Comment by aw1621107
1 year ago
> That said, I don’t see why it wouldn’t be possible to cram in 24 bytes of null-terminated payload (so 23 useful ones, the best you could hope for with null termination) into the same structure the same way by storing the compact version with null termination and ensuring the last byte is also always zero.
I want to say libc++ and maybe MSVC do something along those lines in their std::string implementations.
> For extra style points, define the last byte to be 24 minus payload length instead so you don’t need to recompute the length in the inline case.
IIRC Facebook's FBString from Folly does (did?) that?
> I want to say libc++ and maybe MSVC do something along those lines in their std::string implementations.
Here's Raymond Chen on this topic earlier this same year. As a bonus since you're looking at this in August it's more or less correct now, whereas when it was published it had numerous serious errors. Whether the standard library implementation of such an important type should be so complicated that an expert makes numerous errors is another question...
https://devblogs.microsoft.com/oldnewthing/20240510-00/?p=10...
So, libc++ gets closest, 1 flag byte + 22 bytes of text + 1 byte of ASCII NUL = 24 bytes
The others are much worse, larger (32 bytes on modern computers) yet with lower SSO capacity (15 bytes of text).
Huh, I thought MSVC had a libc++-style SSO implementation. Now I have to wonder where I got that mistaken impression :(