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f917aaa5 RN |
1 | #include <stdint.h> |
2 | ||
3 | #define npowers 87 | |
4 | #define steppowers 8 | |
5 | #define firstpower -348 /* 10 ^ -348 */ | |
6 | ||
7 | #define expmax -32 | |
8 | #define expmin -60 | |
9 | ||
10 | ||
11 | typedef struct Fp { | |
12 | uint64_t frac; | |
13 | int exp; | |
14 | } Fp; | |
15 | ||
16 | static Fp powers_ten[] = { | |
17 | { 18054884314459144840U, -1220 }, { 13451937075301367670U, -1193 }, | |
18 | { 10022474136428063862U, -1166 }, { 14934650266808366570U, -1140 }, | |
19 | { 11127181549972568877U, -1113 }, { 16580792590934885855U, -1087 }, | |
20 | { 12353653155963782858U, -1060 }, { 18408377700990114895U, -1034 }, | |
21 | { 13715310171984221708U, -1007 }, { 10218702384817765436U, -980 }, | |
22 | { 15227053142812498563U, -954 }, { 11345038669416679861U, -927 }, | |
23 | { 16905424996341287883U, -901 }, { 12595523146049147757U, -874 }, | |
24 | { 9384396036005875287U, -847 }, { 13983839803942852151U, -821 }, | |
25 | { 10418772551374772303U, -794 }, { 15525180923007089351U, -768 }, | |
26 | { 11567161174868858868U, -741 }, { 17236413322193710309U, -715 }, | |
27 | { 12842128665889583758U, -688 }, { 9568131466127621947U, -661 }, | |
28 | { 14257626930069360058U, -635 }, { 10622759856335341974U, -608 }, | |
29 | { 15829145694278690180U, -582 }, { 11793632577567316726U, -555 }, | |
30 | { 17573882009934360870U, -529 }, { 13093562431584567480U, -502 }, | |
31 | { 9755464219737475723U, -475 }, { 14536774485912137811U, -449 }, | |
32 | { 10830740992659433045U, -422 }, { 16139061738043178685U, -396 }, | |
33 | { 12024538023802026127U, -369 }, { 17917957937422433684U, -343 }, | |
34 | { 13349918974505688015U, -316 }, { 9946464728195732843U, -289 }, | |
35 | { 14821387422376473014U, -263 }, { 11042794154864902060U, -236 }, | |
36 | { 16455045573212060422U, -210 }, { 12259964326927110867U, -183 }, | |
37 | { 18268770466636286478U, -157 }, { 13611294676837538539U, -130 }, | |
38 | { 10141204801825835212U, -103 }, { 15111572745182864684U, -77 }, | |
39 | { 11258999068426240000U, -50 }, { 16777216000000000000U, -24 }, | |
40 | { 12500000000000000000U, 3 }, { 9313225746154785156U, 30 }, | |
41 | { 13877787807814456755U, 56 }, { 10339757656912845936U, 83 }, | |
42 | { 15407439555097886824U, 109 }, { 11479437019748901445U, 136 }, | |
43 | { 17105694144590052135U, 162 }, { 12744735289059618216U, 189 }, | |
44 | { 9495567745759798747U, 216 }, { 14149498560666738074U, 242 }, | |
45 | { 10542197943230523224U, 269 }, { 15709099088952724970U, 295 }, | |
46 | { 11704190886730495818U, 322 }, { 17440603504673385349U, 348 }, | |
47 | { 12994262207056124023U, 375 }, { 9681479787123295682U, 402 }, | |
48 | { 14426529090290212157U, 428 }, { 10748601772107342003U, 455 }, | |
49 | { 16016664761464807395U, 481 }, { 11933345169920330789U, 508 }, | |
50 | { 17782069995880619868U, 534 }, { 13248674568444952270U, 561 }, | |
51 | { 9871031767461413346U, 588 }, { 14708983551653345445U, 614 }, | |
52 | { 10959046745042015199U, 641 }, { 16330252207878254650U, 667 }, | |
53 | { 12166986024289022870U, 694 }, { 18130221999122236476U, 720 }, | |
54 | { 13508068024458167312U, 747 }, { 10064294952495520794U, 774 }, | |
55 | { 14996968138956309548U, 800 }, { 11173611982879273257U, 827 }, | |
56 | { 16649979327439178909U, 853 }, { 12405201291620119593U, 880 }, | |
57 | { 9242595204427927429U, 907 }, { 13772540099066387757U, 933 }, | |
58 | { 10261342003245940623U, 960 }, { 15290591125556738113U, 986 }, | |
59 | { 11392378155556871081U, 1013 }, { 16975966327722178521U, 1039 }, | |
60 | { 12648080533535911531U, 1066 } | |
61 | }; | |
62 | ||
63 | static Fp find_cachedpow10(int exp, int* k) | |
64 | { | |
65 | const double one_log_ten = 0.30102999566398114; | |
66 | ||
67 | int approx = -(exp + npowers) * one_log_ten; | |
68 | int idx = (approx - firstpower) / steppowers; | |
69 | ||
70 | while(1) { | |
71 | int current = exp + powers_ten[idx].exp + 64; | |
72 | ||
73 | if(current < expmin) { | |
74 | idx++; | |
75 | continue; | |
76 | } | |
77 | ||
78 | if(current > expmax) { | |
79 | idx--; | |
80 | continue; | |
81 | } | |
82 | ||
83 | *k = (firstpower + idx * steppowers); | |
84 | ||
85 | return powers_ten[idx]; | |
86 | } | |
87 | } |