Improve XML scanner memory

[angelozerr]

Improve XML scanner memory

Signed-off-by: azerr azerr@redhat.com

[angelozerr]

This PR improves the XML scanner memory by using static int fields pattern instead of creating for each parse the int array pattern.

If you run https://github.com/eclipse/lemminx/blob/master/org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/performance/XMLScannerPerformance.java you can see the memory which takes around 200MB to parse the large file:

If you start this XMLScannerPerformance inmaster branch, it takes around 300-400MB:

[fbricon]

is there a perf penalty when declaring varargs here? You could still call stream.advanceIfChars(END_COMMENT_PATTERN) with an actual array

[angelozerr]

I prefer updating to int array to force to use of static array. If we let varargs, it means that we could not define static array for future improvement.

[fbricon]

ok fair enough

[fbricon]

Not tested but LGTM

[angelozerr]

Thanks @fbricon !