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rxi 2015-08-11 21:08:33 +01:00
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Copyright (c) 2015 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.

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# ![json.lua](https://cloud.githubusercontent.com/assets/3920290/9207222/24413cbe-4064-11e5-874e-7e2deeb5f8cb.png)
A minimal JSON library for Lua
## Features
* Pure Lua implementation
* Tiny: around 250sloc, 7kb
* Proper error messages, *eg:* `expected '}' or ',' at line 203 col 30`
## Usage
The [json.lua](json.lua?raw=1) file should be dropped into an existing project
and required by it:
```lua
json = require "json"
```
The library provides the following functions:
#### json.encode(value)
Returns a string representing `value` encoded in JSON.
```lua
json.encode({ 1, 2, 3, { x = 10 } }) -- Returns '[1,2,3,{"x":10}]'
```
#### json.decode(str)
Returns a value representing the decoded JSON string.
```lua
json.decode('[1,2,3,{"x":10}]') -- Returns { 1, 2, 3, { x = 10 } }
```
## Notes
* UTF-16 surrogate pairs are not supported
* Tables with the key `1` set are treated as arrays when encoding
* `null` values contained within an array or object are converted to `nil` and
are therefore lost upon decoding
* *Pretty* encoding is not supported, `json.encode()` only encodes to a compact
format
## License
This library is free software; you can redistribute it and/or modify it under
the terms of the MIT license. See [LICENSE](LICENSE) for details.

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--
-- json.lua
--
-- Copyright (c) 2015 rxi
--
-- This library is free software; you can redistribute it and/or modify it
-- under the terms of the MIT license. See LICENSE for details.
--
local json = { _version = "0.0.0" }
-------------------------------------------------------------------------------
-- Encode
-------------------------------------------------------------------------------
local loadstring = loadstring or load
local encode
local escape_char_map = {
[ "\\" ] = "\\\\",
[ "\"" ] = "\\\"",
[ "\b" ] = "\\b",
[ "\f" ] = "\\f",
[ "\n" ] = "\\n",
[ "\r" ] = "\\r",
[ "\t" ] = "\\t",
}
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 val[1] ~= nil then
-- Treat as an array
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
local t = type(k)
if t ~= "string" then
error("expected key of type 'string', got '" .. t .. "'")
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 tostring(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 keywords = create_set("true", "false", "null")
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 parse_unicode_escape(s)
local n = tonumber( s:sub(3), 16 )
if n <= 0x7f then
return string.char(n)
elseif n <= 0x7ff then
return string.char(n / 64 + 192, n % 64 + 128)
end
return string.char(n / 4096 + 224, n % 4096 / 64 + 128, n % 64 + 128)
end
local function parse_string(str, i, chr)
local has_unicode_escape = false
local last
for j = i + 1, #str do
local x = str:sub(j, j)
if x == "\n" then
decode_error(str, j, "unexpected new line in string")
end
if last == "\\" then
if x == "u" then
local hex = str:sub(j + 1, j + 5)
if not hex:find("%x%x%x%x") then
decode_error(str, j, "invalid unicode escape in string")
end
if hex:find("^[dD][89aAbB]") then
decode_error(str, j, "unsupported utf-16 surrogate pair in string")
end
has_unicode_escape = true
end
if not escape_chars[x] then
decode_error(str, j, "invalid escape char '" .. x .. "' in string")
end
elseif x == '"' then
local s = str:sub(i, j)
if has_unicode_escape then
s = s:gsub("\\u....", parse_unicode_escape)
end
return loadstring( "return " .. s )(), j + 1
end
last = x
end
decode_error(str, i, "expected closing quote for string")
end
local function parse_number(str, i, chr)
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_keyword(str, i, chr)
local x = next_char(str, i, delim_chars)
local word = str:sub(i, x - 1)
if not keywords[word] then
decode_error(str, i, "invalid keyword '" .. word .. "'")
end
return (chr == "t") and true or (chr == "f") and false, x
end
local function parse_array(str, i, chr)
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)
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, chr)
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
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)
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,
[ "-" ] = parse_number,
[ "t" ] = parse_keyword,
[ "f" ] = parse_keyword,
[ "n" ] = parse_keyword,
[ "[" ] = 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, chr)
else
decode_error(str, idx, "unexpected character '" .. chr .. "'")
end
end
function json.decode(str)
return ( parse(str, next_char(str, 1, space_chars, true)) )
end
return json