380 lines
8.7 KiB
Lua
380 lines
8.7 KiB
Lua
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--
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-- json.lua
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--
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-- Copyright (c) 2015 rxi
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--
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-- This library is free software; you can redistribute it and/or modify it
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-- under the terms of the MIT license. See LICENSE for details.
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--
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local json = { _version = "0.1.0" }
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-------------------------------------------------------------------------------
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-- Encode
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-------------------------------------------------------------------------------
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local encode
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local escape_char_map = {
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[ "\\" ] = "\\\\",
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[ "\"" ] = "\\\"",
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[ "\b" ] = "\\b",
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[ "\f" ] = "\\f",
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[ "\n" ] = "\\n",
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[ "\r" ] = "\\r",
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[ "\t" ] = "\\t",
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}
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local escape_char_map_inv = { [ "\\/" ] = "/" }
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for k, v in pairs(escape_char_map) do
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escape_char_map_inv[v] = k
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end
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local function escape_char(c)
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return escape_char_map[c] or string.format("\\u%04x", c:byte())
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end
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local function encode_nil(val)
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return "null"
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end
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local function encode_table(val, stack)
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local res = {}
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stack = stack or {}
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-- Circular reference?
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if stack[val] then error("circular reference") end
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stack[val] = true
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if val[1] ~= nil or next(val) == nil then
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-- Treat as array -- check keys are valid and it is not sparse
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local n = 0
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for k in pairs(val) do
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if type(k) ~= "number" then
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error("invalid table: mixed or invalid key types")
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end
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n = n + 1
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end
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if n ~= #val then
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error("invalid table: sparse array")
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end
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-- Encode
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for i, v in ipairs(val) do
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table.insert(res, encode(v, stack))
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end
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stack[val] = nil
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return "[" .. table.concat(res, ",") .. "]"
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else
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-- Treat as an object
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for k, v in pairs(val) do
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if type(k) ~= "string" then
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error("invalid table: mixed or invalid key types")
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end
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table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
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end
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stack[val] = nil
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return "{" .. table.concat(res, ",") .. "}"
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end
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end
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local function encode_string(val)
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return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
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end
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local function encode_number(val)
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-- Check for NaN, -inf and inf
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if val ~= val or val <= -math.huge or val >= math.huge then
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error("unexpected number value '" .. tostring(val) .. "'")
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end
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return string.format("%.3f", val)
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end
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local type_func_map = {
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[ "nil" ] = encode_nil,
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[ "table" ] = encode_table,
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[ "string" ] = encode_string,
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[ "number" ] = encode_number,
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[ "boolean" ] = tostring,
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}
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encode = function(val, stack)
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local t = type(val)
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local f = type_func_map[t]
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if f then
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return f(val, stack)
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end
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error("unexpected type '" .. t .. "'")
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end
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function json.encode(val)
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return ( encode(val) )
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end
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-------------------------------------------------------------------------------
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-- Decode
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-------------------------------------------------------------------------------
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local parse
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local function create_set(...)
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local res = {}
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for i = 1, select("#", ...) do
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res[ select(i, ...) ] = true
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end
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return res
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end
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local space_chars = create_set(" ", "\t", "\r", "\n")
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local delim_chars = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
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local escape_chars = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
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local literals = create_set("true", "false", "null")
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local literal_map = {
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[ "true" ] = true,
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[ "false" ] = false,
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[ "null" ] = nil,
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}
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local function next_char(str, idx, set, negate)
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for i = idx, #str do
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if set[str:sub(i, i)] ~= negate then
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return i
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end
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end
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return #str + 1
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end
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local function decode_error(str, idx, msg)
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local line_count = 1
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local col_count = 1
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for i = 1, idx - 1 do
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col_count = col_count + 1
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if str:sub(i, i) == "\n" then
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line_count = line_count + 1
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col_count = 1
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end
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end
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error( string.format("%s at line %d col %d", msg, line_count, col_count) )
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end
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local function codepoint_to_utf8(n)
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-- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
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local f = math.floor
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if n <= 0x7f then
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return string.char(n)
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elseif n <= 0x7ff then
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return string.char(f(n / 64) + 192, n % 64 + 128)
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elseif n <= 0xffff then
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return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
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elseif n <= 0x10ffff then
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return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
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f(n % 4096 / 64) + 128, n % 64 + 128)
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end
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error( string.format("invalid unicode codepoint '%x'", n) )
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end
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local function parse_unicode_escape(s)
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local n1 = tonumber( s:sub(3, 6), 16 )
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local n2 = tonumber( s:sub(9, 12), 16 )
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-- Surrogate pair?
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if n2 then
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return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
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else
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return codepoint_to_utf8(n1)
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end
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end
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local function parse_string(str, i)
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local has_unicode_escape = false
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local has_surrogate_escape = false
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local has_escape = false
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local last
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for j = i + 1, #str do
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local x = str:byte(j)
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if x < 32 then
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decode_error(str, j, "control character in string")
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end
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if last == 92 then -- "\\" (escape char)
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if x == 117 then -- "u" (unicode escape sequence)
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local hex = str:sub(j + 1, j + 5)
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if not hex:find("%x%x%x%x") then
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decode_error(str, j, "invalid unicode escape in string")
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end
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if hex:find("^[dD][89aAbB]") then
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has_surrogate_escape = true
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else
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has_unicode_escape = true
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end
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else
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local c = string.char(x)
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if not escape_chars[c] then
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decode_error(str, j, "invalid escape char '" .. c .. "' in string")
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end
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has_escape = true
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end
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last = nil
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elseif x == 34 then -- '"' (end of string)
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local s = str:sub(i + 1, j - 1)
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if has_surrogate_escape then
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s = s:gsub("\\u[dD][89aAbB]..\\u....", parse_unicode_escape)
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end
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if has_unicode_escape then
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s = s:gsub("\\u....", parse_unicode_escape)
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end
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if has_escape then
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s = s:gsub("\\.", escape_char_map_inv)
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end
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return s, j + 1
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else
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last = x
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end
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end
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decode_error(str, i, "expected closing quote for string")
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end
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local function parse_number(str, i)
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local x = next_char(str, i, delim_chars)
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local s = str:sub(i, x - 1)
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local n = tonumber(s)
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if not n then
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decode_error(str, i, "invalid number '" .. s .. "'")
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end
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return n, x
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end
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local function parse_literal(str, i)
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local x = next_char(str, i, delim_chars)
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local word = str:sub(i, x - 1)
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if not literals[word] then
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decode_error(str, i, "invalid literal '" .. word .. "'")
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end
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return literal_map[word], x
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end
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local function parse_array(str, i)
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local res = {}
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local n = 1
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i = i + 1
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while 1 do
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local x
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i = next_char(str, i, space_chars, true)
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-- Empty / end of array?
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if str:sub(i, i) == "]" then
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i = i + 1
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break
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end
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-- Read token
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x, i = parse(str, i)
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res[n] = x
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n = n + 1
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-- Next token
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i = next_char(str, i, space_chars, true)
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local chr = str:sub(i, i)
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i = i + 1
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if chr == "]" then break end
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if chr ~= "," then decode_error(str, i, "expected ']' or ','") end
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end
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return res, i
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end
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local function parse_object(str, i)
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local res = {}
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i = i + 1
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while 1 do
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local key, val
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i = next_char(str, i, space_chars, true)
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-- Empty / end of object?
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if str:sub(i, i) == "}" then
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i = i + 1
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break
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end
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-- Read key
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if str:sub(i, i) ~= '"' then
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decode_error(str, i, "expected string for key")
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end
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key, i = parse(str, i)
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-- Read ':' delimiter
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i = next_char(str, i, space_chars, true)
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if str:sub(i, i) ~= ":" then
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decode_error(str, i, "expected ':' after key")
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end
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i = next_char(str, i + 1, space_chars, true)
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-- Read value
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val, i = parse(str, i)
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-- Set
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res[key] = val
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-- Next token
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i = next_char(str, i, space_chars, true)
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local chr = str:sub(i, i)
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i = i + 1
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if chr == "}" then break end
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if chr ~= "," then decode_error(str, i, "expected '}' or ','") end
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end
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return res, i
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end
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local char_func_map = {
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[ '"' ] = parse_string,
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[ "0" ] = parse_number,
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[ "1" ] = parse_number,
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[ "2" ] = parse_number,
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[ "3" ] = parse_number,
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[ "4" ] = parse_number,
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[ "5" ] = parse_number,
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[ "6" ] = parse_number,
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[ "7" ] = parse_number,
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[ "8" ] = parse_number,
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[ "9" ] = parse_number,
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[ "-" ] = parse_number,
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[ "t" ] = parse_literal,
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[ "f" ] = parse_literal,
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[ "n" ] = parse_literal,
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[ "[" ] = parse_array,
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[ "{" ] = parse_object,
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}
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parse = function(str, idx)
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local chr = str:sub(idx, idx)
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local f = char_func_map[chr]
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if f then
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return f(str, idx)
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end
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decode_error(str, idx, "unexpected character '" .. chr .. "'")
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end
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function json.decode(str)
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if type(str) ~= "string" then
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error("expected argument of type string, got " .. type(str))
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end
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return ( parse(str, next_char(str, 1, space_chars, true)) )
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end
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return json
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