73 lines
2.0 KiB
Markdown
73 lines
2.0 KiB
Markdown
# nlohmann::basic_json_document::owns_source
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```
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bool owns_source() const noexcept;
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```
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Returns whether the document holds its own copy of the parsed text or is borrowing the caller's buffer.
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## Return value
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`true` if the document owns the text returned by [`source()`](https://json.nlohmann.me/api/basic_json_document/source/index.md), `false` if it borrows it (or if the document is [discarded](https://json.nlohmann.me/api/basic_json_document/is_discarded/index.md)).
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## Exception safety
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No-throw guarantee: this function never throws exceptions.
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## Complexity
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Constant.
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## Notes
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See the ownership table on [`parse`](https://json.nlohmann.me/api/basic_json_document/parse/#notes) for which inputs are borrowed and which are owned. A borrowed document (`owns_source() == false`) is only valid while the buffer it was parsed from is still alive.
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## Examples
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Example
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```
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#include <iostream>
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#include <string>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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int main()
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{
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std::cout << std::boolalpha;
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std::string text = R"({"a": 1})";
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// borrowed: the document only points into `text`; `text` must outlive it
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json_document borrowed = json_document::parse(text);
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std::cout << borrowed.owns_source() << '\n';
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// owned: parse_copy() always takes its own copy
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json_document copied = json_document::parse_copy(text);
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std::cout << copied.owns_source() << '\n';
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// owned: an rvalue std::string is moved in, not copied, but still owned
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json_document moved_in = json_document::parse(std::string(text));
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std::cout << moved_in.owns_source() << '\n';
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}
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```
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Output:
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```
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false
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true
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true
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```
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## See also
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- [parse](https://json.nlohmann.me/api/basic_json_document/parse/index.md) - deserialize from a compatible input
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- [parse_copy](https://json.nlohmann.me/api/basic_json_document/parse_copy/index.md) - deserialize a copy of a compatible input, always owned
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- [source](https://json.nlohmann.me/api/basic_json_document/source/index.md) - the parsed text
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## Version history
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- Added in version 3.13.0 unreleased.
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