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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
5 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
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6 | |
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7 | JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ |
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8 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
4 | |
9 | |
5 | =head1 SYNOPSIS |
10 | =head1 SYNOPSIS |
6 | |
11 | |
7 | use JSON::XS; |
12 | use JSON::XS; |
8 | |
13 | |
9 | # exported functions, they croak on error |
14 | # exported functions, they croak on error |
10 | # and expect/generate UTF-8 |
15 | # and expect/generate UTF-8 |
11 | |
16 | |
12 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
17 | $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref; |
13 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
18 | $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text; |
14 | |
19 | |
15 | # OO-interface |
20 | # OO-interface |
16 | |
21 | |
17 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
22 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
18 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
23 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
19 | $perl_scalar = $coder->decode ($unicode_json_text); |
24 | $perl_scalar = $coder->decode ($unicode_json_text); |
20 | |
25 | |
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26 | # Note that JSON version 2.0 and above will automatically use JSON::XS |
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27 | # if available, at virtually no speed overhead either, so you should |
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28 | # be able to just: |
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29 | |
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30 | use JSON; |
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31 | |
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32 | # and do the same things, except that you have a pure-perl fallback now. |
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33 | |
21 | =head1 DESCRIPTION |
34 | =head1 DESCRIPTION |
22 | |
35 | |
23 | This module converts Perl data structures to JSON and vice versa. Its |
36 | This module converts Perl data structures to JSON and vice versa. Its |
24 | primary goal is to be I<correct> and its secondary goal is to be |
37 | primary goal is to be I<correct> and its secondary goal is to be |
25 | I<fast>. To reach the latter goal it was written in C. |
38 | I<fast>. To reach the latter goal it was written in C. |
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39 | |
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40 | Beginning with version 2.0 of the JSON module, when both JSON and |
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41 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
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42 | overriden) with no overhead due to emulation (by inheritign constructor |
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43 | and methods). If JSON::XS is not available, it will fall back to the |
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44 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
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45 | gives you a portable JSON API that can be fast when you need and doesn't |
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46 | require a C compiler when that is a problem. |
26 | |
47 | |
27 | As this is the n-th-something JSON module on CPAN, what was the reason |
48 | As this is the n-th-something JSON module on CPAN, what was the reason |
28 | to write yet another JSON module? While it seems there are many JSON |
49 | to write yet another JSON module? While it seems there are many JSON |
29 | modules, none of them correctly handle all corner cases, and in most cases |
50 | modules, none of them correctly handle all corner cases, and in most cases |
30 | their maintainers are unresponsive, gone missing, or not listening to bug |
51 | their maintainers are unresponsive, gone missing, or not listening to bug |
… | |
… | |
37 | |
58 | |
38 | =head2 FEATURES |
59 | =head2 FEATURES |
39 | |
60 | |
40 | =over 4 |
61 | =over 4 |
41 | |
62 | |
42 | =item * correct unicode handling |
63 | =item * correct Unicode handling |
43 | |
64 | |
44 | This module knows how to handle Unicode, and even documents how and when |
65 | This module knows how to handle Unicode, documents how and when it does |
45 | it does so. |
66 | so, and even documents what "correct" means. |
46 | |
67 | |
47 | =item * round-trip integrity |
68 | =item * round-trip integrity |
48 | |
69 | |
49 | When you serialise a perl data structure using only datatypes supported |
70 | When you serialise a perl data structure using only datatypes supported |
50 | by JSON, the deserialised data structure is identical on the Perl level. |
71 | by JSON, the deserialised data structure is identical on the Perl level. |
51 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
72 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
52 | like a number). |
73 | like a number). There minor I<are> exceptions to this, read the MAPPING |
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74 | section below to learn about those. |
53 | |
75 | |
54 | =item * strict checking of JSON correctness |
76 | =item * strict checking of JSON correctness |
55 | |
77 | |
56 | There is no guessing, no generating of illegal JSON texts by default, |
78 | There is no guessing, no generating of illegal JSON texts by default, |
57 | and only JSON is accepted as input by default (the latter is a security |
79 | and only JSON is accepted as input by default (the latter is a security |
58 | feature). |
80 | feature). |
59 | |
81 | |
60 | =item * fast |
82 | =item * fast |
61 | |
83 | |
62 | Compared to other JSON modules, this module compares favourably in terms |
84 | Compared to other JSON modules and other serialisers such as Storable, |
63 | of speed, too. |
85 | this module usually compares favourably in terms of speed, too. |
64 | |
86 | |
65 | =item * simple to use |
87 | =item * simple to use |
66 | |
88 | |
67 | This module has both a simple functional interface as well as an OO |
89 | This module has both a simple functional interface as well as an objetc |
68 | interface. |
90 | oriented interface interface. |
69 | |
91 | |
70 | =item * reasonably versatile output formats |
92 | =item * reasonably versatile output formats |
71 | |
93 | |
72 | You can choose between the most compact guarenteed single-line format |
94 | You can choose between the most compact guaranteed-single-line format |
73 | possible (nice for simple line-based protocols), a pure-ascii format |
95 | possible (nice for simple line-based protocols), a pure-ascii format |
74 | (for when your transport is not 8-bit clean, still supports the whole |
96 | (for when your transport is not 8-bit clean, still supports the whole |
75 | unicode range), or a pretty-printed format (for when you want to read that |
97 | Unicode range), or a pretty-printed format (for when you want to read that |
76 | stuff). Or you can combine those features in whatever way you like. |
98 | stuff). Or you can combine those features in whatever way you like. |
77 | |
99 | |
78 | =back |
100 | =back |
79 | |
101 | |
80 | =cut |
102 | =cut |
81 | |
103 | |
82 | package JSON::XS; |
104 | package JSON::XS; |
83 | |
105 | |
84 | use strict; |
106 | use strict; |
85 | |
107 | |
86 | our $VERSION = '1.4'; |
108 | our $VERSION = '2.1'; |
87 | our @ISA = qw(Exporter); |
109 | our @ISA = qw(Exporter); |
88 | |
110 | |
89 | our @EXPORT = qw(to_json from_json); |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
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112 | |
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113 | sub to_json($) { |
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114 | require Carp; |
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115 | Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call"); |
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116 | } |
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117 | |
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118 | sub from_json($) { |
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119 | require Carp; |
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120 | Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call"); |
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121 | } |
90 | |
122 | |
91 | use Exporter; |
123 | use Exporter; |
92 | use XSLoader; |
124 | use XSLoader; |
93 | |
125 | |
94 | =head1 FUNCTIONAL INTERFACE |
126 | =head1 FUNCTIONAL INTERFACE |
95 | |
127 | |
96 | The following convinience methods are provided by this module. They are |
128 | The following convenience methods are provided by this module. They are |
97 | exported by default: |
129 | exported by default: |
98 | |
130 | |
99 | =over 4 |
131 | =over 4 |
100 | |
132 | |
101 | =item $json_text = to_json $perl_scalar |
133 | =item $json_text = encode_json $perl_scalar |
102 | |
134 | |
103 | Converts the given Perl data structure (a simple scalar or a reference to |
135 | Converts the given Perl data structure to a UTF-8 encoded, binary string |
104 | a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
136 | (that is, the string contains octets only). Croaks on error. |
105 | octets only). Croaks on error. |
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106 | |
137 | |
107 | This function call is functionally identical to: |
138 | This function call is functionally identical to: |
108 | |
139 | |
109 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
140 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
110 | |
141 | |
111 | except being faster. |
142 | except being faster. |
112 | |
143 | |
113 | =item $perl_scalar = from_json $json_text |
144 | =item $perl_scalar = decode_json $json_text |
114 | |
145 | |
115 | The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
146 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
116 | parse that as an UTF-8 encoded JSON text, returning the resulting simple |
147 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
117 | scalar or reference. Croaks on error. |
148 | reference. Croaks on error. |
118 | |
149 | |
119 | This function call is functionally identical to: |
150 | This function call is functionally identical to: |
120 | |
151 | |
121 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
152 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
122 | |
153 | |
… | |
… | |
132 | Perl. |
163 | Perl. |
133 | |
164 | |
134 | =back |
165 | =back |
135 | |
166 | |
136 | |
167 | |
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168 | =head1 A FEW NOTES ON UNICODE AND PERL |
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169 | |
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170 | Since this often leads to confusion, here are a few very clear words on |
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171 | how Unicode works in Perl, modulo bugs. |
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172 | |
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173 | =over 4 |
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174 | |
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175 | =item 1. Perl strings can store characters with ordinal values > 255. |
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176 | |
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177 | This enables you to store Unicode characters as single characters in a |
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178 | Perl string - very natural. |
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179 | |
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180 | =item 2. Perl does I<not> associate an encoding with your strings. |
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181 | |
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182 | ... until you force it to, e.g. when matching it against a regex, or |
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183 | printing the scalar to a file, in which case Perl either interprets your |
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184 | string as locale-encoded text, octets/binary, or as Unicode, depending |
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185 | on various settings. In no case is an encoding stored together with your |
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186 | data, it is I<use> that decides encoding, not any magical meta data. |
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187 | |
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188 | =item 3. The internal utf-8 flag has no meaning with regards to the |
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189 | encoding of your string. |
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190 | |
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191 | Just ignore that flag unless you debug a Perl bug, a module written in |
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192 | XS or want to dive into the internals of perl. Otherwise it will only |
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193 | confuse you, as, despite the name, it says nothing about how your string |
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194 | is encoded. You can have Unicode strings with that flag set, with that |
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195 | flag clear, and you can have binary data with that flag set and that flag |
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196 | clear. Other possibilities exist, too. |
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197 | |
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198 | If you didn't know about that flag, just the better, pretend it doesn't |
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199 | exist. |
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200 | |
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201 | =item 4. A "Unicode String" is simply a string where each character can be |
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202 | validly interpreted as a Unicode codepoint. |
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203 | |
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204 | If you have UTF-8 encoded data, it is no longer a Unicode string, but a |
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205 | Unicode string encoded in UTF-8, giving you a binary string. |
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206 | |
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207 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
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208 | |
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209 | It's a fact. Learn to live with it. |
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210 | |
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211 | =back |
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212 | |
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213 | I hope this helps :) |
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214 | |
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215 | |
137 | =head1 OBJECT-ORIENTED INTERFACE |
216 | =head1 OBJECT-ORIENTED INTERFACE |
138 | |
217 | |
139 | The object oriented interface lets you configure your own encoding or |
218 | The object oriented interface lets you configure your own encoding or |
140 | decoding style, within the limits of supported formats. |
219 | decoding style, within the limits of supported formats. |
141 | |
220 | |
… | |
… | |
152 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
231 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
153 | => {"a": [1, 2]} |
232 | => {"a": [1, 2]} |
154 | |
233 | |
155 | =item $json = $json->ascii ([$enable]) |
234 | =item $json = $json->ascii ([$enable]) |
156 | |
235 | |
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236 | =item $enabled = $json->get_ascii |
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237 | |
157 | If C<$enable> is true (or missing), then the C<encode> method will not |
238 | If C<$enable> is true (or missing), then the C<encode> method will not |
158 | generate characters outside the code range C<0..127> (which is ASCII). Any |
239 | generate characters outside the code range C<0..127> (which is ASCII). Any |
159 | unicode characters outside that range will be escaped using either a |
240 | Unicode characters outside that range will be escaped using either a |
160 | single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, |
241 | single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, |
161 | as per RFC4627. The resulting encoded JSON text can be treated as a native |
242 | as per RFC4627. The resulting encoded JSON text can be treated as a native |
162 | unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, |
243 | Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, |
163 | or any other superset of ASCII. |
244 | or any other superset of ASCII. |
164 | |
245 | |
165 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
246 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
166 | characters unless required by the JSON syntax or other flags. This results |
247 | characters unless required by the JSON syntax or other flags. This results |
167 | in a faster and more compact format. |
248 | in a faster and more compact format. |
168 | |
249 | |
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250 | See also the section I<ENCODING/CODESET FLAG NOTES> later in this |
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251 | document. |
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252 | |
169 | The main use for this flag is to produce JSON texts that can be |
253 | The main use for this flag is to produce JSON texts that can be |
170 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
254 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
171 | contain any 8 bit characters. |
255 | contain any 8 bit characters. |
172 | |
256 | |
173 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
257 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
174 | => ["\ud801\udc01"] |
258 | => ["\ud801\udc01"] |
175 | |
259 | |
176 | =item $json = $json->latin1 ([$enable]) |
260 | =item $json = $json->latin1 ([$enable]) |
177 | |
261 | |
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262 | =item $enabled = $json->get_latin1 |
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263 | |
178 | If C<$enable> is true (or missing), then the C<encode> method will encode |
264 | If C<$enable> is true (or missing), then the C<encode> method will encode |
179 | the resulting JSON text as latin1 (or iso-8859-1), escaping any characters |
265 | the resulting JSON text as latin1 (or iso-8859-1), escaping any characters |
180 | outside the code range C<0..255>. The resulting string can be treated as a |
266 | outside the code range C<0..255>. The resulting string can be treated as a |
181 | latin1-encoded JSON text or a native unicode string. The C<decode> method |
267 | latin1-encoded JSON text or a native Unicode string. The C<decode> method |
182 | will not be affected in any way by this flag, as C<decode> by default |
268 | will not be affected in any way by this flag, as C<decode> by default |
183 | expects unicode, which is a strict superset of latin1. |
269 | expects Unicode, which is a strict superset of latin1. |
184 | |
270 | |
185 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
271 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
186 | characters unless required by the JSON syntax or other flags. |
272 | characters unless required by the JSON syntax or other flags. |
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273 | |
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274 | See also the section I<ENCODING/CODESET FLAG NOTES> later in this |
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275 | document. |
187 | |
276 | |
188 | The main use for this flag is efficiently encoding binary data as JSON |
277 | The main use for this flag is efficiently encoding binary data as JSON |
189 | text, as most octets will not be escaped, resulting in a smaller encoded |
278 | text, as most octets will not be escaped, resulting in a smaller encoded |
190 | size. The disadvantage is that the resulting JSON text is encoded |
279 | size. The disadvantage is that the resulting JSON text is encoded |
191 | in latin1 (and must correctly be treated as such when storing and |
280 | in latin1 (and must correctly be treated as such when storing and |
192 | transfering), a rare encoding for JSON. It is therefore most useful when |
281 | transferring), a rare encoding for JSON. It is therefore most useful when |
193 | you want to store data structures known to contain binary data efficiently |
282 | you want to store data structures known to contain binary data efficiently |
194 | in files or databases, not when talking to other JSON encoders/decoders. |
283 | in files or databases, not when talking to other JSON encoders/decoders. |
195 | |
284 | |
196 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
285 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
197 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
286 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
198 | |
287 | |
199 | =item $json = $json->utf8 ([$enable]) |
288 | =item $json = $json->utf8 ([$enable]) |
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289 | |
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290 | =item $enabled = $json->get_utf8 |
200 | |
291 | |
201 | If C<$enable> is true (or missing), then the C<encode> method will encode |
292 | If C<$enable> is true (or missing), then the C<encode> method will encode |
202 | the JSON result into UTF-8, as required by many protocols, while the |
293 | the JSON result into UTF-8, as required by many protocols, while the |
203 | C<decode> method expects to be handled an UTF-8-encoded string. Please |
294 | C<decode> method expects to be handled an UTF-8-encoded string. Please |
204 | note that UTF-8-encoded strings do not contain any characters outside the |
295 | note that UTF-8-encoded strings do not contain any characters outside the |
205 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
296 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
206 | versions, enabling this option might enable autodetection of the UTF-16 |
297 | versions, enabling this option might enable autodetection of the UTF-16 |
207 | and UTF-32 encoding families, as described in RFC4627. |
298 | and UTF-32 encoding families, as described in RFC4627. |
208 | |
299 | |
209 | If C<$enable> is false, then the C<encode> method will return the JSON |
300 | If C<$enable> is false, then the C<encode> method will return the JSON |
210 | string as a (non-encoded) unicode string, while C<decode> expects thus a |
301 | string as a (non-encoded) Unicode string, while C<decode> expects thus a |
211 | unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
302 | Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
212 | to be done yourself, e.g. using the Encode module. |
303 | to be done yourself, e.g. using the Encode module. |
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304 | |
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305 | See also the section I<ENCODING/CODESET FLAG NOTES> later in this |
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306 | document. |
213 | |
307 | |
214 | Example, output UTF-16BE-encoded JSON: |
308 | Example, output UTF-16BE-encoded JSON: |
215 | |
309 | |
216 | use Encode; |
310 | use Encode; |
217 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
311 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
… | |
… | |
238 | ] |
332 | ] |
239 | } |
333 | } |
240 | |
334 | |
241 | =item $json = $json->indent ([$enable]) |
335 | =item $json = $json->indent ([$enable]) |
242 | |
336 | |
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337 | =item $enabled = $json->get_indent |
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338 | |
243 | If C<$enable> is true (or missing), then the C<encode> method will use a multiline |
339 | If C<$enable> is true (or missing), then the C<encode> method will use a multiline |
244 | format as output, putting every array member or object/hash key-value pair |
340 | format as output, putting every array member or object/hash key-value pair |
245 | into its own line, identing them properly. |
341 | into its own line, indenting them properly. |
246 | |
342 | |
247 | If C<$enable> is false, no newlines or indenting will be produced, and the |
343 | If C<$enable> is false, no newlines or indenting will be produced, and the |
248 | resulting JSON text is guarenteed not to contain any C<newlines>. |
344 | resulting JSON text is guaranteed not to contain any C<newlines>. |
249 | |
345 | |
250 | This setting has no effect when decoding JSON texts. |
346 | This setting has no effect when decoding JSON texts. |
251 | |
347 | |
252 | =item $json = $json->space_before ([$enable]) |
348 | =item $json = $json->space_before ([$enable]) |
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349 | |
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350 | =item $enabled = $json->get_space_before |
253 | |
351 | |
254 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
352 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
255 | optional space before the C<:> separating keys from values in JSON objects. |
353 | optional space before the C<:> separating keys from values in JSON objects. |
256 | |
354 | |
257 | If C<$enable> is false, then the C<encode> method will not add any extra |
355 | If C<$enable> is false, then the C<encode> method will not add any extra |
… | |
… | |
263 | Example, space_before enabled, space_after and indent disabled: |
361 | Example, space_before enabled, space_after and indent disabled: |
264 | |
362 | |
265 | {"key" :"value"} |
363 | {"key" :"value"} |
266 | |
364 | |
267 | =item $json = $json->space_after ([$enable]) |
365 | =item $json = $json->space_after ([$enable]) |
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366 | |
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367 | =item $enabled = $json->get_space_after |
268 | |
368 | |
269 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
369 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
270 | optional space after the C<:> separating keys from values in JSON objects |
370 | optional space after the C<:> separating keys from values in JSON objects |
271 | and extra whitespace after the C<,> separating key-value pairs and array |
371 | and extra whitespace after the C<,> separating key-value pairs and array |
272 | members. |
372 | members. |
… | |
… | |
278 | |
378 | |
279 | Example, space_before and indent disabled, space_after enabled: |
379 | Example, space_before and indent disabled, space_after enabled: |
280 | |
380 | |
281 | {"key": "value"} |
381 | {"key": "value"} |
282 | |
382 | |
|
|
383 | =item $json = $json->relaxed ([$enable]) |
|
|
384 | |
|
|
385 | =item $enabled = $json->get_relaxed |
|
|
386 | |
|
|
387 | If C<$enable> is true (or missing), then C<decode> will accept some |
|
|
388 | extensions to normal JSON syntax (see below). C<encode> will not be |
|
|
389 | affected in anyway. I<Be aware that this option makes you accept invalid |
|
|
390 | JSON texts as if they were valid!>. I suggest only to use this option to |
|
|
391 | parse application-specific files written by humans (configuration files, |
|
|
392 | resource files etc.) |
|
|
393 | |
|
|
394 | If C<$enable> is false (the default), then C<decode> will only accept |
|
|
395 | valid JSON texts. |
|
|
396 | |
|
|
397 | Currently accepted extensions are: |
|
|
398 | |
|
|
399 | =over 4 |
|
|
400 | |
|
|
401 | =item * list items can have an end-comma |
|
|
402 | |
|
|
403 | JSON I<separates> array elements and key-value pairs with commas. This |
|
|
404 | can be annoying if you write JSON texts manually and want to be able to |
|
|
405 | quickly append elements, so this extension accepts comma at the end of |
|
|
406 | such items not just between them: |
|
|
407 | |
|
|
408 | [ |
|
|
409 | 1, |
|
|
410 | 2, <- this comma not normally allowed |
|
|
411 | ] |
|
|
412 | { |
|
|
413 | "k1": "v1", |
|
|
414 | "k2": "v2", <- this comma not normally allowed |
|
|
415 | } |
|
|
416 | |
|
|
417 | =item * shell-style '#'-comments |
|
|
418 | |
|
|
419 | Whenever JSON allows whitespace, shell-style comments are additionally |
|
|
420 | allowed. They are terminated by the first carriage-return or line-feed |
|
|
421 | character, after which more white-space and comments are allowed. |
|
|
422 | |
|
|
423 | [ |
|
|
424 | 1, # this comment not allowed in JSON |
|
|
425 | # neither this one... |
|
|
426 | ] |
|
|
427 | |
|
|
428 | =back |
|
|
429 | |
283 | =item $json = $json->canonical ([$enable]) |
430 | =item $json = $json->canonical ([$enable]) |
|
|
431 | |
|
|
432 | =item $enabled = $json->get_canonical |
284 | |
433 | |
285 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
434 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
286 | by sorting their keys. This is adding a comparatively high overhead. |
435 | by sorting their keys. This is adding a comparatively high overhead. |
287 | |
436 | |
288 | If C<$enable> is false, then the C<encode> method will output key-value |
437 | If C<$enable> is false, then the C<encode> method will output key-value |
289 | pairs in the order Perl stores them (which will likely change between runs |
438 | pairs in the order Perl stores them (which will likely change between runs |
290 | of the same script). |
439 | of the same script). |
291 | |
440 | |
292 | This option is useful if you want the same data structure to be encoded as |
441 | This option is useful if you want the same data structure to be encoded as |
293 | the same JSON text (given the same overall settings). If it is disabled, |
442 | the same JSON text (given the same overall settings). If it is disabled, |
294 | the same hash migh be encoded differently even if contains the same data, |
443 | the same hash might be encoded differently even if contains the same data, |
295 | as key-value pairs have no inherent ordering in Perl. |
444 | as key-value pairs have no inherent ordering in Perl. |
296 | |
445 | |
297 | This setting has no effect when decoding JSON texts. |
446 | This setting has no effect when decoding JSON texts. |
298 | |
447 | |
299 | =item $json = $json->allow_nonref ([$enable]) |
448 | =item $json = $json->allow_nonref ([$enable]) |
|
|
449 | |
|
|
450 | =item $enabled = $json->get_allow_nonref |
300 | |
451 | |
301 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
452 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
302 | non-reference into its corresponding string, number or null JSON value, |
453 | non-reference into its corresponding string, number or null JSON value, |
303 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
454 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
304 | values instead of croaking. |
455 | values instead of croaking. |
… | |
… | |
314 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
465 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
315 | => "Hello, World!" |
466 | => "Hello, World!" |
316 | |
467 | |
317 | =item $json = $json->allow_blessed ([$enable]) |
468 | =item $json = $json->allow_blessed ([$enable]) |
318 | |
469 | |
|
|
470 | =item $enabled = $json->get_allow_blessed |
|
|
471 | |
319 | If C<$enable> is true (or missing), then the C<encode> method will not |
472 | If C<$enable> is true (or missing), then the C<encode> method will not |
320 | barf when it encounters a blessed reference. Instead, the value of the |
473 | barf when it encounters a blessed reference. Instead, the value of the |
321 | B<convert_blessed> option will decide wether C<null> (C<convert_blessed> |
474 | B<convert_blessed> option will decide whether C<null> (C<convert_blessed> |
322 | disabled or no C<to_json> method found) or a representation of the |
475 | disabled or no C<TO_JSON> method found) or a representation of the |
323 | object (C<convert_blessed> enabled and C<to_json> method found) is being |
476 | object (C<convert_blessed> enabled and C<TO_JSON> method found) is being |
324 | encoded. Has no effect on C<decode>. |
477 | encoded. Has no effect on C<decode>. |
325 | |
478 | |
326 | If C<$enable> is false (the default), then C<encode> will throw an |
479 | If C<$enable> is false (the default), then C<encode> will throw an |
327 | exception when it encounters a blessed object. |
480 | exception when it encounters a blessed object. |
328 | |
481 | |
329 | =item $json = $json->convert_blessed ([$enable]) |
482 | =item $json = $json->convert_blessed ([$enable]) |
|
|
483 | |
|
|
484 | =item $enabled = $json->get_convert_blessed |
330 | |
485 | |
331 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
486 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
332 | blessed object, will check for the availability of the C<TO_JSON> method |
487 | blessed object, will check for the availability of the C<TO_JSON> method |
333 | on the object's class. If found, it will be called in scalar context |
488 | on the object's class. If found, it will be called in scalar context |
334 | and the resulting scalar will be encoded instead of the object. If no |
489 | and the resulting scalar will be encoded instead of the object. If no |
… | |
… | |
338 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
493 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
339 | returns other blessed objects, those will be handled in the same |
494 | returns other blessed objects, those will be handled in the same |
340 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
495 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
341 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
496 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
342 | methods called by the Perl core (== not by the user of the object) are |
497 | methods called by the Perl core (== not by the user of the object) are |
343 | usually in upper case letters and to avoid collisions with the C<to_json> |
498 | usually in upper case letters and to avoid collisions with any C<to_json> |
344 | function. |
499 | function or method. |
345 | |
500 | |
346 | This setting does not yet influence C<decode> in any way, but in the |
501 | This setting does not yet influence C<decode> in any way, but in the |
347 | future, global hooks might get installed that influence C<decode> and are |
502 | future, global hooks might get installed that influence C<decode> and are |
348 | enabled by this setting. |
503 | enabled by this setting. |
349 | |
504 | |
… | |
… | |
391 | |
546 | |
392 | As this callback gets called less often then the C<filter_json_object> |
547 | As this callback gets called less often then the C<filter_json_object> |
393 | one, decoding speed will not usually suffer as much. Therefore, single-key |
548 | one, decoding speed will not usually suffer as much. Therefore, single-key |
394 | objects make excellent targets to serialise Perl objects into, especially |
549 | objects make excellent targets to serialise Perl objects into, especially |
395 | as single-key JSON objects are as close to the type-tagged value concept |
550 | as single-key JSON objects are as close to the type-tagged value concept |
396 | as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not |
551 | as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not |
397 | support this in any way, so you need to make sure your data never looks |
552 | support this in any way, so you need to make sure your data never looks |
398 | like a serialised Perl hash. |
553 | like a serialised Perl hash. |
399 | |
554 | |
400 | Typical names for the single object key are C<__class_whatever__>, or |
555 | Typical names for the single object key are C<__class_whatever__>, or |
401 | C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even |
556 | C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even |
… | |
… | |
425 | |
580 | |
426 | { __widget__ => $self->{id} } |
581 | { __widget__ => $self->{id} } |
427 | } |
582 | } |
428 | |
583 | |
429 | =item $json = $json->shrink ([$enable]) |
584 | =item $json = $json->shrink ([$enable]) |
|
|
585 | |
|
|
586 | =item $enabled = $json->get_shrink |
430 | |
587 | |
431 | Perl usually over-allocates memory a bit when allocating space for |
588 | Perl usually over-allocates memory a bit when allocating space for |
432 | strings. This flag optionally resizes strings generated by either |
589 | strings. This flag optionally resizes strings generated by either |
433 | C<encode> or C<decode> to their minimum size possible. This can save |
590 | C<encode> or C<decode> to their minimum size possible. This can save |
434 | memory when your JSON texts are either very very long or you have many |
591 | memory when your JSON texts are either very very long or you have many |
… | |
… | |
452 | strings that look like integers or floats into integers or floats |
609 | strings that look like integers or floats into integers or floats |
453 | internally (there is no difference on the Perl level), saving space. |
610 | internally (there is no difference on the Perl level), saving space. |
454 | |
611 | |
455 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
612 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
456 | |
613 | |
|
|
614 | =item $max_depth = $json->get_max_depth |
|
|
615 | |
457 | Sets the maximum nesting level (default C<512>) accepted while encoding |
616 | Sets the maximum nesting level (default C<512>) accepted while encoding |
458 | or decoding. If the JSON text or Perl data structure has an equal or |
617 | or decoding. If the JSON text or Perl data structure has an equal or |
459 | higher nesting level then this limit, then the encoder and decoder will |
618 | higher nesting level then this limit, then the encoder and decoder will |
460 | stop and croak at that point. |
619 | stop and croak at that point. |
461 | |
620 | |
… | |
… | |
472 | used, which is rarely useful. |
631 | used, which is rarely useful. |
473 | |
632 | |
474 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
633 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
475 | |
634 | |
476 | =item $json = $json->max_size ([$maximum_string_size]) |
635 | =item $json = $json->max_size ([$maximum_string_size]) |
|
|
636 | |
|
|
637 | =item $max_size = $json->get_max_size |
477 | |
638 | |
478 | Set the maximum length a JSON text may have (in bytes) where decoding is |
639 | Set the maximum length a JSON text may have (in bytes) where decoding is |
479 | being attempted. The default is C<0>, meaning no limit. When C<decode> |
640 | being attempted. The default is C<0>, meaning no limit. When C<decode> |
480 | is called on a string longer then this number of characters it will not |
641 | is called on a string longer then this number of characters it will not |
481 | attempt to decode the string but throw an exception. This setting has no |
642 | attempt to decode the string but throw an exception. This setting has no |
… | |
… | |
528 | vice versa. These mappings are designed to "do the right thing" in most |
689 | vice versa. These mappings are designed to "do the right thing" in most |
529 | circumstances automatically, preserving round-tripping characteristics |
690 | circumstances automatically, preserving round-tripping characteristics |
530 | (what you put in comes out as something equivalent). |
691 | (what you put in comes out as something equivalent). |
531 | |
692 | |
532 | For the more enlightened: note that in the following descriptions, |
693 | For the more enlightened: note that in the following descriptions, |
533 | lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> |
694 | lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl> |
534 | refers to the abstract Perl language itself. |
695 | refers to the abstract Perl language itself. |
535 | |
696 | |
536 | |
697 | |
537 | =head2 JSON -> PERL |
698 | =head2 JSON -> PERL |
538 | |
699 | |
539 | =over 4 |
700 | =over 4 |
540 | |
701 | |
541 | =item object |
702 | =item object |
542 | |
703 | |
543 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
704 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
544 | keys is preserved (JSON does not preserver object key ordering itself). |
705 | keys is preserved (JSON does not preserve object key ordering itself). |
545 | |
706 | |
546 | =item array |
707 | =item array |
547 | |
708 | |
548 | A JSON array becomes a reference to an array in Perl. |
709 | A JSON array becomes a reference to an array in Perl. |
549 | |
710 | |
… | |
… | |
553 | are represented by the same codepoints in the Perl string, so no manual |
714 | are represented by the same codepoints in the Perl string, so no manual |
554 | decoding is necessary. |
715 | decoding is necessary. |
555 | |
716 | |
556 | =item number |
717 | =item number |
557 | |
718 | |
558 | A JSON number becomes either an integer or numeric (floating point) |
719 | A JSON number becomes either an integer, numeric (floating point) or |
559 | scalar in perl, depending on its range and any fractional parts. On the |
720 | string scalar in perl, depending on its range and any fractional parts. On |
560 | Perl level, there is no difference between those as Perl handles all the |
721 | the Perl level, there is no difference between those as Perl handles all |
561 | conversion details, but an integer may take slightly less memory and might |
722 | the conversion details, but an integer may take slightly less memory and |
562 | represent more values exactly than (floating point) numbers. |
723 | might represent more values exactly than floating point numbers. |
|
|
724 | |
|
|
725 | If the number consists of digits only, JSON::XS will try to represent |
|
|
726 | it as an integer value. If that fails, it will try to represent it as |
|
|
727 | a numeric (floating point) value if that is possible without loss of |
|
|
728 | precision. Otherwise it will preserve the number as a string value (in |
|
|
729 | which case you lose roundtripping ability, as the JSON number will be |
|
|
730 | re-encoded toa JSON string). |
|
|
731 | |
|
|
732 | Numbers containing a fractional or exponential part will always be |
|
|
733 | represented as numeric (floating point) values, possibly at a loss of |
|
|
734 | precision (in which case you might lose perfect roundtripping ability, but |
|
|
735 | the JSON number will still be re-encoded as a JSON number). |
563 | |
736 | |
564 | =item true, false |
737 | =item true, false |
565 | |
738 | |
566 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
739 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
567 | respectively. They are overloaded to act almost exactly like the numbers |
740 | respectively. They are overloaded to act almost exactly like the numbers |
568 | C<1> and C<0>. You can check wether a scalar is a JSON boolean by using |
741 | C<1> and C<0>. You can check whether a scalar is a JSON boolean by using |
569 | the C<JSON::XS::is_bool> function. |
742 | the C<JSON::XS::is_bool> function. |
570 | |
743 | |
571 | =item null |
744 | =item null |
572 | |
745 | |
573 | A JSON null atom becomes C<undef> in Perl. |
746 | A JSON null atom becomes C<undef> in Perl. |
… | |
… | |
604 | Other unblessed references are generally not allowed and will cause an |
777 | Other unblessed references are generally not allowed and will cause an |
605 | exception to be thrown, except for references to the integers C<0> and |
778 | exception to be thrown, except for references to the integers C<0> and |
606 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
779 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
607 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
780 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
608 | |
781 | |
609 | to_json [\0,JSON::XS::true] # yields [false,true] |
782 | encode_json [\0,JSON::XS::true] # yields [false,true] |
610 | |
783 | |
611 | =item JSON::XS::true, JSON::XS::false |
784 | =item JSON::XS::true, JSON::XS::false |
612 | |
785 | |
613 | These special values become JSON true and JSON false values, |
786 | These special values become JSON true and JSON false values, |
614 | respectively. You cna alos use C<\1> and C<\0> directly if you want. |
787 | respectively. You can also use C<\1> and C<\0> directly if you want. |
615 | |
788 | |
616 | =item blessed objects |
789 | =item blessed objects |
617 | |
790 | |
618 | Blessed objects are not allowed. JSON::XS currently tries to encode their |
791 | Blessed objects are not directly representable in JSON. See the |
619 | underlying representation (hash- or arrayref), but this behaviour might |
792 | C<allow_blessed> and C<convert_blessed> methods on various options on |
620 | change in future versions. |
793 | how to deal with this: basically, you can choose between throwing an |
|
|
794 | exception, encoding the reference as if it weren't blessed, or provide |
|
|
795 | your own serialiser method. |
621 | |
796 | |
622 | =item simple scalars |
797 | =item simple scalars |
623 | |
798 | |
624 | Simple Perl scalars (any scalar that is not a reference) are the most |
799 | Simple Perl scalars (any scalar that is not a reference) are the most |
625 | difficult objects to encode: JSON::XS will encode undefined scalars as |
800 | difficult objects to encode: JSON::XS will encode undefined scalars as |
626 | JSON null value, scalars that have last been used in a string context |
801 | JSON C<null> values, scalars that have last been used in a string context |
627 | before encoding as JSON strings and anything else as number value: |
802 | before encoding as JSON strings, and anything else as number value: |
628 | |
803 | |
629 | # dump as number |
804 | # dump as number |
630 | to_json [2] # yields [2] |
805 | encode_json [2] # yields [2] |
631 | to_json [-3.0e17] # yields [-3e+17] |
806 | encode_json [-3.0e17] # yields [-3e+17] |
632 | my $value = 5; to_json [$value] # yields [5] |
807 | my $value = 5; encode_json [$value] # yields [5] |
633 | |
808 | |
634 | # used as string, so dump as string |
809 | # used as string, so dump as string |
635 | print $value; |
810 | print $value; |
636 | to_json [$value] # yields ["5"] |
811 | encode_json [$value] # yields ["5"] |
637 | |
812 | |
638 | # undef becomes null |
813 | # undef becomes null |
639 | to_json [undef] # yields [null] |
814 | encode_json [undef] # yields [null] |
640 | |
815 | |
641 | You can force the type to be a string by stringifying it: |
816 | You can force the type to be a JSON string by stringifying it: |
642 | |
817 | |
643 | my $x = 3.1; # some variable containing a number |
818 | my $x = 3.1; # some variable containing a number |
644 | "$x"; # stringified |
819 | "$x"; # stringified |
645 | $x .= ""; # another, more awkward way to stringify |
820 | $x .= ""; # another, more awkward way to stringify |
646 | print $x; # perl does it for you, too, quite often |
821 | print $x; # perl does it for you, too, quite often |
647 | |
822 | |
648 | You can force the type to be a number by numifying it: |
823 | You can force the type to be a JSON number by numifying it: |
649 | |
824 | |
650 | my $x = "3"; # some variable containing a string |
825 | my $x = "3"; # some variable containing a string |
651 | $x += 0; # numify it, ensuring it will be dumped as a number |
826 | $x += 0; # numify it, ensuring it will be dumped as a number |
652 | $x *= 1; # same thing, the choise is yours. |
827 | $x *= 1; # same thing, the choice is yours. |
653 | |
828 | |
654 | You can not currently output JSON booleans or force the type in other, |
829 | You can not currently force the type in other, less obscure, ways. Tell me |
655 | less obscure, ways. Tell me if you need this capability. |
830 | if you need this capability (but don't forget to explain why it's needed |
|
|
831 | :). |
|
|
832 | |
|
|
833 | =back |
|
|
834 | |
|
|
835 | |
|
|
836 | =head1 ENCODING/CODESET FLAG NOTES |
|
|
837 | |
|
|
838 | The interested reader might have seen a number of flags that signify |
|
|
839 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
|
|
840 | some confusion on what these do, so here is a short comparison: |
|
|
841 | |
|
|
842 | C<utf8> controls whether the JSON text created by C<encode> (and expected |
|
|
843 | by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only |
|
|
844 | control whether C<encode> escapes character values outside their respective |
|
|
845 | codeset range. Neither of these flags conflict with each other, although |
|
|
846 | some combinations make less sense than others. |
|
|
847 | |
|
|
848 | Care has been taken to make all flags symmetrical with respect to |
|
|
849 | C<encode> and C<decode>, that is, texts encoded with any combination of |
|
|
850 | these flag values will be correctly decoded when the same flags are used |
|
|
851 | - in general, if you use different flag settings while encoding vs. when |
|
|
852 | decoding you likely have a bug somewhere. |
|
|
853 | |
|
|
854 | Below comes a verbose discussion of these flags. Note that a "codeset" is |
|
|
855 | simply an abstract set of character-codepoint pairs, while an encoding |
|
|
856 | takes those codepoint numbers and I<encodes> them, in our case into |
|
|
857 | octets. Unicode is (among other things) a codeset, UTF-8 is an encoding, |
|
|
858 | and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at |
|
|
859 | the same time, which can be confusing. |
|
|
860 | |
|
|
861 | =over 4 |
|
|
862 | |
|
|
863 | =item C<utf8> flag disabled |
|
|
864 | |
|
|
865 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
|
|
866 | and expect Unicode strings, that is, characters with high ordinal Unicode |
|
|
867 | values (> 255) will be encoded as such characters, and likewise such |
|
|
868 | characters are decoded as-is, no canges to them will be done, except |
|
|
869 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
|
|
870 | respectively (to Perl, these are the same thing in strings unless you do |
|
|
871 | funny/weird/dumb stuff). |
|
|
872 | |
|
|
873 | This is useful when you want to do the encoding yourself (e.g. when you |
|
|
874 | want to have UTF-16 encoded JSON texts) or when some other layer does |
|
|
875 | the encoding for you (for example, when printing to a terminal using a |
|
|
876 | filehandle that transparently encodes to UTF-8 you certainly do NOT want |
|
|
877 | to UTF-8 encode your data first and have Perl encode it another time). |
|
|
878 | |
|
|
879 | =item C<utf8> flag enabled |
|
|
880 | |
|
|
881 | If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all |
|
|
882 | characters using the corresponding UTF-8 multi-byte sequence, and will |
|
|
883 | expect your input strings to be encoded as UTF-8, that is, no "character" |
|
|
884 | of the input string must have any value > 255, as UTF-8 does not allow |
|
|
885 | that. |
|
|
886 | |
|
|
887 | The C<utf8> flag therefore switches between two modes: disabled means you |
|
|
888 | will get a Unicode string in Perl, enabled means you get an UTF-8 encoded |
|
|
889 | octet/binary string in Perl. |
|
|
890 | |
|
|
891 | =item C<latin1> or C<ascii> flags enabled |
|
|
892 | |
|
|
893 | With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters |
|
|
894 | with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining |
|
|
895 | characters as specified by the C<utf8> flag. |
|
|
896 | |
|
|
897 | If C<utf8> is disabled, then the result is also correctly encoded in those |
|
|
898 | character sets (as both are proper subsets of Unicode, meaning that a |
|
|
899 | Unicode string with all character values < 256 is the same thing as a |
|
|
900 | ISO-8859-1 string, and a Unicode string with all character values < 128 is |
|
|
901 | the same thing as an ASCII string in Perl). |
|
|
902 | |
|
|
903 | If C<utf8> is enabled, you still get a correct UTF-8-encoded string, |
|
|
904 | regardless of these flags, just some more characters will be escaped using |
|
|
905 | C<\uXXXX> then before. |
|
|
906 | |
|
|
907 | Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8 |
|
|
908 | encoding, while ASCII-encoded strings are. That is because the ISO-8859-1 |
|
|
909 | encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being |
|
|
910 | a subset of Unicode), while ASCII is. |
|
|
911 | |
|
|
912 | Surprisingly, C<decode> will ignore these flags and so treat all input |
|
|
913 | values as governed by the C<utf8> flag. If it is disabled, this allows you |
|
|
914 | to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of |
|
|
915 | Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings. |
|
|
916 | |
|
|
917 | So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag - |
|
|
918 | they only govern when the JSON output engine escapes a character or not. |
|
|
919 | |
|
|
920 | The main use for C<latin1> is to relatively efficiently store binary data |
|
|
921 | as JSON, at the expense of breaking compatibility with most JSON decoders. |
|
|
922 | |
|
|
923 | The main use for C<ascii> is to force the output to not contain characters |
|
|
924 | with values > 127, which means you can interpret the resulting string |
|
|
925 | as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and |
|
|
926 | 8-bit-encoding, and still get the same data structure back. This is useful |
|
|
927 | when your channel for JSON transfer is not 8-bit clean or the encoding |
|
|
928 | might be mangled in between (e.g. in mail), and works because ASCII is a |
|
|
929 | proper subset of most 8-bit and multibyte encodings in use in the world. |
656 | |
930 | |
657 | =back |
931 | =back |
658 | |
932 | |
659 | |
933 | |
660 | =head1 COMPARISON |
934 | =head1 COMPARISON |
… | |
… | |
665 | followed by some benchmark values. JSON::XS was designed not to suffer |
939 | followed by some benchmark values. JSON::XS was designed not to suffer |
666 | from any of these problems or limitations. |
940 | from any of these problems or limitations. |
667 | |
941 | |
668 | =over 4 |
942 | =over 4 |
669 | |
943 | |
|
|
944 | =item JSON 2.xx |
|
|
945 | |
|
|
946 | A marvellous piece of engineering, this module either uses JSON::XS |
|
|
947 | directly when available (so will be 100% compatible with it, including |
|
|
948 | speed), or it uses JSON::PP, which is basically JSON::XS translated to |
|
|
949 | Pure Perl, which should be 100% compatible with JSON::XS, just a bit |
|
|
950 | slower. |
|
|
951 | |
|
|
952 | You cannot really lose by using this module, especially as it tries very |
|
|
953 | hard to work even with ancient Perl versions, while JSON::XS does not. |
|
|
954 | |
670 | =item JSON 1.07 |
955 | =item JSON 1.07 |
671 | |
956 | |
672 | Slow (but very portable, as it is written in pure Perl). |
957 | Slow (but very portable, as it is written in pure Perl). |
673 | |
958 | |
674 | Undocumented/buggy Unicode handling (how JSON handles unicode values is |
959 | Undocumented/buggy Unicode handling (how JSON handles Unicode values is |
675 | undocumented. One can get far by feeding it unicode strings and doing |
960 | undocumented. One can get far by feeding it Unicode strings and doing |
676 | en-/decoding oneself, but unicode escapes are not working properly). |
961 | en-/decoding oneself, but Unicode escapes are not working properly). |
677 | |
962 | |
678 | No roundtripping (strings get clobbered if they look like numbers, e.g. |
963 | No round-tripping (strings get clobbered if they look like numbers, e.g. |
679 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
964 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
680 | decode into the number 2. |
965 | decode into the number 2. |
681 | |
966 | |
682 | =item JSON::PC 0.01 |
967 | =item JSON::PC 0.01 |
683 | |
968 | |
684 | Very fast. |
969 | Very fast. |
685 | |
970 | |
686 | Undocumented/buggy Unicode handling. |
971 | Undocumented/buggy Unicode handling. |
687 | |
972 | |
688 | No roundtripping. |
973 | No round-tripping. |
689 | |
974 | |
690 | Has problems handling many Perl values (e.g. regex results and other magic |
975 | Has problems handling many Perl values (e.g. regex results and other magic |
691 | values will make it croak). |
976 | values will make it croak). |
692 | |
977 | |
693 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
978 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
… | |
… | |
703 | Very inflexible (no human-readable format supported, format pretty much |
988 | Very inflexible (no human-readable format supported, format pretty much |
704 | undocumented. I need at least a format for easy reading by humans and a |
989 | undocumented. I need at least a format for easy reading by humans and a |
705 | single-line compact format for use in a protocol, and preferably a way to |
990 | single-line compact format for use in a protocol, and preferably a way to |
706 | generate ASCII-only JSON texts). |
991 | generate ASCII-only JSON texts). |
707 | |
992 | |
708 | Completely broken (and confusingly documented) Unicode handling (unicode |
993 | Completely broken (and confusingly documented) Unicode handling (Unicode |
709 | escapes are not working properly, you need to set ImplicitUnicode to |
994 | escapes are not working properly, you need to set ImplicitUnicode to |
710 | I<different> values on en- and decoding to get symmetric behaviour). |
995 | I<different> values on en- and decoding to get symmetric behaviour). |
711 | |
996 | |
712 | No roundtripping (simple cases work, but this depends on wether the scalar |
997 | No round-tripping (simple cases work, but this depends on whether the scalar |
713 | value was used in a numeric context or not). |
998 | value was used in a numeric context or not). |
714 | |
999 | |
715 | Dumping hashes may skip hash values depending on iterator state. |
1000 | Dumping hashes may skip hash values depending on iterator state. |
716 | |
1001 | |
717 | Unmaintained (maintainer unresponsive for many months, bugs are not |
1002 | Unmaintained (maintainer unresponsive for many months, bugs are not |
718 | getting fixed). |
1003 | getting fixed). |
719 | |
1004 | |
720 | Does not check input for validity (i.e. will accept non-JSON input and |
1005 | Does not check input for validity (i.e. will accept non-JSON input and |
721 | return "something" instead of raising an exception. This is a security |
1006 | return "something" instead of raising an exception. This is a security |
722 | issue: imagine two banks transfering money between each other using |
1007 | issue: imagine two banks transferring money between each other using |
723 | JSON. One bank might parse a given non-JSON request and deduct money, |
1008 | JSON. One bank might parse a given non-JSON request and deduct money, |
724 | while the other might reject the transaction with a syntax error. While a |
1009 | while the other might reject the transaction with a syntax error. While a |
725 | good protocol will at least recover, that is extra unnecessary work and |
1010 | good protocol will at least recover, that is extra unnecessary work and |
726 | the transaction will still not succeed). |
1011 | the transaction will still not succeed). |
727 | |
1012 | |
728 | =item JSON::DWIW 0.04 |
1013 | =item JSON::DWIW 0.04 |
729 | |
1014 | |
730 | Very fast. Very natural. Very nice. |
1015 | Very fast. Very natural. Very nice. |
731 | |
1016 | |
732 | Undocumented unicode handling (but the best of the pack. Unicode escapes |
1017 | Undocumented Unicode handling (but the best of the pack. Unicode escapes |
733 | still don't get parsed properly). |
1018 | still don't get parsed properly). |
734 | |
1019 | |
735 | Very inflexible. |
1020 | Very inflexible. |
736 | |
1021 | |
737 | No roundtripping. |
1022 | No round-tripping. |
738 | |
1023 | |
739 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
1024 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
740 | result in nothing being output) |
1025 | result in nothing being output) |
741 | |
1026 | |
742 | Does not check input for validity. |
1027 | Does not check input for validity. |
… | |
… | |
744 | =back |
1029 | =back |
745 | |
1030 | |
746 | |
1031 | |
747 | =head2 JSON and YAML |
1032 | =head2 JSON and YAML |
748 | |
1033 | |
749 | You often hear that JSON is a subset (or a close subset) of YAML. This is, |
1034 | You often hear that JSON is a subset of YAML. This is, however, a mass |
750 | however, a mass hysteria and very far from the truth. In general, there is |
1035 | hysteria(*) and very far from the truth (as of the time of this writing), |
751 | no way to configure JSON::XS to output a data structure as valid YAML. |
1036 | so let me state it clearly: I<in general, there is no way to configure |
|
|
1037 | JSON::XS to output a data structure as valid YAML> that works in all |
|
|
1038 | cases. |
752 | |
1039 | |
753 | If you really must use JSON::XS to generate YAML, you should use this |
1040 | If you really must use JSON::XS to generate YAML, you should use this |
754 | algorithm (subject to change in future versions): |
1041 | algorithm (subject to change in future versions): |
755 | |
1042 | |
756 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
1043 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
757 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1044 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
758 | |
1045 | |
759 | This will usually generate JSON texts that also parse as valid |
1046 | This will I<usually> generate JSON texts that also parse as valid |
760 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1047 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
761 | lengths that JSON doesn't have, so you should make sure that your hash |
1048 | lengths that JSON doesn't have and also has different and incompatible |
|
|
1049 | unicode handling, so you should make sure that your hash keys are |
762 | keys are noticably shorter than the 1024 characters YAML allows. |
1050 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
|
|
1051 | you do not have characters with codepoint values outside the Unicode BMP |
|
|
1052 | (basic multilingual page). YAML also does not allow C<\/> sequences in |
|
|
1053 | strings (which JSON::XS does not I<currently> generate, but other JSON |
|
|
1054 | generators might). |
763 | |
1055 | |
764 | There might be other incompatibilities that I am not aware of. In general |
1056 | There might be other incompatibilities that I am not aware of (or the YAML |
|
|
1057 | specification has been changed yet again - it does so quite often). In |
765 | you should not try to generate YAML with a JSON generator or vice versa, |
1058 | general you should not try to generate YAML with a JSON generator or vice |
766 | or try to parse JSON with a YAML parser or vice versa: chances are high |
1059 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
767 | that you will run into severe interoperability problems. |
1060 | high that you will run into severe interoperability problems when you |
|
|
1061 | least expect it. |
|
|
1062 | |
|
|
1063 | =over 4 |
|
|
1064 | |
|
|
1065 | =item (*) |
|
|
1066 | |
|
|
1067 | I have been pressured multiple times by Brian Ingerson (one of the |
|
|
1068 | authors of the YAML specification) to remove this paragraph, despite him |
|
|
1069 | acknowledging that the actual incompatibilities exist. As I was personally |
|
|
1070 | bitten by this "JSON is YAML" lie, I refused and said I will continue to |
|
|
1071 | educate people about these issues, so others do not run into the same |
|
|
1072 | problem again and again. After this, Brian called me a (quote)I<complete |
|
|
1073 | and worthless idiot>(unquote). |
|
|
1074 | |
|
|
1075 | In my opinion, instead of pressuring and insulting people who actually |
|
|
1076 | clarify issues with YAML and the wrong statements of some of its |
|
|
1077 | proponents, I would kindly suggest reading the JSON spec (which is not |
|
|
1078 | that difficult or long) and finally make YAML compatible to it, and |
|
|
1079 | educating users about the changes, instead of spreading lies about the |
|
|
1080 | real compatibility for many I<years> and trying to silence people who |
|
|
1081 | point out that it isn't true. |
|
|
1082 | |
|
|
1083 | =back |
768 | |
1084 | |
769 | |
1085 | |
770 | =head2 SPEED |
1086 | =head2 SPEED |
771 | |
1087 | |
772 | It seems that JSON::XS is surprisingly fast, as shown in the following |
1088 | It seems that JSON::XS is surprisingly fast, as shown in the following |
773 | tables. They have been generated with the help of the C<eg/bench> program |
1089 | tables. They have been generated with the help of the C<eg/bench> program |
774 | in the JSON::XS distribution, to make it easy to compare on your own |
1090 | in the JSON::XS distribution, to make it easy to compare on your own |
775 | system. |
1091 | system. |
776 | |
1092 | |
777 | First comes a comparison between various modules using a very short |
1093 | First comes a comparison between various modules using |
778 | single-line JSON string: |
1094 | a very short single-line JSON string (also available at |
|
|
1095 | L<http://dist.schmorp.de/misc/json/short.json>). |
779 | |
1096 | |
780 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
1097 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
781 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
1098 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
782 | |
1099 | |
783 | It shows the number of encodes/decodes per second (JSON::XS uses |
1100 | It shows the number of encodes/decodes per second (JSON::XS uses |
784 | the functional interface, while JSON::XS/2 uses the OO interface |
1101 | the functional interface, while JSON::XS/2 uses the OO interface |
785 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1102 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
786 | shrink). Higher is better: |
1103 | shrink). Higher is better: |
787 | |
1104 | |
788 | Storable | 15779.925 | 14169.946 | |
|
|
789 | -----------+------------+------------+ |
|
|
790 | module | encode | decode | |
1105 | module | encode | decode | |
791 | -----------|------------|------------| |
1106 | -----------|------------|------------| |
792 | JSON | 4990.842 | 4088.813 | |
1107 | JSON 1.x | 4990.842 | 4088.813 | |
793 | JSON::DWIW | 51653.990 | 71575.154 | |
1108 | JSON::DWIW | 51653.990 | 71575.154 | |
794 | JSON::PC | 65948.176 | 74631.744 | |
1109 | JSON::PC | 65948.176 | 74631.744 | |
795 | JSON::PP | 8931.652 | 3817.168 | |
1110 | JSON::PP | 8931.652 | 3817.168 | |
796 | JSON::Syck | 24877.248 | 27776.848 | |
1111 | JSON::Syck | 24877.248 | 27776.848 | |
797 | JSON::XS | 388361.481 | 227951.304 | |
1112 | JSON::XS | 388361.481 | 227951.304 | |
… | |
… | |
799 | JSON::XS/3 | 338250.323 | 218453.333 | |
1114 | JSON::XS/3 | 338250.323 | 218453.333 | |
800 | Storable | 16500.016 | 135300.129 | |
1115 | Storable | 16500.016 | 135300.129 | |
801 | -----------+------------+------------+ |
1116 | -----------+------------+------------+ |
802 | |
1117 | |
803 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
1118 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
804 | about three times faster on decoding, and over fourty times faster |
1119 | about three times faster on decoding, and over forty times faster |
805 | than JSON, even with pretty-printing and key sorting. It also compares |
1120 | than JSON, even with pretty-printing and key sorting. It also compares |
806 | favourably to Storable for small amounts of data. |
1121 | favourably to Storable for small amounts of data. |
807 | |
1122 | |
808 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1123 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
809 | search API (http://nanoref.com/yahooapis/mgPdGg): |
1124 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
810 | |
1125 | |
811 | module | encode | decode | |
1126 | module | encode | decode | |
812 | -----------|------------|------------| |
1127 | -----------|------------|------------| |
813 | JSON | 55.260 | 34.971 | |
1128 | JSON 1.x | 55.260 | 34.971 | |
814 | JSON::DWIW | 825.228 | 1082.513 | |
1129 | JSON::DWIW | 825.228 | 1082.513 | |
815 | JSON::PC | 3571.444 | 2394.829 | |
1130 | JSON::PC | 3571.444 | 2394.829 | |
816 | JSON::PP | 210.987 | 32.574 | |
1131 | JSON::PP | 210.987 | 32.574 | |
817 | JSON::Syck | 552.551 | 787.544 | |
1132 | JSON::Syck | 552.551 | 787.544 | |
818 | JSON::XS | 5780.463 | 4854.519 | |
1133 | JSON::XS | 5780.463 | 4854.519 | |
… | |
… | |
822 | -----------+------------+------------+ |
1137 | -----------+------------+------------+ |
823 | |
1138 | |
824 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1139 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
825 | decodes faster). |
1140 | decodes faster). |
826 | |
1141 | |
827 | On large strings containing lots of high unicode characters, some modules |
1142 | On large strings containing lots of high Unicode characters, some modules |
828 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1143 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
829 | will be broken due to missing (or wrong) unicode handling. Others refuse |
1144 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
830 | to decode or encode properly, so it was impossible to prepare a fair |
1145 | to decode or encode properly, so it was impossible to prepare a fair |
831 | comparison table for that case. |
1146 | comparison table for that case. |
832 | |
1147 | |
833 | |
1148 | |
834 | =head1 SECURITY CONSIDERATIONS |
1149 | =head1 SECURITY CONSIDERATIONS |
… | |
… | |
840 | any buffer overflows. Obviously, this module should ensure that and I am |
1155 | any buffer overflows. Obviously, this module should ensure that and I am |
841 | trying hard on making that true, but you never know. |
1156 | trying hard on making that true, but you never know. |
842 | |
1157 | |
843 | Second, you need to avoid resource-starving attacks. That means you should |
1158 | Second, you need to avoid resource-starving attacks. That means you should |
844 | limit the size of JSON texts you accept, or make sure then when your |
1159 | limit the size of JSON texts you accept, or make sure then when your |
845 | resources run out, thats just fine (e.g. by using a separate process that |
1160 | resources run out, that's just fine (e.g. by using a separate process that |
846 | can crash safely). The size of a JSON text in octets or characters is |
1161 | can crash safely). The size of a JSON text in octets or characters is |
847 | usually a good indication of the size of the resources required to decode |
1162 | usually a good indication of the size of the resources required to decode |
848 | it into a Perl structure. While JSON::XS can check the size of the JSON |
1163 | it into a Perl structure. While JSON::XS can check the size of the JSON |
849 | text, it might be too late when you already have it in memory, so you |
1164 | text, it might be too late when you already have it in memory, so you |
850 | might want to check the size before you accept the string. |
1165 | might want to check the size before you accept the string. |
851 | |
1166 | |
852 | Third, JSON::XS recurses using the C stack when decoding objects and |
1167 | Third, JSON::XS recurses using the C stack when decoding objects and |
853 | arrays. The C stack is a limited resource: for instance, on my amd64 |
1168 | arrays. The C stack is a limited resource: for instance, on my amd64 |
854 | machine with 8MB of stack size I can decode around 180k nested arrays but |
1169 | machine with 8MB of stack size I can decode around 180k nested arrays but |
855 | only 14k nested JSON objects (due to perl itself recursing deeply on croak |
1170 | only 14k nested JSON objects (due to perl itself recursing deeply on croak |
856 | to free the temporary). If that is exceeded, the program crashes. to be |
1171 | to free the temporary). If that is exceeded, the program crashes. To be |
857 | conservative, the default nesting limit is set to 512. If your process |
1172 | conservative, the default nesting limit is set to 512. If your process |
858 | has a smaller stack, you should adjust this setting accordingly with the |
1173 | has a smaller stack, you should adjust this setting accordingly with the |
859 | C<max_depth> method. |
1174 | C<max_depth> method. |
860 | |
1175 | |
861 | And last but least, something else could bomb you that I forgot to think |
1176 | Something else could bomb you, too, that I forgot to think of. In that |
862 | of. In that case, you get to keep the pieces. I am always open for hints, |
1177 | case, you get to keep the pieces. I am always open for hints, though... |
863 | though... |
1178 | |
|
|
1179 | Also keep in mind that JSON::XS might leak contents of your Perl data |
|
|
1180 | structures in its error messages, so when you serialise sensitive |
|
|
1181 | information you might want to make sure that exceptions thrown by JSON::XS |
|
|
1182 | will not end up in front of untrusted eyes. |
864 | |
1183 | |
865 | If you are using JSON::XS to return packets to consumption |
1184 | If you are using JSON::XS to return packets to consumption |
866 | by javascript scripts in a browser you should have a look at |
1185 | by JavaScript scripts in a browser you should have a look at |
867 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether |
1186 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether |
868 | you are vulnerable to some common attack vectors (which really are browser |
1187 | you are vulnerable to some common attack vectors (which really are browser |
869 | design bugs, but it is still you who will have to deal with it, as major |
1188 | design bugs, but it is still you who will have to deal with it, as major |
870 | browser developers care only for features, not about doing security |
1189 | browser developers care only for features, not about getting security |
871 | right). |
1190 | right). |
872 | |
1191 | |
873 | |
1192 | |
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1193 | =head1 THREADS |
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1194 | |
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1195 | This module is I<not> guaranteed to be thread safe and there are no |
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1196 | plans to change this until Perl gets thread support (as opposed to the |
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1197 | horribly slow so-called "threads" which are simply slow and bloated |
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1198 | process simulations - use fork, it's I<much> faster, cheaper, better). |
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1199 | |
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1200 | (It might actually work, but you have been warned). |
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1201 | |
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1202 | |
874 | =head1 BUGS |
1203 | =head1 BUGS |
875 | |
1204 | |
876 | While the goal of this module is to be correct, that unfortunately does |
1205 | While the goal of this module is to be correct, that unfortunately does |
877 | not mean its bug-free, only that I think its design is bug-free. It is |
1206 | not mean it's bug-free, only that I think its design is bug-free. It is |
878 | still relatively early in its development. If you keep reporting bugs they |
1207 | still relatively early in its development. If you keep reporting bugs they |
879 | will be fixed swiftly, though. |
1208 | will be fixed swiftly, though. |
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1209 | |
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1210 | Please refrain from using rt.cpan.org or any other bug reporting |
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1211 | service. I put the contact address into my modules for a reason. |
880 | |
1212 | |
881 | =cut |
1213 | =cut |
882 | |
1214 | |
883 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
1215 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
884 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |
1216 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |