Re: New JSON library from the maker of Beast!

From: Vinnie Falco (vinnie.falco_at_[hidden])
Date: 2019-10-22 16:25:12

On Tue, Sep 24, 2019 at 7:32 AM Dominique Devienne <ddevienne_at_[hidden]> wrote:
> ...why conflate the array and object APIs in the value
> type, rather than just having as_object() and
> as_array() as you already?

I agree, and these additional APIs have been pruned. I have also
pruned other unnecessary APIs (thanks to advice from Peter Dimov) such
as the local iterator and bucket interfaces in `json::object` (which
needlessly constrain the implementation).

> So I'm curious why it should be different here. Does the doc goes into that already?

`json::value` is not `variant<...>` for the same reason that
`string_view` is not `std::pair<char const*, std::size_t>`.

> On the "compact" side, how compact is your json::value?
> What are the different sizeof on 32 and 64-bit arch?

I've done some work on this. I gave up on using std::string to
represent strings for a few reasons related to performance and API. I
have reimplemented string to have a small buffer optimization and to
work natively with the `json::storage_ptr` type which gives some space
efficiencies (and eliminates some unnecessary atomic operations caused
by std::string's Allocator interface). The new sizes look like this:

32-bit
sizeof(value)  == 40
sizeof(object) == 8
sizeof(array)  == 8
sizeof(string) == 32
sizeof(number) == 24

64-bit
sizeof(value)  == 48
sizeof(object) == 16
sizeof(array)  == 16
sizeof(string) == 40
sizeof(number) == 24

The string type has a 20-byte small buffer which is pretty generous

Thanks