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---
-- Library methods for handling JSON data. It handles JSON encoding and
-- decoding according to RFC 4627.
--
-- There is a test section at the bottom which shows some example
-- parsing. If you want to parse JSON, you can test it by pasting sample JSON
-- into the <code>TESTS</code> table and run the <code>test</code> method
--
-- There is a straightforward mapping between JSON and Lua data types. One
-- exception is JSON <code>NULL</code>, which is not the same as Lua
-- <code>nil</code>. (A better match for Lua <code>nil</code> is JavaScript
-- <code>undefined</code>.) <code>NULL</code> values in JSON are represented by
-- the special value <code>json.NULL</code>.
--
-- @author Martin Holst Swende
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
-- TODO: Unescape/escape unicode
-- Version 0.4
-- Created 01/25/2010 - v0.1 - created by Martin Holst Swende <martin@swende.se>
-- Heavily modified 02/22/2010 - v0.3. Rewrote the parser into an OO-form, to not have to handle
-- all kinds of state with parameters and return values.
-- Modified 02/27/2010 - v0.4 Added unicode handling (written by David Fifield). Renamed toJson
-- and fromJson intogenerate() and parse(), implemented more proper numeric parsing and added some more error checking.
module("json", package.seeall)
require("bit")
require("nsedebug")
--Some local shortcuts
local function dbg(str,...)
stdnse.print_debug("Json:"..str, unpack(arg))
end
local function d4(str,...)
if nmap.debugging() > 3 then dbg(str,unpack(arg)) end
end
local function d3(str,...)
if nmap.debugging() > 2 then dbg(str,unpack(arg)) end
end
--local dbg =stdnse.print_debug
local function dbg_err(str,...)
stdnse.print_debug("json-ERR:"..str, unpack(arg))
end
-- Javascript null representation, see explanation above
NULL = {}
-- See section 2.5 for escapes.
-- For convenience, ESCAPE_TABLE maps to escape sequences complete with
-- backslash, and REVERSE_ESCAPE_TABLE maps from single escape characters
-- (no backslash).
local ESCAPE_TABLE = {}
local REVERSE_ESCAPE_TABLE = {}
do
local escapes = {
[string.char(0x22)] = "\"",
[string.char(0x5C)] = "\\",
[string.char(0x2F)] = "/",
[string.char(0x08)] = "b",
[string.char(0x0C)] = "f",
[string.char(0x0A)] = "n",
[string.char(0x0D)] = "r",
[string.char(0x09)] = "t",
}
for k, v in pairs(escapes) do
ESCAPE_TABLE[k] = "\\" .. v
REVERSE_ESCAPE_TABLE[v] = k
end
end
-- Escapes a string
--@param str the string
--@return a string where the special chars have been escaped
local function escape(str)
return "\"" .. string.gsub(str, ".", ESCAPE_TABLE) .. "\""
end
-- Creates json data from an object
--@param object a table containing data
--@return a string containing valid json
function generate(obj)
-- NULL-check must be performed before
-- checking type == table, since the NULL-object
-- is a table
if obj == NULL then
return "null"
elseif obj == false then
return "false"
elseif obj == true then
return "true"
elseif type(obj) == "number" then
return string.format("%g", obj)
elseif type(obj) == "string" then
return escape(obj)
elseif type(obj) == "table" then
local k, v, elems
elems = {}
if #obj > 0 then
-- Array
for _, v in ipairs(obj) do
elems[#elems + 1] = generate(v)
end
return "[" .. table.concat(elems, ", ") .. "]"
else
-- Object
for k, v in pairs(obj) do
elems[#elems + 1] = escape(k) .. ": " .. generate(v)
end
return "{" .. table.concat(elems, ", ") .. "}"
end
else
error("Unknown data type in generate")
end
end
-- This is the parser, implemented in OO-form to deal with state better
Json = {}
-- Constructor
function Json:new(input)
local o = {}
setmetatable(o, self)
self.__index = self
o.input = input
o.pos = 1 -- Pos is where the NEXT letter will be read
return o
end
-- Gets next character and ups the position
--@return next character
function Json:next()
self.pos = self.pos+1
return self.input:sub(self.pos-1, self.pos-1)
end
-- Updates the position to next non whitespace position
function Json:eatWhiteSpace()
--Find next non-white char
local a,b = self.input:find("%S",self.pos)
if not a then
self:syntaxerror("Empty data")
return
end
self.pos = a
end
-- Jumps to a specified position
--@param position where to go
function Json:jumpTo(position)
self.pos = position
end
-- Returns next character, but without upping position
--@return next character
function Json:peek()
return self.input:sub(self.pos, self.pos)
end
--@return true if more input is in store
function Json:hasMore()
return self.input:len() >= self.pos
end
-- Checks that the following input is equal to a string
-- and updates position so next char will be after that string
-- If false, triggers a syntax error
--@param str the string to test
function Json:assertStr(str)
local content = self.input:sub(self.pos,self.pos+str:len()-1)
if(content == str) then-- All ok
-- Jump forward
self:jumpTo(self.pos+str:len())
return
end
self:syntaxerror(("Expected '%s' but got '%s'"):format( str, content))
end
-- Trigger a syntax error
function Json:syntaxerror(reason)
self.error = ("Syntax error near pos %d: %s input: %s"):format( self.pos, reason, self.input)
dbg(self.error)
end
-- Check if any errors has occurred
function Json:errors()
return self.error ~= nil
end
-- Parses a top-level JSON structure (object or array).
--@return the parsed object or puts error messages in self.error
function Json:parseStart()
-- The top level of JSON only allows an object or an array. Only inside
-- of the outermost container can other types appear.
self:eatWhiteSpace()
local c = self:peek()
if c == '{' then
return self:parseObject()
elseif c == '[' then
return self:parseArray()
else
self:syntaxerror(("JSON must start with object or array (started with %s)"):format(c))
return
end
end
-- Parses a value
--@return the parsed value
function Json:parseValue()
self:eatWhiteSpace()
local c = self:peek()
local value
if c == '{' then
value = self:parseObject()
elseif c == '[' then
value = self:parseArray()
elseif c == '"' then
value = self:parseString()
elseif c == 'n' then
self:assertStr("null")
value = NULL
elseif c == 't' then
self:assertStr("true")
value = true
elseif c == 'f' then
self:assertStr("false")
value = false
else -- numeric
-- number = [ minus ] int [ frac ] [ exp ]
local a,b =self.input:find("-?%d+%.?%d*[eE]?[+-]?%d*", self.pos)
if not a or not b then
self:syntaxerror("Error 1 parsing numeric value")
return
end
value = tonumber(self.input:sub(a,b))
if(value == nil) then
self:syntaxerror("Error 2 parsing numeric value")
return
end
self:jumpTo(b+1)
end
return value
end
-- Parses a json object {}
--@return the object (or triggers a syntax error)
function Json:parseObject()
local object = {}
local _= self:next() -- Eat {
while(self:hasMore() and not self:errors()) do
self:eatWhiteSpace()
local c = self:peek()
if(c == '}') then -- Empty object, probably
self:next() -- Eat it
return object
end
if(c ~= '"') then
self:syntaxerror(("Expected '\"', got '%s'"):format(c))
return
end
local key = self:parseString()
if self:errors() then
return
end
self:eatWhiteSpace()
c = self:next()
if(c ~= ':') then
self:syntaxerror("Expected ':' got "..c)
return
end
local value = self:parseValue()
if self:errors() then
return
end
object[key] = value
self:eatWhiteSpace()
c = self:next()
-- Valid now is , or }
if(c == '}') then
return object
end
if(c ~= ',') then
self:syntaxerror("Expected ',' or '}', got "..c)
return
end
end
end
-- Parses a json array [] or triggers a syntax error
--@return the array object
function Json:parseArray()
local array = {}
self:next()
while(self:hasMore() and not self:errors()) do
self:eatWhiteSpace()
if(self:peek() == ']') then -- Empty array, probably
self:next()
break
end
local value = self:parseValue()
if self:errors() then
return
end
table.insert(array, value)
self:eatWhiteSpace()
local c = self:next()
-- Valid now is , or ]
if(c == ']') then return array end
if(c ~= ',') then
self:syntaxerror(("Expected ',' but got '%s'"):format(c))
return
end
end
return array
end
-- Decode a Unicode escape, assuming that self.pos starts just after the
-- initial \u. May consume an additional escape in the case of a UTF-16
-- surrogate pair. See RFC 2781 for UTF-16.
function Json:parseUnicodeEscape()
local n, cp
local hex, lowhex
local s, e
s, e, hex = self.input:find("^(....)", self.pos)
if not hex then
self:syntaxerror(("EOF in Unicode escape \\u%s"):format(self.input:sub(self.pos)))
return
end
n = tonumber(hex, 16)
if not n then
self:syntaxerror(("Bad unicode escape \\u%s"):format(hex))
return
end
cp = n
self.pos = e + 1
if n < 0xD800 or n > 0xDFFF then
return cp
end
if n >= 0xDC00 and n <= 0xDFFF then
self:syntaxerror(("Not a Unicode character: U+%04X"):format(cp))
return
end
-- Beginning of a UTF-16 surrogate.
s, e, lowhex = self.input:find("^\\u(....)", self.pos)
if not lowhex then
self:syntaxerror(("Bad unicode escape \\u%s (missing low surrogate)"):format(hex))
return
end
n = tonumber(lowhex, 16)
if not n or not (n >= 0xDC00 and n <= 0xDFFF) then
self:syntaxerror(("Bad unicode escape \\u%s\\u%s (bad low surrogate)"):format(hex, lowhex))
return
end
self.pos = e + 1
cp = 0x10000 + bit.band(cp, 0x3FF) * 0x400 + bit.band(n, 0x3FF)
-- also remove last "
return cp
end
-- Encode a Unicode code point to UTF-8. See RFC 3629.
-- Does not check that cp is a real charaacter; that is, doesn't exclude the
-- surrogate range U+D800 - U+DFFF and a handful of others.
local function utf8_enc(cp)
local bytes = {}
local n, mask
if cp % 1.0 ~= 0.0 or cp < 0 then
-- Only defined for nonnegative integers.
return nil
elseif cp <= 0x7F then
-- Special case of one-byte encoding.
return string.char(cp)
elseif cp <= 0x7FF then
n = 2
mask = 0xC0
elseif cp <= 0xFFFF then
n = 3
mask = 0xE0
elseif cp <= 0x10FFFF then
n = 4
mask = 0xF0
else
return nil
end
while n > 1 do
bytes[n] = string.char(0x80 + bit.band(cp, 0x3F))
cp = bit.rshift(cp, 6)
n = n - 1
end
bytes[1] = string.char(mask + cp)
return table.concat(bytes)
end
-- Parses a json string
-- @return the string or triggers syntax error
function Json:parseString()
local val = ''
local c = self:next()
assert( c == '"')
while(self:hasMore()) do
local c = self:next()
if(c == '"') then -- end of string
break
elseif(c == '\\') then-- Escaped char
local d = self:next()
if REVERSE_ESCAPE_TABLE[d] ~= nil then
val = val .. REVERSE_ESCAPE_TABLE[d]
elseif d == 'u' then -- Unicode chars
local codepoint = self:parseUnicodeEscape()
if not codepoint then
return
end
val = val .. utf8_enc(codepoint)
else
self:syntaxerror(("Undefined escape character '%s'"):format(d))
return false
end
else -- Char
val = val .. c
end
end
return val
end
--- Parses json data into an object form
-- This is the method you probably want to use if you
-- use this library from a script.
--@param data a json string
--@return status true if ok, false if bad
--@return an object representing the json, or error message
function parse(data)
local parser = Json:new(data)
local result = parser:parseStart()
if(parser.error) then
return false, parser.error
end
return true, result
end
----------------------------------------------------------------------------------
-- Test-code for debugging purposes below
----------------------------------------------------------------------------------
local TESTS = {
'{"a":1}',
'{"a":true}',
'{"a": false}',
'{"a": null \r\n, \t "b" \f:"ehlo"}',
'{"a\\"a":"a\\"b\\"c\\"d"}',
'{"foo":"gaz\\"onk", "pi":3.14159,"hello":{ "wo":"rld"}}',
'{"a":1, "b":2}',
'{"foo":"gazonk", "pi":3.14159,"hello":{ "wo":"rl\\td"}}',
'[1,2,3,4,5,null,false,true,"\195\164\195\165\195\182\195\177","bar"]',
'[]',-- This will yield {} in toJson, since in lua there is only one basic datatype - and no difference when empty
'{}',
'', -- error
'null', -- error
'"abc"', -- error
'{a":1}', -- error
'{"a" bad :1}', -- error
'["a\\\\t"]', -- Should become Lua {"a\\t"}
'[0.0.0]', -- error
'[-1]',
'[-1.123e-2]',
'[5e3]',
'[5e+3]',
'[5E-3]',
'[5.5e3]',
'["a\\\\"]', -- Should become Lua {"a\\"}
'{"a}": 1}', -- Should become Lua {"a}" = 1}
'["key": "value"]', -- error
'["\\u0041"]', -- Should become Lua {"A"}
'["\\uD800"]', -- error
'["\\uD834\\uDD1EX"]', -- Should become Lua {"\240\157\132\158X"}
}
function test()
print("Tests running")
local i,v,res,status
for i,v in pairs(TESTS) do
print("----------------------------")
print(v)
status,res = parse(v)
if not status then print( res) end
if(status) then
print(generate(res))
else
print("Error:".. res)
end
end
end