forked from danielaparker/jsoncons
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathREADME.html
872 lines (685 loc) · 24.6 KB
/
README.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
<!DOCTYPE html>
<html>
<head>
<title>README</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
/* GitHub stylesheet for MarkdownPad (http://markdownpad.com) */
/* Author: Nicolas Hery - http://nicolashery.com */
/* Version: b13fe65ca28d2e568c6ed5d7f06581183df8f2ff */
/* Source: https://github.com/nicolahery/markdownpad-github */
/* RESET
=============================================================================*/
html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
}
/* BODY
=============================================================================*/
body {
font-family: Helvetica, arial, freesans, clean, sans-serif;
font-size: 14px;
line-height: 1.6;
color: #333;
background-color: #fff;
padding: 20px;
max-width: 960px;
margin: 0 auto;
}
body>*:first-child {
margin-top: 0 !important;
}
body>*:last-child {
margin-bottom: 0 !important;
}
/* BLOCKS
=============================================================================*/
p, blockquote, ul, ol, dl, table, pre {
margin: 15px 0;
}
/* HEADERS
=============================================================================*/
h1, h2, h3, h4, h5, h6 {
margin: 20px 0 10px;
padding: 0;
font-weight: bold;
-webkit-font-smoothing: antialiased;
}
h1 tt, h1 code, h2 tt, h2 code, h3 tt, h3 code, h4 tt, h4 code, h5 tt, h5 code, h6 tt, h6 code {
font-size: inherit;
}
h1 {
font-size: 28px;
color: #000;
}
h2 {
font-size: 24px;
border-bottom: 1px solid #ccc;
color: #000;
}
h3 {
font-size: 18px;
}
h4 {
font-size: 16px;
}
h5 {
font-size: 14px;
}
h6 {
color: #777;
font-size: 14px;
}
body>h2:first-child, body>h1:first-child, body>h1:first-child+h2, body>h3:first-child, body>h4:first-child, body>h5:first-child, body>h6:first-child {
margin-top: 0;
padding-top: 0;
}
a:first-child h1, a:first-child h2, a:first-child h3, a:first-child h4, a:first-child h5, a:first-child h6 {
margin-top: 0;
padding-top: 0;
}
h1+p, h2+p, h3+p, h4+p, h5+p, h6+p {
margin-top: 10px;
}
/* LINKS
=============================================================================*/
a {
color: #4183C4;
text-decoration: none;
}
a:hover {
text-decoration: underline;
}
/* LISTS
=============================================================================*/
ul, ol {
padding-left: 30px;
}
ul li > :first-child,
ol li > :first-child,
ul li ul:first-of-type,
ol li ol:first-of-type,
ul li ol:first-of-type,
ol li ul:first-of-type {
margin-top: 0px;
}
ul ul, ul ol, ol ol, ol ul {
margin-bottom: 0;
}
dl {
padding: 0;
}
dl dt {
font-size: 14px;
font-weight: bold;
font-style: italic;
padding: 0;
margin: 15px 0 5px;
}
dl dt:first-child {
padding: 0;
}
dl dt>:first-child {
margin-top: 0px;
}
dl dt>:last-child {
margin-bottom: 0px;
}
dl dd {
margin: 0 0 15px;
padding: 0 15px;
}
dl dd>:first-child {
margin-top: 0px;
}
dl dd>:last-child {
margin-bottom: 0px;
}
/* CODE
=============================================================================*/
pre, code, tt {
font-size: 12px;
font-family: Consolas, "Liberation Mono", Courier, monospace;
}
code, tt {
margin: 0 0px;
padding: 0px 0px;
white-space: nowrap;
border: 1px solid #eaeaea;
background-color: #f8f8f8;
border-radius: 3px;
}
pre>code {
margin: 0;
padding: 0;
white-space: pre;
border: none;
background: transparent;
}
pre {
background-color: #f8f8f8;
border: 1px solid #ccc;
font-size: 13px;
line-height: 19px;
overflow: auto;
padding: 6px 10px;
border-radius: 3px;
}
pre code, pre tt {
background-color: transparent;
border: none;
}
kbd {
-moz-border-bottom-colors: none;
-moz-border-left-colors: none;
-moz-border-right-colors: none;
-moz-border-top-colors: none;
background-color: #DDDDDD;
background-image: linear-gradient(#F1F1F1, #DDDDDD);
background-repeat: repeat-x;
border-color: #DDDDDD #CCCCCC #CCCCCC #DDDDDD;
border-image: none;
border-radius: 2px 2px 2px 2px;
border-style: solid;
border-width: 1px;
font-family: "Helvetica Neue",Helvetica,Arial,sans-serif;
line-height: 10px;
padding: 1px 4px;
}
/* QUOTES
=============================================================================*/
blockquote {
border-left: 4px solid #DDD;
padding: 0 15px;
color: #777;
}
blockquote>:first-child {
margin-top: 0px;
}
blockquote>:last-child {
margin-bottom: 0px;
}
/* HORIZONTAL RULES
=============================================================================*/
hr {
clear: both;
margin: 15px 0;
height: 0px;
overflow: hidden;
border: none;
background: transparent;
border-bottom: 4px solid #ddd;
padding: 0;
}
/* TABLES
=============================================================================*/
table th {
font-weight: bold;
}
table th, table td {
border: 1px solid #ccc;
padding: 6px 13px;
}
table tr {
border-top: 1px solid #ccc;
background-color: #fff;
}
table tr:nth-child(2n) {
background-color: #f8f8f8;
}
/* IMAGES
=============================================================================*/
img {
max-width: 100%
}
</style>
<style type="text/css">
.highlight { background: #ffffff; }
.highlight .c { color: #999988; font-style: italic } /* Comment */
.highlight .err { color: #a61717; background-color: #e3d2d2 } /* Error */
.highlight .k { font-weight: bold } /* Keyword */
.highlight .o { font-weight: bold } /* Operator */
.highlight .cm { color: #999988; font-style: italic } /* Comment.Multiline */
.highlight .cp { color: #999999; font-weight: bold } /* Comment.Preproc */
.highlight .c1 { color: #999988; font-style: italic } /* Comment.Single */
.highlight .cs { color: #999999; font-weight: bold; font-style: italic } /* Comment.Special */
.highlight .gd { color: #000000; background-color: #ffdddd } /* Generic.Deleted */
.highlight .gd .x { color: #000000; background-color: #ffaaaa } /* Generic.Deleted.Specific */
.highlight .ge { font-style: italic } /* Generic.Emph */
.highlight .gr { color: #aa0000 } /* Generic.Error */
.highlight .gh { color: #999999 } /* Generic.Heading */
.highlight .gi { color: #000000; background-color: #ddffdd } /* Generic.Inserted */
.highlight .gi .x { color: #000000; background-color: #aaffaa } /* Generic.Inserted.Specific */
.highlight .go { color: #888888 } /* Generic.Output */
.highlight .gp { color: #555555 } /* Generic.Prompt */
.highlight .gs { font-weight: bold } /* Generic.Strong */
.highlight .gu { color: #aaaaaa } /* Generic.Subheading */
.highlight .gt { color: #aa0000 } /* Generic.Traceback */
.highlight .kc { font-weight: bold } /* Keyword.Constant */
.highlight .kd { font-weight: bold } /* Keyword.Declaration */
.highlight .kp { font-weight: bold } /* Keyword.Pseudo */
.highlight .kr { font-weight: bold } /* Keyword.Reserved */
.highlight .kt { color: #445588; font-weight: bold } /* Keyword.Type */
.highlight .m { color: #009999 } /* Literal.Number */
.highlight .s { color: #d14 } /* Literal.String */
.highlight .na { color: #008080 } /* Name.Attribute */
.highlight .nb { color: #0086B3 } /* Name.Builtin */
.highlight .nc { color: #445588; font-weight: bold } /* Name.Class */
.highlight .no { color: #008080 } /* Name.Constant */
.highlight .ni { color: #800080 } /* Name.Entity */
.highlight .ne { color: #990000; font-weight: bold } /* Name.Exception */
.highlight .nf { color: #990000; font-weight: bold } /* Name.Function */
.highlight .nn { color: #555555 } /* Name.Namespace */
.highlight .nt { color: #000080 } /* Name.Tag */
.highlight .nv { color: #008080 } /* Name.Variable */
.highlight .ow { font-weight: bold } /* Operator.Word */
.highlight .w { color: #bbbbbb } /* Text.Whitespace */
.highlight .mf { color: #009999 } /* Literal.Number.Float */
.highlight .mh { color: #009999 } /* Literal.Number.Hex */
.highlight .mi { color: #009999 } /* Literal.Number.Integer */
.highlight .mo { color: #009999 } /* Literal.Number.Oct */
.highlight .sb { color: #d14 } /* Literal.String.Backtick */
.highlight .sc { color: #d14 } /* Literal.String.Char */
.highlight .sd { color: #d14 } /* Literal.String.Doc */
.highlight .s2 { color: #d14 } /* Literal.String.Double */
.highlight .se { color: #d14 } /* Literal.String.Escape */
.highlight .sh { color: #d14 } /* Literal.String.Heredoc */
.highlight .si { color: #d14 } /* Literal.String.Interpol */
.highlight .sx { color: #d14 } /* Literal.String.Other */
.highlight .sr { color: #009926 } /* Literal.String.Regex */
.highlight .s1 { color: #d14 } /* Literal.String.Single */
.highlight .ss { color: #990073 } /* Literal.String.Symbol */
.highlight .bp { color: #999999 } /* Name.Builtin.Pseudo */
.highlight .vc { color: #008080 } /* Name.Variable.Class */
.highlight .vg { color: #008080 } /* Name.Variable.Global */
.highlight .vi { color: #008080 } /* Name.Variable.Instance */
.highlight .il { color: #009999 } /* Literal.Number.Integer.Long */
.pl-c {
color: #969896;
}
.pl-c1,.pl-mdh,.pl-mm,.pl-mp,.pl-mr,.pl-s1 .pl-v,.pl-s3,.pl-sc,.pl-sv {
color: #0086b3;
}
.pl-e,.pl-en {
color: #795da3;
}
.pl-s1 .pl-s2,.pl-smi,.pl-smp,.pl-stj,.pl-vo,.pl-vpf {
color: #333;
}
.pl-ent {
color: #63a35c;
}
.pl-k,.pl-s,.pl-st {
color: #a71d5d;
}
.pl-pds,.pl-s1,.pl-s1 .pl-pse .pl-s2,.pl-sr,.pl-sr .pl-cce,.pl-sr .pl-sra,.pl-sr .pl-sre,.pl-src,.pl-v {
color: #df5000;
}
.pl-id {
color: #b52a1d;
}
.pl-ii {
background-color: #b52a1d;
color: #f8f8f8;
}
.pl-sr .pl-cce {
color: #63a35c;
font-weight: bold;
}
.pl-ml {
color: #693a17;
}
.pl-mh,.pl-mh .pl-en,.pl-ms {
color: #1d3e81;
font-weight: bold;
}
.pl-mq {
color: #008080;
}
.pl-mi {
color: #333;
font-style: italic;
}
.pl-mb {
color: #333;
font-weight: bold;
}
.pl-md,.pl-mdhf {
background-color: #ffecec;
color: #bd2c00;
}
.pl-mdht,.pl-mi1 {
background-color: #eaffea;
color: #55a532;
}
.pl-mdr {
color: #795da3;
font-weight: bold;
}
.pl-mo {
color: #1d3e81;
}
.task-list {
padding-left:10px;
margin-bottom:0;
}
.task-list li {
margin-left: 20px;
}
.task-list-item {
list-style-type:none;
padding-left:10px;
}
.task-list-item label {
font-weight:400;
}
.task-list-item.enabled label {
cursor:pointer;
}
.task-list-item+.task-list-item {
margin-top:3px;
}
.task-list-item-checkbox {
display:inline-block;
margin-left:-20px;
margin-right:3px;
vertical-align:1px;
}
</style>
</head>
<body>
<h1>jsoncons: a C++ library for json construction</h1>
<p>jsoncons is a C++ library for the construction of <a href="http://www.json.org">JavaScript Object Notation (JSON)</a>. It supports parsing a JSON file or string into a tree structured <code>json</code> value, building a <code>json</code> value in C++ code, and serializing a <code>json</code> value to a file or string. It also provides an event-based API for reading and writing JSON documents that are too large to fit into available memory, somewhat analogously to SAX processing in the XML world. Consult the wiki for the latest <a href="https://github.com/danielaparker/jsoncons/wiki">documentation and tutorials</a> and <a href="https://github.com/danielaparker/jsoncons/wiki/Roadmap">roadmap</a>. </p>
<p>jsoncons uses some features that are new to C++ 11, particularly move semantics, however, it has been written to be compatible with VC++ 10 SP1 (note that SP1 is required for VC++ 10, it fixes compiler bugs with move semantics.) It has been tested with MS Visual C++ 10 SP1, Intel C++ Studio XE 2013, clang 3.3 and GCC 4.8. </p>
<p>The <a href="https://github.com/danielaparker/jsoncons">code repository</a> and <a href="https://github.com/danielaparker/jsoncons/releases">releases</a> are on github. It is distributed under the <a href="http://www.boost.org/users/license.html">Boost Software License</a></p>
<p>The library has a number of features, which are listed below:</p>
<ul>
<li>Uses the standard C++ input/output streams library</li>
<li>Implements parsing and serializing JSON text in UTF-8 for narrow character strings and streams</li>
<li>Supports UTF16 (UTF32) encodings with size 2 (size 4) wide characters</li>
<li>Correctly handles surrogate pairs in \uXXXX escape sequences</li>
<li>Supports event based JSON parsing and serializing with user defined input and output handlers</li>
<li>Guarantees basic exception safety (no leaks)</li>
<li>Accepts and ignores single line comments that start with //, and multi line comments that start with /* and end with */</li>
<li>Supports optional escaping of the solidus (/) character</li>
<li>Supports Nan, Inf and -Inf replacement</li>
<li>Supports reading multiple json objects from a stream</li>
<li>Supports optional escaping of non-ascii UTF-8 octets</li>
<li>Allows extensions to the types accepted by the json class accessors and modifiers</li>
<li>Supports storing "any" values in a json object or array, with specialized serialization</li>
<li>Supports reading (writing) JSON values from (to) CSV files</li>
</ul>
<h2>What's new on master</h2>
<ul>
<li>Incorporates test suite files from <a href="http://www.json.org/JSON_checker/">http://www.json.org/JSON_checker/</a> into test suite</li>
<li>The <code>jsoncons</code> parser accepts all of the JSON_checker files that its supposed to accept.</li>
<li>Failures to reject incorrect exponential notation (e.g. [0e+-1]) have been fixed.</li>
<li>
<p>The <code>jsoncons</code> parser now rejects all of the JSON_checker files that its supposed to reject except ones with stuff after the end of the document, e.g.</p>
<p>["Extra close"]]</p>
<p>(Currently the <code>jsoncons</code> parser stops after reading a full <code>json</code> document, and supports reading a sequence of documents.) </p>
</li>
</ul>
<h2>Using the code</h2>
<p>The jsoncons library is header-only: it consists solely of header files containing templates and inline functions, and requires no separately-compiled library binaries when linking. It has no dependence on other libraries. The accompanying test suite uses boost, but not the library itself.</p>
<p>To install the jsoncons library, download the zip file, unpack the release, under <code>src</code> find the directory <code>jsoncons</code>, and copy it to your <code>include</code> directory. If you wish to use extensions, copy the <code>jsoncons_ext</code> directory as well. </p>
<p>The jsoncons classes and functions are in namespace <code>jsoncons</code>. Namespace <code>jsoncons</code> includes a name for a null type defined as an empty struct:</p>
<pre><code>struct null_type{}
</code></pre>
<p>These include and using declarations are for the examples that appear below.</p>
<pre><code>#include "jsoncons/json.hpp"
using std::string;
using std::cout;
using std::cerr;
using std::endl;
using jsoncons::json;
using jsoncons::json_exception;
using jsoncons::pretty_print;
</code></pre>
<h3>Reading json values from a file</h3>
<p>Here is a sample file (books.json):</p>
<pre><code>[
{
"title" : "Kafka on the Shore",
"author" : "Haruki Murakami",
"price" : 25.17
},
{
"title" : "Women: A Novel",
"author" : "Charles Bukowski",
"price" : 12.00
},
{
"title" : "Cutter's Way",
"author" : "Ivan Passer"
}
]
</code></pre>
<p>You can read the file into a json value like this</p>
<pre><code>json books = json::parse_file("books.json");
</code></pre>
<p>You can then loop through the books</p>
<pre><code>for (size_t i = 0; i < books.size(); ++i)
{
try
{
json& book = books[i];
string author = book["author"].as<string>();
string title = book["title"].as<string>();
double price = book["price"].as<double>();
cout << author << ", " << title << ", " << price << endl;
}
catch (const json_exception& e)
{
cerr << e.what() << endl;
}
}
</code></pre>
<p>The output is</p>
<pre><code>Haruki Murakami, Kafka on the Shore, 25.17
Charles Bukowski, Women: A Novel, 12
Member price not found.
</code></pre>
<p>Note that the third book is missing a price, which causes an exception to be thrown.</p>
<p>You have a choice of accessors:</p>
<pre><code>book["price"] will throw if there is no price
book.get("price") will return json::null if there is no price
book.get("price",default_value) will return default_value if there is no price
</code></pre>
<p>So if you want to show "n/a" for the missing price, you can use this accessor</p>
<pre><code>string price = book.get("price","n/a").as<string>();
</code></pre>
<p>and the output becomes</p>
<pre><code>Haruki Murakami, Kafka on the Shore, 25.17
Charles Bukowski, Women: A Novel, 12.0
Ivan Passer, Cutter's Way, n/a
</code></pre>
<p>Or you can check if book has a member "price" with the method <code>has_member</code>, and output accordingly,</p>
<pre><code>if (book.has_member("price"))
{
double price = book["price"].as<double>();
cout << price;
}
else
{
cout << "n/a";
}
</code></pre>
<h3>Constructing json values in C++</h3>
<p>To construct an empty json object, use the default constructor:</p>
<pre><code> json image_sizing;
</code></pre>
<p>Serializing it to standard out</p>
<pre><code>cout << image_sizing << endl;
</code></pre>
<p>produces</p>
<pre><code>{}
</code></pre>
<p>Adding some members,</p>
<pre><code>image_sizing["resize_to_fit"] = true; // a boolean
image_sizing["resize_unit"] = "pixels"; // a string
image_sizing["resize_what"] = "long_edge"; // a string
image_sizing["dimension1"] = 9.84; // a double
image_sizing["dimension2"] = json::null; // a null
</code></pre>
<p>Serializing it, this time with pretty print,</p>
<pre><code>cout << pretty_print(image_sizing) << endl;
</code></pre>
<p>produces</p>
<pre><code>{
"dimension1":9.84,
"dimension2":null,
"resize_to_fit":true,
"resize_unit":"pixels",
"resize_what":"long_edge"
}
</code></pre>
<p>To construct a json array, use the copy constructor with a prototype json array:</p>
<pre><code>json image_formats(json::an_array);
</code></pre>
<p>Adding some elements,</p>
<pre><code>image_formats.add("JPEG");
image_formats.add("PSD");
image_formats.add("TIFF");
image_formats.add("DNG");
</code></pre>
<p>Combining the two</p>
<pre><code>json file_export;
file_export["image_formats"] = std::move(image_formats);
file_export["image_sizing"] = std::move(image_sizing);
</code></pre>
<p>and serializing</p>
<pre><code>cout << pretty_print(file_export) << endl;
</code></pre>
<p>produces</p>
<pre><code>{
"image_formats":
["JPEG","PSD","TIFF","DNG"],
"image_sizing":
{
"dimension1":9.84,
"dimension2":null,
"resize_to_fit":true,
"resize_unit":"pixels",
"resize_what":"long_edge"
}
}
</code></pre>
<h3>Iterators</h3>
<p><code>jsoncons::json</code> supports iterators for accessing the members of json objects and the elements of json arrays.</p>
<p>An example of iterating over the name-value pairs of a json object:</p>
<pre><code>json person;
person["first_name"] = "Jane";
person["last_name"] = "Roe";
person["events_attended"] = 10;
person["accept_waiver_of_liability"] = true;
for (auto it = person.begin_members(); it != person.end_members(); ++it)
{
cout << "name=" << it->name() << ", value=" << it->value().as<string>() << endl;
}
</code></pre>
<p>An example of iterating over the elements of a json array:</p>
<pre><code>json cities(json::an_array);
cities.add("Montreal");
cities.add("Toronto");
cities.add("Ottawa");
cities.add("Vancouver");
for (auto it = cities.begin_elements(); it != cities.end_elements(); ++it)
{
cout << it->as<string>() << endl;
}
</code></pre>
<h2>About jsoncons::json</h2>
<p>The json class is an instantiation of the <code>basic_json</code> class template that uses <code>char</code> as the character type<br>
and <code>std::allocator<void></code> as the allocator type,</p>
<pre><code>typedef basic_json<char,std::allocator<void>> json
</code></pre>
<p>The library includes an instantiation for wide characters as well,</p>
<pre><code>typedef basic_json<wchar_t,std::allocator<void>> wjson
</code></pre>
<p>Note that the allocator type allows you to supply a custom allocator for dynamically allocated, <br>
fixed size small objects in the json container, the container rebinds it as necessay. <br>
For instance, you can use the boost <code>fast_pool_allocator</code>:</p>
<pre><code>#include <boost/pool/pool_alloc.hpp>
#include "jsoncons/json.hpp"
typedef jsoncons::basic_json<char, boost::fast_pool_allocator<void>> myjson;
myjson o;
o.set("FirstName","Joe");
o.set("LastName","Smith");
</code></pre>
<p>This results in a json object instance being allocated from the boost memory pool. <br>
The allocator type is not used for structures including vectors and strings that use large or variable amounts of memory, <br>
these always use the default allocators.</p>
<h2>Wide character support</h2>
<p>jsoncons supports wide character strings and streams with <code>wjson</code> and <code>wjson_reader</code>. It supports <code>UTF16</code> encoding if <code>wchar_t</code> has size 2 (Windows) and <code>UTF32</code> encoding if <code>wchar_t</code> has size 4. You can construct a <code>wjson</code> value in exactly the same way as a <code>json</code> value, for instance:</p>
<pre><code>using jsoncons::wjson;
wjson root;
root[L"field1"] = L"test";
root[L"field2"] = 3.9;
root[L"field3"] = true;
std::wcout << root << L"\n";
</code></pre>
<p>which prints</p>
<pre><code>{"field1":"test","field2":3.9,"field3":true}
</code></pre>
<h2>Type extensibility</h2>
<p>In the json class, accessors and modifiers are templated, for example,</p>
<pre><code>template<typename T>
bool is() const
template<typename T>
T as() const
template <typename T>
basic_json& operator=(T val)
</code></pre>
<p>The implementations of these functions and operators make use of the class template <code>json_type_traits</code></p>
<pre><code>template <typename Char, typename Alloc, typename T>
class json_type_traits
{
public:
bool is(const basic_json& val) const {return false;}
T as(const basic_json& val) const;
void assign(basic_json& self, const T val);
};
</code></pre>
<p>This class template is extensible, you as a user can extend <code>json_type_traits</code> in the <code>jsoncons</code> namespace with your own types. You can, for example, extend <code>json_type_traits</code> to access and modify <code>json</code> structures with <code>boost::gregorian::date values</code>, and in your code, write</p>
<pre><code>json deal;
deal["maturity"] = boost::gregorian::date(2015,1,1);
json observation_dates(json::an_array);
observation_dates.add(boost::gregorian::date(2013,10,21));
observation_dates.add(boost::gregorian::date(2013,10,28));
deal["observation_dates"] = std::move(observation_dates);
boost::gregorian::date maturity = deal["maturity"].as<boost::gregorian::date>();
cout << deal << endl;
</code></pre>
<p>producing</p>
<pre><code>{
"maturity":"2015-01-01",
"observation_dates":
["2013-10-21","2013-10-28"]
}
</code></pre>
<h2>json any</h2>
<p>jsoncons provides a class <code>json::any</code> that can contain a value of <br>
any type as long as that type supports copy construction and <br>
assignment. This allows you to, for example, insert a boost matrix into a <code>json</code> object, <br>
and to retrieve it back cast to the appropriate type. You can do so by wrapping it in<br>
a <code>json::any value</code>, like this:</p>
<pre><code>#include "jsoncons/json.hpp"
#include <boost/numeric/ublas/matrix.hpp>
using jsoncons::json;
using boost::numeric::ublas::matrix;
json obj;
matrix<double> A(2,2);
A(0,0) = 1;
A(0,1) = 2;
A(1,0) = 3;
A(1,1) = 4;
obj.set("mydata",json::any(A));
matrix<double>& B = obj["mydata"].any_cast<matrix<double>>();
</code></pre>
<h3>Acknowledgements</h3>
<p>Special thanks to our <a href="https://github.com/danielaparker/jsoncons/blob/master/acknowledgements.txt">contributors</a></p>
</body>
</html>
<!-- This document was created with MarkdownPad, the Markdown editor for Windows (http://markdownpad.com) -->