public DekiScriptOutputBuffer.Range Visit(DekiScriptSwitch expr, DekiScriptExpressionEvaluationState state)
{
DekiScriptLiteral value = state.Pop(expr.Value.VisitWith(this, state));
DekiScriptSwitch.CaseBlock caseBlock = null;
// have to use for instead of foreach, since a fallthrough default case needs to be able to look ahead
for (int i = 0; i < expr.Cases.Length; i++)
{
DekiScriptSwitch.CaseBlock current = expr.Cases[i];
// check for default case
foreach (DekiScriptExpression condition in current.Conditions)
{
if (condition == null)
{
// check if this is the first default we've found
if (caseBlock == null)
{
caseBlock = current;
}
// continue in case loop, since default only gets executed if there is no match
continue;
}
// evaluate test
DekiScriptExpression test = DekiScriptExpression.BinaryOp(current.Location, DekiScriptBinary.Op.Equal, value, condition);
DekiScriptLiteral caseMatch = state.Pop(test.VisitWith(this, state));
// evaluate body on success
if (!caseMatch.IsNilFalseZero)
{
// found a matching cast statement
caseBlock = current;
break;
}
}
}
// haven't found a match yet, so if we have a default, return it
if (caseBlock != null)
{
int marker = state.Buffer.Marker;
try {
return(caseBlock.Body.VisitWith(this, state));
} catch (DekiScriptBreakException) {
// nothing to do
}
return(state.Buffer.Since(marker));
}
return(DekiScriptOutputBuffer.Range.Empty);
}
private object Optimize(DekiScriptSwitch.CaseBlock expr, DekiScriptExpression value, DekiScriptExpressionEvaluationState state, out bool isDefaultCase)
{
List <DekiScriptExpression> conditions = new List <DekiScriptExpression>();
isDefaultCase = false;
for (int i = 0; i < expr.Conditions.Length; i++)
{
if (expr.Conditions[i] != null)
{
DekiScriptExpression condition = expr.Conditions[i].VisitWith(this, state);
// check if condition always succeeds or always fails
if ((value is DekiScriptLiteral) && (condition is DekiScriptLiteral))
{
var test = DekiScriptExpression.BinaryOp(Location.None, DekiScriptBinary.Op.Equal, value, condition);
var result = state.Pop(test.VisitWith(DekiScriptExpressionEvaluation.Instance, state));
if (!result.IsNilFalseZero)
{
// NOTE (steveb): we wrap the outcome into a sequence to ensure proper handling of break/continue statements
// condition succeeded, return it
return(DekiScriptExpression.Block(expr.Location, new[] { expr.Body.VisitWith(this, state) }));
}
}
else
{
conditions.Add(condition);
}
}
else
{
isDefaultCase = true;
conditions.Add(null);
}
}
// check if any conditions were true or unknown
if (conditions.Count == 0)
{
return(null);
}
DekiScriptExpression body = expr.Body.VisitWith(this, state);
return(new DekiScriptSwitch.CaseBlock(expr.Location, conditions.ToArray(), body));
}
