CachedPowers.java revision 1507:549f06563f1c 
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58package jdk.nashorn.internal.runtime.doubleconv;
59
60public class CachedPowers {
61
62    static class CachedPower {
63        final private long significand;
64        final private int binaryExponent;
65        final private int decimalExponent;
66
67        CachedPower(final long significand, final int binaryExponent, final int decimalExponent) {
68            this.significand = significand;
69            this.binaryExponent = binaryExponent;
70            this.decimalExponent = decimalExponent;
71        }
72    }
73
74    static private final CachedPower[] kCachedPowers = {
75            new CachedPower(0xfa8fd5a0081c0288L, -1220, -348),
76            new CachedPower(0xbaaee17fa23ebf76L, -1193, -340),
77            new CachedPower(0x8b16fb203055ac76L, -1166, -332),
78            new CachedPower(0xcf42894a5dce35eaL, -1140, -324),
79            new CachedPower(0x9a6bb0aa55653b2dL, -1113, -316),
80            new CachedPower(0xe61acf033d1a45dfL, -1087, -308),
81            new CachedPower(0xab70fe17c79ac6caL, -1060, -300),
82            new CachedPower(0xff77b1fcbebcdc4fL, -1034, -292),
83            new CachedPower(0xbe5691ef416bd60cL, -1007, -284),
84            new CachedPower(0x8dd01fad907ffc3cL, -980, -276),
85            new CachedPower(0xd3515c2831559a83L, -954, -268),
86            new CachedPower(0x9d71ac8fada6c9b5L, -927, -260),
87            new CachedPower(0xea9c227723ee8bcbL, -901, -252),
88            new CachedPower(0xaecc49914078536dL, -874, -244),
89            new CachedPower(0x823c12795db6ce57L, -847, -236),
90            new CachedPower(0xc21094364dfb5637L, -821, -228),
91            new CachedPower(0x9096ea6f3848984fL, -794, -220),
92            new CachedPower(0xd77485cb25823ac7L, -768, -212),
93            new CachedPower(0xa086cfcd97bf97f4L, -741, -204),
94            new CachedPower(0xef340a98172aace5L, -715, -196),
95            new CachedPower(0xb23867fb2a35b28eL, -688, -188),
96            new CachedPower(0x84c8d4dfd2c63f3bL, -661, -180),
97            new CachedPower(0xc5dd44271ad3cdbaL, -635, -172),
98            new CachedPower(0x936b9fcebb25c996L, -608, -164),
99            new CachedPower(0xdbac6c247d62a584L, -582, -156),
100            new CachedPower(0xa3ab66580d5fdaf6L, -555, -148),
101            new CachedPower(0xf3e2f893dec3f126L, -529, -140),
102            new CachedPower(0xb5b5ada8aaff80b8L, -502, -132),
103            new CachedPower(0x87625f056c7c4a8bL, -475, -124),
104            new CachedPower(0xc9bcff6034c13053L, -449, -116),
105            new CachedPower(0x964e858c91ba2655L, -422, -108),
106            new CachedPower(0xdff9772470297ebdL, -396, -100),
107            new CachedPower(0xa6dfbd9fb8e5b88fL, -369, -92),
108            new CachedPower(0xf8a95fcf88747d94L, -343, -84),
109            new CachedPower(0xb94470938fa89bcfL, -316, -76),
110            new CachedPower(0x8a08f0f8bf0f156bL, -289, -68),
111            new CachedPower(0xcdb02555653131b6L, -263, -60),
112            new CachedPower(0x993fe2c6d07b7facL, -236, -52),
113            new CachedPower(0xe45c10c42a2b3b06L, -210, -44),
114            new CachedPower(0xaa242499697392d3L, -183, -36),
115            new CachedPower(0xfd87b5f28300ca0eL, -157, -28),
116            new CachedPower(0xbce5086492111aebL, -130, -20),
117            new CachedPower(0x8cbccc096f5088ccL, -103, -12),
118            new CachedPower(0xd1b71758e219652cL, -77, -4),
119            new CachedPower(0x9c40000000000000L, -50, 4),
120            new CachedPower(0xe8d4a51000000000L, -24, 12),
121            new CachedPower(0xad78ebc5ac620000L, 3, 20),
122            new CachedPower(0x813f3978f8940984L, 30, 28),
123            new CachedPower(0xc097ce7bc90715b3L, 56, 36),
124            new CachedPower(0x8f7e32ce7bea5c70L, 83, 44),
125            new CachedPower(0xd5d238a4abe98068L, 109, 52),
126            new CachedPower(0x9f4f2726179a2245L, 136, 60),
127            new CachedPower(0xed63a231d4c4fb27L, 162, 68),
128            new CachedPower(0xb0de65388cc8ada8L, 189, 76),
129            new CachedPower(0x83c7088e1aab65dbL, 216, 84),
130            new CachedPower(0xc45d1df942711d9aL, 242, 92),
131            new CachedPower(0x924d692ca61be758L, 269, 100),
132            new CachedPower(0xda01ee641a708deaL, 295, 108),
133            new CachedPower(0xa26da3999aef774aL, 322, 116),
134            new CachedPower(0xf209787bb47d6b85L, 348, 124),
135            new CachedPower(0xb454e4a179dd1877L, 375, 132),
136            new CachedPower(0x865b86925b9bc5c2L, 402, 140),
137            new CachedPower(0xc83553c5c8965d3dL, 428, 148),
138            new CachedPower(0x952ab45cfa97a0b3L, 455, 156),
139            new CachedPower(0xde469fbd99a05fe3L, 481, 164),
140            new CachedPower(0xa59bc234db398c25L, 508, 172),
141            new CachedPower(0xf6c69a72a3989f5cL, 534, 180),
142            new CachedPower(0xb7dcbf5354e9beceL, 561, 188),
143            new CachedPower(0x88fcf317f22241e2L, 588, 196),
144            new CachedPower(0xcc20ce9bd35c78a5L, 614, 204),
145            new CachedPower(0x98165af37b2153dfL, 641, 212),
146            new CachedPower(0xe2a0b5dc971f303aL, 667, 220),
147            new CachedPower(0xa8d9d1535ce3b396L, 694, 228),
148            new CachedPower(0xfb9b7cd9a4a7443cL, 720, 236),
149            new CachedPower(0xbb764c4ca7a44410L, 747, 244),
150            new CachedPower(0x8bab8eefb6409c1aL, 774, 252),
151            new CachedPower(0xd01fef10a657842cL, 800, 260),
152            new CachedPower(0x9b10a4e5e9913129L, 827, 268),
153            new CachedPower(0xe7109bfba19c0c9dL, 853, 276),
154            new CachedPower(0xac2820d9623bf429L, 880, 284),
155            new CachedPower(0x80444b5e7aa7cf85L, 907, 292),
156            new CachedPower(0xbf21e44003acdd2dL, 933, 300),
157            new CachedPower(0x8e679c2f5e44ff8fL, 960, 308),
158            new CachedPower(0xd433179d9c8cb841L, 986, 316),
159            new CachedPower(0x9e19db92b4e31ba9L, 1013, 324),
160            new CachedPower(0xeb96bf6ebadf77d9L, 1039, 332),
161            new CachedPower(0xaf87023b9bf0ee6bL, 1066, 340)
162    };
163
164    static final int kCachedPowersOffset = 348;  // -1 * the first decimal_exponent.
165    static final double kD_1_LOG2_10 = 0.30102999566398114;  //  1 / lg(10)
166    // Difference between the decimal exponents in the table above.
167    static final int kDecimalExponentDistance = 8;
168    static final int kMinDecimalExponent = -348;
169    static final int kMaxDecimalExponent = 340;
170
171    static int getCachedPowerForBinaryExponentRange(
172            final int min_exponent,
173            final int max_exponent,
174            final DiyFp power) {
175        final int kQ = DiyFp.kSignificandSize;
176        final double k = Math.ceil((min_exponent + kQ - 1) * kD_1_LOG2_10);
177        final int index =
178                (kCachedPowersOffset + (int) k - 1) / kDecimalExponentDistance + 1;
179        assert (0 <= index && index < kCachedPowers.length);
180        final CachedPower cached_power = kCachedPowers[index];
181        assert (min_exponent <= cached_power.binaryExponent);
182        assert (cached_power.binaryExponent <= max_exponent);
183        power.setF(cached_power.significand);
184        power.setE(cached_power.binaryExponent);
185        return cached_power.decimalExponent;
186    }
187
188
189    static int getCachedPowerForDecimalExponent(final int requested_exponent,
190                                                final DiyFp power) {
191        assert (kMinDecimalExponent <= requested_exponent);
192        assert (requested_exponent < kMaxDecimalExponent + kDecimalExponentDistance);
193        final int index =
194                (requested_exponent + kCachedPowersOffset) / kDecimalExponentDistance;
195        final CachedPower cached_power = kCachedPowers[index];
196        power.setF(cached_power.significand);
197        power.setE(cached_power.binaryExponent);
198        final int found_exponent = cached_power.decimalExponent;
199        assert (found_exponent <= requested_exponent);
200        assert (requested_exponent < found_exponent + kDecimalExponentDistance);
201        return cached_power.decimalExponent;
202    }
203
204}
205