@title[JSON]
@snap[midpoint slide1]
<h1>JSON</h1>
<br/>
<b style="color: crimson;">J</b>ava<b style="color: crimson;">S</b>cript
<b style="color: crimson;">O</b>bject
<b style="color: crimson;">N</b>otation
@snapend
@snap[south-east author-box]
@fa[envelope](prataprc@gmail.com - R Pratap Chakravarthy) <br/>
@fa[github](https://github.com/bnclabs/jsondata) <br/>
@snapend
---
Why JSON ?
==========
<br/>
@snap[fragment text-center text-blue]
Web standard for data exchange.
@snapend
@snap[mt30 fragment text-center text-green]
Inter-operability with several languages.
@snapend
@snap[mt30 fragment text-center text-black]
Human friendly as apposed to machine friendly.
@snapend
---
Data types
==========
JSON defines the least common subset of data types across
sevaral languages.
@snap[fragment mt30]
<b>Primitive types</b>
@snapend
@ul
* **null**, equivalent of None, nil, null in many languages.
* **number**, base 10 representation.
* **bool**, true or false. Both represented in lowercase.
* **string**, double quoted, utf8 encoded plain text.
@ulend
@snap[fragment mt30]
<b>Structured types</b>
@snapend
@ul
* **Array**, heterogenous collection of other types, with number index.
* **Object**, heterogenous collection of other types, with string index.
@ulend
+++
Examples
========
@snap[fragment text-center text-12]
"Hello world!"
@snapend
<br/>
@snap[fragment text-center text-12]
42
@snapend
<br/>
@snap[fragment text-center text-12]
true
@snapend
<br/>
@snap[fragment text-center text-12]
null
@snapend
+++
Examples: Numbers
=================
@snap[west ml20 text-12]
<pre style="line-height: 2em">
132837
-132837
0
.123
0.123
-0.123
-.123
1e2
</pre>
@snapend
@snap[east mr20 text-12]
<pre style="line-height: 2em">
-1e+2
1e-2
-1e-2
.123e2
0.123e+2
-0.123e-2
-.123e+2
-1.123e+2
</pre>
@snapend
---
Numbers
=======
@snap[mt30 fragment]
Integer numbers within the range [-(2^53)+1, (2^53)-1] are generally considered interoperable.
@snapend
@snap[mt30 fragment]
Floating point numbers shall support accuracy and precision defined by IEEE 754 binary64 (double precision).
@snapend
---
Strings
=======
```bnf
string: '"' utf8-unicode-chars '"'.
```
@snap[mt30 fragment]
Unicode chars that needs to be escaped:
@snapend
@ul[mt30]
* Quotation mark (").
* Reverse solidus (\\).
* Control characters (U+0000 through U+001F)
@ulend
---
Example: object
===============
```json
{
"Image": {
"Width": 800,
"Height": 600,
"Title": "View from 15th Floor",
"Thumbnail": {
"Url": "http://www.example.com/image/481989943",
"Height": 125,
"Width": 100
},
"Animated" : false,
"IDs": [116, 943, 234, 38793]
}
}
```
---
Example: array
==============
```json
[
{
"precision": "zip",
"Latitude": 37.7668,
"Longitude": -122.3959,
"Address": "",
"Country": "US"
},
{
"precision": "zip",
"Latitude": 37.371991,
"Longitude": -122.026020,
"Address": "",
"Country": "US"
}
]
```
---
Grammar
=======
```bnf
string : '"' chars '"'.
number : "-"? int frac? exp?.
exp : ("e"|"E") (-|+)? [0-9]+.
object : "{" property \*(comma property) "}".
property : string ":" value.
array : "[" value \*(comma value) "]".
```
+++
Whitespace
==========
JSON has a free-form syntax, meaning all forms of whitespace
serve only to separate tokens in the grammar, and have no
semantic significance.
```bnf
horizontal-tab : %x09
new-line : %x0A
cr : %x0D // Carriage-Return
```
---
128-bit integers
================
@snap[mt30 fragment]
[JSON specification](https://tools.ietf.org/html/rfc8259) do not define
the precision for integer numbers.
@snapend
@snap[mt30 fragment]
While most implementation of JSON handles number as 64-bit floating-point,
[jsondata](https://github.com/bnclabs/jsondata), a rust implementation
to process JSON, support serialization and de-serialisation of signed
128-bit integers.
@snapend
---
Numbers: Deferred conversion
============================
@snap[mt30 fragment]
When used in context of a document-database, parsing JSON data is a
repeated operation, and many times only specific fields within
a JSON document need to be lookedup.
@snapend
@snap[mt30 fragment]
To that end, [jsondata](https://github.com/bnclabs/jsondata) supports
deferred conversion of numbers.
@snapend
+++
Benchmark results
=================
```rust
Without deferred conversion:
test json_test::bench_no_deferred 1,093 ns/iter (+/- 88)
test json_test::bench_num 109 ns/iter (+/- 19)
With deferred conversion:
test json_test::bench_deferred 1,004 ns/iter (+/- 215)
test json_test::bench_num 77 ns/iter (+/- 4)
```
An improvement around 10-30%.
```rust
// bench_no_deferred uses the following sample
r#"[10123.1231, 1231.123123, 1233.123123, 123.1231231, 12312e10]"#;
// bench_num uses the following sample
"123121.2234234"
```
---
JSON Pointer
============
[JSON Pointer][jptr] defines a string syntax for identifying a specific value
within a JSON document.
@snap[fragment]
A JSON pointer text is made of path components separated by @color[blue](/).
@snapend
<div class="fragment mt30">
For Example: @color[blue](/users/0/name) <br/>
@css[text-07]({"users": [ {"name": "joe", age: 20}, {"name": "jack", age: 30}, {"name": "jane", age: 25} ])
<table style="margin: unset" class="mt30">
<tr> <th> path </th> <th> meaning </th> </tr>
<tr> <td>/users</td> <td> fetch the member value with matching key - @color[blue](users) </td> </tr>
<tr> <td>/0 </td> <td> fetch the @color[blue](first value) from an array </td> </tr>
<tr> <td>/name </td> <td> fetch the member value with matching key - @color[blue](name) </td> </tr>
</table>
</div>
[jptr]: https://tools.ietf.org/html/rfc6901
+++
Path matching
=============
@css[text-bold fragment](String-escape)
@snap[fragment]
All instances of quotation mark '"' (%x22), reverse solidus '\' (%x5C),
and control (%x00-1F) characters MUST be un-escaped.
@snapend
@css[text-bold fragment](Tilde-escape)
@snap[fragment]
All instances of ~0 and ~1 must be un-escaped to ~ and /.
@snapend
@css[text-bold fragment](Comparison)
@ul
* If current reference value is an object, path-fragment is compared byte-by-byte with the property name.
* If currently referenced value is a JSON array, path-fragment is interpreted as base-10 integer in ASCII and converted to zero-based index.
@ulend
+++
Example: Result
===============
@img[west jptr-eg span-45](./template/jpt-eg.png)
<table class="east jptr-eg span-45">
<tr><th>pointer-text</th> <th>result</th></tr>
<tr><td>""</td> <td>// the whole document</td></tr>
<tr><td>"/foo"</td> <td>["bar", "baz"]</td></tr>
<tr><td>"/foo/0"</td> <td>"bar"</td></tr>
<tr><td>"/"</td> <td>0</td></tr>
<tr><td>"/a~1b"</td> <td>1</td></tr>
<tr><td>"/c%d"</td> <td>2</td></tr>
<tr><td>"/e^f"</td> <td>3</td></tr>
<tr><td>"/g|h"</td> <td>4</td></tr>
<tr><td>"/i\\j"</td> <td>5</td></tr>
<tr><td>"/k\"l"</td> <td>6</td></tr>
<tr><td>"/ "</td> <td>7</td></tr>
<tr><td>"/m~0n"</td> <td>8</td></tr>
</table>
+++
Grammar
=======
<br/>
```bnf
json-pointer = *( "/" reference-token )
reference-token = *( unescaped | escaped )
```
@ul[mt30]
* %x2F ('/') and %x7E ('~') are excluded from 'unescaped'
* @color[blue](~0) means @color[blue](~)
* @color[blue](~1) means @color[blue](/).
* @color[blue](~) escaping is not applied recursively. @color[blue](~01) literally becomes @color[blue](~1).
@ulend
---
Json5
=====
Corner cases and good to have features that was left out in JSON.
@ul
* Object keys may be an ECMAScript 5.1 IdentifierName.
* Objects may have a single trailing comma.
* Arrays may have a single trailing comma.
* Strings may be single quoted.
* Strings may span multiple lines by escaping new line characters.
* Strings may include character escapes.
* Numbers may be hexadecimal.
* Numbers may have a leading or trailing decimal point.
* Numbers may be IEEE 754 positive infinity, negative infinity, and NaN.
* Numbers may begin with an explicit plus sign.
* Single and multi-line comments are allowed.
* Additional white space characters are allowed.
@ulend
+++
Identifier for bbject key
=========================
<br/>
```json
{
width: 1920,
height: 1080,
}
```
and
```json
{
"width": 1920,
"height": 1080,
}
```
are equivalent.
+++
Trailing comma
==============
<br/>
```json
[
{ name: 'Joe', age: 27, },
{ name: 'Jane', age: 32 },
]
```
and
```json
[
{ name: 'Joe', age: 27 },
{ name: 'Jane', age: 32 }
]
```
are equivalent.
+++
Single quoted strings
=====================
```json
{
image: {
width: 1920,
height: 1080,
'aspect-ratio': '16:9',
}
}
```
and
```json
{
image: {
width: 1920,
height: 1080,
"aspect-ratio": "16:9",
}
}
```
are equivalent.
+++
Multi-line strings
==================
<br/>
```json
"Lorem ipsum dolor sit amet, \
consectetur adipiscing elit."
```
and
```json
'Lorem ipsum dolor sit amet, consectetur adipiscing elit.'
```
are equivalent.
+++
Character escapes in strings
============================
A string containing only a single reverse solidus character
may be represented as ``\x5C`` or ``\u005C``.
A string containing only the musical score character
🎼 (U+1F3BC) may be represented as '\uD83C\uDFBC'.
\' | Apostrophe | U+0027
\" | Quotation mark | U+0022
\\ | Reverse solidus | U+005C
\b | Backspace | U+0008
\f | Form feed | U+000C
\n | Line feed | U+000A
\r | Carriage return | U+000D
\t | Horizontal tab | U+0009
\v | Vertical tab | U+000B
\0 | Null | U+0000
+++
Hexadecimal numbers
===================
<br/>
```json
{
positiveHex: 0xdecaf,
negativeHex: -0xC0FFEE,
}
```
and
```json
{
positiveHex: 912559,
negativeHex: -12648430,
}
```
are equivalent.
+++
Leading/Trailing decimal point
==============================
<br/>
```json
{
integer: 123,
withFractionPart: 123.456,
onlyFractionPart: .456,
trailingPoint: 456.,
withExponent: 123e-456,
}
```
+++
+/- infinity and NaN
====================
<br/>
```json
{
positiveInfinity: Infinity,
negativeInfinity: -Infinity,
notANumber: NaN,
}
```
+++
+ Numbers
=========
<br/>
```json
{
impliedPositive: 123,
explicitPositive: +123,
}
```
+++
Comments
========
<br/>
```json
// This is a single line comment.
/* This is a multi-
line comment. */
```
+++
White space characters
======================
Additional whitespace chars:
U+0009 | Horizontal tab
U+000A | Line feed
U+000B | Vertical tab
U+000C | Form feed
U+000D | Carriage return
U+0020 | Space
U+00A0 | Non-breaking space
U+2028 | Line separator
U+2029 | Paragraph separator
U+FEFF | Byte order mark
Unicode Zs category | Any other character in the Space Separator Unicode category
---
@snap[midpoint]
<h1>Thank you</h1>
@snapend