RFR: 8359707: Add classfile modification code to RedefineClassHelper [v2]

[Coleen Phillimore]

On Mon, 23 Jun 2025 21:18:09 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add a byte buffer version and rename parameters.
>
> test/lib/RedefineClassHelper.java line 87:
> 
>> 85:         }
>> 86:         return 0;
>> 87:     }
> 
> I understand, that this is copy of the old code, but this method does not look good.
> - it would be better to return -1 if the string not found (0 is valid offset)
> - calculation of the buf's upper bound is incorrect when offset > 0
> I'd suggest to update it to something like (not tested, also need to update callers to compare with -1)
> 
> 
> private static int getStringIndex(String needle, byte[] buf, int offset) {
>     byte[] needleArray = needle.getBytes(StandardCharsets.US_ASCII);
>     for (int i = offset; i < buf.length - needleArray.length; i++) 
>         if (Arrays.equals(buf, offset, offset + needleArray.length,
>                           needleArray, 0, needleArray.length)) {
>             return offset;
>         }
>     }
>     return -1;
> }

I did copy this code.  I was hoping instead of class byte modifications that someone would suggest a Classfile API way to modify the class file bytes. @liach ? That way the class names don't have to be the same length.  Above seems better  code but I have to debug it now.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25857#discussion_r2163791674