From 8f4b616d6576e9b7d73d621515b82fe475e3ffe7 Mon Sep 17 00:00:00 2001
From: Vern Paxson <vern@corelight.com>
Date: Mon, 4 Jan 2021 14:17:56 -0800
Subject: [PATCH] changes to Frames to support access to
 captured-by-copy-semantics variables

---
 src/Frame.cc | 35 +++++++++++++++++++++++++++++------
 src/Frame.h  | 25 ++++++++++++++++++++++---
 2 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/src/Frame.cc b/src/Frame.cc
index 12a01bb57e..05f4d3117f 100644
--- a/src/Frame.cc
+++ b/src/Frame.cc
@@ -30,6 +30,15 @@ Frame::Frame(int arg_size, const ScriptFunc* func, const zeek::Args* fn_args)
 	delayed = false;
 
 	closure = nullptr;
+
+	// We could Ref()/Unref() the captures frame, but there's really
+	// no need because by definition this current frame exists to
+	// enable execution of the function, and its captures frame won't
+	// go away until the function itself goes away, which can only be
+	// after this frame does.
+	captures = function ? function->GetCapturesFrame() : nullptr;
+	captures_offset_map =
+		function ? function->GetCapturesOffsetMap() : nullptr;
 	}
 
 Frame::~Frame()
@@ -80,11 +89,18 @@ void Frame::SetElementWeak(int n, Val* v)
 
 void Frame::SetElement(const ID* id, ValPtr v)
 	{
-	if ( closure )
+	if ( closure && IsOuterID(id) )
 		{
-		if ( IsOuterID(id) )
+		closure->SetElement(id, std::move(v));
+		return;
+		}
+
+	if ( captures )
+		{
+		auto cap_off = captures_offset_map->find(id->Name());
+		if ( cap_off != captures_offset_map->end() )
 			{
-			closure->SetElement(id, std::move(v));
+			captures->SetElement(cap_off->second, std::move(v));
 			return;
 			}
 		}
@@ -109,10 +125,14 @@ void Frame::SetElement(const ID* id, ValPtr v)
 
 const ValPtr& Frame::GetElementByID(const ID* id) const
 	{
-	if ( closure )
+	if ( closure && IsOuterID(id) )
+		return closure->GetElementByID(id);
+
+	if ( captures )
 		{
-		if ( IsOuterID(id) )
-			return closure->GetElementByID(id);
+		auto cap_off = captures_offset_map->find(id->Name());
+		if ( cap_off != captures_offset_map->end() )
+			return captures->GetElement(cap_off->second);
 		}
 
 	// do we have an offset for it?
@@ -185,6 +205,9 @@ Frame* Frame::Clone() const
 		if ( frame[i].val )
 			other->frame[i].val = frame[i].val->Clone();
 
+	// Note, there's no need to clone "captures" or "captures_offset_map"
+	// since those get created fresh when constructing "other".
+
 	return other;
 	}
 
diff --git a/src/Frame.h b/src/Frame.h
index e78bdcf492..7f5abd0e4c 100644
--- a/src/Frame.h
+++ b/src/Frame.h
@@ -286,9 +286,12 @@ private:
 	 */
 	void ClearElement(int n);
 
-	/** Have we captured this id? */
+	/** Have we captured this id?  Version for deprecated semantics. */
 	bool IsOuterID(const ID* in) const;
 
+	/** Have we captured this id?  Version for current semantics. */
+	bool IsCaptureID(const ID* in) const;
+
 	/** Serializes an offset_map */
 	static broker::expected<broker::data>
 	SerializeOffsetMap(const OffsetMap& in);
@@ -316,10 +319,12 @@ private:
 	/** Associates ID's offsets with values. */
 	std::unique_ptr<Element[]> frame;
 
-	/** The enclosing frame of this frame. */
+	/** The enclosing frame of this frame. Used for reference semantics. */
 	Frame* closure;
 
-	/** ID's used in this frame from the enclosing frame. */
+	/** ID's used in this frame from the enclosing frame, when using
+	 * reference semantics (closure != nullptr).
+	 */
 	IDPList outer_ids;
 
 	/**
@@ -328,8 +333,22 @@ private:
 	 */
 	std::unique_ptr<OffsetMap> offset_map;
 
+	/** Frame used for captures (if any) with copy semantics. */
+	Frame* captures;
+
+	/** Maps IDs to offsets into the "captures" frame.  If the ID
+	 * isn't present, then it's not a capture.
+	 *
+	 * We keep this separate from offset_map to help ensure we don't
+	 * confuse code from the deprecated semantics with the current
+	 * semantics.
+	 */
+	const OffsetMap* captures_offset_map;
+
 	/** The function this frame is associated with. */
 	const ScriptFunc* function;
+
+	// The following is only needed for the debugger.
 	/** The arguments to the function that this Frame is associated with. */
 	const zeek::Args* func_args;