1 files changed, 120 insertions, 0 deletions
diff --git a/tex/context/base/node-mig.lua b/tex/context/base/node-mig.lua
new file mode 100644
index 000000000..f9f0ad231
--- /dev/null
+++ b/tex/context/base/node-mig.lua
@@ -0,0 +1,120 @@
+if not modules then modules = { } end modules ['node-mig'] = {
+    version   = 1.001,
+    comment   = "companion to node-mig.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local format = string.format
+
+local hlist  = node.id('hlist')
+local vlist  = node.id('vlist')
+local insert = node.id('ins')
+local mark   = node.id('mark')
+
+local has_attribute = node.has_attribute
+local set_attribute = node.set_attribute
+local remove_nodes  = nodes.remove
+
+local migrated = attributes.private("migrated")
+
+local trace_migrations = false
+
+trackers.register("nodes.migrations", function(v) trace_migrations = v end)
+
+local migrate_inserts, migrate_marks
+
+local t_inserts, t_marks, t_sweeps = 0, 0, 0
+
+local function locate(head,first,last,ni,nm)
+    local current = head
+    while current do
+        local id = current.id
+        if id == vlist or id == hlist then
+            current.list, first, last, ni, nm = locate(current.list,first,last,ni,nm)
+            current= current.next
+        elseif migrate_inserts and id == insert then
+            local insert
+            head, current, insert = remove_nodes(head,current)
+            insert.next = nil
+            if first then
+                insert.prev, last.next = last, insert
+            else
+                insert.prev, first = nil, insert
+            end
+            last, ni = insert, ni + 1
+        elseif migrate_marks and id == mark then
+            local mark
+            head, current, mark = remove_nodes(head,current)
+            mark.next = nil
+            if first then
+                mark.prev, last.next = last, mark
+            else
+                mark.prev, first = nil, mark
+            end
+            last, nm = mark, nm + 1
+        else
+            current= current.next
+        end
+    end
+    return head, first, last, ni, nm
+end
+
+function nodes.migrate_outwards(head,where)
+    local done = false
+    if head then
+        local current = head
+        while current do
+            local id = current.id
+            if id == vlist or id == hlist and not has_attribute(current,migrated) then
+                set_attribute(current,migrated,1)
+                t_sweeps = t_sweeps + 1
+                local h = current.list
+                local first, last, ni, nm
+                while h do
+                    local id = h.id
+                    if id == vlist or id == hlist then
+                        h, first, last, ni, nm = locate(h,first,last,0,0)
+                    end
+                    h = h.next
+                end
+                if first then
+                    t_inserts, t_marks = t_inserts + ni, t_marks + nm
+                    if trace_migrations and (ni > 0 or nm > 0) then
+                        logs.report("nodes","sweep %s, %s inserts and %s marks migrated outwards",t_sweeps,ni,nm)
+                    end
+                    -- inserts after head
+                    local n = current.next
+                    if n then
+                        last.next, n.prev = n, last
+                    end
+                    current.next, first.prev = first, current
+                    done, current = true, last
+                end
+            end
+            current = current.next
+        end
+        return head, done
+    end
+end
+
+experiments.register("marks.migrate", function(v)
+    if v then
+        tasks.enableaction("mvlbuilders", "nodes.migrate_outwards")
+    end
+    migrate_marks = v
+end)
+
+experiments.register("inserts.migrate", function(v)
+    if v then
+        tasks.enableaction("mvlbuilders", "nodes.migrate_outwards")
+    end
+    migrate_inserts = v
+end)
+
+statistics.register("node migrations", function()
+    if trace_migrations and t_sweeps > 0 then
+        return format("%s sweeps, %s inserts moved, %s marks moved",t_sweeps,t_inserts,t_marks)
+    end
+end)