if not modules then modules = { } end modules ['lxml-tab'] = {
    version   = 1.001,
    comment   = "this module is the basis for the lxml-* ones",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- this module needs a cleanup: check latest lpeg, passing args, (sub)grammar, etc etc
-- stripping spaces from e.g. cont-en.xml saves .2 sec runtime so it's not worth the
-- trouble

-- todo: when serializing optionally remap named entities to hex (if known in char-ent.lua)
-- maybe when letter -> utf, else name .. then we need an option to the serializer .. a bit
-- of work so we delay this till we cleanup

local trace_entities = false  trackers.register("xml.entities", function(v) trace_entities = v end)

local report_xml = logs and logs.reporter("xml","core") or function(...) print(string.format(...)) end

--[[ldx--
<p>The parser used here is inspired by the variant discussed in the lua book, but
handles comment and processing instructions, has a different structure, provides
parent access; a first version used different trickery but was less optimized to we
went this route. First we had a find based parser, now we have an <l n='lpeg'/> based one.
The find based parser can be found in l-xml-edu.lua along with other older code.</p>

<p>Beware, the interface may change. For instance at, ns, tg, dt may get more
verbose names. Once the code is stable we will also remove some tracing and
optimize the code.</p>

<p>I might even decide to reimplement the parser using the latest <l n='lpeg'/> trickery
as the current variant was written when <l n='lpeg'/> showed up and it's easier now to
build tables in one go.</p>
--ldx]]--

xml = xml or { }
local xml = xml

--~ local xml = xml

local concat, remove, insert = table.concat, table.remove, table.insert
local type, next, setmetatable, getmetatable, tonumber = type, next, setmetatable, getmetatable, tonumber
local lower, find, match, gsub = string.lower, string.find, string.match, string.gsub
local utfchar = utf.char
local lpegmatch = lpeg.match
local P, S, R, C, V, C, Cs = lpeg.P, lpeg.S, lpeg.R, lpeg.C, lpeg.V, lpeg.C, lpeg.Cs
local formatters = string.formatters

--[[ldx--
<p>First a hack to enable namespace resolving. A namespace is characterized by
a <l n='url'/>. The following function associates a namespace prefix with a
pattern. We use <l n='lpeg'/>, which in this case is more than twice as fast as a
find based solution where we loop over an array of patterns. Less code and
much cleaner.</p>
--ldx]]--

xml.xmlns = xml.xmlns or { }

local check = P(false)
local parse = check

--[[ldx--
<p>The next function associates a namespace prefix with an <l n='url'/>. This
normally happens independent of parsing.</p>

<typing>
xml.registerns("mml","mathml")
</typing>
--ldx]]--

function xml.registerns(namespace, pattern) -- pattern can be an lpeg
    check = check + C(P(lower(pattern))) / namespace
    parse = P { P(check) + 1 * V(1) }
end

--[[ldx--
<p>The next function also registers a namespace, but this time we map a
given namespace prefix onto a registered one, using the given
<l n='url'/>. This used for attributes like <t>xmlns:m</t>.</p>

<typing>
xml.checkns("m","http://www.w3.org/mathml")
</typing>
--ldx]]--

function xml.checkns(namespace,url)
    local ns = lpegmatch(parse,lower(url))
    if ns and namespace ~= ns then
        xml.xmlns[namespace] = ns
    end
end

--[[ldx--
<p>Next we provide a way to turn an <l n='url'/> into a registered
namespace. This used for the <t>xmlns</t> attribute.</p>

<typing>
resolvedns = xml.resolvens("http://www.w3.org/mathml")
</typing>

This returns <t>mml</t>.
--ldx]]--

function xml.resolvens(url)
     return lpegmatch(parse,lower(url)) or ""
end

--[[ldx--
<p>A namespace in an element can be remapped onto the registered
one efficiently by using the <t>xml.xmlns</t> table.</p>
--ldx]]--

--[[ldx--
<p>This version uses <l n='lpeg'/>. We follow the same approach as before, stack and top and
such. This version is about twice as fast which is mostly due to the fact that
we don't have to prepare the stream for cdata, doctype etc etc. This variant is
is dedicated to Luigi Scarso, who challenged me with 40 megabyte <l n='xml'/> files that
took 12.5 seconds to load (1.5 for file io and the rest for tree building). With
the <l n='lpeg'/> implementation we got that down to less 7.3 seconds. Loading the 14
<l n='context'/> interface definition files (2.6 meg) went down from 1.05 seconds to 0.55.</p>

<p>Next comes the parser. The rather messy doctype definition comes in many
disguises so it is no surprice that later on have to dedicate quite some
<l n='lpeg'/> code to it.</p>

<typing>
<!DOCTYPE Something PUBLIC "... ..." "..." [ ... ] >
<!DOCTYPE Something PUBLIC "... ..." "..." >
<!DOCTYPE Something SYSTEM "... ..." [ ... ] >
<!DOCTYPE Something SYSTEM "... ..." >
<!DOCTYPE Something [ ... ] >
<!DOCTYPE Something >
</typing>

<p>The code may look a bit complex but this is mostly due to the fact that we
resolve namespaces and attach metatables. There is only one public function:</p>

<typing>
local x = xml.convert(somestring)
</typing>

<p>An optional second boolean argument tells this function not to create a root
element.</p>

<p>Valid entities are:</p>

<typing>
<!ENTITY xxxx SYSTEM "yyyy" NDATA zzzz>
<!ENTITY xxxx PUBLIC "yyyy" >
<!ENTITY xxxx "yyyy" >
</typing>
--ldx]]--

-- not just one big nested table capture (lpeg overflow)

local nsremap, resolvens = xml.xmlns, xml.resolvens

local stack              = { }
local top                = { }
local dt                 = { }
local at                 = { }
local xmlns              = { }
local errorstr           = nil
local entities           = { }
local strip              = false
local cleanup            = false
local utfize             = false
local resolve_predefined = false
local unify_predefined   = false

local dcache             = { }
local hcache             = { }
local acache             = { }

local mt = { }

local function initialize_mt(root)
    mt = { __index = root } -- will be redefined later
end

function xml.setproperty(root,k,v)
    getmetatable(root).__index[k] = v
end

function xml.checkerror(top,toclose)
    return "" -- can be set
end

local function add_attribute(namespace,tag,value)
    if cleanup and #value > 0 then
        value = cleanup(value) -- new
    end
    if tag == "xmlns" then
        xmlns[#xmlns+1] = resolvens(value)
        at[tag] = value
    elseif namespace == "" then
        at[tag] = value
    elseif namespace == "xmlns" then
        xml.checkns(tag,value)
        at["xmlns:" .. tag] = value
    else
        -- for the moment this way:
        at[namespace .. ":" .. tag] = value
    end
end

local function add_empty(spacing, namespace, tag)
    if #spacing > 0 then
        dt[#dt+1] = spacing
    end
    local resolved = namespace == "" and xmlns[#xmlns] or nsremap[namespace] or namespace
    top = stack[#stack]
    dt = top.dt
    local t = { ns=namespace or "", rn=resolved, tg=tag, at=at, dt={}, __p__ = top }
    dt[#dt+1] = t
    setmetatable(t, mt)
    if at.xmlns then
        remove(xmlns)
    end
    at = { }
end

local function add_begin(spacing, namespace, tag)
    if #spacing > 0 then
        dt[#dt+1] = spacing
    end
    local resolved = namespace == "" and xmlns[#xmlns] or nsremap[namespace] or namespace
    top = { ns=namespace or "", rn=resolved, tg=tag, at=at, dt={}, __p__ = stack[#stack] }
    setmetatable(top, mt)
    dt = top.dt
    stack[#stack+1] = top
    at = { }
end

local function add_end(spacing, namespace, tag)
    if #spacing > 0 then
        dt[#dt+1] = spacing
    end
    local toclose = remove(stack)
    top = stack[#stack]
    if #stack < 1 then
        errorstr = formatters["unable to close %s %s"](tag,xml.checkerror(top,toclose) or "")
    elseif toclose.tg ~= tag then -- no namespace check
        errorstr = formatters["unable to close %s with %s %s"](toclose.tg,tag,xml.checkerror(top,toclose) or "")
    end
    dt = top.dt
    dt[#dt+1] = toclose
 -- dt[0] = top -- nasty circular reference when serializing table
    if toclose.at.xmlns then
        remove(xmlns)
    end
end

local function add_text(text)
    if cleanup and #text > 0 then
        dt[#dt+1] = cleanup(text)
    else
        dt[#dt+1] = text
    end
end

local function add_special(what, spacing, text)
    if #spacing > 0 then
        dt[#dt+1] = spacing
    end
    if strip and (what == "@cm@" or what == "@dt@") then
        -- forget it
    else
        dt[#dt+1] = { special=true, ns="", tg=what, dt={ text } }
    end
end

local function set_message(txt)
    errorstr = "garbage at the end of the file: " .. gsub(txt,"([ \n\r\t]*)","")
end

local reported_attribute_errors = { }

local function attribute_value_error(str)
    if not reported_attribute_errors[str] then
        report_xml("invalid attribute value %a",str)
        reported_attribute_errors[str] = true
        at._error_ = str
    end
    return str
end

local function attribute_specification_error(str)
    if not reported_attribute_errors[str] then
        report_xml("invalid attribute specification %a",str)
        reported_attribute_errors[str] = true
        at._error_ = str
    end
    return str
end

xml.placeholders = {
    unknown_dec_entity = function(str) return str == "" and "&error;" or formatters["&%s;"](str) end,
    unknown_hex_entity = function(str) return formatters["&#x%s;"](str) end,
    unknown_any_entity = function(str) return formatters["&#x%s;"](str) end,
}

local placeholders = xml.placeholders

local function fromhex(s)
    local n = tonumber(s,16)
    if n then
        return utfchar(n)
    else
        return formatters["h:%s"](s), true
    end
end

local function fromdec(s)
    local n = tonumber(s)
    if n then
        return utfchar(n)
    else
        return formatters["d:%s"](s), true
    end
end

-- one level expansion (simple case), no checking done

local rest = (1-P(";"))^0
local many = P(1)^0

local parsedentity =
    P("&") * (P("#x")*(rest/fromhex) + P("#")*(rest/fromdec)) * P(";") * P(-1) +
             (P("#x")*(many/fromhex) + P("#")*(many/fromdec))

-- parsing in the xml file

local predefined_unified = {
    [38] = "&amp;",
    [42] = "&quot;",
    [47] = "&apos;",
    [74] = "&lt;",
    [76] = "&gt;",
}

local predefined_simplified = {
    [38] = "&", amp  = "&",
    [42] = '"', quot = '"',
    [47] = "'", apos = "'",
    [74] = "<", lt   = "<",
    [76] = ">", gt   = ">",
}

local nofprivates = 0xF0000 -- shared but seldom used

local privates_u = { -- unescaped
    [ [[&]] ] = "&amp;",
    [ [["]] ] = "&quot;",
    [ [[']] ] = "&apos;",
    [ [[<]] ] = "&lt;",
    [ [[>]] ] = "&gt;",
}

local privates_p = {
}

local privates_n = {
    -- keeps track of defined ones
}

local escaped = utf.remapper(privates_u)

local function unescaped(s)
    local p = privates_n[s]
    if not p then
        nofprivates = nofprivates + 1
        p = utfchar(nofprivates)
        privates_n[s] = p
        s = "&" .. s .. ";" -- todo: use char-ent to map to hex
        privates_u[p] = s
        privates_p[p] = s
    end
    return p
end

local unprivatized = utf.remapper(privates_p)

xml.privatetoken = unescaped
xml.unprivatized = unprivatized
xml.privatecodes = privates_n

local function handle_hex_entity(str)
    local h = hcache[str]
    if not h then
        local n = tonumber(str,16)
        h = unify_predefined and predefined_unified[n]
        if h then
            if trace_entities then
                report_xml("utfize, converting hex entity &#x%s; into %a",str,h)
            end
        elseif utfize then
            h = (n and utfchar(n)) or xml.unknown_hex_entity(str) or ""
            if not n then
                report_xml("utfize, ignoring hex entity &#x%s;",str)
            elseif trace_entities then
                report_xml("utfize, converting hex entity &#x%s; into %a",str,h)
            end
        else
            if trace_entities then
                report_xml("found entity &#x%s;",str)
            end
            h = "&#x" .. str .. ";"
        end
        hcache[str] = h
    end
    return h
end

local function handle_dec_entity(str)
    local d = dcache[str]
    if not d then
        local n = tonumber(str)
        d = unify_predefined and predefined_unified[n]
        if d then
            if trace_entities then
                report_xml("utfize, converting dec entity &#%s; into %a",str,d)
            end
        elseif utfize then
            d = (n and utfchar(n)) or placeholders.unknown_dec_entity(str) or ""
            if not n then
                report_xml("utfize, ignoring dec entity &#%s;",str)
            elseif trace_entities then
                report_xml("utfize, converting dec entity &#%s; into %a",str,d)
            end
        else
            if trace_entities then
                report_xml("found entity &#%s;",str)
            end
            d = "&#" .. str .. ";"
        end
        dcache[str] = d
    end
    return d
end

xml.parsedentitylpeg = parsedentity

local function handle_any_entity(str)
    if resolve then
        local a = acache[str] -- per instance ! todo
        if not a then
            a = resolve_predefined and predefined_simplified[str]
            if a then
                if trace_entities then
                    report_xml("resolving entity &%s; to predefined %a",str,a)
                end
            else
                if type(resolve) == "function" then
                    a = resolve(str) or entities[str]
                else
                    a = entities[str]
                end
                if a then
                    if type(a) == "function" then
                        if trace_entities then
                            report_xml("expanding entity &%s; to function call",str)
                        end
                        a = a(str) or ""
                    end
                    a = lpegmatch(parsedentity,a) or a -- for nested
                    if trace_entities then
                        report_xml("resolving entity &%s; to internal %a",str,a)
                    end
                else
                    local unknown_any_entity = placeholders.unknown_any_entity
                    if unknown_any_entity then
                        a = unknown_any_entity(str) or ""
                    end
                    if a then
                        if trace_entities then
                            report_xml("resolving entity &%s; to external %s",str,a)
                        end
                    else
                        if trace_entities then
                            report_xml("keeping entity &%s;",str)
                        end
                        if str == "" then
                            a = "&error;"
                        else
                            a = "&" .. str .. ";"
                        end
                    end
                end
            end
            acache[str] = a
        elseif trace_entities then
            if not acache[str] then
                report_xml("converting entity &%s; to %a",str,a)
                acache[str] = a
            end
        end
        return a
    else
        local a = acache[str]
        if not a then
            a = resolve_predefined and predefined_simplified[str]
            if a then
                -- one of the predefined
                acache[str] = a
                if trace_entities then
                    report_xml("entity &%s; becomes %a",str,a)
                end
            elseif str == "" then
                if trace_entities then
                    report_xml("invalid entity &%s;",str)
                end
                a = "&error;"
                acache[str] = a
            else
                if trace_entities then
                    report_xml("entity &%s; is made private",str)
                end
             -- a = "&" .. str .. ";"
                a = unescaped(str)
                acache[str] = a
            end
        end
        return a
    end
end

local function handle_end_entity(chr)
    report_xml("error in entity, %a found instead of %a",chr,";")
end

local space            = S(' \r\n\t')
local open             = P('<')
local close            = P('>')
local squote           = S("'")
local dquote           = S('"')
local equal            = P('=')
local slash            = P('/')
local colon            = P(':')
local semicolon        = P(';')
local ampersand        = P('&')
local valid            = R('az', 'AZ', '09') + S('_-.')
local name_yes         = C(valid^1) * colon * C(valid^1)
local name_nop         = C(P(true)) * C(valid^1)
local name             = name_yes + name_nop
local utfbom           = lpeg.patterns.utfbom -- no capture
local spacing          = C(space^0)

----- entitycontent    = (1-open-semicolon)^0
local anyentitycontent = (1-open-semicolon-space-close)^0
local hexentitycontent = R("AF","af","09")^0
local decentitycontent = R("09")^0
local parsedentity     = P("#")/"" * (
                                P("x")/"" * (hexentitycontent/handle_hex_entity) +
                                            (decentitycontent/handle_dec_entity)
                            ) +             (anyentitycontent/handle_any_entity)
local entity           = ampersand/"" * parsedentity * ( (semicolon/"") + #(P(1)/handle_end_entity))

local text_unparsed    = C((1-open)^1)
local text_parsed      = Cs(((1-open-ampersand)^1 + entity)^1)

local somespace        = space^1
local optionalspace    = space^0

----- value            = (squote * C((1 - squote)^0) * squote) + (dquote * C((1 - dquote)^0) * dquote) -- ampersand and < also invalid in value
local value            = (squote * Cs((entity + (1 - squote))^0) * squote) + (dquote * Cs((entity + (1 - dquote))^0) * dquote) -- ampersand and < also invalid in value

local endofattributes  = slash * close + close -- recovery of flacky html
local whatever         = space * name * optionalspace * equal
----- wrongvalue       = C(P(1-whatever-close)^1 + P(1-close)^1) / attribute_value_error
----- wrongvalue       = C(P(1-whatever-endofattributes)^1 + P(1-endofattributes)^1) / attribute_value_error
----- wrongvalue       = C(P(1-space-endofattributes)^1) / attribute_value_error
local wrongvalue       = Cs(P(entity + (1-space-endofattributes))^1) / attribute_value_error

local attributevalue   = value + wrongvalue

local attribute        = (somespace * name * optionalspace * equal * optionalspace * attributevalue) / add_attribute
----- attributes       = (attribute)^0

local attributes       = (attribute + somespace^-1 * (((1-endofattributes)^1)/attribute_specification_error))^0

local parsedtext       = text_parsed   / add_text
local unparsedtext     = text_unparsed / add_text
local balanced         = P { "[" * ((1 - S"[]") + V(1))^0 * "]" } -- taken from lpeg manual, () example

local emptyelement     = (spacing * open         * name * attributes * optionalspace * slash * close) / add_empty
local beginelement     = (spacing * open         * name * attributes * optionalspace         * close) / add_begin
local endelement       = (spacing * open * slash * name              * optionalspace         * close) / add_end

local begincomment     = open * P("!--")
local endcomment       = P("--") * close
local begininstruction = open * P("?")
local endinstruction   = P("?") * close
local begincdata       = open * P("![CDATA[")
local endcdata         = P("]]") * close

local someinstruction  = C((1 - endinstruction)^0)
local somecomment      = C((1 - endcomment    )^0)
local somecdata        = C((1 - endcdata      )^0)

local function normalentity(k,v  ) entities[k] = v end
local function systementity(k,v,n) entities[k] = v end
local function publicentity(k,v,n) entities[k] = v end

-- todo: separate dtd parser

local begindoctype     = open * P("!DOCTYPE")
local enddoctype       = close
local beginset         = P("[")
local endset           = P("]")
local doctypename      = C((1-somespace-close)^0)
local elementdoctype   = optionalspace * P("<!ELEMENT") * (1-close)^0 * close

local basiccomment     = begincomment * ((1 - endcomment)^0) * endcomment

local normalentitytype = (doctypename * somespace * value)/normalentity
local publicentitytype = (doctypename * somespace * P("PUBLIC") * somespace * value)/publicentity
local systementitytype = (doctypename * somespace * P("SYSTEM") * somespace * value * somespace * P("NDATA") * somespace * doctypename)/systementity
local entitydoctype    = optionalspace * P("<!ENTITY") * somespace * (systementitytype + publicentitytype + normalentitytype) * optionalspace * close

-- we accept comments in doctypes

local doctypeset       = beginset * optionalspace * P(elementdoctype + entitydoctype + basiccomment + space)^0 * optionalspace * endset
local definitiondoctype= doctypename * somespace * doctypeset
local publicdoctype    = doctypename * somespace * P("PUBLIC") * somespace * value * somespace * value * somespace * doctypeset
local systemdoctype    = doctypename * somespace * P("SYSTEM") * somespace * value * somespace * doctypeset
local simpledoctype    = (1-close)^1 -- * balanced^0
local somedoctype      = C((somespace * (publicdoctype + systemdoctype + definitiondoctype + simpledoctype) * optionalspace)^0)
local somedoctype      = C((somespace * (publicdoctype + systemdoctype + definitiondoctype + simpledoctype) * optionalspace)^0)

local instruction      = (spacing * begininstruction * someinstruction * endinstruction) / function(...) add_special("@pi@",...) end
local comment          = (spacing * begincomment     * somecomment     * endcomment    ) / function(...) add_special("@cm@",...) end
local cdata            = (spacing * begincdata       * somecdata       * endcdata      ) / function(...) add_special("@cd@",...) end
local doctype          = (spacing * begindoctype     * somedoctype     * enddoctype    ) / function(...) add_special("@dt@",...) end

--  nicer but slower:
--
--  local instruction = (Cc("@pi@") * spacing * begininstruction * someinstruction * endinstruction) / add_special
--  local comment     = (Cc("@cm@") * spacing * begincomment     * somecomment     * endcomment    ) / add_special
--  local cdata       = (Cc("@cd@") * spacing * begincdata       * somecdata       * endcdata      ) / add_special
--  local doctype     = (Cc("@dt@") * spacing * begindoctype     * somedoctype     * enddoctype    ) / add_special

local trailer = space^0 * (text_unparsed/set_message)^0

--  comment + emptyelement + text + cdata + instruction + V("parent"), -- 6.5 seconds on 40 MB database file
--  text + comment + emptyelement + cdata + instruction + V("parent"), -- 5.8
--  text + V("parent") + emptyelement + comment + cdata + instruction, -- 5.5

local grammar_parsed_text = P { "preamble",
    preamble = utfbom^0 * instruction^0 * (doctype + comment + instruction)^0 * V("parent") * trailer,
    parent   = beginelement * V("children")^0 * endelement,
    children = parsedtext + V("parent") + emptyelement + comment + cdata + instruction,
}

local grammar_unparsed_text = P { "preamble",
    preamble = utfbom^0 * instruction^0 * (doctype + comment + instruction)^0 * V("parent") * trailer,
    parent   = beginelement * V("children")^0 * endelement,
    children = unparsedtext + V("parent") + emptyelement + comment + cdata + instruction,
}

-- maybe we will add settings to result as well

local function _xmlconvert_(data, settings)
    settings           = settings or { } -- no_root strip_cm_and_dt given_entities parent_root error_handler
    --
    strip              = settings.strip_cm_and_dt
    utfize             = settings.utfize_entities
    resolve            = settings.resolve_entities
    resolve_predefined = settings.resolve_predefined_entities -- in case we have escaped entities
    unify_predefined   = settings.unify_predefined_entities -- &#038; -> &amp;
    cleanup            = settings.text_cleanup
    entities           = settings.entities or { }
    --
    if utfize == nil then
        settings.utfize_entities = true
        utfize = true
    end
    if resolve_predefined == nil then
        settings.resolve_predefined_entities = true
        resolve_predefined = true
    end
    --
    stack, top, at, xmlns, errorstr = { }, { }, { }, { }, nil
    acache, hcache, dcache = { }, { }, { } -- not stored
    reported_attribute_errors = { }
    if settings.parent_root then
        mt = getmetatable(settings.parent_root)
    else
        initialize_mt(top)
    end
    stack[#stack+1] = top
    top.dt = { }
    dt = top.dt
    if not data or data == "" then
        errorstr = "empty xml file"
    elseif utfize or resolve then
        if lpegmatch(grammar_parsed_text,data) then
            errorstr = ""
        else
            errorstr = "invalid xml file - parsed text"
        end
    elseif type(data) == "string" then
        if lpegmatch(grammar_unparsed_text,data) then
            errorstr = ""
        else
            errorstr = "invalid xml file - unparsed text"
        end
    else
        errorstr = "invalid xml file - no text at all"
    end
    local result
    if errorstr and errorstr ~= "" then
        result = { dt = { { ns = "", tg = "error", dt = { errorstr }, at={ }, er = true } } }
        setmetatable(stack, mt)
        local errorhandler = settings.error_handler
        if errorhandler == false then
            -- no error message
        else
            errorhandler = errorhandler or xml.errorhandler
            if errorhandler then
                local currentresource = settings.currentresource
                if currentresource and currentresource ~= "" then
                    xml.errorhandler(formatters["load error in [%s]: %s"](currentresource,errorstr))
                else
                    xml.errorhandler(formatters["load error: %s"](errorstr))
                end
            end
        end
    else
        result = stack[1]
    end
    if not settings.no_root then
        result = { special = true, ns = "", tg = '@rt@', dt = result.dt, at={ }, entities = entities, settings = settings }
        setmetatable(result, mt)
        local rdt = result.dt
        for k=1,#rdt do
            local v = rdt[k]
            if type(v) == "table" and not v.special then -- always table -)
                result.ri = k -- rootindex
                v.__p__ = result  -- new, experiment, else we cannot go back to settings, we need to test this !
                break
            end
        end
    end
    if errorstr and errorstr ~= "" then
        result.error = true
    end
    result.statistics = {
        entities = {
            decimals     = dcache,
            hexadecimals = hcache,
            names        = acache,
        }
    }
    strip, utfize, resolve, resolve_predefined = nil, nil, nil, nil
    unify_predefined, cleanup, entities = nil, nil, nil
    stack, top, at, xmlns, errorstr = nil, nil, nil, nil, nil
    acache, hcache, dcache = nil, nil, nil
    reported_attribute_errors, mt, errorhandler = nil, nil, nil
    return result
end

-- Because we can have a crash (stack issues) with faulty xml, we wrap this one
-- in a protector:

function xmlconvert(data,settings)
    local ok, result = pcall(function() return _xmlconvert_(data,settings) end)
    if ok then
        return result
    else
        return _xmlconvert_("",settings)
    end
end

xml.convert = xmlconvert

function xml.inheritedconvert(data,xmldata) -- xmldata is parent
    local settings = xmldata.settings
    if settings then
        settings.parent_root = xmldata -- to be tested
    end
 -- settings.no_root = true
    local xc = xmlconvert(data,settings) -- hm, we might need to locate settings
 -- xc.settings = nil
 -- xc.entities = nil
 -- xc.special = nil
 -- xc.ri = nil
 -- print(xc.tg)
    return xc
end

--[[ldx--
<p>Packaging data in an xml like table is done with the following
function. Maybe it will go away (when not used).</p>
--ldx]]--

function xml.is_valid(root)
    return root and root.dt and root.dt[1] and type(root.dt[1]) == "table" and not root.dt[1].er
end

function xml.package(tag,attributes,data)
    local ns, tg = match(tag,"^(.-):?([^:]+)$")
    local t = { ns = ns, tg = tg, dt = data or "", at = attributes or {} }
    setmetatable(t, mt)
    return t
end

function xml.is_valid(root)
    return root and not root.error
end

xml.errorhandler = report_xml

--[[ldx--
<p>We cannot load an <l n='lpeg'/> from a filehandle so we need to load
the whole file first. The function accepts a string representing
a filename or a file handle.</p>
--ldx]]--

function xml.load(filename,settings)
    local data = ""
    if type(filename) == "string" then
     -- local data = io.loaddata(filename) - -todo: check type in io.loaddata
        local f = io.open(filename,'r') -- why not 'rb'
        if f then
            data = f:read("*all") -- io.readall(f) ... only makes sense for large files
            f:close()
        end
    elseif filename then -- filehandle
        data = filename:read("*all") -- io.readall(f) ... only makes sense for large files
    end
    if settings then
        settings.currentresource = filename
        local result = xmlconvert(data,settings)
        settings.currentresource = nil
        return result
    else
        return xmlconvert(data,{ currentresource = filename })
    end
end

--[[ldx--
<p>When we inject new elements, we need to convert strings to
valid trees, which is what the next function does.</p>
--ldx]]--

local no_root = { no_root = true }

function xml.toxml(data)
    if type(data) == "string" then
        local root = { xmlconvert(data,no_root) }
        return (#root > 1 and root) or root[1]
    else
        return data
    end
end

--[[ldx--
<p>For copying a tree we use a dedicated function instead of the
generic table copier. Since we know what we're dealing with we
can speed up things a bit. The second argument is not to be used!</p>
--ldx]]--

local function copy(old,tables)
    if old then
        tables = tables or { }
        local new = { }
        if not tables[old] then
            tables[old] = new
        end
        for k,v in next, old do
            new[k] = (type(v) == "table" and (tables[v] or copy(v, tables))) or v
        end
        local mt = getmetatable(old)
        if mt then
            setmetatable(new,mt)
        end
        return new
    else
        return { }
    end
end

xml.copy = copy

--[[ldx--
<p>In <l n='context'/> serializing the tree or parts of the tree is a major
actitivity which is why the following function is pretty optimized resulting
in a few more lines of code than needed. The variant that uses the formatting
function for all components is about 15% slower than the concatinating
alternative.</p>
--ldx]]--

-- todo: add <?xml version='1.0' standalone='yes'?> when not present

function xml.checkbom(root) -- can be made faster
    if root.ri then
        local dt = root.dt
        for k=1,#dt do
            local v = dt[k]
            if type(v) == "table" and v.special and v.tg == "@pi@" and find(v.dt[1],"xml.*version=") then
                return
            end
        end
        insert(dt, 1, { special = true, ns = "", tg = "@pi@", dt = { "xml version='1.0' standalone='yes'" } } )
        insert(dt, 2, "\n" )
    end
end

--[[ldx--
<p>At the cost of some 25% runtime overhead you can first convert the tree to a string
and then handle the lot.</p>
--ldx]]--

-- new experimental reorganized serialize

local function verbose_element(e,handlers) -- options
    local handle = handlers.handle
    local serialize = handlers.serialize
    local ens, etg, eat, edt, ern = e.ns, e.tg, e.at, e.dt, e.rn
    local ats = eat and next(eat) and { }
    if ats then
        for k,v in next, eat do
            ats[#ats+1] = formatters['%s=%q'](k,escaped(v))
        end
    end
    if ern and trace_entities and ern ~= ens then
        ens = ern
    end
    if ens ~= "" then
        if edt and #edt > 0 then
            if ats then
                handle("<",ens,":",etg," ",concat(ats," "),">")
            else
                handle("<",ens,":",etg,">")
            end
            for i=1,#edt do
                local e = edt[i]
                if type(e) == "string" then
                    handle(escaped(e))
                else
                    serialize(e,handlers)
                end
            end
            handle("</",ens,":",etg,">")
        else
            if ats then
                handle("<",ens,":",etg," ",concat(ats," "),"/>")
            else
                handle("<",ens,":",etg,"/>")
            end
        end
    else
        if edt and #edt > 0 then
            if ats then
                handle("<",etg," ",concat(ats," "),">")
            else
                handle("<",etg,">")
            end
            for i=1,#edt do
                local e = edt[i]
                if type(e) == "string" then
                    handle(escaped(e)) -- option: hexify escaped entities
                else
                    serialize(e,handlers)
                end
            end
            handle("</",etg,">")
        else
            if ats then
                handle("<",etg," ",concat(ats," "),"/>")
            else
                handle("<",etg,"/>")
            end
        end
    end
end

local function verbose_pi(e,handlers)
    handlers.handle("<?",e.dt[1],"?>")
end

local function verbose_comment(e,handlers)
    handlers.handle("<!--",e.dt[1],"-->")
end

local function verbose_cdata(e,handlers)
    handlers.handle("<![CDATA[", e.dt[1],"]]>")
end

local function verbose_doctype(e,handlers)
    handlers.handle("<!DOCTYPE ",e.dt[1],">")
end

local function verbose_root(e,handlers)
    handlers.serialize(e.dt,handlers)
end

local function verbose_text(e,handlers)
    handlers.handle(escaped(e))
end

local function verbose_document(e,handlers)
    local serialize = handlers.serialize
    local functions = handlers.functions
    for i=1,#e do
        local ei = e[i]
        if type(ei) == "string" then
            functions["@tx@"](ei,handlers)
        else
            serialize(ei,handlers)
        end
    end
end

local function serialize(e,handlers,...)
    local initialize = handlers.initialize
    local finalize   = handlers.finalize
    local functions  = handlers.functions
    if initialize then
        local state = initialize(...)
        if not state == true then
            return state
        end
    end
    local etg = e.tg
    if etg then
        (functions[etg] or functions["@el@"])(e,handlers)
 -- elseif type(e) == "string" then
 --     functions["@tx@"](e,handlers)
    else
        functions["@dc@"](e,handlers) -- dc ?
    end
    if finalize then
        return finalize()
    end
end

local function xserialize(e,handlers)
    local functions = handlers.functions
    local etg = e.tg
    if etg then
        (functions[etg] or functions["@el@"])(e,handlers)
 -- elseif type(e) == "string" then
 --     functions["@tx@"](e,handlers)
    else
        functions["@dc@"](e,handlers)
    end
end

local handlers = { }

local function newhandlers(settings)
    local t = table.copy(handlers[settings and settings.parent or "verbose"] or { }) -- merge
    if settings then
        for k,v in next, settings do
            if type(v) == "table" then
                local tk = t[k] if not tk then tk = { } t[k] = tk end
                for kk,vv in next, v do
                    tk[kk] = vv
                end
            else
                t[k] = v
            end
        end
        if settings.name then
            handlers[settings.name] = t
        end
    end
    utilities.storage.mark(t)
    return t
end

local nofunction = function() end

function xml.sethandlersfunction(handler,name,fnc)
    handler.functions[name] = fnc or nofunction
end

function xml.gethandlersfunction(handler,name)
    return handler.functions[name]
end

function xml.gethandlers(name)
    return handlers[name]
end

newhandlers {
    name       = "verbose",
    initialize = false, -- faster than nil and mt lookup
    finalize   = false, -- faster than nil and mt lookup
    serialize  = xserialize,
    handle     = print,
    functions  = {
        ["@dc@"]   = verbose_document,
        ["@dt@"]   = verbose_doctype,
        ["@rt@"]   = verbose_root,
        ["@el@"]   = verbose_element,
        ["@pi@"]   = verbose_pi,
        ["@cm@"]   = verbose_comment,
        ["@cd@"]   = verbose_cdata,
        ["@tx@"]   = verbose_text,
    }
}

--[[ldx--
<p>How you deal with saving data depends on your preferences. For a 40 MB database
file the timing on a 2.3 Core Duo are as follows (time in seconds):</p>

<lines>
1.3 : load data from file to string
6.1 : convert string into tree
5.3 : saving in file using xmlsave
6.8 : converting to string using xml.tostring
3.6 : saving converted string in file
</lines>

<p>Beware, these were timing with the old routine but measurements will not be that
much different I guess.</p>
--ldx]]--

-- maybe this will move to lxml-xml

local result

local xmlfilehandler = newhandlers {
    name       = "file",
    initialize = function(name)
        result = io.open(name,"wb")
        return result
    end,
    finalize   = function()
        result:close()
        return true
    end,
    handle     = function(...)
        result:write(...)
    end,
}

-- no checking on writeability here but not faster either
--
-- local xmlfilehandler = newhandlers {
--     initialize = function(name)
--         io.output(name,"wb")
--         return true
--     end,
--     finalize   = function()
--         io.close()
--         return true
--     end,
--     handle     = io.write,
-- }

function xml.save(root,name)
    serialize(root,xmlfilehandler,name)
end

local result

local xmlstringhandler = newhandlers {
    name       = "string",
    initialize = function()
        result = { }
        return result
    end,
    finalize   = function()
        return concat(result)
    end,
    handle     = function(...)
        result[#result+1] = concat { ... }
    end,
}

local function xmltostring(root) -- 25% overhead due to collecting
    if not root then
        return ""
    elseif type(root) == "string" then
        return root
    else -- if next(root) then -- next is faster than type (and >0 test)
        return serialize(root,xmlstringhandler) or ""
    end
end

local function __tostring(root) -- inline
    return (root and xmltostring(root)) or ""
end

initialize_mt = function(root) -- redefinition
    mt = { __tostring = __tostring, __index = root }
end

xml.defaulthandlers = handlers
xml.newhandlers     = newhandlers
xml.serialize       = serialize
xml.tostring        = xmltostring

--[[ldx--
<p>The next function operated on the content only and needs a handle function
that accepts a string.</p>
--ldx]]--

local function xmlstring(e,handle)
    if not handle or (e.special and e.tg ~= "@rt@") then
        -- nothing
    elseif e.tg then
        local edt = e.dt
        if edt then
            for i=1,#edt do
                xmlstring(edt[i],handle)
            end
        end
    else
        handle(e)
    end
end

xml.string = xmlstring

--[[ldx--
<p>A few helpers:</p>
--ldx]]--

--~ xmlsetproperty(root,"settings",settings)

function xml.settings(e)
    while e do
        local s = e.settings
        if s then
            return s
        else
            e = e.__p__
        end
    end
    return nil
end

function xml.root(e)
    local r = e
    while e do
        e = e.__p__
        if e then
            r = e
        end
    end
    return r
end

function xml.parent(root)
    return root.__p__
end

function xml.body(root)
    return root.ri and root.dt[root.ri] or root -- not ok yet
end

function xml.name(root)
    if not root then
        return ""
    end
    local ns = root.ns
    local tg = root.tg
    if ns == "" then
        return tg
    else
        return ns .. ":" .. tg
    end
end

--[[ldx--
<p>The next helper erases an element but keeps the table as it is,
and since empty strings are not serialized (effectively) it does
not harm. Copying the table would take more time. Usage:</p>
--ldx]]--

function xml.erase(dt,k)
    if dt then
        if k then
            dt[k] = ""
        else for k=1,#dt do
            dt[1] = { "" }
        end end
    end
end

--[[ldx--
<p>The next helper assigns a tree (or string). Usage:</p>

<typing>
dt[k] = xml.assign(root) or xml.assign(dt,k,root)
</typing>
--ldx]]--

function xml.assign(dt,k,root)
    if dt and k then
        dt[k] = type(root) == "table" and xml.body(root) or root
        return dt[k]
    else
        return xml.body(root)
    end
end

-- the following helpers may move

--[[ldx--
<p>The next helper assigns a tree (or string). Usage:</p>
<typing>
xml.tocdata(e)
xml.tocdata(e,"error")
</typing>
--ldx]]--

function xml.tocdata(e,wrapper) -- a few more in the aux module
    local whatever = type(e) == "table" and xmltostring(e.dt) or e or ""
    if wrapper then
        whatever = formatters["<%s>%s</%s>"](wrapper,whatever,wrapper)
    end
    local t = { special = true, ns = "", tg = "@cd@", at = { }, rn = "", dt = { whatever }, __p__ = e }
    setmetatable(t,getmetatable(e))
    e.dt = { t }
end

function xml.makestandalone(root)
    if root.ri then
        local dt = root.dt
        for k=1,#dt do
            local v = dt[k]
            if type(v) == "table" and v.special and v.tg == "@pi@" then
                local txt = v.dt[1]
                if find(txt,"xml.*version=") then
                    v.dt[1] = txt .. " standalone='yes'"
                    break
                end
            end
        end
    end
    return root
end

function xml.kind(e)
    local dt = e and e.dt
    if dt then
        local n = #dt
        if n == 1 then
            local d = dt[1]
            if d.special then
                local tg = d.tg
                if tg == "@cd@" then
                    return "cdata"
                elseif tg == "@cm" then
                    return "comment"
                elseif tg == "@pi@" then
                    return "instruction"
                elseif tg == "@dt@" then
                    return "declaration"
                end
            elseif type(d) == "string" then
                return "text"
            end
            return "element"
        elseif n > 0 then
            return "mixed"
        end
    end
    return "empty"
end
