63c10a51fc
* Review and extend the documentation, and check it in CI A review of all documentation pages found factual errors, dead links, missing cross-references, and gaps in examples. This fixes them and adds checks so the same problems are caught automatically. Fixes: - wrong signatures and version histories (operator!= C++20 member, binary() subtype type, get<PointerType>(), JSON_NO_THREAD_LOCAL, ...) - stale descriptions (number parsing since #5283, UBJSON table, SAX example that no longer compiled, tsl::ordered_map advice) - dead internal and external links; repology.org badges (the domain is suspended) replaced by badges that query the registries directly - deprecation notes link the migration guide; the guide itself fixed Additions: - "See also" sections, cross-references, 25 runnable examples, 12 Mermaid diagrams, new API pages for json_pointer::operator<=> and byte_container_with_subtype::operator==/!= - landing page, guides for untrusted input and performance - "unreleased" badge after versions newer than the latest release Checks: - strict documentation build (broken links/anchors fail it); CI and the publish workflow fetch the full history the build needs - weekly external link check, Mermaid syntax check in CI - check_structure.py: example titles, heading levels, alt texts, header links, docset index coverage; its unused-example check works again - all examples produce the same output on every platform Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Keep the customer links that could not be fixed A dead link on the customers page is still the evidence of where the use of the library was documented. Keep the original URLs of the entries without a working replacement (Marne, Cisco Webex Desk Camera, Philips Hue, CyberArk) and exclude exactly these URLs from the link check. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Correct the duplicate-key recipe's claim about SAX positions The SAX interface's key() receives no position either; only parse_error() does. Also note that the recipe does not report the path to the repeated key (see discussion #5085). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Say the library is available as a single header and mention json_fwd.hpp Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Correct documentation errors found while hunting for bugs - patch/patch_inplace: list the JSON pointer errors parse_error.106-109 and out_of_range.402/404, and quote the actual parse_error.105 message. - unflatten: list parse_error.106/107/108 and out_of_range.404. - to_bson: list out_of_range.415 (binary subtype above 255) and note that 412 and 415 are new in 3.13.0. - to_string: state that string_t must be convertible to std::string, also in the StringType requirements table. - JSON Lines: a `while (input >> j)` loop also throws after the last value for concatenated JSON values; show a loop that works for both. - BON8: a string gets 0xFF only if nothing follows it in the message; a string at the end of an array or object is ended by 0xFE. - custom_string_type.hpp: add operator+=(char), which the "Always required" list asks for (json_pointer::to_string, flatten, unflatten, and diff did not compile), and an ADL int_to_string for diff and items. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Cache the release headers with functools.lru_cache Codacy (Pylint) flagged the mutable default argument that header() used as its cache. functools.lru_cache keeps the same memoization without it. The script's output is unchanged. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
3.8 KiB
nlohmann::basic_json::number_integer_t
using number_integer_t = NumberIntegerType;
The type used to store JSON numbers (integers).
RFC 8259 describes numbers as follows:
The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is
known whether the number is a signed integer, an unsigned integer, or a floating-point number. Therefore, three different
types, number_integer_t, number_unsigned_t and number_float_t are
used.
To store integer numbers in C++, a type is defined by the template parameter NumberIntegerType which chooses the type
to use.
Template parameters
NumberIntegerType- the type to store signed integers. It must be a signed integral type (
#!cpp std::is_integral) with a#!cpp std::numeric_limitsspecialization, and it is stored directly inside abasic_jsonvalue. See Template Parameter Requirements.
Notes
Default type
With the default values for NumberIntegerType (std::int64_t), the default value for number_integer_t is
#!cpp std::int64_t.
Default behavior
- The restrictions about leading zeros are not enforced in C++. Instead, leading zeros in integer literals lead to an
interpretation as an octal number. Internally, the value will be stored as a decimal number. For instance, the C++
integer literal
010will be serialized to8. During deserialization, leading zeros yield an error.
Limits
RFC 8259 specifies:
An implementation may set limits on the range and precision of numbers.
When the default type is used, the maximal integer number that can be stored is 9223372036854775807 (INT64_MAX) and
the minimal integer number that can be stored is -9223372036854775808 (INT64_MIN). Integer numbers that are out of
range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers
will automatically be stored as number_unsigned_t or number_float_t.
RFC 8259 further states:
Note that when such software is used, numbers that are integers and are in the range [-253+1, 253-1] are interoperable in the sense that implementations will agree exactly on their numeric values.
As this range is a subrange of the exactly supported range [INT64_MIN, INT64_MAX], this class's integer type is interoperable.
Storage
Integer number values are stored directly inside a basic_json type.
Examples
??? example
The following code shows that `number_integer_t` is by default, a typedef to `#!cpp std::int64_t`.
```cpp
--8<-- "examples/number_integer_t.cpp"
```
Output:
```json
--8<-- "examples/number_integer_t.output"
```
See also
- number_unsigned_t the type used to store JSON unsigned integer numbers
- number_float_t the type used to store JSON floating-point numbers
- is_number_integer checks whether the JSON value is a signed integer number
- Number Handling - the article on number handling
Version history
- Added in version 1.0.0.