// Copyright 2010 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
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// Ported to Java from Mozilla's version of V8-dtoa by Hannes Wallnoefer.
// The original revision was 67d1049b0bf9 from the mozilla-central tree.

package org.mozilla.javascript.v8dtoa;

public class CachedPowers {

    static final double kD_1_LOG2_10 = 0.30102999566398114; //  1 / lg(10)

    static class CachedPower {
        long significand;
        short binaryExponent;
        short decimalExponent;

        CachedPower(long significand, short binaryExponent, short decimalExponent) {
            this.significand = significand;
            this.binaryExponent = binaryExponent;
            this.decimalExponent = decimalExponent;
        }
    }

    static int getCachedPower(int e, int alpha, int gamma, DiyFp c_mk) {
        int kQ = DiyFp.kSignificandSize;
        double k = Math.ceil((alpha - e + kQ - 1) * kD_1_LOG2_10);
        int index = (GRISU_CACHE_OFFSET + (int) k - 1) / CACHED_POWERS_SPACING + 1;
        CachedPower cachedPower = CACHED_POWERS[index];

        c_mk.setF(cachedPower.significand);
        c_mk.setE(cachedPower.binaryExponent);
        assert ((alpha <= c_mk.e() + e) && (c_mk.e() + e <= gamma));
        return cachedPower.decimalExponent;
    }

    // Code below is converted from GRISU_CACHE_NAME(8) in file "powers-ten.h"
    // Regexp to convert this from original C++ source:
    // \{GRISU_UINT64_C\((\w+), (\w+)\), (\-?\d+), (\-?\d+)\}

    // interval between entries  of the powers cache below
    static final int CACHED_POWERS_SPACING = 8;

    static final CachedPower[] CACHED_POWERS = {
        new CachedPower(0xe61acf033d1a45dfL, (short) -1087, (short) -308),
        new CachedPower(0xab70fe17c79ac6caL, (short) -1060, (short) -300),
        new CachedPower(0xff77b1fcbebcdc4fL, (short) -1034, (short) -292),
        new CachedPower(0xbe5691ef416bd60cL, (short) -1007, (short) -284),
        new CachedPower(0x8dd01fad907ffc3cL, (short) -980, (short) -276),
        new CachedPower(0xd3515c2831559a83L, (short) -954, (short) -268),
        new CachedPower(0x9d71ac8fada6c9b5L, (short) -927, (short) -260),
        new CachedPower(0xea9c227723ee8bcbL, (short) -901, (short) -252),
        new CachedPower(0xaecc49914078536dL, (short) -874, (short) -244),
        new CachedPower(0x823c12795db6ce57L, (short) -847, (short) -236),
        new CachedPower(0xc21094364dfb5637L, (short) -821, (short) -228),
        new CachedPower(0x9096ea6f3848984fL, (short) -794, (short) -220),
        new CachedPower(0xd77485cb25823ac7L, (short) -768, (short) -212),
        new CachedPower(0xa086cfcd97bf97f4L, (short) -741, (short) -204),
        new CachedPower(0xef340a98172aace5L, (short) -715, (short) -196),
        new CachedPower(0xb23867fb2a35b28eL, (short) -688, (short) -188),
        new CachedPower(0x84c8d4dfd2c63f3bL, (short) -661, (short) -180),
        new CachedPower(0xc5dd44271ad3cdbaL, (short) -635, (short) -172),
        new CachedPower(0x936b9fcebb25c996L, (short) -608, (short) -164),
        new CachedPower(0xdbac6c247d62a584L, (short) -582, (short) -156),
        new CachedPower(0xa3ab66580d5fdaf6L, (short) -555, (short) -148),
        new CachedPower(0xf3e2f893dec3f126L, (short) -529, (short) -140),
        new CachedPower(0xb5b5ada8aaff80b8L, (short) -502, (short) -132),
        new CachedPower(0x87625f056c7c4a8bL, (short) -475, (short) -124),
        new CachedPower(0xc9bcff6034c13053L, (short) -449, (short) -116),
        new CachedPower(0x964e858c91ba2655L, (short) -422, (short) -108),
        new CachedPower(0xdff9772470297ebdL, (short) -396, (short) -100),
        new CachedPower(0xa6dfbd9fb8e5b88fL, (short) -369, (short) -92),
        new CachedPower(0xf8a95fcf88747d94L, (short) -343, (short) -84),
        new CachedPower(0xb94470938fa89bcfL, (short) -316, (short) -76),
        new CachedPower(0x8a08f0f8bf0f156bL, (short) -289, (short) -68),
        new CachedPower(0xcdb02555653131b6L, (short) -263, (short) -60),
        new CachedPower(0x993fe2c6d07b7facL, (short) -236, (short) -52),
        new CachedPower(0xe45c10c42a2b3b06L, (short) -210, (short) -44),
        new CachedPower(0xaa242499697392d3L, (short) -183, (short) -36),
        new CachedPower(0xfd87b5f28300ca0eL, (short) -157, (short) -28),
        new CachedPower(0xbce5086492111aebL, (short) -130, (short) -20),
        new CachedPower(0x8cbccc096f5088ccL, (short) -103, (short) -12),
        new CachedPower(0xd1b71758e219652cL, (short) -77, (short) -4),
        new CachedPower(0x9c40000000000000L, (short) -50, (short) 4),
        new CachedPower(0xe8d4a51000000000L, (short) -24, (short) 12),
        new CachedPower(0xad78ebc5ac620000L, (short) 3, (short) 20),
        new CachedPower(0x813f3978f8940984L, (short) 30, (short) 28),
        new CachedPower(0xc097ce7bc90715b3L, (short) 56, (short) 36),
        new CachedPower(0x8f7e32ce7bea5c70L, (short) 83, (short) 44),
        new CachedPower(0xd5d238a4abe98068L, (short) 109, (short) 52),
        new CachedPower(0x9f4f2726179a2245L, (short) 136, (short) 60),
        new CachedPower(0xed63a231d4c4fb27L, (short) 162, (short) 68),
        new CachedPower(0xb0de65388cc8ada8L, (short) 189, (short) 76),
        new CachedPower(0x83c7088e1aab65dbL, (short) 216, (short) 84),
        new CachedPower(0xc45d1df942711d9aL, (short) 242, (short) 92),
        new CachedPower(0x924d692ca61be758L, (short) 269, (short) 100),
        new CachedPower(0xda01ee641a708deaL, (short) 295, (short) 108),
        new CachedPower(0xa26da3999aef774aL, (short) 322, (short) 116),
        new CachedPower(0xf209787bb47d6b85L, (short) 348, (short) 124),
        new CachedPower(0xb454e4a179dd1877L, (short) 375, (short) 132),
        new CachedPower(0x865b86925b9bc5c2L, (short) 402, (short) 140),
        new CachedPower(0xc83553c5c8965d3dL, (short) 428, (short) 148),
        new CachedPower(0x952ab45cfa97a0b3L, (short) 455, (short) 156),
        new CachedPower(0xde469fbd99a05fe3L, (short) 481, (short) 164),
        new CachedPower(0xa59bc234db398c25L, (short) 508, (short) 172),
        new CachedPower(0xf6c69a72a3989f5cL, (short) 534, (short) 180),
        new CachedPower(0xb7dcbf5354e9beceL, (short) 561, (short) 188),
        new CachedPower(0x88fcf317f22241e2L, (short) 588, (short) 196),
        new CachedPower(0xcc20ce9bd35c78a5L, (short) 614, (short) 204),
        new CachedPower(0x98165af37b2153dfL, (short) 641, (short) 212),
        new CachedPower(0xe2a0b5dc971f303aL, (short) 667, (short) 220),
        new CachedPower(0xa8d9d1535ce3b396L, (short) 694, (short) 228),
        new CachedPower(0xfb9b7cd9a4a7443cL, (short) 720, (short) 236),
        new CachedPower(0xbb764c4ca7a44410L, (short) 747, (short) 244),
        new CachedPower(0x8bab8eefb6409c1aL, (short) 774, (short) 252),
        new CachedPower(0xd01fef10a657842cL, (short) 800, (short) 260),
        new CachedPower(0x9b10a4e5e9913129L, (short) 827, (short) 268),
        new CachedPower(0xe7109bfba19c0c9dL, (short) 853, (short) 276),
        new CachedPower(0xac2820d9623bf429L, (short) 880, (short) 284),
        new CachedPower(0x80444b5e7aa7cf85L, (short) 907, (short) 292),
        new CachedPower(0xbf21e44003acdd2dL, (short) 933, (short) 300),
        new CachedPower(0x8e679c2f5e44ff8fL, (short) 960, (short) 308),
        new CachedPower(0xd433179d9c8cb841L, (short) 986, (short) 316),
        new CachedPower(0x9e19db92b4e31ba9L, (short) 1013, (short) 324),
        new CachedPower(0xeb96bf6ebadf77d9L, (short) 1039, (short) 332),
        new CachedPower(0xaf87023b9bf0ee6bL, (short) 1066, (short) 340)
    };

    static final int GRISU_CACHE_MAX_DISTANCE = 27;
    // nb elements (8): 82

    static final int GRISU_CACHE_OFFSET = 308;
}
