8343829: Unify decimal and hexadecimal parsing in FloatingDecimal

[rgiulietti]

See the JBS bug for some details.

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Issue

• JDK-8343829: Unify decimal and hexadecimal parsing in FloatingDecimal (Enhancement - P4)

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[mlbridge]

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[j3graham]

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.

[rgiulietti]

Thanks for the suggestion @j3graham.
I'll consider it for the next commits.