RFR: 8343829: Unify decimal and hexadecimal parsing in FloatingDecimal [v3]

[j3graham]

On Fri, 13 Dec 2024 16:06:53 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> See the JBS bug for some details.
>
> Raffaello Giulietti 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 five additional commits since the last revision:
> 
>  - Merge branch 'master' into 8343829
>  - Minors in comments.
>  - Removed repeated comment.
>  - Refactoring some code and comments.
>  - 8343829: Unify decimal and hexadecimal parsing in FloatingDecimal

src/java.base/share/classes/jdk/internal/math/FloatingDecimal.java line 2354:

> 2352: 
> 2353:     /* The precision of the format. */
> 2354:     private static final int[] P = {

What about organizing these constants as as a record - something like this:


record FloatFmt(int ix, int p, int epMin, int epMax, int w, int eMin, int eMax, int qMin, int hexCount) {

    public static final FloatFmt BINARY_16 = build(0, 11, -8, 6);
    public static final FloatFmt BINARY_32 = build(1, 24, -46, 40);
    public static final FloatFmt BINARY_64 = build(2, 53, -324, 310);
    public static final FloatFmt BINARY_128 = build(3, 113, -4_966, 4934);
    public static final FloatFmt BINARY_256 = build(4, 237, -78_985, 78_915);

    private static FloatFmt build(int ix, int p, int epMin, int epMax) {
        int w = (1 << 4 + ix) - p;
        int eMin = (-1 << w - 1) + 2;
        int eMax = (1 << w - 1) - 1;
        int qMin = eMin - p + 1;
        int hexCount = p / 4 + 2;

        return new FloatFmt(ix, p, epMin, epMax, w, eMin, eMax, qMin, hexCount);
    }
}



Methods could then be parameterized with the static instances rather than integers. I believe these values would inline well as constants.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22737#discussion_r1885896862