d9a71e7bc5
A new section describes the 16-byte node: its fields, how integers, floats, and object members are stored, how views navigate without pointers, and a worked example. The feature page and the pages of basic_json_document and node_count link to it where they mention the 16 bytes. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2.9 KiB
nlohmann::basic_json_document
Defined in header <nlohmann/json_view.hpp>
template<typename BasicJsonType>
class basic_json_document;
A parsed JSON text, held as a flat index of its values
(16 bytes per value) instead of a tree of BasicJsonType values.
Strings and numbers stay in the source text; only strings that contain escapes are decoded, into one buffer owned by
the document. basic_json_view is a read-only handle to one value of a
basic_json_document; materialize() turns a subtree back into the
BasicJsonType value that BasicJsonType::parse() would have produced for it.
A document may borrow the text it was parsed from (the caller's buffer must then outlive the document) or own
it (a copy, or an rvalue #!cpp std::string that was moved in); see owns_source. basic_json_document
is move-only: copying a document would either duplicate a potentially large index and text, or leave two documents
claiming to borrow the same buffer, so it is disabled.
Template parameters
BasicJsonType- a specialization of
basic_json, for instancejsonorordered_json. Only 64-bitnumber_integer_t/number_unsigned_ttypes are supported; this is checked with astatic_assert.
Specializations
- json_document - documents of the default specialization
json - ordered_json_document - documents of
ordered_json
Member types
- view_type - the type of view returned by
root()(#!cpp basic_json_view<BasicJsonType>) - value_t - the JSON type enumeration, see
basic_json::value_t
Member functions
- (constructor)
- parse (static) - deserialize from a compatible input, borrowing or owning it as appropriate
- parse_copy (static) - deserialize a copy of a compatible input
- accept (static) - check whether the input is valid JSON
- read - (re-)parse into this document, reusing its memory
- root - the view of the root value
- is_discarded - return whether the last parse failed
- source - the parsed text
- owns_source - return whether the document holds its own copy of the text
- node_count - the number of index entries (values plus object keys)
- memory_usage - the number of bytes held by the document
- shrink_to_fit - release unused index capacity
Version history
- Added in version 3.13.0.