RFR: 8343110: Add getChars(int, int, char[], int) to CharSequence and CharBuffer [v5]

[Chen Liang]

On Sun, 30 Mar 2025 12:34:06 GMT, Markus KARG <duke at openjdk.org> wrote:

>> This Pull Request proposes an implementation for [JDK-8343110](https://bugs.openjdk.org/browse/JDK-8343110): Adding the new method `public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` to the `CharSequence` interface, providing a **bulk-read** facility including a default implementation iterating over `charAt(int)`.
>> 
>> In addition, this Pull Request proposes to replace the implementation of `Reader.of(CharSequence).read(char[] cbuf, int off, int len)` to invoke `CharSequence.getChars(next, next + n, cbuf, off)` instead of utilizing pattern matching for switch. Also, this PR proposes to implement `CharBuffer.getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` as an alias for `CharBuffer.get(srcBegin, dst, dstBegin, srcEnd - srcBegin)`.
>> 
>> To ensure quality...
>> * ...the method signature and JavaDocs are adapted from `AbstractStringBuilder.getChars(...)`.
>> * ...this PR relies upon the existing tests for `Reader.of(CharSequence)`, as these provide sufficient coverage of all changes introduced by this PR.
>
> Markus KARG has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Applied changes requested by Chen: 'We might need to specify the IOOBE behavior - when an IOOBE is thrown, some characters may be already transferred (this is important for concurrent char sequences)'

Should we ask hotspot compiler engineers for inputs on how useful this API is for allowing batch/vectorized copy and eliminating overheads of defensive copy array allocation?

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PR Comment: https://git.openjdk.org/jdk/pull/21730#issuecomment-2787292309