lua/json/decode/strings.lua

   1 --[[
   2         Licensed according to the included 'LICENSE' document
   3         Author: Thomas Harning Jr <harningt@gmail.com>
   4 ]]
   5 local lpeg = require("lpeg")
   6 local util = require("json.decode.util")
   7 local merge = require("json.util").merge
   8
   9 local tonumber = tonumber
  10 local string_char = require("string").char
  11 local floor = require("math").floor
  12 local table_concat = require("table").concat
  13
  14 local error = error
  15
  16 local is_52 = _VERSION == "Lua 5.2"
  17 local _G = _G
  18
  19 if is_52 then
  20         _ENV = nil
  21 end
  22
  23 local function get_error(item)
  24         local fmt_string = item .. " in string [%q] @ %i:%i"
  25         return function(data, index)
  26                 local line, line_index, bad_char, last_line = util.get_invalid_character_info(data, index)
  27                 local err = fmt_string:format(bad_char, line, line_index)
  28                 error(err)
  29         end
  30 end
  31
  32 local bad_unicode   = get_error("Illegal unicode escape")
  33 local bad_hex       = get_error("Illegal hex escape")
  34 local bad_character = get_error("Illegal character")
  35 local bad_escape    = get_error("Illegal escape")
  36
  37 local knownReplacements = {
  38         ["'"] = "'",
  39         ['"'] = '"',
  40         ['\\'] = '\\',
  41         ['/'] = '/',
  42         b = '\b',
  43         f = '\f',
  44         n = '\n',
  45         r = '\r',
  46         t = '\t',
  47         v = '\v',
  48         z = '\z'
  49 }
  50
  51 -- according to the table at http://da.wikipedia.org/wiki/UTF-8
  52 local function utf8DecodeUnicode(code1, code2)
  53         code1, code2 = tonumber(code1, 16), tonumber(code2, 16)
  54         if code1 == 0 and code2 < 0x80 then
  55                 return string_char(code2)
  56         end
  57         if code1 < 0x08 then
  58                 return string_char(
  59                         0xC0 + code1 * 4 + floor(code2 / 64),
  60                         0x80 + code2 % 64)
  61         end
  62         return string_char(
  63                 0xE0 + floor(code1 / 16),
  64                 0x80 + (code1 % 16) * 4 + floor(code2 / 64),
  65                 0x80 + code2 % 64)
  66 end
  67
  68 local function decodeX(code)
  69         code = tonumber(code, 16)
  70         return string_char(code)
  71 end
  72
  73 local doSimpleSub = lpeg.C(lpeg.S("'\"\\/bfnrtvz")) / knownReplacements
  74 local doUniSub = lpeg.P('u') * (lpeg.C(util.hexpair) * lpeg.C(util.hexpair) + lpeg.P(bad_unicode))
  75 local doXSub = lpeg.P('x') * (lpeg.C(util.hexpair) + lpeg.P(bad_hex))
  76
  77 local defaultOptions = {
  78         badChars = '',
  79         additionalEscapes = false, -- disallow untranslated escapes
  80         escapeCheck = #lpeg.S('bfnrtv/\\"xu\'z'), -- no check on valid characters
  81         decodeUnicode = utf8DecodeUnicode,
  82         strict_quotes = false
  83 }
  84
  85 local default = nil -- Let the buildCapture optimization take place
  86
  87 local strict = {
  88         badChars = '\b\f\n\r\t\v',
  89         additionalEscapes = false, -- no additional escapes
  90         escapeCheck = #lpeg.S('bfnrtv/\\"u'), --only these chars are allowed to be escaped
  91         strict_quotes = true
  92 }
  93
  94 local function buildCaptureString(quote, badChars, escapeMatch)
  95         local captureChar = (1 - lpeg.S("\\" .. badChars .. quote)) + (lpeg.P("\\") / "" * escapeMatch)
  96         captureChar = captureChar + (-#lpeg.P(quote) * lpeg.P(bad_character))
  97         local captureString = captureChar^0
  98         return lpeg.P(quote) * lpeg.Cs(captureString) * lpeg.P(quote)
  99 end
 100
 101 local function buildCapture(options)
 102         options = options and merge({}, defaultOptions, options) or defaultOptions
 103         local quotes = { '"' }
 104         if not options.strict_quotes then
 105                 quotes[#quotes + 1] = "'"
 106         end
 107         local escapeMatch = doSimpleSub
 108         escapeMatch = escapeMatch + doXSub / decodeX
 109         escapeMatch = escapeMatch + doUniSub / options.decodeUnicode
 110         if options.additionalEscapes then
 111                 escapeMatch = escapeMatch + options.additionalEscapes
 112         end
 113         if options.escapeCheck then
 114                 escapeMatch = options.escapeCheck * escapeMatch + lpeg.P(bad_escape)
 115         end
 116         local captureString
 117         for i = 1, #quotes do
 118                 local cap = buildCaptureString(quotes[i], options.badChars, escapeMatch)
 119                 if captureString == nil then
 120                         captureString = cap
 121                 else
 122                         captureString = captureString + cap
 123                 end
 124         end
 125         return captureString
 126 end
 127
 128 local function register_types()
 129         util.register_type("STRING")
 130 end
 131
 132 local function load_types(options, global_options, grammar)
 133         local capture = buildCapture(options)
 134         local string_id = util.types.STRING
 135         grammar[string_id] = capture
 136         util.append_grammar_item(grammar, "VALUE", lpeg.V(string_id))
 137 end
 138
 139 local strings = {
 140         default = default,
 141         strict = strict,
 142         register_types = register_types,
 143         load_types = load_types
 144 }
 145
 146 if not is_52 then
 147         _G.json = _G.json or {}
 148         _G.json.decode = _G.json.decode or {}
 149         _G.json.decode.strings = strings
 150 end
 151
 152 return strings