Hi Martin,
nice to see you again on board.
Am 19.03.2013 20:18, schrieb Martin Buchholz:
Thanks! Webrev updated.
Character:
Maybe I'm blind, is there any semantical difference between
char c1 = seq.charAt(index++);
if (isHighSurrogate(c1)) {
if (index < seq.length()) {
and
char c1 = seq.charAt(index);
if (isHighSurrogate(c1) && ++index < seq.length()) {
, or is it just for beautifying the code?
AbstractStringBuilder:
Instead
270 public int codePointBefore(int index) {
271 int i = index - 1;
272 if ((i < 0) || (i >= count)) {
273 throw new StringIndexOutOfBoundsException(index);
274 }
I suggest
270 public int codePointBefore(int index) {
271 if ((--index < 0) || (index >= count)) {
272 throw new StringIndexOutOfBoundsException(index);
273 }
, because if e.g. the initial value of index is 0, then -1 reflects the out-of-bound condition, but
not the initial 0 to report in the StringIndexOutOfBoundsException.
(Hopefully the following redundant i < 0 bounds check from value[i] becomes
elimited by JIT.)
If there is some register pressure, you could avoid potential register swapping for temp, temp2,
hasSurrogate, j and n - j if you would reorder following lines to:
1390 char temp = value[j];
1391 char temp2 = value[j] = value[n - j];
1397 value[n - j] = temp;
1392 if (!hasSurrogate) {
1393 hasSurrogate = (Character.isSurrogate(temp) ||
1394 Character.isSurrogate(temp2));
1395 }
(Nomination for "performance expert II" ?)
I, ummmm... am a "performance expert".
How about, if I can ever measure any performance win in a micro-benchmark,
we're allowed to keep the lower-level code?
Yes I remember ;-)
As IMHO better alternative you could proof the JIT result by hsdis.
I think, you independently should test
static int codePointAtImpl(char[] a, int index, int limit) {...}
to don't read out-of-bounds trailing surrogate.
... and you additionally should provide a test for
static int codePointBeforeImpl(char[] a, int index, int start) {...}
to don't read out-of-bounds precursory surrogate.
-Ulf
