67 lines
1.6 KiB
Markdown
67 lines
1.6 KiB
Markdown
# <small>nlohmann::basic_json_document::</small>node_count
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```cpp
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std::size_t node_count() const noexcept;
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```
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Returns the number of entries in the document's flat index.
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## Return value
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The number of index entries: one per value (of any type, at any nesting depth) plus one per object key. `0` for a
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[discarded](is_discarded.md) document.
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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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Each index entry is [16 bytes](../../home/architecture.md#node-index-of-json-views), so `#!cpp node_count() * 16` is
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the size of the index itself (part, but not all, of [`memory_usage()`](memory_usage.md), which also counts decoded
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strings and, for an owned document, the text).
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## Examples
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??? example
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```cpp
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#include <iostream>
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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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// node_count() is the size of the flat index: one 16-byte node per value,
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// plus one per object key (values and keys are all the index stores)
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json_document scalar = json_document::parse("42");
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std::cout << scalar.node_count() << '\n';
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json_document doc = json_document::parse(R"({"a": 1, "b": [1, 2]})");
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std::cout << doc.node_count() << '\n';
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}
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```
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Output:
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```json
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1
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7
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```
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## See also
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- [memory_usage](memory_usage.md) - the number of bytes held by the document
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- [shrink_to_fit](shrink_to_fit.md) - release unused index capacity
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## Version history
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- Added in version 3.13.0.
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