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* 🔥 consolidate documentation
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2021-12-29 13:41:01 +01:00

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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.

Reads from a compatible input.
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"
```

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.

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