cc-utils/types/dkjson/index.lua

-- Module options:
local always_use_lpeg = false
local register_global_module_table = false
local global_module_name = 'json'

--[==[

David Kolf's JSON module for Lua 5.1 - 5.4

Version 2.8


For the documentation see the corresponding readme.txt or visit
<http://dkolf.de/dkjson-lua/>.

You can contact the author by sending an e-mail to 'david' at the
domain 'dkolf.de'.


Copyright (C) 2010-2024 David Heiko Kolf

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

--]==]

-- global dependencies:
local pairs, type, tostring, tonumber, getmetatable, setmetatable =
    pairs, type, tostring, tonumber, getmetatable, setmetatable
local error, require, pcall, select = error, require, pcall, select
local floor, huge = math.floor, math.huge
local strrep, gsub, strsub, strbyte, strchar, strfind, strlen, strformat =
    string.rep, string.gsub, string.sub, string.byte, string.char,
    string.find, string.len, string.format
local strmatch = string.match
local concat = table.concat

local json = { version = "dkjson 2.8" }

local jsonlpeg = {}

if register_global_module_table then
    if always_use_lpeg then
        _G[global_module_name] = jsonlpeg
    else
        _G[global_module_name] = json
    end
end

local _ENV = nil -- blocking globals in Lua 5.2 and later

pcall(function()
    -- Enable access to blocked metatables.
    -- Don't worry, this module doesn't change anything in them.
    local debmeta = require "debug".getmetatable
    if debmeta then getmetatable = debmeta end
end)

json.null = setmetatable({}, {
    __tojson = function() return "null" end
})

local function isarray(tbl)
    local max, n, arraylen = 0, 0, 0
    for k, v in pairs(tbl) do
        if k == 'n' and type(v) == 'number' then
            arraylen = v
            if v > max then
                max = v
            end
        else
            if type(k) ~= 'number' or k < 1 or floor(k) ~= k then
                return false
            end
            if k > max then
                max = k
            end
            n = n + 1
        end
    end
    if max > 10 and max > arraylen and max > n * 2 then
        return false -- don't create an array with too many holes
    end
    return true, max
end

local escapecodes = {
    ["\""] = "\\\"",
    ["\\"] = "\\\\",
    ["\b"] = "\\b",
    ["\f"] = "\\f",
    ["\n"] = "\\n",
    ["\r"] = "\\r",
    ["\t"] = "\\t"
}

local function escapeutf8(uchar)
    local value = escapecodes[uchar]
    if value then
        return value
    end
    local a, b, c, d = strbyte(uchar, 1, 4)
    a, b, c, d = a or 0, b or 0, c or 0, d or 0
    if a <= 0x7f then
        value = a
    elseif 0xc0 <= a and a <= 0xdf and b >= 0x80 then
        value = (a - 0xc0) * 0x40 + b - 0x80
    elseif 0xe0 <= a and a <= 0xef and b >= 0x80 and c >= 0x80 then
        value = ((a - 0xe0) * 0x40 + b - 0x80) * 0x40 + c - 0x80
    elseif 0xf0 <= a and a <= 0xf7 and b >= 0x80 and c >= 0x80 and d >= 0x80 then
        value = (((a - 0xf0) * 0x40 + b - 0x80) * 0x40 + c - 0x80) * 0x40 + d - 0x80
    else
        return ""
    end
    if value <= 0xffff then
        return strformat("\\u%.4x", value)
    elseif value <= 0x10ffff then
        -- encode as UTF-16 surrogate pair
        value = value - 0x10000
        local highsur, lowsur = 0xD800 + floor(value / 0x400), 0xDC00 + (value % 0x400)
        return strformat("\\u%.4x\\u%.4x", highsur, lowsur)
    else
        return ""
    end
end

local function fsub(str, pattern, repl)
    -- gsub always builds a new string in a buffer, even when no match
    -- exists. First using find should be more efficient when most strings
    -- don't contain the pattern.
    if strfind(str, pattern) then
        return gsub(str, pattern, repl)
    else
        return str
    end
end

local function quotestring(value)
    -- based on the regexp "escapable" in https://github.com/douglascrockford/JSON-js
    value = fsub(value, "[%z\1-\31\"\\\127]", escapeutf8)
    if strfind(value, "[\194\216\220\225\226\239]") then
        value = fsub(value, "\194[\128-\159\173]", escapeutf8)
        value = fsub(value, "\216[\128-\132]", escapeutf8)
        value = fsub(value, "\220\143", escapeutf8)
        value = fsub(value, "\225\158[\180\181]", escapeutf8)
        value = fsub(value, "\226\128[\140-\143\168-\175]", escapeutf8)
        value = fsub(value, "\226\129[\160-\175]", escapeutf8)
        value = fsub(value, "\239\187\191", escapeutf8)
        value = fsub(value, "\239\191[\176-\191]", escapeutf8)
    end
    return "\"" .. value .. "\""
end
json.quotestring = quotestring

local function replace(str, o, n)
    local i, j = strfind(str, o, 1, true)
    if i then
        return strsub(str, 1, i - 1) .. n .. strsub(str, j + 1, -1)
    else
        return str
    end
end

-- locale independent num2str and str2num functions
local decpoint, numfilter

local function updatedecpoint()
    decpoint = strmatch(tostring(0.5), "([^05+])")
    -- build a filter that can be used to remove group separators
    numfilter = "[^0-9%-%+eE" .. gsub(decpoint, "[%^%$%(%)%%%.%[%]%*%+%-%?]", "%%%0") .. "]+"
end

updatedecpoint()

local function num2str(num)
    return replace(fsub(tostring(num), numfilter, ""), decpoint, ".")
end

local function str2num(str)
    local num = tonumber(replace(str, ".", decpoint))
    if not num then
        updatedecpoint()
        num = tonumber(replace(str, ".", decpoint))
    end
    return num
end

local function addnewline2(level, buffer, buflen)
    buffer[buflen + 1] = "\n"
    buffer[buflen + 2] = strrep("  ", level)
    buflen = buflen + 2
    return buflen
end

function json.addnewline(state)
    if state.indent then
        state.bufferlen = addnewline2(state.level or 0,
            state.buffer, state.bufferlen or #(state.buffer))
    end
end

local encode2 -- forward declaration

local function addpair(key, value, prev, indent, level, buffer, buflen, tables, globalorder, state)
    local kt = type(key)
    if kt ~= 'string' and kt ~= 'number' then
        return nil, "type '" .. kt .. "' is not supported as a key by JSON."
    end
    if prev then
        buflen = buflen + 1
        buffer[buflen] = ","
    end
    if indent then
        buflen = addnewline2(level, buffer, buflen)
    end
    -- When Lua is compiled with LUA_NOCVTN2S this will fail when
    -- numbers are mixed into the keys of the table. JSON keys are always
    -- strings, so this would be an implicit conversion too and the failure
    -- is intentional.
    buffer[buflen + 1] = quotestring(key)
    buffer[buflen + 2] = ":"
    return encode2(value, indent, level, buffer, buflen + 2, tables, globalorder, state)
end

local function appendcustom(res, buffer, state)
    local buflen = state.bufferlen
    if type(res) == 'string' then
        buflen = buflen + 1
        buffer[buflen] = res
    end
    return buflen
end

local function exception(reason, value, state, buffer, buflen, defaultmessage)
    defaultmessage = defaultmessage or reason
    local handler = state.exception
    if not handler then
        return nil, defaultmessage
    else
        state.bufferlen = buflen
        local ret, msg = handler(reason, value, state, defaultmessage)
        if not ret then return nil, msg or defaultmessage end
        return appendcustom(ret, buffer, state)
    end
end

function json.encodeexception(reason, value, state, defaultmessage)
    return quotestring("<" .. defaultmessage .. ">")
end

encode2 = function(value, indent, level, buffer, buflen, tables, globalorder, state)
    local valtype = type(value)
    local valmeta = getmetatable(value)
    valmeta = type(valmeta) == 'table' and valmeta -- only tables
    local valtojson = valmeta and valmeta.__tojson
    if valtojson then
        if tables[value] then
            return exception('reference cycle', value, state, buffer, buflen)
        end
        tables[value] = true
        state.bufferlen = buflen
        local ret, msg = valtojson(value, state)
        if not ret then return exception('custom encoder failed', value, state, buffer, buflen, msg) end
        tables[value] = nil
        buflen = appendcustom(ret, buffer, state)
    elseif value == nil then
        buflen = buflen + 1
        buffer[buflen] = "null"
    elseif valtype == 'number' then
        local s
        if value ~= value or value >= huge or -value >= huge then
            -- This is the behaviour of the original JSON implementation.
            s = "null"
        else
            s = num2str(value)
        end
        buflen = buflen + 1
        buffer[buflen] = s
    elseif valtype == 'boolean' then
        buflen = buflen + 1
        buffer[buflen] = value and "true" or "false"
    elseif valtype == 'string' then
        buflen = buflen + 1
        buffer[buflen] = quotestring(value)
    elseif valtype == 'table' then
        if tables[value] then
            return exception('reference cycle', value, state, buffer, buflen)
        end
        tables[value] = true
        level = level + 1
        local isa, n = isarray(value)
        if n == 0 and valmeta and valmeta.__jsontype == 'object' then
            isa = false
        end
        local msg
        if isa then -- JSON array
            buflen = buflen + 1
            buffer[buflen] = "["
            for i = 1, n do
                buflen, msg = encode2(value[i], indent, level, buffer, buflen, tables, globalorder, state)
                if not buflen then return nil, msg end
                if i < n then
                    buflen = buflen + 1
                    buffer[buflen] = ","
                end
            end
            buflen = buflen + 1
            buffer[buflen] = "]"
        else -- JSON object
            local prev = false
            buflen = buflen + 1
            buffer[buflen] = "{"
            local order = valmeta and valmeta.__jsonorder or globalorder
            if order then
                local used = {}
                n = #order
                for i = 1, n do
                    local k = order[i]
                    local v = value[k]
                    if v ~= nil then
                        used[k] = true
                        buflen, msg = addpair(k, v, prev, indent, level, buffer, buflen, tables, globalorder, state)
                        if not buflen then return nil, msg end
                        prev = true -- add a seperator before the next element
                    end
                end
                for k, v in pairs(value) do
                    if not used[k] then
                        buflen, msg = addpair(k, v, prev, indent, level, buffer, buflen, tables, globalorder, state)
                        if not buflen then return nil, msg end
                        prev = true -- add a seperator before the next element
                    end
                end
            else -- unordered
                for k, v in pairs(value) do
                    buflen, msg = addpair(k, v, prev, indent, level, buffer, buflen, tables, globalorder, state)
                    if not buflen then return nil, msg end
                    prev = true -- add a seperator before the next element
                end
            end
            if indent then
                buflen = addnewline2(level - 1, buffer, buflen)
            end
            buflen = buflen + 1
            buffer[buflen] = "}"
        end
        tables[value] = nil
    else
        return exception('unsupported type', value, state, buffer, buflen,
            "type '" .. valtype .. "' is not supported by JSON.")
    end
    return buflen
end

function json.encode(value, state)
    state = state or {}
    local oldbuffer = state.buffer
    local buffer = oldbuffer or {}
    state.buffer = buffer
    updatedecpoint()
    local ret, msg = encode2(value, state.indent, state.level or 0,
        buffer, state.bufferlen or 0, state.tables or {}, state.keyorder, state)
    if not ret then
        error(msg, 2)
    elseif oldbuffer == buffer then
        state.bufferlen = ret
        return true
    else
        state.bufferlen = nil
        state.buffer = nil
        return concat(buffer)
    end
end

local function loc(str, where)
    local line, pos, linepos = 1, 1, 0
    while true do
        pos = strfind(str, "\n", pos, true)
        if pos and pos < where then
            line = line + 1
            linepos = pos
            pos = pos + 1
        else
            break
        end
    end
    return strformat("line %d, column %d", line, where - linepos)
end

local function unterminated(str, what, where)
    return nil, strlen(str) + 1, "unterminated " .. what .. " at " .. loc(str, where)
end

local function scanwhite(str, pos)
    while true do
        pos = strfind(str, "%S", pos)
        if not pos then return nil end
        local sub2 = strsub(str, pos, pos + 1)
        if sub2 == "\239\187" and strsub(str, pos + 2, pos + 2) == "\191" then
            -- UTF-8 Byte Order Mark
            pos = pos + 3
        elseif sub2 == "//" then
            pos = strfind(str, "[\n\r]", pos + 2)
            if not pos then return nil end
        elseif sub2 == "/*" then
            pos = strfind(str, "*/", pos + 2)
            if not pos then return nil end
            pos = pos + 2
        else
            return pos
        end
    end
end

local escapechars = {
    ["\""] = "\"",
    ["\\"] = "\\",
    ["/"] = "/",
    ["b"] = "\b",
    ["f"] = "\f",
    ["n"] = "\n",
    ["r"] = "\r",
    ["t"] = "\t"
}

local function unichar(value)
    if value < 0 then
        return nil
    elseif value <= 0x007f then
        return strchar(value)
    elseif value <= 0x07ff then
        return strchar(0xc0 + floor(value / 0x40),
            0x80 + (floor(value) % 0x40))
    elseif value <= 0xffff then
        return strchar(0xe0 + floor(value / 0x1000),
            0x80 + (floor(value / 0x40) % 0x40),
            0x80 + (floor(value) % 0x40))
    elseif value <= 0x10ffff then
        return strchar(0xf0 + floor(value / 0x40000),
            0x80 + (floor(value / 0x1000) % 0x40),
            0x80 + (floor(value / 0x40) % 0x40),
            0x80 + (floor(value) % 0x40))
    else
        return nil
    end
end

local function scanstring(str, pos)
    local lastpos = pos + 1
    local buffer, n = {}, 0
    while true do
        local nextpos = strfind(str, "[\"\\]", lastpos)
        if not nextpos then
            return unterminated(str, "string", pos)
        end
        if nextpos > lastpos then
            n = n + 1
            buffer[n] = strsub(str, lastpos, nextpos - 1)
        end
        if strsub(str, nextpos, nextpos) == "\"" then
            lastpos = nextpos + 1
            break
        else
            local escchar = strsub(str, nextpos + 1, nextpos + 1)
            local value
            if escchar == "u" then
                value = tonumber(strsub(str, nextpos + 2, nextpos + 5), 16)
                if value then
                    local value2
                    if 0xD800 <= value and value <= 0xDBff then
                        -- we have the high surrogate of UTF-16. Check if there is a
                        -- low surrogate escaped nearby to combine them.
                        if strsub(str, nextpos + 6, nextpos + 7) == "\\u" then
                            value2 = tonumber(strsub(str, nextpos + 8, nextpos + 11), 16)
                            if value2 and 0xDC00 <= value2 and value2 <= 0xDFFF then
                                value = (value - 0xD800) * 0x400 + (value2 - 0xDC00) + 0x10000
                            else
                                value2 = nil -- in case it was out of range for a low surrogate
                            end
                        end
                    end
                    value = value and unichar(value)
                    if value then
                        if value2 then
                            lastpos = nextpos + 12
                        else
                            lastpos = nextpos + 6
                        end
                    end
                end
            end
            if not value then
                value = escapechars[escchar] or escchar
                lastpos = nextpos + 2
            end
            n = n + 1
            buffer[n] = value
        end
    end
    if n == 1 then
        return buffer[1], lastpos
    elseif n > 1 then
        return concat(buffer), lastpos
    else
        return "", lastpos
    end
end

local scanvalue -- forward declaration

local function scantable(what, closechar, str, startpos, nullval, objectmeta, arraymeta)
    local tbl, n = {}, 0
    local pos = startpos + 1
    if what == 'object' then
        setmetatable(tbl, objectmeta)
    else
        setmetatable(tbl, arraymeta)
    end
    while true do
        pos = scanwhite(str, pos)
        if not pos then return unterminated(str, what, startpos) end
        local char = strsub(str, pos, pos)
        if char == closechar then
            return tbl, pos + 1
        end
        local val1, err
        val1, pos, err = scanvalue(str, pos, nullval, objectmeta, arraymeta)
        if err then return nil, pos, err end
        pos = scanwhite(str, pos)
        if not pos then return unterminated(str, what, startpos) end
        char = strsub(str, pos, pos)
        if char == ":" then
            if val1 == nil then
                return nil, pos, "cannot use nil as table index (at " .. loc(str, pos) .. ")"
            end
            pos = scanwhite(str, pos + 1)
            if not pos then return unterminated(str, what, startpos) end
            local val2
            val2, pos, err = scanvalue(str, pos, nullval, objectmeta, arraymeta)
            if err then return nil, pos, err end
            tbl[val1] = val2
            pos = scanwhite(str, pos)
            if not pos then return unterminated(str, what, startpos) end
            char = strsub(str, pos, pos)
        else
            n = n + 1
            tbl[n] = val1
        end
        if char == "," then
            pos = pos + 1
        end
    end
end

scanvalue = function(str, pos, nullval, objectmeta, arraymeta)
    pos = pos or 1
    pos = scanwhite(str, pos)
    if not pos then
        return nil, strlen(str) + 1, "no valid JSON value (reached the end)"
    end
    local char = strsub(str, pos, pos)
    if char == "{" then
        return scantable('object', "}", str, pos, nullval, objectmeta, arraymeta)
    elseif char == "[" then
        return scantable('array', "]", str, pos, nullval, objectmeta, arraymeta)
    elseif char == "\"" then
        return scanstring(str, pos)
    else
        local pstart, pend = strfind(str, "^%-?[%d%.]+[eE]?[%+%-]?%d*", pos)
        if pstart then
            local number = str2num(strsub(str, pstart, pend))
            if number then
                return number, pend + 1
            end
        end
        pstart, pend = strfind(str, "^%a%w*", pos)
        if pstart then
            local name = strsub(str, pstart, pend)
            if name == "true" then
                return true, pend + 1
            elseif name == "false" then
                return false, pend + 1
            elseif name == "null" then
                return nullval, pend + 1
            end
        end
        return nil, pos, "no valid JSON value at " .. loc(str, pos)
    end
end

local function optionalmetatables(...)
    if select("#", ...) > 0 then
        return ...
    else
        return { __jsontype = 'object' }, { __jsontype = 'array' }
    end
end

function json.decode(str, pos, nullval, ...)
    local objectmeta, arraymeta = optionalmetatables(...)
    return scanvalue(str, pos, nullval, objectmeta, arraymeta)
end

-- function json.use_lpeg ()
--   local g = require ("lpeg")

--   if type(g.version) == 'function' and g.version() == "0.11" then
--     error "due to a bug in LPeg 0.11, it cannot be used for JSON matching"
--   end

--   local pegmatch = g.match
--   local P, S, R = g.P, g.S, g.R

--   local function ErrorCall (str, pos, msg, state)
--     if not state.msg then
--       state.msg = msg .. " at " .. loc (str, pos)
--       state.pos = pos
--     end
--     return false
--   end

--   local function Err (msg)
--     return g.Cmt (g.Cc (msg) * g.Carg (2), ErrorCall)
--   end

--   local function ErrorUnterminatedCall (str, pos, what, state)
--     return ErrorCall (str, pos - 1, "unterminated " .. what, state)
--   end

--   local SingleLineComment = P"//" * (1 - S"\n\r")^0
--   local MultiLineComment = P"/*" * (1 - P"*/")^0 * P"*/"
--   local Space = (S" \n\r\t" + P"\239\187\191" + SingleLineComment + MultiLineComment)^0

--   local function ErrUnterminated (what)
--     return g.Cmt (g.Cc (what) * g.Carg (2), ErrorUnterminatedCall)
--   end

--   local PlainChar = 1 - S"\"\\\n\r"
--   local EscapeSequence = (P"\\" * g.C (S"\"\\/bfnrt" + Err "unsupported escape sequence")) / escapechars
--   local HexDigit = R("09", "af", "AF")
--   local function UTF16Surrogate (match, pos, high, low)
--     high, low = tonumber (high, 16), tonumber (low, 16)
--     if 0xD800 <= high and high <= 0xDBff and 0xDC00 <= low and low <= 0xDFFF then
--       return true, unichar ((high - 0xD800)  * 0x400 + (low - 0xDC00) + 0x10000)
--     else
--       return false
--     end
--   end
--   local function UTF16BMP (hex)
--     return unichar (tonumber (hex, 16))
--   end
--   local U16Sequence = (P"\\u" * g.C (HexDigit * HexDigit * HexDigit * HexDigit))
--   local UnicodeEscape = g.Cmt (U16Sequence * U16Sequence, UTF16Surrogate) + U16Sequence/UTF16BMP
--   local Char = UnicodeEscape + EscapeSequence + PlainChar
--   local String = P"\"" * (g.Cs (Char ^ 0) * P"\"" + ErrUnterminated "string")
--   local Integer = P"-"^(-1) * (P"0" + (R"19" * R"09"^0))
--   local Fractal = P"." * R"09"^0
--   local Exponent = (S"eE") * (S"+-")^(-1) * R"09"^1
--   local Number = (Integer * Fractal^(-1) * Exponent^(-1))/str2num
--   local Constant = P"true" * g.Cc (true) + P"false" * g.Cc (false) + P"null" * g.Carg (1)
--   local SimpleValue = Number + String + Constant
--   local ArrayContent, ObjectContent

--   -- The functions parsearray and parseobject parse only a single value/pair
--   -- at a time and store them directly to avoid hitting the LPeg limits.
--   local function parsearray (str, pos, nullval, state)
--     local obj, cont
--     local start = pos
--     local npos
--     local t, nt = {}, 0
--     repeat
--       obj, cont, npos = pegmatch (ArrayContent, str, pos, nullval, state)
--       if cont == 'end' then
--         return ErrorUnterminatedCall (str, start, "array", state)
--       end
--       pos = npos
--       if cont == 'cont' or cont == 'last' then
--         nt = nt + 1
--         t[nt] = obj
--       end
--     until cont ~= 'cont'
--     return pos, setmetatable (t, state.arraymeta)
--   end

--   local function parseobject (str, pos, nullval, state)
--     local obj, key, cont
--     local start = pos
--     local npos
--     local t = {}
--     repeat
--       key, obj, cont, npos = pegmatch (ObjectContent, str, pos, nullval, state)
--       if cont == 'end' then
--         return ErrorUnterminatedCall (str, start, "object", state)
--       end
--       pos = npos
--       if cont == 'cont' or cont == 'last' then
--         t[key] = obj
--       end
--     until cont ~= 'cont'
--     return pos, setmetatable (t, state.objectmeta)
--   end

--   local Array = P"[" * g.Cmt (g.Carg(1) * g.Carg(2), parsearray)
--   local Object = P"{" * g.Cmt (g.Carg(1) * g.Carg(2), parseobject)
--   local Value = Space * (Array + Object + SimpleValue)
--   local ExpectedValue = Value + Space * Err "value expected"
--   local ExpectedKey = String + Err "key expected"
--   local End = P(-1) * g.Cc'end'
--   local ErrInvalid = Err "invalid JSON"
--   ArrayContent = (Value * Space * (P"," * g.Cc'cont' + P"]" * g.Cc'last'+ End + ErrInvalid)  + g.Cc(nil) * (P"]" * g.Cc'empty' + End  + ErrInvalid)) * g.Cp()
--   local Pair = g.Cg (Space * ExpectedKey * Space * (P":" + Err "colon expected") * ExpectedValue)
--   ObjectContent = (g.Cc(nil) * g.Cc(nil) * P"}" * g.Cc'empty' + End + (Pair * Space * (P"," * g.Cc'cont' + P"}" * g.Cc'last' + End + ErrInvalid) + ErrInvalid)) * g.Cp()
--   local DecodeValue = ExpectedValue * g.Cp ()

--   jsonlpeg.version = json.version
--   jsonlpeg.encode = json.encode
--   jsonlpeg.null = json.null
--   jsonlpeg.quotestring = json.quotestring
--   jsonlpeg.addnewline = json.addnewline
--   jsonlpeg.encodeexception = json.encodeexception
--   jsonlpeg.using_lpeg = true

--   function jsonlpeg.decode (str, pos, nullval, ...)
--     local state = {}
--     state.objectmeta, state.arraymeta = optionalmetatables(...)
--     local obj, retpos = pegmatch (DecodeValue, str, pos, nullval, state)
--     if state.msg then
--       return nil, state.pos, state.msg
--     else
--       return obj, retpos
--     end
--   end

--   -- cache result of this function:
--   json.use_lpeg = function () return jsonlpeg end
--   jsonlpeg.use_lpeg = json.use_lpeg

--   return jsonlpeg
-- end

-- if always_use_lpeg then
--   return json.use_lpeg()
-- end

return json