Small Buffer Optimization for string and friends

[Andrei Alexandrescu]

On 4/8/12 4:54 AM, Manu wrote:
> On 8 April 2012 12:46, Vladimir Panteleev <vladimir at thecybershadow.net
> <mailto:vladimir at thecybershadow.net>> wrote:
>
>     On Sunday, 8 April 2012 at 05:56:36 UTC, Andrei Alexandrescu wrote:
>
>         Walter and I discussed today about using the small string
>         optimization in string and other arrays of immutable small objects.
>
>         On 64 bit machines, string occupies 16 bytes. We could use the
>         first byte as discriminator, which means that all strings under
>         16 chars need no memory allocation at all.
>
>
>     Don't use the first byte. Use the last byte.
>
>     The last byte is the highest-order byte of the length. Limiting
>     arrays to 18.37 exabytes, as opposed to 18.45 exabytes, is a much
>     nicer limitation than making assumptions about the memory layout.
>
>
> What is the plan for 32bit?

We can experiment with making strings shorter than 8 chars in-situ. The 
drawback will be that length will be limited to 29 bits, i.e. 512MB.

Andrei