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Add json_document and json_view, a read-only, zero-copy index of a JSON text, as the first public slice of the zero-copy view (#5295). A parse produces a flat array of 16-byte nodes in document order, one per value and one per object key. Strings stay in the source text; escaped strings are decoded into an arena. Integers are converted while their digits are in the cache; floats keep only their digit layout and are converted on read. Containers store the size of their subtree, so a reader can step over one in constant time. A document makes a handful of allocations, however many values it has. The parser accepts exactly what json::parse accepts, with every combination of ignore_comments and ignore_trailing_commas, with and without a trailing NUL, and under JSON_STRICT_NUL_HANDLING. It is portable C++11 and does not depend on byte order. basic_json_document adds parse, parse_copy, accept, read (reuses a document's memory), root, is_discarded, source, owns_source, node_count, memory_usage, and shrink_to_fit. basic_json_view adds type, the is_* queries, operator bool, size, empty, materialize, and source_offset. A parse error throws the same exception basic_json::parse would throw for the same input, message and position included. detail::abi_config keeps JSON_STRICT_NUL_HANDLING and JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON readable after json.hpp undefines them, in the ABI namespace so they always match the basic_json in use. A NUL byte that ends a // comment is the end of the input, as in parse() since #5696. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
36 lines
754 B
Markdown
36 lines
754 B
Markdown
# <small>nlohmann::</small>json_document
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<small>Defined in header `<nlohmann/json_view.hpp>`</small>
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```cpp
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using json_document = basic_json_document<json>;
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```
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This type is a [`basic_json_document`](basic_json_document/index.md) of the default [`json`](json.md)
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specialization.
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## Examples
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??? example
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The example below demonstrates how to use the type `nlohmann::json_document`.
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```cpp
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--8<-- "examples/json_document.cpp"
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```
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Output:
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```json
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--8<-- "examples/json_document.output"
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```
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## See also
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- [json_view](json_view.md) - a view of a value of a `json_document`
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- [ordered_json_document](ordered_json_document.md) - the corresponding document for `ordered_json`
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## Version history
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Since version 3.13.0.
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