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|
### jsoncons data model
The jsoncons data model supports the familiar JSON types - nulls,
booleans, numbers, strings, arrays, objects - plus byte strings.
Type|Description
----|-----------
null|
bool|
uint64|
int64|
half|Half precision floating point
double|Double precision floating point
string|
byte string|
array|
object|
In addition, jsoncons supports semantic tagging of values, allows it to preserve
these type semantics when parsing JSON-like data formats such as CBOR that have them.
Tag|Description
---|-----------
undefined |
datetime |
epoch_second |
epoch_milli |
epoch_nano |
bigint |
bigdec |
float128 |
bigfloat |
base16 |
base64 |
base64url |
uri |
clamped |
multi_dim_row_major |
multi_dim_column_major |
ext |
id |
regex |
code |
### Examples
#### Mappings between CBOR and jsoncons data items
CBOR data item|CBOR tag | jsoncons data item|jsoncons tag
---------------|------------------------------------------------| --------------|------------------
null |  | null |
undefined |  | null | undefined
true or false |  | bool |
unsigned or negative integer |  | int64 |
unsigned or negative integer | 1 (epoch-based date/time) | int64 | seconds
unsigned integer |  | uint64 |
unsigned integer | 1 (epoch-based date/time) | uint64 | seconds
half-precision float, float, or double |  | half |
float or double |  | double |
double | 1 (epoch-based date/time) | double | seconds
string |  | string |
byte string | 2 (positive bignum) or 2 (negative bignum) | string | bigint
array | 4 (decimal fraction) | string | bigdec
array | 5 (bigfloat) | string | bigfloat
string | 0 (date/time string) | string | datetime
string | 32 (uri) | string | uri
string | 33 (base64url) | string | base64url
string | 34 (base64) | string | base64
byte string |  | byte_string |
byte string | 21 (Expected conversion to base64url encoding) | byte_string | base64url
byte string | 22 (Expected conversion to base64 encoding) | byte_string | base64
byte string | 23 (Expected conversion to base16 encoding) | byte_string | base16
array |  | array |
map |  | object |
#### json value to CBOR item
```cpp
#include <jsoncons/json.hpp>
#include <jsoncons_ext/cbor/cbor.hpp>
using namespace jsoncons;
int main()
{
json j(json_array_arg);
j.emplace_back("foo");
std::vector<uint8_t> bstr = {'b','a','r'};
j.emplace_back(byte_string_arg, bstr);
j.emplace_back("-18446744073709551617", semantic_tag::bigint);
j.emplace_back("273.15", semantic_tag::bigdec);
j.emplace_back("2018-10-19 12:41:07-07:00", semantic_tag::datetime);
j.emplace_back(1431027667, semantic_tag::epoch_second);
j.emplace_back(-1431027667, semantic_tag::epoch_second);
j.emplace_back(1431027667.5, semantic_tag::epoch_second);
std::cout << "(1)\n" << pretty_print(j) << "\n\n";
std::vector<uint8_t> bytes;
cbor::encode_cbor(j, bytes);
std::cout << "(2)\n" << byte_string_view(bytes) << "\n\n";
/*
88 -- Array of length 8
63 -- String value of length 3
666f6f -- "foo"
43 -- Byte string value of length 3
626172 -- 'b''a''r'
c3 -- Tag 3 (negative bignum)
49 Byte string value of length 9
010000000000000000 -- Bytes content
c4 - Tag 4 (decimal fraction)
82 -- Array of length 2
21 -- -2
19 6ab3 -- 27315
c0 -- Tag 0 (date-time)
78 19 -- Length (25)
323031382d31302d31392031323a34313a30372d30373a3030 -- "2018-10-19 12:41:07-07:00"
c1 -- Tag 1 (epoch time)
1a -- uint32_t
554bbfd3 -- 1431027667
c1
3a
554bbfd2
c1
fb
41d552eff4e00000
*/
}
```
Output
```
(1)
[
"foo",
"YmFy",
"-18446744073709551617",
"273.15",
"2018-10-19 12:41:07-07:00",
1431027667,
-1431027667,
1431027667.5
]
(2)
88,63,66,6f,6f,43,62,61,72,c3,49,01,00,00,00,00,00,00,00,00,c4,82,21,19,6a,b3,c0,78,19,32,30,31,38,2d,31,30,2d,31,39,20,31,32,3a,34,31,3a,30,37,2d,30,37,3a,30,30,c1,1a,55,4b,bf,d3,c1,3a,55,4b,bf,d2,c1,fb,41,d5,52,ef,f4,e0,00,00
```
#### CBOR item to json value
```cpp
#include <jsoncons/json.hpp>
#include <jsoncons_ext/cbor/cbor.hpp>
using namespace jsoncons;
void main()
{
std::vector<uint8_t> bytes;
cbor::cbor_bytes_encoder encoder(bytes);
encoder.begin_array(); // indefinite length outer array
encoder.string_value("foo");
encoder.byte_string_value(byte_string{'b','a','r'});
encoder.string_value("-18446744073709551617", semantic_tag::bigint);
encoder.string_value("273.15", semantic_tag::bigdec);
encoder.string_value("2018-10-19 12:41:07-07:00", semantic_tag::datetime) ;
encoder.int64_value(1431027667, semantic_tag::epoch_second);
encoder.int64_value(-1431027667, semantic_tag::epoch_second);
encoder.double_value(1431027667.5, semantic_tag::epoch_second);
encoder.end_array();
encoder.flush();
std::cout << "(1)\n" << byte_string_view(bytes) << "\n\n";
/*
9f -- Start indefinite length array
63 -- String value of length 3
666f6f -- "foo"
43 -- Byte string value of length 3
626172 -- 'b''a''r'
c3 -- Tag 3 (negative bignum)
49 Byte string value of length 9
010000000000000000 -- Bytes content
c4 - Tag 4 (decimal fraction)
82 -- Array of length 2
21 -- -2
19 6ab3 -- 27315
c0 -- Tag 0 (date-time)
78 19 -- Length (25)
323031382d31302d31392031323a34313a30372d30373a3030 -- "2018-10-19 12:41:07-07:00"
c1 -- Tag 1 (epoch time)
1a -- uint32_t
554bbfd3 -- 1431027667
c1
3a
554bbfd2
c1
fb
41d552eff4e00000
ff -- "break"
*/
json j = cbor::decode_cbor<json>(bytes);
std::cout << "(2)\n" << pretty_print(j) << "\n\n";
```
Output:
```
(1)
9f,63,66,6f,6f,43,62,61,72,c3,49,01,00,00,00,00,00,00,00,00,c4,82,21,19,6a,b3,c0,78,19,32,30,31,38,2d,31,30,2d,31,39,20,31,32,3a,34,31,3a,30,37,2d,30,37,3a,30,30,c1,1a,55,4b,bf,d3,c1,3a,55,4b,bf,d2,c1,fb,41,d5,52,ef,f4,e0,00,00,ff
(2)
[
"foo",
"YmFy",
"-18446744073709551617",
"273.15",
"2018-10-19 12:41:07-07:00",
1431027667,
-1431027667,
1431027667.5
]
```
|
