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Diffstat (limited to 'deps/fpconv/fpconv_powers.h')
| -rw-r--r-- | deps/fpconv/fpconv_powers.h | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/deps/fpconv/fpconv_powers.h b/deps/fpconv/fpconv_powers.h new file mode 100644 index 000000000..bc488f6dd --- /dev/null +++ b/deps/fpconv/fpconv_powers.h @@ -0,0 +1,133 @@ +/* fpconv_powers.h -- floating point conversion utilities. + * + * Fast and accurate double to string conversion based on Florian Loitsch's + * Grisu-algorithm[1]. + * + * [1] https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf + * ---------------------------------------------------------------------------- + * + * Copyright (c) 2021, Redis Labs + * Copyright (c) 2013-2019, night-shift <as.smljk at gmail dot com> + * Copyright (c) 2009, Florian Loitsch < florian.loitsch at inria dot fr > + * All rights reserved. + * + * Boost Software License - Version 1.0 - August 17th, 2003 + * + * Permission is hereby granted, free of charge, to any person or organization + * obtaining a copy of the software and accompanying documentation covered by + * this license (the "Software") to use, reproduce, display, distribute, + * execute, and transmit the Software, and to prepare derivative works of the + * Software, and to permit third-parties to whom the Software is furnished to + * do so, all subject to the following: + * + * The copyright notices in the Software and this entire statement, including + * the above license grant, this restriction and the following disclaimer, + * must be included in all copies of the Software, in whole or in part, and + * all derivative works of the Software, unless such copies or derivative + * works are solely in the form of machine-executable object code generated by + * a source language processor. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT + * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE + * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER + * DEALINGS IN THE SOFTWARE. + */ + +#include <stdint.h> + +#define npowers 87 +#define steppowers 8 +#define firstpower -348 /* 10 ^ -348 */ + +#define expmax -32 +#define expmin -60 + + +typedef struct Fp { + uint64_t frac; + int exp; +} Fp; + +static Fp powers_ten[] = { + { 18054884314459144840U, -1220 }, { 13451937075301367670U, -1193 }, + { 10022474136428063862U, -1166 }, { 14934650266808366570U, -1140 }, + { 11127181549972568877U, -1113 }, { 16580792590934885855U, -1087 }, + { 12353653155963782858U, -1060 }, { 18408377700990114895U, -1034 }, + { 13715310171984221708U, -1007 }, { 10218702384817765436U, -980 }, + { 15227053142812498563U, -954 }, { 11345038669416679861U, -927 }, + { 16905424996341287883U, -901 }, { 12595523146049147757U, -874 }, + { 9384396036005875287U, -847 }, { 13983839803942852151U, -821 }, + { 10418772551374772303U, -794 }, { 15525180923007089351U, -768 }, + { 11567161174868858868U, -741 }, { 17236413322193710309U, -715 }, + { 12842128665889583758U, -688 }, { 9568131466127621947U, -661 }, + { 14257626930069360058U, -635 }, { 10622759856335341974U, -608 }, + { 15829145694278690180U, -582 }, { 11793632577567316726U, -555 }, + { 17573882009934360870U, -529 }, { 13093562431584567480U, -502 }, + { 9755464219737475723U, -475 }, { 14536774485912137811U, -449 }, + { 10830740992659433045U, -422 }, { 16139061738043178685U, -396 }, + { 12024538023802026127U, -369 }, { 17917957937422433684U, -343 }, + { 13349918974505688015U, -316 }, { 9946464728195732843U, -289 }, + { 14821387422376473014U, -263 }, { 11042794154864902060U, -236 }, + { 16455045573212060422U, -210 }, { 12259964326927110867U, -183 }, + { 18268770466636286478U, -157 }, { 13611294676837538539U, -130 }, + { 10141204801825835212U, -103 }, { 15111572745182864684U, -77 }, + { 11258999068426240000U, -50 }, { 16777216000000000000U, -24 }, + { 12500000000000000000U, 3 }, { 9313225746154785156U, 30 }, + { 13877787807814456755U, 56 }, { 10339757656912845936U, 83 }, + { 15407439555097886824U, 109 }, { 11479437019748901445U, 136 }, + { 17105694144590052135U, 162 }, { 12744735289059618216U, 189 }, + { 9495567745759798747U, 216 }, { 14149498560666738074U, 242 }, + { 10542197943230523224U, 269 }, { 15709099088952724970U, 295 }, + { 11704190886730495818U, 322 }, { 17440603504673385349U, 348 }, + { 12994262207056124023U, 375 }, { 9681479787123295682U, 402 }, + { 14426529090290212157U, 428 }, { 10748601772107342003U, 455 }, + { 16016664761464807395U, 481 }, { 11933345169920330789U, 508 }, + { 17782069995880619868U, 534 }, { 13248674568444952270U, 561 }, + { 9871031767461413346U, 588 }, { 14708983551653345445U, 614 }, + { 10959046745042015199U, 641 }, { 16330252207878254650U, 667 }, + { 12166986024289022870U, 694 }, { 18130221999122236476U, 720 }, + { 13508068024458167312U, 747 }, { 10064294952495520794U, 774 }, + { 14996968138956309548U, 800 }, { 11173611982879273257U, 827 }, + { 16649979327439178909U, 853 }, { 12405201291620119593U, 880 }, + { 9242595204427927429U, 907 }, { 13772540099066387757U, 933 }, + { 10261342003245940623U, 960 }, { 15290591125556738113U, 986 }, + { 11392378155556871081U, 1013 }, { 16975966327722178521U, 1039 }, + { 12648080533535911531U, 1066 } +}; + +/** + * Grisu needs a cache of precomputed powers-of-ten. + * This function, given an exponent and an integer k + * return the normalized floating-point approximation of the power of 10. + * @param exp + * @param k + * @return + */ +static Fp find_cachedpow10(int exp, int* k) +{ + const double one_log_ten = 0.30102999566398114; + + const int approx = -(exp + npowers) * one_log_ten; + int idx = (approx - firstpower) / steppowers; + + while(1) { + int current = exp + powers_ten[idx].exp + 64; + + if(current < expmin) { + idx++; + continue; + } + + if(current > expmax) { + idx--; + continue; + } + + *k = (firstpower + idx * steppowers); + + return powers_ten[idx]; + } +} |