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◆ max_size()
template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer, class BinaryType = std::vector<std::uint8_t>>
size_type nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::max_size |
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Returns the maximum number of elements a JSON value is able to hold due to system or library implementation limitations, i.e. std::distance(begin(), end()) for the JSON value.
- Returns
- The return value depends on the different types and is defined as follows:
Value type | return value |
null | 0 (same as size() ) |
boolean | 1 (same as size() ) |
string | 1 (same as size() ) |
number | 1 (same as size() ) |
binary | 1 (same as size() ) |
object | result of function object_t::max_size() |
array | result of function array_t::max_size() |
- Example
- The following code calls
max_size() on the different value types. Note the output is implementation specific.
2#include <nlohmann/json.hpp>
10 json j_boolean = true;
11 json j_number_integer = 17;
12 json j_number_float = 23.42;
13 json j_object = {{ "one", 1}, { "two", 2}};
14 json j_array = {1, 2, 4, 8, 16};
15 json j_string = "Hello, world";
18 std::cout << j_null.max_size() << '\n';
19 std::cout << j_boolean.max_size() << '\n';
20 std::cout << j_number_integer.max_size() << '\n';
21 std::cout << j_number_float.max_size() << '\n';
22 std::cout << j_object.max_size() << '\n';
23 std::cout << j_array.max_size() << '\n';
24 std::cout << j_string.max_size() << '\n';
basic_json<> json default JSON class
Output (play with this example online): 0
1
1
1
256204778801521550
1152921504606846975
1
The example code above can be translated with g++ -std=c++11 -Isingle_include doc/examples/max_size.cpp -o max_size
- Complexity
- Constant, as long as array_t and object_t satisfy the Container concept; that is, their
max_size() functions have constant complexity.
- Iterator validity
- No changes.
- Exception safety
- No-throw guarantee: this function never throws exceptions.
- Requirements
- This function helps
basic_json satisfying the Container requirements:
- The complexity is constant.
- Has the semantics of returning
b.size() where b is the largest possible JSON value.
- See also
- see size() – returns the number of elements
- Since
- version 1.0.0
Definition at line 22790 of file json.hpp.
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