varName, arg);
}
else
{
_scope.ClearVar(varName);
}
}
else
{
// Increment the iterator argument
var idx = _scope.GetVar(iterName).AsInt() + 1;
var iter = new ASTNode(ASTNodeType.INTEGER, idx.ToString(), node, 0);
_scope.SetVar(iterName, new Argument(this, iter));
// Update the user-chosen variable
var arg = Interpreter.GetListValue(listName, idx);
if (arg != null)
{
_scope.SetVar(varName, arg);
}
else
{
_scope.ClearVar(varName);
}
}
// Check loop condition
var i = _scope.GetVar(varName);
if (i != null)
{
// enter the loop
_statement = _statement.Next();
}
else
{
// Walk until the end of the loop
_statement = _statement.Next();
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.FOR ||
node.Type == ASTNodeType.FOREACH)
{
depth++;
}
else if (node.Type == ASTNodeType.ENDFOR)
{
if (depth == 0)
{
PopScope();
// Go one past the end so the loop doesn't repeat
_statement = _statement.Next();
break;
}
depth--;
}
_statement = _statement.Next();
}
}
break;
}
case ASTNodeType.ENDFOR:
// Walk backward to the for statement
_statement = _statement.Prev();
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.FOR ||
node.Type == ASTNodeType.FOREACH)
{
break;
}
_statement = _statement.Prev();
}
if (_statement == null)
{
throw new RunTimeError(node, "Unexpected endfor");
}
break;
case ASTNodeType.BREAK:
// Walk until the end of the loop
_statement = _statement.Next();
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.WHILE ||
node.Type == ASTNodeType.FOR ||
node.Type == ASTNodeType.FOREACH)
{
depth++;
}
else if (node.Type == ASTNodeType.ENDWHILE ||
node.Type == ASTNodeType.ENDFOR)
{
if (depth == 0)
{
PopScope();
// Go one past the end so the loop doesn't repeat
_statement = _statement.Next();
break;
}
depth--;
}
_statement = _statement.Next();
}
PopScope();
break;
case ASTNodeType.CONTINUE:
// Walk backward to the loop statement
_statement = _statement.Prev();
depth = 0;
while (_statement != null)
{
node = _statement.FirstChild();
if (node.Type == ASTNodeType.ENDWHILE ||
node.Type == ASTNodeType.ENDFOR)
{
depth++;
}
else if (node.Type == ASTNodeType.WHILE ||
node.Type == ASTNodeType.FOR ||
node.Type == ASTNodeType.FOREACH)
{
if (depth == 0)
{
break;
}
depth--;
}
_statement = _statement.Prev();
}
if (_statement == null)
{
throw new RunTimeError(node, "Unexpected continue");
}
break;
case ASTNodeType.STOP:
_statement = null;
break;
case ASTNodeType.REPLAY:
_statement = _statement.Parent.FirstChild();
break;
case ASTNodeType.QUIET:
case ASTNodeType.FORCE:
case ASTNodeType.COMMAND:
if (ExecuteCommand(node))
{
_statement = _statement.Next();
}
break;
}
return((_statement != null) ? true : false);
}
public void SetVar(string name, Argument val)
{
_namespace[name] = val;
}