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    -- Module options:
    local always_try_using_lpeg = true
    local register_global_module_table = false
    local global_module_name = 'json'

    --[==[

David Kolf's JSON module for Lua 5.1/5.2
========================================

*Version 2.4*

In the default configuration this module writes no global values, not even
the module table. Import it using

    json = require ("dkjson")

In environments where `require` or a similiar function are not available
and you cannot receive the return value of the module, you can set the
option `register_global_module_table` to `true`.  The module table will
then be saved in the global variable with the name given by the option
`global_module_name`.

Exported functions and values:

`json.encode (object [, state])`
--------------------------------

Create a string representing the object. `Object` can be a table,
a string, a number, a boolean, `nil`, `json.null` or any object with
a function `__tojson` in its metatable. A table can only use strings
and numbers as keys and its values have to be valid objects as
well. It raises an error for any invalid data types or reference
cycles.

`state` is an optional table with the following fields:

  - `indent`  
    When `indent` (a boolean) is set, the created string will contain
    newlines and indentations. Otherwise it will be one long line.
  - `keyorder`  
    `keyorder` is an array to specify the ordering of keys in the
    encoded output. If an object has keys which are not in this array
    they are written after the sorted keys.
  - `level`  
    This is the initial level of indentation used when `indent` is
    set. For each level two spaces are added. When absent it is set
    to 0.
  - `buffer`  
    `buffer` is an array to store the strings for the result so they
    can be concatenated at once. When it isn't given, the encode
    function will create it temporary and will return the
    concatenated result.
  - `bufferlen`  
    When `bufferlen` is set, it has to be the index of the last
    element of `buffer`.
  - `tables`  
    `tables` is a set to detect reference cycles. It is created
    temporary when absent. Every table that is currently processed
    is used as key, the value is `true`.

When `state.buffer` was set, the return value will be `true` on
success. Without `state.buffer` the return value will be a string.

`json.decode (string [, position [, null]])`
--------------------------------------------

Decode `string` starting at `position` or at 1 if `position` was
omitted.

`null` is an optional value to be returned for null values. The
default is `nil`, but you could set it to `json.null` or any other
value.

The return values are the object or `nil`, the position of the next
character that doesn't belong to the object, and in case of errors
an error message.

Two metatables are created. Every array or object that is decoded gets
a metatable with the `__jsontype` field set to either `array` or
`object`. If you want to provide your own metatables use the syntax

    json.decode (string, position, null, objectmeta, arraymeta)

To prevent the assigning of metatables pass `nil`:

    json.decode (string, position, null, nil)

`<metatable>.__jsonorder`
-------------------------

`__jsonorder` can overwrite the `keyorder` for a specific table.

`<metatable>.__jsontype`
------------------------

`__jsontype` can be either `"array"` or `"object"`. This value is only
checked for empty tables. (The default for empty tables is `"array"`).

`<metatable>.__tojson (self, state)`
------------------------------------

You can provide your own `__tojson` function in a metatable. In this
function you can either add directly to the buffer and return true,
or you can return a string. On errors nil and a message should be
returned.

`json.null`
-----------

You can use this value for setting explicit `null` values.

`json.version`
--------------

Set to `"dkjson 2.4"`.

`json.quotestring (string)`
---------------------------

Quote a UTF-8 string and escape critical characters using JSON
escape sequences. This function is only necessary when you build
your own `__tojson` functions.

`json.addnewline (state)`
-------------------------

When `state.indent` is set, add a newline to `state.buffer` and spaces
according to `state.level`.

LPeg support
------------

When the local configuration variable `always_try_using_lpeg` is set,
this module tries to load LPeg to replace the `decode` function. The
speed increase is significant. You can get the LPeg module at
  <http://www.inf.puc-rio.br/~roberto/lpeg/>.
When LPeg couldn't be loaded, the pure Lua functions stay active.

In case you don't want this module to require LPeg on its own,
disable the option `always_try_using_lpeg` in the options section at
the top of the module.

In this case you can later load LPeg support using

### `json.use_lpeg ()`

Require the LPeg module and replace the functions `quotestring` and
and `decode` with functions that use LPeg patterns.
This function returns the module table, so you can load the module
using:

    json = require "dkjson".use_lpeg()

Alternatively you can use `pcall` so the JSON module still works when
LPeg isn't found.

    json = require "dkjson"
    pcall (json.use_lpeg)

### `json.using_lpeg`

This variable is set to `true` when LPeg was loaded successfully.

---------------------------------------------------------------------

Contact
-------

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

---------------------------------------------------------------------

*Copyright (C) 2010-2013 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.

<!-- This documentation can be parsed using Markdown to generate HTML.
     The source code is enclosed in a HTML comment so it won't be displayed
     by browsers, but it should be removed from the final HTML file as
     it isn't a valid HTML comment (and wastes space).
  -->

<!--]==]

-- global dependencies:
local pairs, type, tostring, tonumber, getmetatable, setmetatable, rawset =
      pairs, type, tostring, tonumber, getmetatable, setmetatable, rawset
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 2.4" }

if register_global_module_table then
  _G[global_module_name] = json
end

local _ENV = nil -- blocking globals in Lua 5.2

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)
  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
  buffer[buflen+1] = quotestring (key)
  buffer[buflen+2] = ":"
  return encode2 (value, indent, level, buffer, buflen + 2, tables, globalorder)
end

encode2 = function (value, indent, level, buffer, buflen, tables, globalorder)
  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 nil, "reference cycle"
    end
    tables[value] = true
    local state = {
        indent = indent, level = level, buffer = buffer,
        bufferlen = buflen, tables = tables, keyorder = globalorder
    }
    local ret, msg = valtojson (value, state)
    if not ret then return nil, msg end
    tables[value] = nil
    buflen = state.bufferlen
    if type (ret) == 'string' then
      buflen = buflen + 1
      buffer[buflen] = ret
    end
  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 nil, "reference cycle"
    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)
        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 then
            used[k] = true
            buflen, msg = addpair (k, v, prev, indent, level, buffer, buflen, tables, globalorder)
            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)
            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)
          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 nil, "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 {}
  updatedecpoint()
  local ret, msg = encode2 (value, state.indent, state.level or 0,
                   buffer, state.bufferlen or 0, state.tables or {}, state.keyorder)
  if not ret then
    error (msg, 2)
  elseif oldbuffer then
    state.bufferlen = ret
    return true
  else
    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 "line " .. line .. ", column " .. (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
    if strsub (str, pos, pos + 2) == "\239\187\191" then
      -- UTF-8 Byte Order Mark
      pos = pos + 3
    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 len = strlen (str)
  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 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 Space = (S" \n\r\t" + P"\239\187\191")^0

  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"\"" + Err "unterminated 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 npos
    local t, nt = {}, 0
    repeat
      obj, cont, npos = pegmatch (ArrayContent, str, pos, nullval, state)
      if not npos then break end
      pos = npos
      nt = nt + 1
      t[nt] = obj
    until cont == 'last'
    return pos, setmetatable (t, state.arraymeta)
  end

  local function parseobject (str, pos, nullval, state)
    local obj, key, cont
    local npos
    local t = {}
    repeat
      key, obj, cont, npos = pegmatch (ObjectContent, str, pos, nullval, state)
      if not npos then break end
      pos = npos
      t[key] = obj
    until cont == 'last'
    return pos, setmetatable (t, state.objectmeta)
  end

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

  function json.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

  -- use this function only once:
  json.use_lpeg = function () return json end

  json.using_lpeg = true

  return json -- so you can get the module using json = require "dkjson".use_lpeg()
end

if always_try_using_lpeg then
  pcall (json.use_lpeg)
end

return json

-->

Author comment

taken verbatim from http://dkolf.de/src/dkjson-lua.fsl/home (loaded 22 Dec 2013)

download  show line numbers   

Travelled to 9 computer(s): aoiabmzegqzx, cbybwowwnfue, gwrvuhgaqvyk, ishqpsrjomds, lpdgvwnxivlt, mqqgnosmbjvj, tslmcundralx, tvejysmllsmz, znullqslnikg

Comments [hide]

ID Author/Program Comment Date
934 #1000604 (pitcher) 2015-08-20 15:28:24
933 #1000610 Edit suggestion:
!636
!629

main {
static Object androidContext;
static String programID;

public static void main(String[] args) throws Exception {
-- Module options:
local always_try_using_lpeg = true
local register_global_module_table = false
local global_module_name = 'json'

--[==[

David Kolf's JSON module for Lua 5.1/5.2
========================================

*Version 2.4*

In the default configuration this module writes no global values, not even
the module table. Import it using

json = require ("dkjson")

In environments where `require` or a similiar function are not available
and you cannot receive the return value of the module, you can set the
option `register_global_module_table` to `true`. The module table will
then be saved in the global variable with the name given by the option
`global_module_name`.

Exported functions and values:

`json.encode (object [, state])`
--------------------------------

Create a string representing the object. `Object` can be a table,
a string, a number, a boolean, `nil`, `json.null` or any object with
a function `__tojson` in its metatable. A table can only use strings
and numbers as keys and its values have to be valid objects as
well. It raises an error for any invalid data types or reference
cycles.

`state` is an optional table with the following fields:

- `indent`
When `indent` (a boolean) is set, the created string will contain
newlines and indentations. Otherwise it will be one long line.
- `keyorder`
`keyorder` is an array to specify the ordering of keys in the
encoded output. If an object has keys which are not in this array
they are written after the sorted keys.
- `level`
This is the initial level of indentation used when `indent` is
set. For each level two spaces are added. When absent it is set
to 0.
- `buffer`
`buffer` is an array to store the strings for the result so they
can be concatenated at once. When it isn't given, the encode
function will create it temporary and will return the
concatenated result.
- `bufferlen`
When `bufferlen` is set, it has to be the index of the last
element of `buffer`.
- `tables`
`tables` is a set to detect reference cycles. It is created
temporary when absent. Every table that is currently processed
is used as key, the value is `true`.

When `state.buffer` was set, the return value will be `true` on
success. Without `state.buffer` the return value will be a string.

`json.decode (string [, position [, null]])`
--------------------------------------------

Decode `string` starting at `position` or at 1 if `position` was
omitted.

`null` is an optional value to be returned for null values. The
default is `nil`, but you could set it to `json.null` or any other
value.

The return values are the object or `nil`, the position of the next
character that doesn't belong to the object, and in case of errors
an error message.

Two metatables are created. Every array or object that is decoded gets
a metatable with the `__jsontype` field set to either `array` or
`object`. If you want to provide your own metatables use the syntax

json.decode (string, position, null, objectmeta, arraymeta)

To prevent the assigning of metatables pass `nil`:

json.decode (string, position, null, nil)

`<metatable>.__jsonorder`
-------------------------

`__jsonorder` can overwrite the `keyorder` for a specific table.

`<metatable>.__jsontype`
------------------------

`__jsontype` can be either `"array"` or `"object"`. This value is only
checked for empty tables. (The default for empty tables is `"array"`).

`<metatable>.__tojson (self, state)`
------------------------------------

You can provide your own `__tojson` function in a metatable. In this
function you can either add directly to the buffer and return true,
or you can return a string. On errors nil and a message should be
returned.

`json.null`
-----------

You can use this value for setting explicit `null` values.

`json.version`
--------------

Set to `"dkjson 2.4"`.

`json.quotestring (string)`
---------------------------

Quote a UTF-8 string and escape critical characters using JSON
escape sequences. This function is only necessary when you build
your own `__tojson` functions.

`json.addnewline (state)`
-------------------------

When `state.indent` is set, add a newline to `state.buffer` and spaces
according to `state.level`.

LPeg support
------------

When the local configuration variable `always_try_using_lpeg` is set,
this module tries to load LPeg to replace the `decode` function. The
speed increase is significant. You can get the LPeg module at
<http://www.inf.puc-rio.br/~roberto/lpeg/>.
When LPeg couldn't be loaded, the pure Lua functions stay active.

In case you don't want this module to require LPeg on its own,
disable the option `always_try_using_lpeg` in the options section at
the top of the module.

In this case you can later load LPeg support using

### `json.use_lpeg ()`

Require the LPeg module and replace the functions `quotestring` and
and `decode` with functions that use LPeg patterns.
This function returns the module table, so you can load the module
using:

json = require "dkjson".use_lpeg()

Alternatively you can use `pcall` so the JSON module still works when
LPeg isn't found.

json = require "dkjson"
pcall (json.use_lpeg)

### `json.using_lpeg`

This variable is set to `true` when LPeg was loaded successfully.

---------------------------------------------------------------------

Contact
-------

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

---------------------------------------------------------------------

*Copyright (C) 2010-2013 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.

<!-- This documentation can be parsed using Markdown to generate HTML.
The source code is enclosed in a HTML comment so it won't be displayed
by browsers, but it should be removed from the final HTML file as
it isn't a valid HTML comment (and wastes space).
-->

<!--]==]

-- global dependencies:
local pairs, type, tostring, tonumber, getmetatable, setmetatable, rawset =
pairs, type, tostring, tonumber, getmetatable, setmetatable, rawset
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 2.4" }

if register_global_module_table then
_G[global_module_name] = json
end

local _ENV = nil -- blocking globals in Lua 5.2

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)
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
buffer[buflen+1] = quotestring (key)
buffer[buflen+2] = ":"
return encode2 (value, indent, level, buffer, buflen + 2, tables, globalorder)
end

encode2 = function (value, indent, level, buffer, buflen, tables, globalorder)
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 nil, "reference cycle"
end
tables[value] = true
local state = {
indent = indent, level = level, buffer = buffer,
bufferlen = buflen, tables = tables, keyorder = globalorder
}
local ret, msg = valtojson (value, state)
if not ret then return nil, msg end
tables[value] = nil
buflen = state.bufferlen
if type (ret) == 'string' then
buflen = buflen + 1
buffer[buflen] = ret
end
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 nil, "reference cycle"
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)
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 then
used[k] = true
buflen, msg = addpair (k, v, prev, indent, level, buffer, buflen, tables, globalorder)
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)
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)
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 nil, "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 {}
updatedecpoint()
local ret, msg = encode2 (value, state.indent, state.level or 0,
buffer, state.bufferlen or 0, state.tables or {}, state.keyorder)
if not ret then
error (msg, 2)
elseif oldbuffer then
state.bufferlen = ret
return true
else
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 "line " .. line .. ", column " .. (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
if strsub (str, pos, pos + 2) == "\239\187\191" then
-- UTF-8 Byte Order Mark
pos = pos + 3
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 len = strlen (str)
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 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 Space = (S" \n\r\t" + P"\239\187\191")^0

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"\"" + Err "unterminated 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 npos
local t, nt = {}, 0
repeat
obj, cont, npos = pegmatch (ArrayContent, str, pos, nullval, state)
if not npos then break end
pos = npos
nt = nt + 1
t[nt] = obj
until cont == 'last'
return pos, setmetatable (t, state.arraymeta)
end

local function parseobject (str, pos, nullval, state)
local obj, key, cont
local npos
local t = {}
repeat
key, obj, cont, npos = pegmatch (ObjectContent, str, pos, nullval, state)
if not npos then break end
pos = npos
t[key] = obj
until cont == 'last'
return pos, setmetatable (t, state.objectmeta)
end

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

function json.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

-- use this function only once:
json.use_lpeg = function () return json end

json.using_lpeg = true

return json -- so you can get the module using json = require "dkjson".use_lpeg()
end

if always_try_using_lpeg then
pcall (json.use_lpeg)
end

return json

-->
}}
2015-08-20 05:49:11  delete 

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Recognizer Recognition Result Visualize Recalc
#308 27434 [visualize]

Snippet ID: #44
Snippet name: dkjson
Eternal ID of this version: #44/1
Text MD5: 1e9ad6209dbe9669f78ba5694022fb5e
Author: stefan
Category:
Type: Source file
Public (visible to everyone): Yes
Archived (hidden from active list): No
Created/modified: 2013-12-22 13:48:02
Source code size: 27434 bytes / 843 lines
Pitched / IR pitched: No / Yes
Views / Downloads: 1461 / 533
Referenced in: [show references]

Formerly at http://tinybrain.de/44 & http://44.tinybrain.de