jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#include <AK/CharacterTypes.h>
8#include <AK/FloatingPointStringConversions.h>
9#include <AK/JsonArray.h>
10#include <AK/JsonObject.h>
11#include <AK/JsonParser.h>
12#include <math.h>
13
14namespace AK {
15
16constexpr bool is_space(int ch)
17{
18 return ch == '\t' || ch == '\n' || ch == '\r' || ch == ' ';
19}
20
21ErrorOr<DeprecatedString> JsonParser::consume_and_unescape_string()
22{
23 if (!consume_specific('"'))
24 return Error::from_string_literal("JsonParser: Expected '\"'");
25 StringBuilder final_sb;
26
27 for (;;) {
28 size_t peek_index = m_index;
29 char ch = 0;
30 for (;;) {
31 if (peek_index == m_input.length())
32 break;
33 ch = m_input[peek_index];
34 if (ch == '"' || ch == '\\')
35 break;
36 if (is_ascii_c0_control(ch))
37 return Error::from_string_literal("JsonParser: Error while parsing string");
38 ++peek_index;
39 }
40
41 while (peek_index != m_index) {
42 final_sb.append(m_input[m_index]);
43 m_index++;
44 }
45
46 if (m_index == m_input.length())
47 break;
48 if (ch == '"')
49 break;
50 if (ch != '\\') {
51 final_sb.append(consume());
52 continue;
53 }
54 ignore();
55 if (next_is('"')) {
56 ignore();
57 final_sb.append('"');
58 continue;
59 }
60
61 if (next_is('\\')) {
62 ignore();
63 final_sb.append('\\');
64 continue;
65 }
66
67 if (next_is('/')) {
68 ignore();
69 final_sb.append('/');
70 continue;
71 }
72
73 if (next_is('n')) {
74 ignore();
75 final_sb.append('\n');
76 continue;
77 }
78
79 if (next_is('r')) {
80 ignore();
81 final_sb.append('\r');
82 continue;
83 }
84
85 if (next_is('t')) {
86 ignore();
87 final_sb.append('\t');
88 continue;
89 }
90
91 if (next_is('b')) {
92 ignore();
93 final_sb.append('\b');
94 continue;
95 }
96
97 if (next_is('f')) {
98 ignore();
99 final_sb.append('\f');
100 continue;
101 }
102
103 if (next_is('u')) {
104 ignore();
105 if (tell_remaining() < 4)
106 return Error::from_string_literal("JsonParser: EOF while parsing Unicode escape");
107
108 auto code_point = AK::StringUtils::convert_to_uint_from_hex(consume(4));
109 if (code_point.has_value()) {
110 final_sb.append_code_point(code_point.value());
111 continue;
112 }
113 return Error::from_string_literal("JsonParser: Error while parsing Unicode escape");
114 }
115
116 return Error::from_string_literal("JsonParser: Error while parsing string");
117 }
118 if (!consume_specific('"'))
119 return Error::from_string_literal("JsonParser: Expected '\"'");
120
121 return final_sb.to_deprecated_string();
122}
123
124ErrorOr<JsonValue> JsonParser::parse_object()
125{
126 JsonObject object;
127 if (!consume_specific('{'))
128 return Error::from_string_literal("JsonParser: Expected '{'");
129 for (;;) {
130 ignore_while(is_space);
131 if (peek() == '}')
132 break;
133 ignore_while(is_space);
134 auto name = TRY(consume_and_unescape_string());
135 if (name.is_null())
136 return Error::from_string_literal("JsonParser: Expected object property name");
137 ignore_while(is_space);
138 if (!consume_specific(':'))
139 return Error::from_string_literal("JsonParser: Expected ':'");
140 ignore_while(is_space);
141 auto value = TRY(parse_helper());
142 object.set(name, move(value));
143 ignore_while(is_space);
144 if (peek() == '}')
145 break;
146 if (!consume_specific(','))
147 return Error::from_string_literal("JsonParser: Expected ','");
148 ignore_while(is_space);
149 if (peek() == '}')
150 return Error::from_string_literal("JsonParser: Unexpected '}'");
151 }
152 if (!consume_specific('}'))
153 return Error::from_string_literal("JsonParser: Expected '}'");
154 return JsonValue { move(object) };
155}
156
157ErrorOr<JsonValue> JsonParser::parse_array()
158{
159 JsonArray array;
160 if (!consume_specific('['))
161 return Error::from_string_literal("JsonParser: Expected '['");
162 for (;;) {
163 ignore_while(is_space);
164 if (peek() == ']')
165 break;
166 auto element = TRY(parse_helper());
167 array.append(move(element));
168 ignore_while(is_space);
169 if (peek() == ']')
170 break;
171 if (!consume_specific(','))
172 return Error::from_string_literal("JsonParser: Expected ','");
173 ignore_while(is_space);
174 if (peek() == ']')
175 return Error::from_string_literal("JsonParser: Unexpected ']'");
176 }
177 ignore_while(is_space);
178 if (!consume_specific(']'))
179 return Error::from_string_literal("JsonParser: Expected ']'");
180 return JsonValue { move(array) };
181}
182
183ErrorOr<JsonValue> JsonParser::parse_string()
184{
185 auto string = TRY(consume_and_unescape_string());
186 return JsonValue(move(string));
187}
188
189ErrorOr<JsonValue> JsonParser::parse_number()
190{
191 Vector<char, 32> number_buffer;
192
193 auto start_index = tell();
194
195 bool negative = false;
196 if (peek() == '-') {
197 number_buffer.append('-');
198 ++m_index;
199 negative = true;
200
201 if (!is_ascii_digit(peek()))
202 return Error::from_string_literal("JsonParser: Unexpected '-' without further digits");
203 }
204
205 auto fallback_to_double_parse = [&]() -> ErrorOr<JsonValue> {
206#ifdef KERNEL
207# error JSONParser is currently not available for the Kernel because it disallows floating point. \
208 If you want to make this KERNEL compatible you can just make this fallback_to_double \
209 function fail with an error in KERNEL mode.
210#endif
211 // FIXME: Since we know all the characters so far are ascii digits (and one . or e) we could
212 // use that in the floating point parser.
213
214 // The first part should be just ascii digits
215 StringView view = m_input.substring_view(start_index);
216
217 char const* start = view.characters_without_null_termination();
218 auto parse_result = parse_first_floating_point(start, start + view.length());
219
220 if (parse_result.parsed_value()) {
221 auto characters_parsed = parse_result.end_ptr - start;
222 m_index = start_index + characters_parsed;
223
224 return JsonValue(parse_result.value);
225 }
226 return Error::from_string_literal("JsonParser: Invalid floating point");
227 };
228
229 if (peek() == '0') {
230 if (is_ascii_digit(peek(1)))
231 return Error::from_string_literal("JsonParser: Cannot have leading zeros");
232
233 // Leading zeros are not allowed, however we can have a '.' or 'e' with
234 // valid digits after just a zero. These cases will be detected by having the next element
235 // start with a '.' or 'e'.
236 }
237
238 bool all_zero = true;
239 for (;;) {
240 char ch = peek();
241 if (ch == '.') {
242 if (!is_ascii_digit(peek(1)))
243 return Error::from_string_literal("JsonParser: Must have digits after decimal point");
244
245 return fallback_to_double_parse();
246 }
247 if (ch == 'e' || ch == 'E') {
248 char next = peek(1);
249 if (!is_ascii_digit(next) && ((next != '+' && next != '-') || !is_ascii_digit(peek(2))))
250 return Error::from_string_literal("JsonParser: Must have digits after exponent with an optional sign inbetween");
251
252 return fallback_to_double_parse();
253 }
254
255 if (is_ascii_digit(ch)) {
256 if (ch != '0')
257 all_zero = false;
258
259 number_buffer.append(ch);
260 ++m_index;
261 continue;
262 }
263
264 break;
265 }
266
267 // Negative zero is always a double
268 if (negative && all_zero)
269 return JsonValue(-0.0);
270
271 StringView number_string(number_buffer.data(), number_buffer.size());
272
273 auto to_unsigned_result = number_string.to_uint<u64>();
274 if (to_unsigned_result.has_value()) {
275 if (*to_unsigned_result <= NumericLimits<u32>::max())
276 return JsonValue((u32)*to_unsigned_result);
277
278 return JsonValue(*to_unsigned_result);
279 } else if (auto signed_number = number_string.to_int<i64>(); signed_number.has_value()) {
280
281 if (*signed_number <= NumericLimits<i32>::max())
282 return JsonValue((i32)*signed_number);
283
284 return JsonValue(*signed_number);
285 }
286
287 // It's possible the unsigned value is bigger than u64 max
288 return fallback_to_double_parse();
289}
290
291ErrorOr<JsonValue> JsonParser::parse_true()
292{
293 if (!consume_specific("true"))
294 return Error::from_string_literal("JsonParser: Expected 'true'");
295 return JsonValue(true);
296}
297
298ErrorOr<JsonValue> JsonParser::parse_false()
299{
300 if (!consume_specific("false"))
301 return Error::from_string_literal("JsonParser: Expected 'false'");
302 return JsonValue(false);
303}
304
305ErrorOr<JsonValue> JsonParser::parse_null()
306{
307 if (!consume_specific("null"))
308 return Error::from_string_literal("JsonParser: Expected 'null'");
309 return JsonValue(JsonValue::Type::Null);
310}
311
312ErrorOr<JsonValue> JsonParser::parse_helper()
313{
314 ignore_while(is_space);
315 auto type_hint = peek();
316 switch (type_hint) {
317 case '{':
318 return parse_object();
319 case '[':
320 return parse_array();
321 case '"':
322 return parse_string();
323 case '-':
324 case '0':
325 case '1':
326 case '2':
327 case '3':
328 case '4':
329 case '5':
330 case '6':
331 case '7':
332 case '8':
333 case '9':
334 return parse_number();
335 case 'f':
336 return parse_false();
337 case 't':
338 return parse_true();
339 case 'n':
340 return parse_null();
341 }
342
343 return Error::from_string_literal("JsonParser: Unexpected character");
344}
345
346ErrorOr<JsonValue> JsonParser::parse()
347{
348 auto result = TRY(parse_helper());
349 ignore_while(is_space);
350 if (!is_eof())
351 return Error::from_string_literal("JsonParser: Didn't consume all input");
352 return result;
353}
354
355}