Add a string version of numbers

[schmidtw]

This change adds storing the string version of numbers during decoding
so that large or precise numbers can be handled by the program without
the need for cJSON to directly deal with the numbers. There is still a
63 character limit, but this change enables applications to handle 64
bit numbers while enabling cJSON to maintain C89 support.

[schmidtw]

@Alanscut any thoughts on adding this feature? It allows cJSON to punt on large number handling to the users. The problem of 64bit numbers not being supported keeps growing worse as more users move to larger numbers because they are widely supported today.

For some projects I'm working on I have been waiting for feedback or acceptance of this PR, but if the project isn't adding new features then I'll find alternatives.

[VelGer]

We would also benefit from this feature.

[Alanscut]

@Alanscut any thoughts on adding this feature? It allows cJSON to punt on large number handling to the users. The problem of 64bit numbers not being supported keeps growing worse as more users move to larger numbers because they are widely supported today.

For some projects I'm working on I have been waiting for feedback or acceptance of this PR, but if the project isn't adding new features then I'll find alternatives.

@schmidtw Thanks your great contribution! I'm sorry for the late reply. Limited by the support for c89, it is not perfect when processing numbers. I once thought about whether it is necessary to abandon the support for c89, but considering that this breaking change will have an adverse effect on many existing embedded software, so I give up.

I think your approach is a good way, while taking into account the support of 64-bit numbers and c89. one little thing, not everyone hope to store the number as valuestring, should we add a new function to implement this?

[VelGer]

@Alanscut Did you mean:

1. To have a function (like "cJSON_GetNumberValueAsString()") that delivers the Number value as string? Or
2. To have a function with which the functionality (making number available as string in the structure during parsing) can be turned on?

I think implementing both can be a good idea, so that in the normal case, the functionality is not active and the number is not stored as string (this maintins backwards compatability and reduces CPU load), but if the user wants to be able to read the number value as string, he can turn the functionality on, then parse his input JSON String and finally read the number as string using a method like "cJSON_GetNumberValueAsString()".

Is there a struct in memory where such cJSON configuration details are stored? What do you guys think?

[schmidtw]

That's good feedback. Looking at the patch again, it is making a strdup() call for each integer even if it perfectly converts. I'm going to do some work on this (performance) & see if I can add a function or two to ease useage.

[schmidtw]

It's a bit more code than I had hoped, but this provides 4 new functions and keeps the existing behavior otherwise.

cJSON_ParseWithLengthNumStringOpts();
cJSON_GetNumberValueAsString();
cJSON_CreateNumberAsString();
cJSON_SetNumberValueAsString();

These will validate the the input string is a legit JSON number before it lets you set it. They also will update the double and int versions. If you want number strings you get them all or you (default) don't get any. Trying to figure out if a number is exactly represented is fairly hard given the way the system is assembled, so it's all or none.

I added some changes locally to verify I have tests to cover the new code. Happy to share - it just seemed like a separate PR.

Thoughts?

[schmidtw]

@VelGer or @Alanscut any thoughts?

[VelGer]

@schmidtw Sorry for the delayed response, I have been out of the office for a while. I think it looks good, it keeps backwards compatability and works like I would expect.

What do you think about making the parsing function expandable by giving it a general name and replacing all the optional bools with a single int. So that functionality can be turned on / off by using bitwise operators? This way we can have a single parsing function that can be used with future functionality expansions:

We can then add a define for each function that the user can enable, like:

#define CJSON_REQUIRE_NULL_TERMINATED (1 << 0)
#define CJSON_ENABLE_NUMBER_STRINGS (1 << 1)

Usage would then be:
cjsonStruct = cJSON_ParseOpts("{ ...JSON String... }", CJSON_REQUIRE_NULL_TERMINATED & CJSON_ENABLE_NUMBER_STRINGS );
or:
cjsonStruct = cJSON_ParseOptsLen("{ ...JSON String... }", 45, CJSON_REQUIRE_NULL_TERMINATED & CJSON_ENABLE_NUMBER_STRINGS );

[schmidtw]

@VelGer I don't have any strong opinions on the cJSON_ParseOpts() ... but I'd like to get the functionality generally in. I've been busy with some other things, but if you want to send my repo a PR I'd be happy to review/merge.