RFR: 8343962: [REDO] Move getChars to DecimalDigits [v4]

[Shaojin Wen]

On Tue, 10 Dec 2024 12:24:34 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 17 additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'upstream/master' into int_get_chars_dedup_202411
>>  - Merge remote-tracking branch 'upstream/master' into int_get_chars_dedup_202411
>>  - Merge remote-tracking branch 'upstream/master' into int_get_chars_dedup_202411
>>  - fix unsafe address overflow
>>  - add benchmark
>>  - remove comments, from @liach
>>  - Merge remote-tracking branch 'upstream/master' into int_get_chars_dedup_202410
>>  - fix Helper
>>  - fix Helper
>>  - fix Helper
>>  - ... and 7 more: https://git.openjdk.org/jdk/compare/f354c08b...a05c2f5f
>
> src/java.base/share/classes/java/math/BigDecimal.java line 4213:
> 
>> 4211:         if (intCompact != INFLATED) {
>> 4212:             coeff = new char[19];
>> 4213:             offset = DecimalDigits.getChars(Math.abs(intCompact), coeff.length, coeff);
> 
> `StringBuilderHelper.putIntCompact` asserts that `Math.abs(intCompact)` is non-negative, but there is no such assert in `DecimalDigits.getChars`. I'm not too familiar with `BigDecimal` and maybe `intCompact` wouldn't be set for `Long.MIN_VALUE`. If so perhaps this should use `StrictMath#absExact(long)` for clarity rather than lean on an assert?

static final long INFLATED = Long.MIN_VALUE;


INFLATED is Long.MIN_VALUE, and a pre-judgment is made here

if (intCompact != INFLATED) {
      offset = DecimalDigits.getChars(Math.abs(intCompact), coeff.length, coeff);
}

So Math.abs(intCompact) here will not have overflow problems

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PR Review Comment: https://git.openjdk.org/jdk/pull/22023#discussion_r1878234662