RFR: 8333843: Provide methods on MemorySegment to read strings with known lengths

[Maurizio Cimadamore]

On Wed, 28 Aug 2024 09:52:10 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR proposes to add a new overload to `MemorySegment::getString` whereby it is possible to pass in a known byte length of the content in a segment that should be converted to a String. This is useful in case one already knows the byte length and thereby does not need to scan for a null terminator.
>
> src/java.base/share/classes/java/lang/foreign/MemorySegment.java line 1316:
> 
>> 1314: 
>> 1315:     /**
>> 1316:      * Reads a string using the given byte length from this segment at the given offset,
> 
> What happens is there's a null terminator before `length` ? Seems like we're just copying it? IMHO, this is the tension with this API.

Overall, I guess I'm not overly convinced that it's worth adding a method like this for:

byte[] bytes = new byte[len];
MemorySegment.copy(segment, JAVA_BYTE, offset, bytes, 0, len);
return new String(bytes, charset);

e.g. the API provides string shortcuts for the common case. The more convoluted case can still be achieve via `copy`. Is there anything I'm missing here?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20725#discussion_r1734367933