[External] : Re: MemorySegment APIs for reading and writing strings with known lengths

[Maurizio Cimadamore]

On 12/11/2025 11:40, Liam Miller-Cushon wrote:
>
>     For the non-\0 terminated strings, you have the String-based
>     MemorySegment::copy I described - e.g.
>
>     void copy(String srcString, Charset srcCharset, int srcIndex,
>     MemorySegment dstSegment, long dstOffset, int length);
>
>     With this, we also have two cases:
>
>     * if the charset is compatible with the string buffer, we just
>     bulk-copy the string buffer (or a portion of it) into the dest segment
>     * otherwise we can encode the srcString directly into the dest segment
>
> Thanks! I think I'm caught up now. My misunderstanding was whether 
> MS::ofString was being suggested instead of and not in addition to the 
> bulk copy.

Ah, gotcha.

I think MS::ofString is a possible add-on. To be fair, since writing the 
document I think we've grown a little colder on it, as such a view would 
make for a pretty big footgun, as it would allow a native function 
(invoked via critical downcall handle) to directly modify the string 
buffer (at least in some cases). There's also some question about how 
`MemorySegment::equals` should work in this case, as `equals` for heap 
segments takes into account the identity of the underlying heap object.

So, if we could get there with the new `getString`/`copy` + maybe some 
way to determine the length of an encoded string, I think it would be 
preferrable/less risky. We could always add `ofString` later, if we find 
a way to address and/or mitigate the issues above.

Maurizio
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