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

[Alex Menkov]

On Wed, 18 Jun 2025 11:52:17 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> I copied this code for another test in the Valhalla repo and thought it would be a good utility function.  It might be better written using the Classfile API.
>> Tested with test.
>
> 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;
}

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PR Review Comment: https://git.openjdk.org/jdk/pull/25857#discussion_r2162549862