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Complete documentation for 3.11.0 (#3464)

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* 👥 update contributor and sponsor list

* 🚧 document BJData format

* 🚧 document BJData format

* 📝 clarified documentation of [json.exception.parse_error.112]

* ✏️ adjust titles

* 📝 add more examples

* 🚨 adjust warnings for index.md files

* 📝 add more examples

* 🔥 remove example for deprecated code

* 📝 add missing enum entry

* 📝 overwork table for binary formats

* ✅ add test to create table for binary formats

* 📝 fix wording in example

* 📝 add more examples

* Update iterators.md (#3481)

* ✨ add check for overloads to linter #3455

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* 🎨 fix indentation

* 🔥 remove example for destructor

* 📝 overwork documentation

* Updated BJData documentation, #3464 (#3493)

* update bjdata.md for #3464

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Co-authored-by: Chaoqi Zhang <prncoprs@163.com>
Co-authored-by: Qianqian Fang <fangqq@gmail.com>
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Niels Lohmann
2022-05-17 13:08:56 +02:00
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docs/mkdocs/docs/features/binary_values.md
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@@ -1,8 +1,12 @@
# Binary Values
The library implements several [binary formats](binary_formats/index.md) that encode JSON in an efficient way. Most of these formats support binary values; that is, values that have semantics define outside the library and only define a sequence of bytes to be stored.
The library implements several [binary formats](binary_formats/index.md) that encode JSON in an efficient way. Most of
these formats support binary values; that is, values that have semantics define outside the library and only define a
sequence of bytes to be stored.
JSON itself does not have a binary value. As such, binary values are an extension that this library implements to store values received by a binary format. Binary values are never created by the JSON parser, and are only part of a serialized JSON text if they have been created manually or via a binary format.
JSON itself does not have a binary value. As such, binary values are an extension that this library implements to store
values received by a binary format. Binary values are never created by the JSON parser, and are only part of a
serialized JSON text if they have been created manually or via a binary format.
## API for binary values
@@ -19,7 +23,9 @@ class json::binary_t {
"std::vector<uint8_t>" <|-- json::binary_t
```
By default, binary values are stored as `std::vector<std::uint8_t>`. This type can be changed by providing a template parameter to the `basic_json` type. To store binary subtypes, the storage type is extended and exposed as `json::binary_t`:
By default, binary values are stored as `std::vector<std::uint8_t>`. This type can be changed by providing a template
parameter to the `basic_json` type. To store binary subtypes, the storage type is extended and exposed as
`json::binary_t`:
```cpp
auto binary = json::binary_t({0xCA, 0xFE, 0xBA, 0xBE});
@@ -87,7 +93,9 @@ Binary values are serialized differently according to the formats.
### JSON
JSON does not have a binary type, and this library does not introduce a new type as this would break conformance. Instead, binary values are serialized as an object with two keys: `bytes` holds an array of integers, and `subtype` is an integer or `null`.
JSON does not have a binary type, and this library does not introduce a new type as this would break conformance.
Instead, binary values are serialized as an object with two keys: `bytes` holds an array of integers, and `subtype`
is an integer or `null`.
??? example
@@ -115,11 +123,72 @@ JSON does not have a binary type, and this library does not introduce a new type
!!! warning "No roundtrip for binary values"
The JSON parser will not parse the objects generated by binary values back to binary values. This is by design to remain standards compliant. Serializing binary values to JSON is only implemented for debugging purposes.
The JSON parser will not parse the objects generated by binary values back to binary values. This is by design to
remain standards compliant. Serializing binary values to JSON is only implemented for debugging purposes.
### BJData
[BJData](binary_formats/bjdata.md) neither supports binary values nor subtypes, and proposes to serialize binary values
as array of uint8 values. This translation is implemented by the library.
??? example
Code:
```cpp
// create a binary value of subtype 42 (will be ignored in BJData)
json j;
j["binary"] = json::binary({0xCA, 0xFE, 0xBA, 0xBE}, 42);
// convert to BJData
auto v = json::to_bjdata(j);
```
`v` is a `std::vector<std::uint8t>` with the following 20 elements:
```c
0x7B // '{'
0x69 0x06 // i 6 (length of the key)
0x62 0x69 0x6E 0x61 0x72 0x79 // "binary"
0x5B // '['
0x55 0xCA 0x55 0xFE 0x55 0xBA 0x55 0xBE // content (each byte prefixed with 'U')
0x5D // ']'
0x7D // '}'
```
The following code uses the type and size optimization for UBJSON:
```cpp
// convert to UBJSON using the size and type optimization
auto v = json::to_bjdata(j, true, true);
```
The resulting vector has 22 elements; the optimization is not effective for examples with few values:
```c
0x7B // '{'
0x23 0x69 0x01 // '#' 'i' type of the array elements: unsigned integers
0x69 0x06 // i 6 (length of the key)
0x62 0x69 0x6E 0x61 0x72 0x79 // "binary"
0x5B // '[' array
0x24 0x55 // '$' 'U' type of the array elements: unsigned integers
0x23 0x69 0x04 // '#' i 4 number of array elements
0xCA 0xFE 0xBA 0xBE // content
```
Note that subtype (42) is **not** serialized and that UBJSON has **no binary type**, and deserializing `v` would
yield the following value:
```json
{
"binary": [202, 254, 186, 190]
}
```
### BSON
[BSON](binary_formats/bson.md) supports binary values and subtypes. If a subtype is given, it is used and added as unsigned 8-bit integer. If no subtype is given, the generic binary subtype 0x00 is used.
[BSON](binary_formats/bson.md) supports binary values and subtypes. If a subtype is given, it is used and added as
unsigned 8-bit integer. If no subtype is given, the generic binary subtype 0x00 is used.
??? example
@@ -159,7 +228,9 @@ JSON does not have a binary type, and this library does not introduce a new type
### CBOR
[CBOR](binary_formats/cbor.md) supports binary values, but no subtypes. Subtypes will be serialized as tags. Any binary value will be serialized as byte strings. The library will choose the smallest representation using the length of the byte array.
[CBOR](binary_formats/cbor.md) supports binary values, but no subtypes. Subtypes will be serialized as tags. Any binary
value will be serialized as byte strings. The library will choose the smallest representation using the length of the
byte array.
??? example
@@ -185,7 +256,8 @@ JSON does not have a binary type, and this library does not introduce a new type
0xCA 0xFE 0xBA 0xBE // content
```
Note that the subtype is serialized as tag. However, parsing tagged values yield a parse error unless `json::cbor_tag_handler_t::ignore` or `json::cbor_tag_handler_t::store` is passed to `json::from_cbor`.
Note that the subtype is serialized as tag. However, parsing tagged values yield a parse error unless
`json::cbor_tag_handler_t::ignore` or `json::cbor_tag_handler_t::store` is passed to `json::from_cbor`.
```json
{
@@ -198,7 +270,9 @@ JSON does not have a binary type, and this library does not introduce a new type
### MessagePack
[MessagePack](binary_formats/messagepack.md) supports binary values and subtypes. If a subtype is given, the ext family is used. The library will choose the smallest representation among fixext1, fixext2, fixext4, fixext8, ext8, ext16, and ext32. The subtype is then added as signed 8-bit integer.
[MessagePack](binary_formats/messagepack.md) supports binary values and subtypes. If a subtype is given, the ext family
is used. The library will choose the smallest representation among fixext1, fixext2, fixext4, fixext8, ext8, ext16, and
ext32. The subtype is then added as signed 8-bit integer.
If no subtype is given, the bin family (bin8, bin16, bin32) is used.
@@ -239,7 +313,8 @@ If no subtype is given, the bin family (bin8, bin16, bin32) is used.
### UBJSON
[UBJSON](binary_formats/ubjson.md) neither supports binary values nor subtypes, and proposes to serialize binary values as array of uint8 values. This translation is implemented by the library.
[UBJSON](binary_formats/ubjson.md) neither supports binary values nor subtypes, and proposes to serialize binary values
as array of uint8 values. This translation is implemented by the library.
??? example
@@ -251,7 +326,7 @@ If no subtype is given, the bin family (bin8, bin16, bin32) is used.
j["binary"] = json::binary({0xCA, 0xFE, 0xBA, 0xBE}, 42);
// convert to UBJSON
auto v = json::to_msgpack(j);
auto v = json::to_ubjson(j);
```
`v` is a `std::vector<std::uint8t>` with the following 20 elements:
@@ -287,7 +362,8 @@ If no subtype is given, the bin family (bin8, bin16, bin32) is used.
0xCA 0xFE 0xBA 0xBE // content
```
Note that subtype (42) is **not** serialized and that UBJSON has **no binary type**, and deserializing `v` would yield the following value:
Note that subtype (42) is **not** serialized and that UBJSON has **no binary type**, and deserializing `v` would
yield the following value:
```json
{