1 files changed, 91 insertions, 0 deletions
diff --git a/kalyptus/Ast.pm b/kalyptus/Ast.pm
new file mode 100644
index 0000000..0fb4bd0
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+++ b/kalyptus/Ast.pm
@@ -0,0 +1,91 @@
+package Ast;
+use strict;
+
+use vars qw/ $this $pack @endCodes /;
+
+#-----------------------------------------------------------------------------
+# This package is used  to create a simple Abstract Syntax tree. Each node
+# in the AST is an associative array and supports two kinds of properties -
+# scalars and lists of scalars.
+# See SchemParser.pm for an example of usage.
+#                                                               ... Sriram
+#-----------------------------------------------------------------------------
+
+# Constructor 
+# e.g AST::New ("personnel")
+# Stores the argument in a property called astNodeName whose sole purpose
+# is to support Print()
+
+sub New {
+	my ($this) = {"astNodeName" => $_[0]};
+	bless ($this);
+	return $this;
+}
+
+# Add a property to this object
+# $astNode->AddProp("className", "Employee");
+
+sub AddProp {
+	my ($this) = $_[0];
+	$this->{$_[1]} = $_[2];
+}
+
+# Equivalent to AddProp, except the property name is associated
+# with a list of values
+# $classAstNode->AddProp("attrList", $attrAstNode);
+
+sub AddPropList {
+	my ($this) = $_[0];
+	if (! exists $this->{$_[1]}) {
+		$this->{$_[1]} = [];
+	}
+	push (@{$this->{$_[1]}}, $_[2]);
+}
+
+# Returns a list of all the property names of this object
+sub GetProps {
+	my ($this) = $_[0];
+	return keys %{$this};
+}
+
+sub Visit {
+    # Converts each of this AstNode's properties into global variables.
+    # The global variables are introduced into package "main"
+    # At the same time, a piece of code is  formed to undo this work above -
+    # $endCode essentially contains the values of these global variables
+    # before  they are mangled. endCode gets pushed into a stack (endCodes),
+    # which is unwound by UnVisit().
+
+    local ($this, $pack) = @_;
+
+
+    my $code = ""; 
+    my $endCode = "";
+
+
+    foreach my $k (keys %{$this}) {
+
+	my $glob = $pack."::".$k;
+
+	if ( defined $$glob ) {
+
+		if ( ${$glob} ne "" ) {
+			$$glob =~ s/\'/\\\'/g; 
+		}
+
+	    $endCode .= '$'.$pack.'::'.$k. " = '".$$glob."';";
+	} else {
+	    $endCode .= '$'.$pack . "::". $k . ' = "";';
+	}
+	$code .= '$'.$pack . "::" . $k . "= \$this->{\"$k\"};";
+    }
+    push (@endCodes, $endCode);
+    eval($code) if $code;
+}
+
+sub UnVisit {
+    my $code = pop(@endCodes);
+    eval($code) if ($code);
+}
+
+1;