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 ( ) const

inlinenoexcept

returns the maximum possible number of elements

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()

@liveexample{The following code calls max_size() on the different value types. Note the output is implementation specific.,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.

@iterators No changes.

@exceptionsafety No-throw guarantee: this function never throws exceptions.

@requirement 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 22990 of file json.hpp.

    {
        switch (m_type)
        {
            case value_t::array:
            {
                // delegate call to array_t::max_size()
                return m_value.array->max_size();
            }
 
            case value_t::object:
            {
                // delegate call to object_t::max_size()
                return m_value.object->max_size();
            }
 
            case value_t::null:
            case value_t::string:
            case value_t::boolean:
            case value_t::number_integer:
            case value_t::number_unsigned:
            case value_t::number_float:
            case value_t::binary:
            case value_t::discarded:
            default:
            {
                // all other types have max_size() == size()
                return size();
            }
        }
    }