Differentiate between int and uint type in jsoncpp

Question

I'd like to parse some json data after reading it with jsoncpp which differentiates between int and uint data type.

The meaning of these types is clear to me, but when I read data like value: 7, jsoncpp recognizes this as int. Of course, value may also be negative in a different situation but if jsoncpp only knows the current situation why doesn't it parse value as uint?

Valid jsoncpp types are listed here. I check the type like this:

switch(root->type()) {
    case Json::intValue:    serializeInt(root->asInt(), key);       break;
    case Json::uintValue:   serializeUInt(root->asUInt(), key);     break;

Only the int case is executed.

So my question basically is, how can I express in json that a value is unsigned so that jsoncpp parses it like this?

What "valuable information" is gleaned from the type that can't be gotten from the sign? — Scott Hunter, Apr 25 '19 at 13:08
When I know that my variable is of type `uint`, I do not have to check the sign explicitly later. — lukasl1991, Apr 25 '19 at 13:14

Jarod42 · Accepted Answer · 2019-04-25T13:10:59.227

2

jsoncpp uses unsigned int when the value doesn't fit in int.

You might try with value like INT_MAX + 1.

edited Apr 25 '19 at 13:10

answered Apr 25 '19 at 13:06

Jarod42

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Yes, this produces an `uint`. This wasn't obvious to me. Thanks! So there is no possibility in `json` to say that a value that fits into an `int` should be treated as `uint`? – lukasl1991 Apr 25 '19 at 13:19
1

The `json`'s spec only has *Number*, it doesn't have `int`, `uint`, `double` (but C++ has). So from json, you can't, but from `jsoncpp`, you might be able to, but information would be lost anyway once exported to json. – Jarod42 Apr 25 '19 at 13:26

Differentiate between int and uint type in jsoncpp

1 Answers1