91 lines
2.1 KiB
Markdown
91 lines
2.1 KiB
Markdown
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# basic_json::accept
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```cpp
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// (1)
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template<typename InputType>
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static bool accept(InputType&& i,
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const bool ignore_comments = false);
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// (2)
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template<typename IteratorType>
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static bool accept(IteratorType first, IteratorType last,
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const bool ignore_comments = false);
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```
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Checks whether the input is valid JSON.
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1. Reads from a compatible input.
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2. Reads from a pair of character iterators
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The value_type of the iterator must be a integral type with size of 1, 2 or 4 bytes, which will be interpreted
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respectively as UTF-8, UTF-16 and UTF-32.
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Unlike the [`parse`](parse.md) function, this function neither throws an exception in case of invalid JSON input
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(i.e., a parse error) nor creates diagnostic information.
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## Template parameters
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`InputType`
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: A compatible input, for instance:
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- an `std::istream` object
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- a `FILE` pointer
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- a C-style array of characters
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- a pointer to a null-terminated string of single byte characters
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- an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.
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`IteratorType`
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: a compatible iterator type
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## Parameters
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`i` (in)
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: Input to parse from.
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`ignore_comments` (in)
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: whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
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(`#!cpp false`); (optional, `#!cpp false` by default)
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`first` (in)
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: iterator to start of character range
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`last` (in)
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: iterator to end of character range
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## Return value
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Whether the input is valid JSON.
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## Exception safety
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Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
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## Complexity
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Linear in the length of the input. The parser is a predictive LL(1) parser.
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## Notes
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(1) A UTF-8 byte order mark is silently ignored.
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## Examples
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??? example
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The example below demonstrates the `accept()` function reading from a string.
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```cpp
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--8<-- "examples/accept__string.cpp"
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```
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Output:
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```json
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--8<-- "examples/accept__string.output"
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```
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## Version history
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- Added in version 3.0.0.
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- Ignoring comments via `ignore_comments` added in version 3.9.0.
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