--

-- json.lua

--

-- Copyright (c) 2020 rxi

--

-- 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.

--

local json = {_version = "0.1.2"}

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

-- Encode

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

local encode

local escape_char_map = {

["\\"] = "\\",

["\""] = "\"",

["\b"] = "b",

["\f"] = "f",

["\n"] = "n",

["\r"] = "r",

["\t"] = "t"

}

local escape_char_map_inv = {["/"] = "/"}

for k, v in pairs(escape_char_map) do escape_char_map_inv[v] = k end

local function escape_char(c)

return "\\" .. (escape_char_map[c] or string.format("u%04x", c:byte()))

end

local function encode_nil(val) return "null" end

local function encode_table(val, stack)

local res = {}

stack = stack or {}

-- Circular reference?

if stack[val] then error("circular reference") end

stack[val] = true

if rawget(val, 1) ~= nil or next(val) == nil then

-- Treat as array -- check keys are valid and it is not sparse

local n = 0

for k in pairs(val) do

if type(k) ~= "number" then

error("invalid table: mixed or invalid key types")

end

n = n + 1

end

if n ~= #val then error("invalid table: sparse array") end

-- Encode

for i, v in ipairs(val) do table.insert(res, encode(v, stack)) end

stack[val] = nil

return "[" .. table.concat(res, ",") .. "]"

else

-- Treat as an object

for k, v in pairs(val) do

if type(k) ~= "string" then

error("invalid table: mixed or invalid key types")

end

table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))

end

stack[val] = nil

return "{" .. table.concat(res, ",") .. "}"

end

end

local function encode_string(val)

return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'

end

local function encode_number(val)

-- Check for NaN, -inf and inf

if val ~= val or val <= -math.huge or val >= math.huge then

error("unexpected number value '" .. tostring(val) .. "'")

end

return string.format("%.14g", val)

end

local type_func_map = {

["nil"] = encode_nil,

["table"] = encode_table,

["string"] = encode_string,

["number"] = encode_number,

["boolean"] = tostring

}

encode = function(val, stack)

local t = type(val)

local f = type_func_map[t]

if f then return f(val, stack) end

error("unexpected type '" .. t .. "'")

end

function json.encode(val) return (encode(val)) end

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

-- Decode

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

local parse

local function create_set(...)

local res = {}

for i = 1, select("#", ...) do res[select(i, ...)] = true end

return res

end

local space_chars = create_set(" ", "\t", "\r", "\n")

local delim_chars = create_set(" ", "\t", "\r", "\n", "]", "}", ",")

local escape_chars = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")

local literals = create_set("true", "false", "null")

local literal_map = {["true"] = true, ["false"] = false, ["null"] = nil}

local function next_char(str, idx, set, negate)

for i = idx, #str do if set[str:sub(i, i)] ~= negate then return i end end

return #str + 1

end

local function decode_error(str, idx, msg)

local line_count = 1

local col_count = 1

for i = 1, idx - 1 do

col_count = col_count + 1

if str:sub(i, i) == "\n" then

line_count = line_count + 1

col_count = 1

end

end

error(string.format("%s at line %d col %d", msg, line_count, col_count))

end

local function codepoint_to_utf8(n)

-- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa

local f = math.floor

if n <= 0x7f then

return string.char(n)

elseif n <= 0x7ff then

return string.char(f(n / 64) + 192, n % 64 + 128)

elseif n <= 0xffff then

return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128,

n % 64 + 128)

elseif n <= 0x10ffff then

return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,

f(n % 4096 / 64) + 128, n % 64 + 128)

end

error(string.format("invalid unicode codepoint '%x'", n))

end

local function parse_unicode_escape(s)

local n1 = tonumber(s:sub(1, 4), 16)

local n2 = tonumber(s:sub(7, 10), 16)

-- Surrogate pair?

if n2 then

return

codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)

else

return codepoint_to_utf8(n1)

end

end

local function parse_string(str, i)

local res = ""

local j = i + 1

local k = j

while j <= #str do

local x = str:byte(j)

if x < 32 then

decode_error(str, j, "control character in string")

elseif x == 92 then -- `\`: Escape

res = res .. str:sub(k, j - 1)

j = j + 1

local c = str:sub(j, j)

if c == "u" then

local hex = str:match("^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1) or

str:match("^%x%x%x%x", j + 1) or

decode_error(str, j - 1,

"invalid unicode escape in string")

res = res .. parse_unicode_escape(hex)

j = j + #hex

else

if not escape_chars[c] then

decode_error(str, j - 1,

"invalid escape char '" .. c .. "' in string")

end

res = res .. escape_char_map_inv[c]

end

k = j + 1

elseif x == 34 then -- `"`: End of string

res = res .. str:sub(k, j - 1)

return res, j + 1

end

j = j + 1

end

decode_error(str, i, "expected closing quote for string")

end

local function parse_number(str, i)

local x = next_char(str, i, delim_chars)

local s = str:sub(i, x - 1)

local n = tonumber(s)

if not n then decode_error(str, i, "invalid number '" .. s .. "'") end

return n, x

end

local function parse_literal(str, i)

local x = next_char(str, i, delim_chars)

local word = str:sub(i, x - 1)

if not literals[word] then

decode_error(str, i, "invalid literal '" .. word .. "'")

end

return literal_map[word], x

end

local function parse_array(str, i)

local res = {}

local n = 1

i = i + 1

while 1 do

local x

i = next_char(str, i, space_chars, true)

-- Empty / end of array?

if str:sub(i, i) == "]" then

i = i + 1

break

end

-- Read token

x, i = parse(str, i)

res[n] = x

n = n + 1

-- Next token

i = next_char(str, i, space_chars, true)

local chr = str:sub(i, i)

i = i + 1

if chr == "]" then break end

if chr ~= "," then decode_error(str, i, "expected ']' or ','") end

end

return res, i

end

local function parse_object(str, i)

local res = {}

i = i + 1

while 1 do

local key, val

i = next_char(str, i, space_chars, true)

-- Empty / end of object?

if str:sub(i, i) == "}" then

i = i + 1

break

end

-- Read key

if str:sub(i, i) ~= '"' then

decode_error(str, i, "expected string for key")

end

key, i = parse(str, i)

-- Read ':' delimiter

i = next_char(str, i, space_chars, true)

if str:sub(i, i) ~= ":" then

decode_error(str, i, "expected ':' after key")

end

i = next_char(str, i + 1, space_chars, true)

-- Read value

val, i = parse(str, i)

-- Set

res[key] = val

-- Next token

i = next_char(str, i, space_chars, true)

local chr = str:sub(i, i)

i = i + 1

if chr == "}" then break end

if chr ~= "," then decode_error(str, i, "expected '}' or ','") end

end

return res, i

end

local char_func_map = {

['"'] = parse_string,

["0"] = parse_number,

["1"] = parse_number,

["2"] = parse_number,

["3"] = parse_number,

["4"] = parse_number,

["5"] = parse_number,

["6"] = parse_number,

["7"] = parse_number,

["8"] = parse_number,

["9"] = parse_number,

["-"] = parse_number,

["t"] = parse_literal,

["f"] = parse_literal,

["n"] = parse_literal,

["["] = parse_array,

["{"] = parse_object

}

parse = function(str, idx)

local chr = str:sub(idx, idx)

local f = char_func_map[chr]

if f then return f(str, idx) end

decode_error(str, idx, "unexpected character '" .. chr .. "'")

end

function json.decode(str)

if type(str) ~= "string" then

error("expected argument of type string, got " .. type(str))

end

local res, idx = parse(str, next_char(str, 1, space_chars, true))

idx = next_char(str, idx, space_chars, true)

if idx <= #str then decode_error(str, idx, "trailing garbage") end

return res

end

return json