separate object_t::key_type from basic_json::key_type, and use an allocator which returns object_t::key_type

[timprepscius]

• What

I would like the key_type which is searched for:
json j = { "hi", "there" };
j.at("hi") <--- that "hi" is a going to be object_t::key_type, I believe.

To be different from the internal key type
for instance object_t::key_type might be string_view,
but the parameter types, might still be string... but most likely would be string_view (if the internal type is string_view).

• Why?

I deal with json which has many millions of objects containing the same keys.
I would like there to be an allocator type which allocates strings in a big set of strings. And returns the string_view of that string, rather than a new string, (or a may even return a const char * of the string.c_str())

This is close to the way the jvm allocates strings.

In this way, I would save a lot of memory, and also, key/value lookups in maps would be faster.

[timprepscius]

I made a patch which separates the internal map key type from the external map key type. This allows for string_view to be used. Which, in my case, collapses memory allocation considerably. This is just a simple rough cut, will need to be redone later.

I purposefully did not do all the templatization, because I figure the owner of this repository would have clear ideas about how that should be done.

make_string_view_as_map_key_possible.diff.txt

[nlohmann]

Thanks! A PR would still be very welcomed!

[stale]

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