Read-only view of ByteArrayInputStream content

[Martin Desruisseaux]

Hello Archie, thanks for the reply.

Le 2024-07-09 à 18 h 17, Archie Cobbs a écrit :

> The difference in the old vs. new behavior is the use of a 128k 
> temporary transfer buffer. So if I understand this correctly the 
> performance problem you are addressing (in terms of blown cache) is 
> not proportional to the size of the original BLOB, but to at most 128K

No, in the previous JDK implementation, no 128 kb transfer buffer was 
used. The implementation before commit 5cacf21 (September 2023) was as 
below:

    public synchronized long transferTo(OutputStream out) throws IOException {
         int len = count - pos;
         out.write(buf, pos, len);
         pos = count;
         return len;
    }

In above code, buf is a protected field of ByteArrayInputStream with a 
value specified by user at construction time, so the array can have any 
size. I was using a custom OutputStream implementation for getting the 
value of that field, avoiding any form of copy. But this trick does not 
work anymore since a transfer buffer has been introduced in commit 
b0d1450 (December 2023). A read-only ByteBuffer would make possible to 
continue to avoid a copy.

     Martin

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