mirror of https://github.com/nlohmann/json.git synced 2026-09-30 22:15:19 +00:00

Files

Niels Lohmann 54455afa40 Document json_document and json_view

- API pages for basic_json_document and basic_json_view, one per member,
  and for the four aliases, each with an example
- features/json_view.md: the problem the view solves, ownership and
  lifetime, what matches basic_json::parse() and what differs, and when
  to choose json, ordered_json, SAX, or the view
- the examples show why one would use the view, not only how: borrowed
  vs. owned input, reading a few fields and materializing one subtree,
  reusing a document across many messages
- registered in the mkdocs navigation, llms.txt, the docset, the
  exceptions page (out_of_range.416), architecture.md, the integration
  page, and the README; the yyjson credit is added to the README and
  license.md

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

2026-09-29 14:02:43 +02:00

1.7 KiB

Raw Blame History

nlohmann::basic_json_view::source_offset

std::size_t source_offset() const noexcept;

Returns the byte offset of this value in the document's source() text, without materializing anything.

Return value

For a string with no escapes, a number, #!json true/#!json false/#!json null, an array, or an object: the byte offset of the first byte of the value's token (for a string: the first byte after the opening quote) in source().
#!cpp static_cast<std::size_t>(-1) for a discarded view, and for a string that contains escapes -- such a string was decoded once into the document's own buffer, so there is no single byte range in source() left to point at.

Exception safety

No-throw guarantee: this function never throws exceptions.

Complexity

Constant.

Notes

This is a raw offset, not a length: the API does not (yet) expose how many bytes the token occupies in the source text, so source_offset() alone is enough to report where a value came from (for an error message, for syntax highlighting, ...) but not to slice its exact text back out of source() for a string, whose token length is not the same as its decoded size().

Examples

??? example

```cpp
--8<-- "examples/basic_json_view__source_offset.cpp"
```

Output:

```json
--8<-- "examples/basic_json_view__source_offset.output"
```

Version history

Added in version 3.13.0.

1.7 KiB Raw Blame History