1 /*
2 * Copyright (c) Facebook, Inc. and its affiliates.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <folly/json_pointer.h>
18
19 #include <folly/String.h>
20
21 namespace folly {
22
23 // static, public
try_parse(StringPiece const str)24 Expected<json_pointer, json_pointer::parse_error> json_pointer::try_parse(
25 StringPiece const str) {
26 // pointer describes complete document
27 if (str.empty()) {
28 return json_pointer{};
29 }
30
31 if (str.at(0) != '/') {
32 return makeUnexpected(parse_error::invalid_first_character);
33 }
34
35 std::vector<std::string> tokens;
36 splitTo<std::string>("/", str, std::inserter(tokens, tokens.begin()));
37 tokens.erase(tokens.begin());
38
39 for (auto& token : tokens) {
40 if (!unescape(token)) {
41 return makeUnexpected(parse_error::invalid_escape_sequence);
42 }
43 }
44
45 return json_pointer(std::move(tokens));
46 }
47
48 // static, public
parse(StringPiece const str)49 json_pointer json_pointer::parse(StringPiece const str) {
50 auto res = try_parse(str);
51 if (res.hasValue()) {
52 return std::move(res.value());
53 }
54 switch (res.error()) {
55 case parse_error::invalid_first_character:
56 throw json_pointer::parse_exception(
57 "non-empty JSON pointer string does not start with '/'");
58 case parse_error::invalid_escape_sequence:
59 throw json_pointer::parse_exception(
60 "Invalid escape sequence in JSON pointer string");
61 default:
62 assume_unreachable();
63 }
64 }
65
is_prefix_of(json_pointer const & other) const66 bool json_pointer::is_prefix_of(json_pointer const& other) const noexcept {
67 auto const& other_tokens = other.tokens();
68 if (tokens_.size() > other_tokens.size()) {
69 return false;
70 }
71 auto const other_begin = other_tokens.cbegin();
72 auto const other_end = other_tokens.cbegin() + tokens_.size();
73 return std::equal(tokens_.cbegin(), tokens_.cend(), other_begin, other_end);
74 }
75
tokens() const76 std::vector<std::string> const& json_pointer::tokens() const {
77 return tokens_;
78 }
79
80 // private
json_pointer(std::vector<std::string> tokens)81 json_pointer::json_pointer(std::vector<std::string> tokens) noexcept
82 : tokens_{std::move(tokens)} {}
83
84 // private, static
unescape(std::string & str)85 bool json_pointer::unescape(std::string& str) {
86 char* out = &str[0];
87 char const* begin = out;
88 char const* end = begin + str.size();
89 char const* decode = begin;
90 while (decode < end) {
91 if (*decode != '~') {
92 *out++ = *decode++;
93 continue;
94 }
95 if (decode + 1 == end) {
96 return false;
97 }
98 switch (decode[1]) {
99 case '1':
100 *out++ = '/';
101 break;
102 case '0':
103 *out++ = '~';
104 break;
105 default:
106 return false;
107 }
108 decode += 2;
109 }
110 str.resize(out - begin);
111 return true;
112 }
113
114 } // namespace folly
115