1 files changed, 118 insertions, 0 deletions
diff --git a/otfl-data-con.lua b/otfl-data-con.lua
new file mode 100644
index 0000000..ec146f0
--- /dev/null
+++ b/otfl-data-con.lua
@@ -0,0 +1,118 @@
+if not modules then modules = { } end modules ['data-con'] = {
+    version   = 1.001,
+    comment   = "companion to luat-lib.tex",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local format, lower, gsub = string.format, string.lower, string.gsub
+
+local trace_cache      = false  trackers.register("resolvers.cache",      function(v) trace_cache      = v end)
+local trace_containers = false  trackers.register("resolvers.containers", function(v) trace_containers = v end)
+local trace_storage    = false  trackers.register("resolvers.storage",    function(v) trace_storage    = v end)
+local trace_verbose    = false  trackers.register("resolvers.verbose",    function(v) trace_verbose    = v end)
+local trace_locating   = false  trackers.register("resolvers.locating",   function(v) trace_locating   = v trackers.enable("resolvers.verbose") end)
+
+--[[ldx--
+<p>Once we found ourselves defining similar cache constructs
+several times, containers were introduced. Containers are used
+to collect tables in memory and reuse them when possible based
+on (unique) hashes (to be provided by the calling function).</p>
+
+<p>Caching to disk is disabled by default. Version numbers are
+stored in the saved table which makes it possible to change the
+table structures without bothering about the disk cache.</p>
+
+<p>Examples of usage can be found in the font related code.</p>
+--ldx]]--
+
+containers = containers or { }
+
+containers.usecache = true
+
+local function report(container,tag,name)
+    if trace_cache or trace_containers then
+        logs.report(format("%s cache",container.subcategory),"%s: %s",tag,name or 'invalid')
+    end
+end
+
+local allocated = { }
+
+-- tracing
+
+function containers.define(category, subcategory, version, enabled)
+    return function()
+        if category and subcategory then
+            local c = allocated[category]
+            if not c then
+                c  = { }
+                allocated[category] = c
+            end
+            local s = c[subcategory]
+            if not s then
+                s = {
+                    category = category,
+                    subcategory = subcategory,
+                    storage = { },
+                    enabled = enabled,
+                    version = version or 1.000,
+                    trace = false,
+                    path = caches and caches.setpath(category,subcategory),
+                }
+                c[subcategory] = s
+            end
+            return s
+        else
+            return nil
+        end
+    end
+end
+
+function containers.is_usable(container, name)
+    return container.enabled and caches and caches.iswritable(container.path, name)
+end
+
+function containers.is_valid(container, name)
+    if name and name ~= "" then
+        local storage = container.storage[name]
+        return storage and not table.is_empty(storage) and storage.cache_version == container.version
+    else
+        return false
+    end
+end
+
+function containers.read(container,name)
+    if container.enabled and caches and not container.storage[name] and containers.usecache then
+        container.storage[name] = caches.loaddata(container.path,name)
+        if containers.is_valid(container,name) then
+            report(container,"loaded",name)
+        else
+            container.storage[name] = nil
+        end
+    end
+    if container.storage[name] then
+        report(container,"reusing",name)
+    end
+    return container.storage[name]
+end
+
+function containers.write(container, name, data)
+    if data then
+        data.cache_version = container.version
+        if container.enabled and caches then
+            local unique, shared = data.unique, data.shared
+            data.unique, data.shared = nil, nil
+            caches.savedata(container.path, name, data)
+            report(container,"saved",name)
+            data.unique, data.shared = unique, shared
+        end
+        report(container,"stored",name)
+        container.storage[name] = data
+    end
+    return data
+end
+
+function containers.content(container,name)
+    return container.storage[name]
+end