nlohmann::basic_json::from_bson

// (1)
template<typename InputType>
static basic_json from_bson(InputType&& i,
                            const bool strict = true,
                            const bool allow_exceptions = true);
// (2)
template<typename IteratorType>
static basic_json from_bson(IteratorType first, IteratorType last,
                            const bool strict = true,
                            const bool allow_exceptions = true);

Deserializes a given input to a JSON value using the BSON (Binary JSON) serialization format.

1. Reads from a compatible input.
2. Reads from an iterator range.

The exact mapping and its limitations is described on a dedicated page.

Template parameters

InputType : A compatible input, for instance:

- an `std::istream` object
- a `FILE` pointer
- a C-style array of characters
- a pointer to a null-terminated string of single byte characters
- an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.

IteratorType : a compatible iterator type

Parameters

i (in) : an input in BSON format convertible to an input adapter

first (in) : iterator to start of the input

last (in) : iterator to end of the input

strict (in) : whether to expect the input to be consumed until EOF (#!cpp true by default)

allow_exceptions (in) : whether to throw exceptions in case of a parse error (optional, #!cpp true by default)

Return value

deserialized JSON value; in case of a parse error and allow_exceptions set to #!cpp false, the return value will be value_t::discarded. The latter can be checked with is_discarded.

Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

Exceptions

Throws parse_error.114 if an unsupported BSON record type is encountered.

Complexity

Linear in the size of the input.

Examples

??? example

The example shows the deserialization of a byte vector in BSON format to a JSON value.
 
```cpp
--8<-- "examples/from_bson.cpp"
```

Output:

```json
--8<-- "examples/from_bson.output"
```

See also

• BSON specification
• to_bson for the analogous serialization
• from_cbor for the related CBOR format
• from_msgpack for the related MessagePack format
• from_ubjson for the related UBJSON format

Version history

• Added in version 3.4.0.

!!! warning “Deprecation”

- Overload (2) replaces calls to `from_bson` with a pointer and a length as first two parameters, which has been
  deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
  `#!cpp from_bson(ptr, len, ...);` with `#!cpp from_bson(ptr, ptr+len, ...);`.
- Overload (2) replaces calls to `from_bson` with a pair of iterators as their first parameter, which has been
  deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
  `#!cpp from_bson({ptr, ptr+len}, ...);` with `#!cpp from_bson(ptr, ptr+len, ...);`.

You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
function.