On Mon, 20 Nov 2023 19:35:27 GMT, Roger Riggs <rri...@openjdk.org> wrote:
>> Strings, after construction, are immutable but may be constructed from
>> mutable arrays of bytes, characters, or integers.
>> The string constructors should guard against the effects of mutating the
>> arrays during construction that might invalidate internal invariants for the
>> correct behavior of operations on the resulting strings. In particular, a
>> number of operations have optimizations for operations on pairs of latin1
>> strings and pairs of non-latin1 strings, while operations between latin1 and
>> non-latin1 strings use a more general implementation.
>>
>> The changes include:
>>
>> - Adding a warning to each constructor with an array as an argument to
>> indicate that the results are indeterminate
>> if the input array is modified before the constructor returns.
>> The resulting string may contain any combination of characters sampled
>> from the input array.
>>
>> - Ensure that strings that are represented as non-latin1 contain at least
>> one non-latin1 character.
>> For latin1 inputs, whether the arrays contain ASCII, ISO-8859-1, UTF8, or
>> another encoding decoded to latin1 the scanning and compression is unchanged.
>> If a non-latin1 character is found, the string is represented as
>> non-latin1 with the added verification that a non-latin1 character is
>> present at the same index.
>> If that character is found to be latin1, then the input array has been
>> modified and the result of the scan may be incorrect.
>> Though a ConcurrentModificationException could be thrown, the risk to an
>> existing application of an unexpected exception should be avoided.
>> Instead, the non-latin1 copy of the input is re-scanned and compressed;
>> that scan determines whether the latin1 or the non-latin1 representation is
>> returned.
>>
>> - The methods that scan for non-latin1 characters and their intrinsic
>> implementations are updated to return the index of the non-latin1 character.
>>
>> - String construction from StringBuilder and CharSequence must also be
>> guarded as their contents may be modified during construction.
>
> Roger Riggs has updated the pull request incrementally with one additional
> commit since the last revision:
>
> undo noise chars
Looks good.
Maybe use `StringUTF16.coderFromArrayLen()` where suggested in the comments
before integrating.
src/java.base/share/classes/java/lang/String.java line 359:
> 357: if (COMPACT_STRINGS) {
> 358: byte[] val = StringUTF16.compress(codePoints, offset, count);
> 359: this.coder = (val.length == count) ? LATIN1 : UTF16;
Maybe worth using `StringUTF16.coderFromArrayLen()` even here.
src/java.base/share/classes/java/lang/String.java line 4845:
> 4843: if (COMPACT_STRINGS && asb.maybeLatin1) {
> 4844: this.value = StringUTF16.compress(val, 0, length);
> 4845: this.coder = (this.value.length == length) ? LATIN1 :
> UTF16;
`StringUTF16.coderFromArrayLen()`?
-------------
Marked as reviewed by rgiulietti (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/16425#pullrequestreview-1740808291
PR Review Comment: https://git.openjdk.org/jdk/pull/16425#discussion_r1399824712
PR Review Comment: https://git.openjdk.org/jdk/pull/16425#discussion_r1399825374
