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

-- special functions that deal with io

local format, lower = string.format, string.lower
local unpack = unpack or table.unpack

local trace_locating = false trackers.register("resolvers.locating", function(v) trace_locating = v end)

local texiowrite_nl = (texio and texio.write_nl) or print
local texiowrite    = (texio and texio.write) or print

local finders, openers, loaders = resolvers.finders, resolvers.openers, resolvers.loaders

function finders.generic(tag,filename,filetype)
    local foundname = resolvers.find_file(filename,filetype)
    if foundname and foundname ~= "" then
        if trace_locating then
            logs.report("fileio","%s finder: file '%s' found",tag,filename)
        end
        return foundname
    else
        if trace_locating then
            logs.report("fileio","%s finder: unknown file '%s'",tag,filename)
        end
        return unpack(finders.notfound)
    end
end

--~ local lpegmatch = lpeg.match
--~ local getlines = lpeg.Ct(lpeg.patterns.textline)

local input_translator, utf_translator, user_translator = nil, nil, nil

function resolvers.install_text_filter(name,func)
        if name == "input" then input_translator = func
    elseif name == "utf"   then utf_translator   = func
    elseif name == "user"  then user_translator  = func end
end

function openers.text_opener(filename,file_handle,tag)
    local u = unicode.utftype(file_handle)
    local t = { }
    if u > 0  then
        if trace_locating then
            logs.report("fileio","%s opener, file '%s' opened using method '%s'",tag,filename,unicode.utfname[u])
        end
        local l
        if u > 2 then
            l = unicode.utf32_to_utf8(file_handle:read("*a"),u==4)
        else
            l = unicode.utf16_to_utf8(file_handle:read("*a"),u==2)
        end
        file_handle:close()
        t = {
            utftype = u, -- may go away
            lines = l,
            current = 0, -- line number, not really needed
            handle = nil,
            noflines = #l,
            close = function()
                if trace_locating then
                    logs.report("fileio","%s closer, file '%s' closed",tag,filename)
                end
                logs.show_close(filename)
                t = nil
            end,
            reader = function(self)
                self = self or t
                local current, lines = self.current, self.lines
                if current >= #lines then
                    return nil
                else
                    current = current + 1
                    self.current = current
                    local line = lines[current]
                    if not line then
                        return nil
                    elseif line == "" then
                        return ""
                    else
                        if input_translator then
                            line = input_translator(line)
                        end
                        if utf_translator then
                            line = utf_translator(line)
                        end
                        if user_translator then
                            line = user_translator(line)
                        end
                        return line
                    end
                end
            end
        }
    else
        if trace_locating then
            logs.report("fileio","%s opener, file '%s' opened",tag,filename)
        end
        -- todo: file;name -> freeze / eerste regel scannen -> freeze
        --~ local data = lpegmatch(getlines,file_handle:read("*a"))
        --~ local n = 0
        t = {
            reader = function() -- self
                local line = file_handle:read()
                --~ n = n + 1
                --~ local line = data[n]
                --~ print(line)
                if not line then
                    return nil
                elseif line == "" then
                    return ""
                else
                    if input_translator then
                        line = input_translator(line)
                    end
                    if utf_translator then
                        line = utf_translator(line)
                    end
                    if user_translator then
                        line = user_translator(line)
                    end
                    return line
                end
            end,
            close = function()
                if trace_locating then
                    logs.report("fileio","%s closer, file '%s' closed",tag,filename)
                end
                logs.show_close(filename)
                file_handle:close()
                t = nil
                collectgarbage("step") -- saves some memory
            end,
            handle = function()
                return file_handle
            end,
            noflines = function()
                t.noflines = io.noflines(file_handle)
                return t.noflines
            end
        }
    end
    return t
end

function openers.generic(tag,filename)
    if filename and filename ~= "" then
        local f = io.open(filename,"r")
        if f then
            logs.show_open(filename) -- todo
            if trace_locating then
                logs.report("fileio","%s opener, file '%s' opened",tag,filename)
            end
            return openers.text_opener(filename,f,tag)
        end
    end
    if trace_locating then
        logs.report("fileio","%s opener, file '%s' not found",tag,filename)
    end
    return unpack(openers.notfound)
end

function loaders.generic(tag,filename)
    if filename and filename ~= "" then
        local f = io.open(filename,"rb")
        if f then
            logs.show_load(filename)
            if trace_locating then
                logs.report("fileio","%s loader, file '%s' loaded",tag,filename)
            end
            local s = f:read("*a")
            if garbagecollector and garbagecollector.check then garbagecollector.check(#s) end
            f:close()
            if s then
                return true, s, #s
            end
        end
    end
    if trace_locating then
        logs.report("fileio","%s loader, file '%s' not found",tag,filename)
    end
    return unpack(loaders.notfound)
end

function finders.tex(filename,filetype)
    return finders.generic('tex',filename,filetype)
end

function openers.tex(filename)
    return openers.generic('tex',filename)
end

function loaders.tex(filename)
    return loaders.generic('tex',filename)
end

function resolvers.findtexfile(filename, filetype)
    return resolvers.methodhandler('finders',filename, filetype)
end

function resolvers.opentexfile(filename)
    return resolvers.methodhandler('openers',filename)
end

function resolvers.openfile(filename)
    local fullname = resolvers.findtexfile(filename)
    if fullname and (fullname ~= "") then
        return resolvers.opentexfile(fullname)
    else
        return nil
    end
end

function resolvers.texdatablob(filename, filetype)
    local ok, data, size = resolvers.loadbinfile(filename, filetype)
    return data or ""
end

resolvers.loadtexfile = resolvers.texdatablob