public static Expression Rewrite(Expression expression, out LabelTarget exitLabel, out ParameterExpression pendingBranch, out IDictionary<LabelTarget, LeaveLabelData> leaveLabels)
{
pendingBranch = Expression.Parameter(typeof(int), "__pendingBranch");
exitLabel = Expression.Label("__leave");
var labelScanner = new LabelScanner();
labelScanner.Visit(expression);
var gotoScanner = new GotoScanner(labelScanner.Labels, exitLabel, pendingBranch);
var res = gotoScanner.Visit(expression);
leaveLabels = gotoScanner.LeaveLabels;
return res;
}
public static Expression Rewrite(Expression expression, out LabelTarget exitLabel, out ParameterExpression pendingBranch, out IDictionary <LabelTarget, LeaveLabelData> leaveLabels)
{
pendingBranch = Expression.Parameter(typeof(int), "__pendingBranch");
exitLabel = Expression.Label("__leave");
var labelScanner = new LabelScanner();
labelScanner.Visit(expression);
var gotoScanner = new GotoScanner(labelScanner.Labels, exitLabel, pendingBranch);
var res = gotoScanner.Visit(expression);
leaveLabels = gotoScanner.LeaveLabels;
return(res);
}
private Expression RewriteHandler(Expression body)
{
//
// 1. Get accessors to the resulting Value and Index.
//
var leaveResultValue = Expression.PropertyOrField(_leaveResult, "Value");
//
// 2. Compute gotos that leave the body.
//
var gotoScanner = new GotoScanner(_labelScanner.Labels);
gotoScanner.Visit(body);
//
// 3. Rewrite body.
//
var leaveLabel = Expression.Label(typeof(LeaveHandlerData));
var rewriter = new Rewriter(leaveLabel, gotoScanner.LeaveLabels);
var newBody = rewriter.Rewrite(body);
//
// 4. Create dispatch table.
//
if (gotoScanner.LeaveLabels.Count > 0)
{
_jumpTable.AddRange(gotoScanner.LeaveLabels.Select(kv =>
{
var index = Expression.Constant(kv.Value);
var label = kv.Key;
var value = label.Type == typeof(void) ? null : Expression.Convert(leaveResultValue, label.Type);
var jump = Expression.Goto(label, value);
return(Expression.SwitchCase(jump, index));
}));
}
return(newBody);
}
private Expression RewriteHandler(Expression body)
{
//
// 1. Get accessors to the resulting Value and Index.
//
var leaveResultValue = Expression.PropertyOrField(_leaveResult, "Value");
//
// 2. Compute gotos that leave the body.
//
var gotoScanner = new GotoScanner(_labelScanner.Labels);
gotoScanner.Visit(body);
//
// 3. Rewrite body.
//
var leaveLabel = Expression.Label(typeof(LeaveHandlerData));
var rewriter = new Rewriter(leaveLabel, gotoScanner.LeaveLabels);
var newBody = rewriter.Rewrite(body);
//
// 4. Create dispatch table.
//
if (gotoScanner.LeaveLabels.Count > 0)
{
_jumpTable.AddRange(gotoScanner.LeaveLabels.Select(kv =>
{
var index = Expression.Constant(kv.Value);
var label = kv.Key;
var value = label.Type == typeof(void) ? null : Expression.Convert(leaveResultValue, label.Type);
var jump = Expression.Goto(label, value);
return Expression.SwitchCase(jump, index);
}));
}
return newBody;
}