RFR 8170155: StringBuffer and StringBuilder stream methods are not late-binding (original) (raw)
Paul Sandoz paul.sandoz at oracle.com
Wed Nov 23 22:39:42 UTC 2016
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Hi,
Please review:
http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8170155-string-buffer-builder-late-binding/webrev/
This patch:
updates the StringBuilder/StringBuffer.chars()/codePoints() so they are late binding.
refactors the spliterator late binding and fail fast tests, separating them out, and to the former additional tests are added for CharSequence implementations and BitSet.
The code in AbstractStringBuilder has the following bounds check call to checkOffset:
1558 return StreamSupport.intStream( 1559 () -> { 1560 byte[] val = this.value; int count = this.count; 1561 checkOffset(count, val.length >> coder); 1562 return coder == LATIN1 1563 ? new StringLatin1.CharsSpliterator(val, 0, count, 0) 1564 : new StringUTF16.CharsSpliterator(val, 0, count, 0); 1565 }, 1566 Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED, 1567 false);
(Separately checkOffset could be replaced with the internal Preconditions.checkIndex.)
On initial inspection that should be a no-op, but talking to Sherman we believe it is required for UTF-16 access, since the intrinsics do not perform bounds checks, so they need to be guarded (for conformance purposes if a no-op).
If so i propose the following to make this clearer:
return StreamSupport.intStream( () -> { byte[] val = this.value; int count = this.count; if (coder == LATIN1) { return new StringLatin1.CharsSpliterator(val, 0, count, 0); } else { // Perform an explicit bounds check since HotSpot // intrinsics to access UTF-16 characters in the byte[] // array will not perform bounds checks checkOffset(count, val.length >> coder); return new StringUTF16.CharsSpliterator(val, 0, count, 0); } }, Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED, false);
Paul.
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