[fontloader] reorganize under the new import scheme

For better orientation, the fontloader tree now contains two
subdirectories into which files have been reorganized:

The two files required at runtime for the fontloader and luaotfload-tool
are:

      × ``fontloader-basics-gen.lua``
      × ``fontloader-fontloader.lua``

They are now kept in the ``src/fontloader/runtime/`` subdirectory.

All other files from upstream are now located in
``src/fontloader/misc``. This includes a number of files that have not
yet been part of Luaotfload. Currently, the *misc* set of files is not
packaged along with Luaotfload. This may change in the future when there
is an option to switch the merged fontloader for its constituent files,
or even for upstream.

1 files changed, 906 insertions, 0 deletions

diff --git a/src/fontloader/misc/fontloader-font-otp.lua b/src/fontloader/misc/fontloader-font-otp.lua
new file mode 100644
index 0000000..63e4184
--- /dev/null
+++ b/src/fontloader/misc/fontloader-font-otp.lua
@@ -0,0 +1,906 @@
+if not modules then modules = { } end modules ['font-otp'] = {
+    version   = 1.001,
+    comment   = "companion to font-otf.lua (packing)",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+-- todo: pack math (but not that much to share)
+--
+-- pitfall 5.2: hashed tables can suddenly become indexed with nil slots
+
+local next, type = next, type
+local sort, concat = table.sort, table.concat
+local sortedhash = table.sortedhash
+
+local trace_packing = false  trackers.register("otf.packing", function(v) trace_packing = v end)
+local trace_loading = false  trackers.register("otf.loading", function(v) trace_loading = v end)
+
+local report_otf    = logs.reporter("fonts","otf loading")
+
+-- also used in other scripts so we need to check some tables:
+
+fonts               = fonts or { }
+
+local handlers      = fonts.handlers or { }
+fonts.handlers      = handlers
+
+local otf           = handlers.otf or { }
+handlers.otf        = otf
+
+local enhancers     = otf.enhancers or { }
+otf.enhancers       = enhancers
+
+local glists        = otf.glists or { "gsub", "gpos" }
+otf.glists          = glists
+
+local criterium     = 1
+local threshold     = 0
+
+local function tabstr_normal(t)
+    local s = { }
+    local n = 0
+    for k, v in next, t do
+        n = n + 1
+        if type(v) == "table" then
+            s[n] = k .. ">" .. tabstr_normal(v)
+        elseif v == true then
+            s[n] = k .. "+" -- "=true"
+        elseif v then
+            s[n] = k .. "=" .. v
+        else
+            s[n] = k .. "-" -- "=false"
+        end
+    end
+    if n == 0 then
+        return ""
+    elseif n == 1 then
+        return s[1]
+    else
+        sort(s) -- costly but needed (occasional wrong hit otherwise)
+        return concat(s,",")
+    end
+end
+
+local function tabstr_flat(t)
+    local s = { }
+    local n = 0
+    for k, v in next, t do
+        n = n + 1
+        s[n] = k .. "=" .. v
+    end
+    if n == 0 then
+        return ""
+    elseif n == 1 then
+        return s[1]
+    else
+        sort(s) -- costly but needed (occasional wrong hit otherwise)
+        return concat(s,",")
+    end
+end
+
+local function tabstr_mixed(t) -- indexed
+    local s = { }
+    local n = #t
+    if n == 0 then
+        return ""
+    elseif n == 1 then
+        local k = t[1]
+        if k == true then
+            return "++" -- we need to distinguish from "true"
+        elseif k == false then
+            return "--" -- we need to distinguish from "false"
+        else
+            return tostring(k) -- number or string
+        end
+    else
+        for i=1,n do
+            local k = t[i]
+            if k == true then
+                s[i] = "++" -- we need to distinguish from "true"
+            elseif k == false then
+                s[i] = "--" -- we need to distinguish from "false"
+            else
+                s[i] = k -- number or string
+            end
+        end
+        return concat(s,",")
+    end
+end
+
+local function tabstr_boolean(t)
+    local s = { }
+    local n = 0
+    for k, v in next, t do
+        n = n + 1
+        if v then
+            s[n] = k .. "+"
+        else
+            s[n] = k .. "-"
+        end
+    end
+    if n == 0 then
+        return ""
+    elseif n == 1 then
+        return s[1]
+    else
+        sort(s) -- costly but needed (occasional wrong hit otherwise)
+        return concat(s,",")
+    end
+end
+
+-- tabstr_boolean_x = tabstr_boolean
+
+-- tabstr_boolean = function(t)
+--     local a = tabstr_normal(t)
+--     local b = tabstr_boolean_x(t)
+--     print(a)
+--     print(b)
+--     return b
+-- end
+
+-- beware: we cannot unpack and repack the same table because then sharing
+-- interferes (we could catch this if needed) .. so for now: save, reload
+-- and repack in such cases (never needed anyway) .. a tricky aspect is that
+-- we then need to sort more thanks to random hashing
+
+local function packdata(data)
+    if data then
+     -- stripdata(data)
+        local h, t, c = { }, { }, { }
+        local hh, tt, cc = { }, { }, { }
+        local nt, ntt = 0, 0
+        local function pack_normal(v)
+            local tag = tabstr_normal(v)
+            local ht = h[tag]
+            if ht then
+                c[ht] = c[ht] + 1
+                return ht
+            else
+                nt = nt + 1
+                t[nt] = v
+                h[tag] = nt
+                c[nt] = 1
+                return nt
+            end
+        end
+        local function pack_flat(v)
+            local tag = tabstr_flat(v)
+            local ht = h[tag]
+            if ht then
+                c[ht] = c[ht] + 1
+                return ht
+            else
+                nt = nt + 1
+                t[nt] = v
+                h[tag] = nt
+                c[nt] = 1
+                return nt
+            end
+        end
+        local function pack_boolean(v)
+            local tag = tabstr_boolean(v)
+            local ht = h[tag]
+            if ht then
+                c[ht] = c[ht] + 1
+                return ht
+            else
+                nt = nt + 1
+                t[nt] = v
+                h[tag] = nt
+                c[nt] = 1
+                return nt
+            end
+        end
+        local function pack_indexed(v)
+            local tag = concat(v," ")
+            local ht = h[tag]
+            if ht then
+                c[ht] = c[ht] + 1
+                return ht
+            else
+                nt = nt + 1
+                t[nt] = v
+                h[tag] = nt
+                c[nt] = 1
+                return nt
+            end
+        end
+        local function pack_mixed(v)
+            local tag = tabstr_mixed(v)
+            local ht = h[tag]
+            if ht then
+                c[ht] = c[ht] + 1
+                return ht
+            else
+                nt = nt + 1
+                t[nt] = v
+                h[tag] = nt
+                c[nt] = 1
+                return nt
+            end
+        end
+        local function pack_final(v)
+            -- v == number
+            if c[v] <= criterium then
+                return t[v]
+            else
+                -- compact hash
+                local hv = hh[v]
+                if hv then
+                    return hv
+                else
+                    ntt = ntt + 1
+                    tt[ntt] = t[v]
+                    hh[v] = ntt
+                    cc[ntt] = c[v]
+                    return ntt
+                end
+            end
+        end
+        local function success(stage,pass)
+            if nt == 0 then
+                if trace_loading or trace_packing then
+                    report_otf("pack quality: nothing to pack")
+                end
+                return false
+            elseif nt >= threshold then
+                local one, two, rest = 0, 0, 0
+                if pass == 1 then
+                    for k,v in next, c do
+                        if v == 1 then
+                            one = one + 1
+                        elseif v == 2 then
+                            two = two + 1
+                        else
+                            rest = rest + 1
+                        end
+                    end
+                else
+                    for k,v in next, cc do
+                        if v > 20 then
+                            rest = rest + 1
+                        elseif v > 10 then
+                            two = two + 1
+                        else
+                            one = one + 1
+                        end
+                    end
+                    data.tables = tt
+                end
+                if trace_loading or trace_packing then
+                    report_otf("pack quality: stage %s, pass %s, %s packed, 1-10:%s, 11-20:%s, rest:%s (criterium: %s)", stage, pass, one+two+rest, one, two, rest, criterium)
+                end
+                return true
+            else
+                if trace_loading or trace_packing then
+                    report_otf("pack quality: stage %s, pass %s, %s packed, aborting pack (threshold: %s)", stage, pass, nt, threshold)
+                end
+                return false
+            end
+        end
+        local function packers(pass)
+            if pass == 1 then
+                return pack_normal, pack_indexed, pack_flat, pack_boolean, pack_mixed
+            else
+                return pack_final, pack_final, pack_final, pack_final, pack_final
+            end
+        end
+        local resources = data.resources
+        local lookuptypes = resources.lookuptypes
+        for pass=1,2 do
+            if trace_packing then
+                report_otf("start packing: stage 1, pass %s",pass)
+            end
+            local pack_normal, pack_indexed, pack_flat, pack_boolean, pack_mixed = packers(pass)
+            for unicode, description in next, data.descriptions do
+                local boundingbox = description.boundingbox
+                if boundingbox then
+                    description.boundingbox = pack_indexed(boundingbox)
+                end
+                local slookups = description.slookups
+                if slookups then
+                    for tag, slookup in next, slookups do
+                        local what = lookuptypes[tag]
+                        if what == "pair" then
+                            local t = slookup[2] if t then slookup[2] = pack_indexed(t) end
+                            local t = slookup[3] if t then slookup[3] = pack_indexed(t) end
+                        elseif what ~= "substitution" then
+                            slookups[tag] = pack_indexed(slookup) -- true is new
+                        end
+                    end
+                end
+                local mlookups = description.mlookups
+                if mlookups then
+                    for tag, mlookup in next, mlookups do
+                        local what = lookuptypes[tag]
+                        if what == "pair" then
+                            for i=1,#mlookup do
+                                local lookup = mlookup[i]
+                                local t = lookup[2] if t then lookup[2] = pack_indexed(t) end
+                                local t = lookup[3] if t then lookup[3] = pack_indexed(t) end
+                            end
+                        elseif what ~= "substitution" then
+                            for i=1,#mlookup do
+                                mlookup[i] = pack_indexed(mlookup[i]) -- true is new
+                            end
+                        end
+                    end
+                end
+                local kerns = description.kerns
+                if kerns then
+                    for tag, kern in next, kerns do
+                        kerns[tag] = pack_flat(kern)
+                    end
+                end
+                local math = description.math
+                if math then
+                    local kerns = math.kerns
+                    if kerns then
+                        for tag, kern in next, kerns do
+                            kerns[tag] = pack_normal(kern)
+                        end
+                    end
+                end
+                local anchors = description.anchors
+                if anchors then
+                    for what, anchor in next, anchors do
+                        if what == "baselig" then
+                            for _, a in next, anchor do
+                                for k=1,#a do
+                                    a[k] = pack_indexed(a[k])
+                                end
+                            end
+                        else
+                            for k, v in next, anchor do
+                                anchor[k] = pack_indexed(v)
+                            end
+                        end
+                    end
+                end
+                local altuni = description.altuni
+                if altuni then
+                    for i=1,#altuni do
+                        altuni[i] = pack_flat(altuni[i])
+                    end
+                end
+            end
+            local lookups = data.lookups
+            if lookups then
+                for _, lookup in next, lookups do
+                    local rules = lookup.rules
+                    if rules then
+                        for i=1,#rules do
+                            local rule = rules[i]
+                            local r = rule.before       if r then for i=1,#r do r[i] = pack_boolean(r[i]) end end
+                            local r = rule.after        if r then for i=1,#r do r[i] = pack_boolean(r[i]) end end
+                            local r = rule.current      if r then for i=1,#r do r[i] = pack_boolean(r[i]) end end
+                            local r = rule.replacements if r then rule.replacements  = pack_flat   (r)    end -- can have holes
+                            local r = rule.lookups      if r then rule.lookups       = pack_indexed(r)    end -- can have ""
+                         -- local r = rule.lookups      if r then rule.lookups       = pack_flat(r)       end -- can have holes (already taken care of some cases)
+                        end
+                    end
+                end
+            end
+            local anchor_to_lookup  = resources.anchor_to_lookup
+            if anchor_to_lookup then
+                for anchor, lookup in next, anchor_to_lookup do
+                    anchor_to_lookup[anchor] = pack_normal(lookup)
+                end
+            end
+            local lookup_to_anchor = resources.lookup_to_anchor
+            if lookup_to_anchor then
+                for lookup, anchor in next, lookup_to_anchor do
+                    lookup_to_anchor[lookup] = pack_normal(anchor)
+                end
+            end
+            local sequences = resources.sequences
+            if sequences then
+                for feature, sequence in next, sequences do
+                    local flags = sequence.flags
+                    if flags then
+                        sequence.flags = pack_normal(flags)
+                    end
+                    local subtables = sequence.subtables
+                    if subtables then
+                        sequence.subtables = pack_normal(subtables)
+                    end
+                    local features = sequence.features
+                    if features then
+                        for script, feature in next, features do
+                            features[script] = pack_normal(feature)
+                        end
+                    end
+                    local order = sequence.order
+                    if order then
+                        sequence.order = pack_indexed(order)
+                    end
+                    local markclass = sequence.markclass
+                    if markclass then
+                        sequence.markclass = pack_boolean(markclass)
+                    end
+                end
+            end
+            local lookups = resources.lookups
+            if lookups then
+                for name, lookup in next, lookups do
+                    local flags = lookup.flags
+                    if flags then
+                        lookup.flags = pack_normal(flags)
+                    end
+                    local subtables = lookup.subtables
+                    if subtables then
+                        lookup.subtables = pack_normal(subtables)
+                    end
+                end
+            end
+            local features = resources.features
+            if features then
+                for _, what in next, glists do
+                    local list = features[what]
+                    if list then
+                        for feature, spec in next, list do
+                            list[feature] = pack_normal(spec)
+                        end
+                    end
+                end
+            end
+            if not success(1,pass) then
+                return
+            end
+        end
+        if nt > 0 then
+            for pass=1,2 do
+                if trace_packing then
+                    report_otf("start packing: stage 2, pass %s",pass)
+                end
+                local pack_normal, pack_indexed, pack_flat, pack_boolean, pack_mixed = packers(pass)
+                for unicode, description in next, data.descriptions do
+                    local kerns = description.kerns
+                    if kerns then
+                        description.kerns = pack_normal(kerns)
+                    end
+                    local math = description.math
+                    if math then
+                        local kerns = math.kerns
+                        if kerns then
+                            math.kerns = pack_normal(kerns)
+                        end
+                    end
+                    local anchors = description.anchors
+                    if anchors then
+                        description.anchors = pack_normal(anchors)
+                    end
+                    local mlookups = description.mlookups
+                    if mlookups then
+                        for tag, mlookup in next, mlookups do
+                            mlookups[tag] = pack_normal(mlookup)
+                        end
+                    end
+                    local altuni = description.altuni
+                    if altuni then
+                        description.altuni = pack_normal(altuni)
+                    end
+                end
+                local lookups = data.lookups
+                if lookups then
+                    for _, lookup in next, lookups do
+                        local rules = lookup.rules
+                        if rules then
+                            for i=1,#rules do -- was next loop
+                                local rule = rules[i]
+                                local r = rule.before  if r then rule.before  = pack_normal(r) end
+                                local r = rule.after   if r then rule.after   = pack_normal(r) end
+                                local r = rule.current if r then rule.current = pack_normal(r) end
+                            end
+                        end
+                    end
+                end
+                local sequences = resources.sequences
+                if sequences then
+                    for feature, sequence in next, sequences do
+                        sequence.features = pack_normal(sequence.features)
+                    end
+                end
+                if not success(2,pass) then
+                 -- return
+                end
+            end
+
+            for pass=1,2 do
+                local pack_normal, pack_indexed, pack_flat, pack_boolean, pack_mixed = packers(pass)
+                for unicode, description in next, data.descriptions do
+                    local slookups = description.slookups
+                    if slookups then
+                        description.slookups = pack_normal(slookups)
+                    end
+                    local mlookups = description.mlookups
+                    if mlookups then
+                        description.mlookups = pack_normal(mlookups)
+                    end
+                end
+            end
+
+        end
+    end
+end
+
+local unpacked_mt = {
+    __index =
+        function(t,k)
+            t[k] = false
+            return k -- next time true
+        end
+}
+
+local function unpackdata(data)
+    if data then
+        local tables = data.tables
+        if tables then
+            local resources = data.resources
+            local lookuptypes = resources.lookuptypes
+            local unpacked = { }
+            setmetatable(unpacked,unpacked_mt)
+            for unicode, description in next, data.descriptions do
+                local tv = tables[description.boundingbox]
+                if tv then
+                    description.boundingbox = tv
+                end
+                local slookups = description.slookups
+                if slookups then
+                    local tv = tables[slookups]
+                    if tv then
+                        description.slookups = tv
+                        slookups = unpacked[tv]
+                    end
+                    if slookups then
+                        for tag, lookup in next, slookups do
+                            local what = lookuptypes[tag]
+                            if what == "pair" then
+                                local tv = tables[lookup[2]]
+                                if tv then
+                                    lookup[2] = tv
+                                end
+                                local tv = tables[lookup[3]]
+                                if tv then
+                                    lookup[3] = tv
+                                end
+                            elseif what ~= "substitution" then
+                                local tv = tables[lookup]
+                                if tv then
+                                    slookups[tag] = tv
+                                end
+                            end
+                        end
+                    end
+                end
+                local mlookups = description.mlookups
+                if mlookups then
+                    local tv = tables[mlookups]
+                    if tv then
+                        description.mlookups = tv
+                        mlookups = unpacked[tv]
+                    end
+                    if mlookups then
+                        for tag, list in next, mlookups do
+                            local tv = tables[list]
+                            if tv then
+                                mlookups[tag] = tv
+                                list = unpacked[tv]
+                            end
+                            if list then
+                                local what = lookuptypes[tag]
+                                if what == "pair" then
+                                    for i=1,#list do
+                                        local lookup = list[i]
+                                        local tv = tables[lookup[2]]
+                                        if tv then
+                                            lookup[2] = tv
+                                        end
+                                        local tv = tables[lookup[3]]
+                                        if tv then
+                                            lookup[3] = tv
+                                        end
+                                    end
+                                elseif what ~= "substitution" then
+                                    for i=1,#list do
+                                        local tv = tables[list[i]]
+                                        if tv then
+                                            list[i] = tv
+                                        end
+                                    end
+                                end
+                            end
+                        end
+                    end
+                end
+                local kerns = description.kerns
+                if kerns then
+                    local tm = tables[kerns]
+                    if tm then
+                        description.kerns = tm
+                        kerns = unpacked[tm]
+                    end
+                    if kerns then
+                        for k, kern in next, kerns do
+                            local tv = tables[kern]
+                            if tv then
+                                kerns[k] = tv
+                            end
+                        end
+                    end
+                end
+                local math = description.math
+                if math then
+                    local kerns = math.kerns
+                    if kerns then
+                        local tm = tables[kerns]
+                        if tm then
+                            math.kerns = tm
+                            kerns = unpacked[tm]
+                        end
+                        if kerns then
+                            for k, kern in next, kerns do
+                                local tv = tables[kern]
+                                if tv then
+                                    kerns[k] = tv
+                                end
+                            end
+                        end
+                    end
+                end
+                local anchors = description.anchors
+                if anchors then
+                    local ta = tables[anchors]
+                    if ta then
+                        description.anchors = ta
+                        anchors = unpacked[ta]
+                    end
+                    if anchors then
+                        for tag, anchor in next, anchors do
+                            if tag == "baselig" then
+                                for _, list in next, anchor do
+                                    for i=1,#list do
+                                        local tv = tables[list[i]]
+                                        if tv then
+                                            list[i] = tv
+                                        end
+                                    end
+                                end
+                            else
+                                for a, data in next, anchor do
+                                    local tv = tables[data]
+                                    if tv then
+                                        anchor[a] = tv
+                                    end
+                                end
+                            end
+                        end
+                    end
+                end
+                local altuni = description.altuni
+                if altuni then
+                    local altuni = tables[altuni]
+                    if altuni then
+                        description.altuni = altuni
+                        for i=1,#altuni do
+                            local tv = tables[altuni[i]]
+                            if tv then
+                                altuni[i] = tv
+                            end
+                        end
+                    end
+                end
+            end
+            local lookups = data.lookups
+            if lookups then
+                for _, lookup in next, lookups do
+                    local rules = lookup.rules
+                    if rules then
+                        for i=1,#rules do -- was next loop
+                            local rule = rules[i]
+                            local before = rule.before
+                            if before then
+                                local tv = tables[before]
+                                if tv then
+                                    rule.before = tv
+                                    before = unpacked[tv]
+                                end
+                                if before then
+                                    for i=1,#before do
+                                        local tv = tables[before[i]]
+                                        if tv then
+                                            before[i] = tv
+                                        end
+                                    end
+                                end
+                            end
+                            local after = rule.after
+                            if after then
+                                local tv = tables[after]
+                                if tv then
+                                    rule.after = tv
+                                    after = unpacked[tv]
+                                end
+                                if after then
+                                    for i=1,#after do
+                                        local tv = tables[after[i]]
+                                        if tv then
+                                            after[i] = tv
+                                        end
+                                    end
+                                end
+                            end
+                            local current = rule.current
+                            if current then
+                                local tv = tables[current]
+                                if tv then
+                                    rule.current = tv
+                                    current = unpacked[tv]
+                                end
+                                if current then
+                                    for i=1,#current do
+                                        local tv = tables[current[i]]
+                                        if tv then
+                                            current[i] = tv
+                                        end
+                                    end
+                                end
+                            end
+                            local replacements = rule.replacements
+                            if replacements then
+                                local tv = tables[replacements]
+                                if tv then
+                                    rule.replacements = tv
+                                end
+                            end
+                         -- local fore = rule.fore
+                         -- if fore then
+                         --     local tv = tables[fore]
+                         --     if tv then
+                         --         rule.fore = tv
+                         --     end
+                         -- end
+                         -- local back = rule.back
+                         -- if back then
+                         --     local tv = tables[back]
+                         --     if tv then
+                         --         rule.back = tv
+                         --     end
+                         -- end
+                         -- local names = rule.names
+                         -- if names then
+                         --     local tv = tables[names]
+                         --     if tv then
+                         --         rule.names = tv
+                         --     end
+                         -- end
+                            --
+                            local lookups = rule.lookups
+                            if lookups then
+                                local tv = tables[lookups]
+                                if tv then
+                                    rule.lookups = tv
+                                end
+                            end
+                        end
+                    end
+                end
+            end
+            local anchor_to_lookup = resources.anchor_to_lookup
+            if anchor_to_lookup then
+                for anchor, lookup in next, anchor_to_lookup do
+                    local tv = tables[lookup]
+                    if tv then
+                        anchor_to_lookup[anchor] = tv
+                    end
+                end
+            end
+            local lookup_to_anchor = resources.lookup_to_anchor
+            if lookup_to_anchor then
+                for lookup, anchor in next, lookup_to_anchor do
+                    local tv = tables[anchor]
+                    if tv then
+                        lookup_to_anchor[lookup] = tv
+                    end
+                end
+            end
+            local ls = resources.sequences
+            if ls then
+                for _, feature in next, ls do
+                    local flags = feature.flags
+                    if flags then
+                        local tv = tables[flags]
+                        if tv then
+                            feature.flags = tv
+                        end
+                    end
+                    local subtables = feature.subtables
+                    if subtables then
+                        local tv = tables[subtables]
+                        if tv then
+                            feature.subtables = tv
+                        end
+                    end
+                    local features = feature.features
+                    if features then
+                        local tv = tables[features]
+                        if tv then
+                            feature.features = tv
+                            features = unpacked[tv]
+                        end
+                        if features then
+                            for script, data in next, features do
+                                local tv = tables[data]
+                                if tv then
+                                    features[script] = tv
+                                end
+                            end
+                        end
+                    end
+                    local order = feature.order
+                    if order then
+                        local tv = tables[order]
+                        if tv then
+                            feature.order = tv
+                        end
+                    end
+                    local markclass = feature.markclass
+                    if markclass then
+                        local tv = tables[markclass]
+                        if tv then
+                            feature.markclass = tv
+                        end
+                    end
+                end
+            end
+            local lookups = resources.lookups
+            if lookups then
+                for _, lookup in next, lookups do
+                    local flags = lookup.flags
+                    if flags then
+                        local tv = tables[flags]
+                        if tv then
+                            lookup.flags = tv
+                        end
+                    end
+                    local subtables = lookup.subtables
+                    if subtables then
+                        local tv = tables[subtables]
+                        if tv then
+                            lookup.subtables = tv
+                        end
+                    end
+                end
+            end
+            local features = resources.features
+            if features then
+                for _, what in next, glists do
+                    local feature = features[what]
+                    if feature then
+                        for tag, spec in next, feature do
+                            local tv = tables[spec]
+                            if tv then
+                                feature[tag] = tv
+                            end
+                        end
+                    end
+                end
+            end
+            data.tables = nil
+        end
+    end
+end
+
+if otf.enhancers.register then
+
+    otf.enhancers.register(  "pack",  packdata)
+    otf.enhancers.register("unpack",unpackdata)
+
+-- todo: directive
+
+end
+
+otf.enhancers.unpack = unpackdata -- used elsewhere
+otf.enhancers.pack   = packdata   -- used elsewhere