How to find the size of a json object?

[muhamedsuhail]

I am trying to limit the size of the JSON object to 16KB. Is it possible to check the size of the JSON object and cap it to 16KB?

[nlohmann]

• What would be measured? The memory footprint? The number of bytes needed to serialize the object?
• When should the size be enforced? While parsing?

[muhamedsuhail]

This is my requirement. I need to cap the JSON object to 16kb. I am dumping the JSON object as a value in a text file.

[nlohmann]

As a hack, you could call j.dump().size() which creates a string representation and then asks for the size in bytes. If this is too inefficient, you could write your own recursive function to traverse the JSON object - see the implementation of size() for an example.

[muhamedsuhail]

Thank you, Neils! I decided to write my own function.

[DUOLabs333]

I have a similar question, due to trying to track down the cause of a stack overflow --- I specifically want the size of the json object (along with all its sub objects, etc.) in memory.

[gregmarr]

You're looking for stack size, in that case, which is pretty much fixed at 16 for a local variable. All storage underneath that is going to be heap storage, and not affect your stack overflow.

[amdjachenko]

I need to use http bulk API that limits the size of json text representation I can send. So I would like to have an efficient way of doing something like upper_bound_size function with the same signature as dump but not allocating/faster than dump().size()

json bulk;
size_t upperBound = 0;

for (const auto& event : json_events)
{
    upperBound += event.upper_bound_size();
    if (upperBound < threshold)
        bulk.push_back(event);
    else
        break;
}

send(bulk);