if not modules then modules = { } end modules ['grph-mem'] = {
    version   = 1.001,
    comment   = "companion to grph-inc.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- very experimental and likely to change
--
-- \startluacode
--     figures.setmemstream("whatever",io.loaddata("t:/sources/cow.pdf"))
-- \stopluacode
--
-- \externalfigure[memstream:///t:/sources/cow.pdf]
-- \externalfigure[memstream:///whatever]

local gsub = string.gsub

local report = logs.reporter("memstream")
local trace  = false  trackers.register  ("graphics.memstreams", function(v) trace = v end)
local data   = { }

if pdfe then

    local function setmemstream(name,stream,once)
        if once and data[name] then
            if trace then
                report("not overloading %a",name) --
            end
            return data[name]
        end
        local kind       = figures.guessfromstring(stream)
        local identifier = false
        if kind == "pdf" then
            identifier = pdfe.new(stream,#stream,name)
            if not identifier then
                report("no valid pdf stream %a",name)
            elseif trace then
                report("setting %a with identifier %a",name,identifier)
            end
        else
            identifier = "m_k_i_v_memstream_" .. name .. "." .. kind
            io.savedata(identifier,stream)
        end
        if not identifier then
            identifier = "invalid-memstream"
        end
        data[name] = identifier
        return identifier
    end

    resolvers.setmemstream = setmemstream

    function resolvers.finders.memstream(specification)
        local name       = specification.path
        local identifier = data[name]
        if identifier then
            if trace then
                report("reusing %a with identifier %a",name,identifier)
            end
            return identifier
        end
        local stream = io.loaddata(name)
        if stream and stream ~= "" then
            return setmemstream(name,stream)
        end
        if trace then
            report("no valid memstream %a",name)
        end
        return resolvers.finders.notfound()
    end

    local flush = { }

    function resolvers.resetmemstream(name,afterpage)
        if afterpage then
            flush[#flush+1] = name
        end
    end

    luatex.registerpageactions(function()
        if #flush > 0 then
            for i=1,#flush do
                local identifier = data[name]
                if identifier then
                    os.remove(identifier)
                    data[name] = nil
                end
            end
            flush = { }
        end
    end)

else

    local opened = { }

    local function setmemstream(name,stream,once)
        if once and data[name] then
            if trace then
                report("not overloading %a",name) --
            end
            return data[name]
        end
        local memstream, identifier = epdf.openMemStream(stream,#stream,name)
        if not identifier then
            report("no valid stream %a",name)
            identifier = "invalid-memstream"
        elseif trace then
            report("setting %a with identifier %a",name,identifier)
        end
        data  [name] = identifier
        opened[name] = memstream
        return identifier
    end

    resolvers.setmemstream = setmemstream

    function resolvers.finders.memstream(specification)
        local name       = specification.path
        local identifier = data[name]
        if identifier then
            if trace then
                report("reusing %a with identifier %a",name,identifier)
            end
            return identifier
        end
        local stream = io.loaddata(name)
        if not stream or stream == "" then
            if trace then
                report("no valid file %a",name)
            end
            return resolvers.finders.notfound()
        else
            return setmemstream(name,stream)
        end
    end

    local flush = { }

    function resolvers.resetmemstream(name,afterpage)
        if afterpage then
            flush[#flush+1] = name
        else
            opened[name] = nil
        end
    end

    luatex.registerpageactions(function()
        if #flush > 0 then
            for i=1,#flush do
                opened[flush[i]] = nil -- we keep of course data[name] because of reuse
            end
            flush = { }
        end
    end)

end

figures.identifiers.list[#figures.identifiers.list+1] = function(specification)
    local name = specification.request.name
    if name then
        local base = gsub(name,"^memstream:///","")
        if base ~= name then
            local identifier = data[base]
            if identifier then
                if trace then
                    report("requested %a has identifier %s",name,identifier)
                end
                specification.status.status = 1
                specification.used.fullname = name
            else
                if trace then
                    report("requested %a is not found",name)
                end
            end
        end
    end
end

figures.setmemstream = resolvers.setmemstream
