json.lua

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Alex Alex Commit Server upload 18/10/2026 23:38
1--
2-- json.lua
3--
4-- Copyright (c) 2018 rxi
5--
6-- Permission is hereby granted, free of charge, to any person obtaining a copy of
7-- this software and associated documentation files (the "Software"), to deal in
8-- the Software without restriction, including without limitation the rights to
9-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
10-- of the Software, and to permit persons to whom the Software is furnished to do
11-- so, subject to the following conditions:
12--
13-- The above copyright notice and this permission notice shall be included in all
14-- copies or substantial portions of the Software.
15--
16-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22-- SOFTWARE.
23--
24
25json = { _version = "0.1.1" }
26
27-------------------------------------------------------------------------------
28-- Encode
29-------------------------------------------------------------------------------
30
31local encode
32
33local escape_char_map = {
34 [ "\\" ] = "\\\\",
35 [ "\"" ] = "\\\"",
36 [ "\b" ] = "\\b",
37 [ "\f" ] = "\\f",
38 [ "\n" ] = "\\n",
39 [ "\r" ] = "\\r",
40 [ "\t" ] = "\\t",
41}
42
43local escape_char_map_inv = { [ "\\/" ] = "/" }
44for k, v in pairs(escape_char_map) do
45 escape_char_map_inv[v] = k
46end
47
48
49local function escape_char(c)
50 return escape_char_map[c] or string.format("\\u%04x", c:byte())
51end
52
53
54local function encode_nil(val)
55 return "null"
56end
57
58
59local function encode_table(val, stack)
60 local res = {}
61 stack = stack or {}
62
63 -- Circular reference?
64 if stack[val] then error("circular reference") end
65
66 stack[val] = true
67
68 if val[1] ~= nil or next(val) == nil then
69 -- Treat as array -- check keys are valid and it is not sparse
70 local n = 0
71 for k in pairs(val) do
72 if type(k) ~= "number" then
73 error("invalid table: mixed or invalid key types")
74 end
75 n = n + 1
76 end
77 if n ~= #val then
78 error("invalid table: sparse array")
79 end
80 -- Encode
81 for i, v in ipairs(val) do
82 table.insert(res, encode(v, stack))
83 end
84 stack[val] = nil
85 return "[" .. table.concat(res, ",") .. "]"
86
87 else
88 -- Treat as an object
89 for k, v in pairs(val) do
90 if type(k) ~= "string" then
91 error("invalid table: mixed or invalid key types")
92 end
93 table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
94 end
95 stack[val] = nil
96 return "{" .. table.concat(res, ",") .. "}"
97 end
98end
99
100
101local function encode_string(val)
102 return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
103end
104
105
106local function encode_number(val)
107 -- Check for NaN, -inf and inf
108 if val ~= val or val <= -math.huge or val >= math.huge then
109 error("unexpected number value '" .. tostring(val) .. "'")
110 end
111 return string.format("%.14g", val)
112end
113
114
115local type_func_map = {
116 [ "nil" ] = encode_nil,
117 [ "table" ] = encode_table,
118 [ "string" ] = encode_string,
119 [ "number" ] = encode_number,
120 [ "boolean" ] = tostring,
121}
122
123
124encode = function(val, stack)
125 local t = type(val)
126 local f = type_func_map[t]
127 if f then
128 return f(val, stack)
129 end
130 error("unexpected type '" .. t .. "'")
131end
132
133
134function json.encode(val)
135 return ( encode(val) )
136end
137
138
139-------------------------------------------------------------------------------
140-- Decode
141-------------------------------------------------------------------------------
142
143local parse
144
145local function create_set(...)
146 local res = {}
147 for i = 1, select("#", ...) do
148 res[ select(i, ...) ] = true
149 end
150 return res
151end
152
153local space_chars = create_set(" ", "\t", "\r", "\n")
154local delim_chars = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
155local escape_chars = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
156local literals = create_set("true", "false", "null")
157
158local literal_map = {
159 [ "true" ] = true,
160 [ "false" ] = false,
161 [ "null" ] = nil,
162}
163
164
165local function next_char(str, idx, set, negate)
166 for i = idx, #str do
167 if set[str:sub(i, i)] ~= negate then
168 return i
169 end
170 end
171 return #str + 1
172end
173
174
175local function decode_error(str, idx, msg)
176 local line_count = 1
177 local col_count = 1
178 for i = 1, idx - 1 do
179 col_count = col_count + 1
180 if str:sub(i, i) == "\n" then
181 line_count = line_count + 1
182 col_count = 1
183 end
184 end
185 error( string.format("%s at line %d col %d", msg, line_count, col_count) )
186end
187
188
189local function codepoint_to_utf8(n)
190 -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
191 local f = math.floor
192 if n <= 0x7f then
193 return string.char(n)
194 elseif n <= 0x7ff then
195 return string.char(f(n / 64) + 192, n % 64 + 128)
196 elseif n <= 0xffff then
197 return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
198 elseif n <= 0x10ffff then
199 return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
200 f(n % 4096 / 64) + 128, n % 64 + 128)
201 end
202 error( string.format("invalid unicode codepoint '%x'", n) )
203end
204
205
206local function parse_unicode_escape(s)
207 local n1 = tonumber( s:sub(3, 6), 16 )
208 local n2 = tonumber( s:sub(9, 12), 16 )
209 -- Surrogate pair?
210 if n2 then
211 return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
212 else
213 return codepoint_to_utf8(n1)
214 end
215end
216
217
218local function parse_string(str, i)
219 local has_unicode_escape = false
220 local has_surrogate_escape = false
221 local has_escape = false
222 local last
223 for j = i + 1, #str do
224 local x = str:byte(j)
225
226 if x < 32 then
227 decode_error(str, j, "control character in string")
228 end
229
230 if last == 92 then -- "\\" (escape char)
231 if x == 117 then -- "u" (unicode escape sequence)
232 local hex = str:sub(j + 1, j + 5)
233 if not hex:find("%x%x%x%x") then
234 decode_error(str, j, "invalid unicode escape in string")
235 end
236 if hex:find("^[dD][89aAbB]") then
237 has_surrogate_escape = true
238 else
239 has_unicode_escape = true
240 end
241 else
242 local c = string.char(x)
243 if not escape_chars[c] then
244 decode_error(str, j, "invalid escape char '" .. c .. "' in string")
245 end
246 has_escape = true
247 end
248 last = nil
249
250 elseif x == 34 then -- '"' (end of string)
251 local s = str:sub(i + 1, j - 1)
252 if has_surrogate_escape then
253 s = s:gsub("\\u[dD][89aAbB]..\\u....", parse_unicode_escape)
254 end
255 if has_unicode_escape then
256 s = s:gsub("\\u....", parse_unicode_escape)
257 end
258 if has_escape then
259 s = s:gsub("\\.", escape_char_map_inv)
260 end
261 return s, j + 1
262
263 else
264 last = x
265 end
266 end
267 decode_error(str, i, "expected closing quote for string")
268end
269
270
271local function parse_number(str, i)
272 local x = next_char(str, i, delim_chars)
273 local s = str:sub(i, x - 1)
274 local n = tonumber(s)
275 if not n then
276 decode_error(str, i, "invalid number '" .. s .. "'")
277 end
278 return n, x
279end
280
281
282local function parse_literal(str, i)
283 local x = next_char(str, i, delim_chars)
284 local word = str:sub(i, x - 1)
285 if not literals[word] then
286 decode_error(str, i, "invalid literal '" .. word .. "'")
287 end
288 return literal_map[word], x
289end
290
291
292local function parse_array(str, i)
293 local res = {}
294 local n = 1
295 i = i + 1
296 while 1 do
297 local x
298 i = next_char(str, i, space_chars, true)
299 -- Empty / end of array?
300 if str:sub(i, i) == "]" then
301 i = i + 1
302 break
303 end
304 -- Read token
305 x, i = parse(str, i)
306 res[n] = x
307 n = n + 1
308 -- Next token
309 i = next_char(str, i, space_chars, true)
310 local chr = str:sub(i, i)
311 i = i + 1
312 if chr == "]" then break end
313 if chr ~= "," then decode_error(str, i, "expected ']' or ','") end
314 end
315 return res, i
316end
317
318
319local function parse_object(str, i)
320 local res = {}
321 i = i + 1
322 while 1 do
323 local key, val
324 i = next_char(str, i, space_chars, true)
325 -- Empty / end of object?
326 if str:sub(i, i) == "}" then
327 i = i + 1
328 break
329 end
330 -- Read key
331 if str:sub(i, i) ~= '"' then
332 decode_error(str, i, "expected string for key")
333 end
334 key, i = parse(str, i)
335 -- Read ':' delimiter
336 i = next_char(str, i, space_chars, true)
337 if str:sub(i, i) ~= ":" then
338 decode_error(str, i, "expected ':' after key")
339 end
340 i = next_char(str, i + 1, space_chars, true)
341 -- Read value
342 val, i = parse(str, i)
343 -- Set
344 res[key] = val
345 -- Next token
346 i = next_char(str, i, space_chars, true)
347 local chr = str:sub(i, i)
348 i = i + 1
349 if chr == "}" then break end
350 if chr ~= "," then decode_error(str, i, "expected '}' or ','") end
351 end
352 return res, i
353end
354
355
356local char_func_map = {
357 [ '"' ] = parse_string,
358 [ "0" ] = parse_number,
359 [ "1" ] = parse_number,
360 [ "2" ] = parse_number,
361 [ "3" ] = parse_number,
362 [ "4" ] = parse_number,
363 [ "5" ] = parse_number,
364 [ "6" ] = parse_number,
365 [ "7" ] = parse_number,
366 [ "8" ] = parse_number,
367 [ "9" ] = parse_number,
368 [ "-" ] = parse_number,
369 [ "t" ] = parse_literal,
370 [ "f" ] = parse_literal,
371 [ "n" ] = parse_literal,
372 [ "[" ] = parse_array,
373 [ "{" ] = parse_object,
374}
375
376
377parse = function(str, idx)
378 local chr = str:sub(idx, idx)
379 local f = char_func_map[chr]
380 if f then
381 return f(str, idx)
382 end
383 decode_error(str, idx, "unexpected character '" .. chr .. "'")
384end
385
386
387function json.decode(str)
388 if type(str) ~= "string" then
389 error("expected argument of type string, got " .. type(str))
390 end
391 local res, idx = parse(str, next_char(str, 1, space_chars, true))
392 idx = next_char(str, idx, space_chars, true)
393 if idx <= #str then
394 decode_error(str, idx, "trailing garbage")
395 end
396 return res
397end
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