vendor.github.com.andybalholm.brotli.fast_log.go Maven / Gradle / Ivy
The newest version!
package brotli
import (
"math"
"math/bits"
)
/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Utilities for fast computation of logarithms. */
func log2FloorNonZero(n uint) uint32 {
return uint32(bits.Len(n)) - 1
}
/* A lookup table for small values of log2(int) to be used in entropy
computation.
", ".join(["%.16ff" % x for x in [0.0]+[log2(x) for x in range(1, 256)]]) */
var kLog2Table = []float32{
0.0000000000000000,
0.0000000000000000,
1.0000000000000000,
1.5849625007211563,
2.0000000000000000,
2.3219280948873622,
2.5849625007211561,
2.8073549220576042,
3.0000000000000000,
3.1699250014423126,
3.3219280948873626,
3.4594316186372978,
3.5849625007211565,
3.7004397181410922,
3.8073549220576037,
3.9068905956085187,
4.0000000000000000,
4.0874628412503400,
4.1699250014423122,
4.2479275134435852,
4.3219280948873626,
4.3923174227787607,
4.4594316186372973,
4.5235619560570131,
4.5849625007211570,
4.6438561897747244,
4.7004397181410926,
4.7548875021634691,
4.8073549220576037,
4.8579809951275728,
4.9068905956085187,
4.9541963103868758,
5.0000000000000000,
5.0443941193584534,
5.0874628412503400,
5.1292830169449664,
5.1699250014423122,
5.2094533656289501,
5.2479275134435852,
5.2854022188622487,
5.3219280948873626,
5.3575520046180838,
5.3923174227787607,
5.4262647547020979,
5.4594316186372973,
5.4918530963296748,
5.5235619560570131,
5.5545888516776376,
5.5849625007211570,
5.6147098441152083,
5.6438561897747244,
5.6724253419714961,
5.7004397181410926,
5.7279204545631996,
5.7548875021634691,
5.7813597135246599,
5.8073549220576046,
5.8328900141647422,
5.8579809951275719,
5.8826430493618416,
5.9068905956085187,
5.9307373375628867,
5.9541963103868758,
5.9772799234999168,
6.0000000000000000,
6.0223678130284544,
6.0443941193584534,
6.0660891904577721,
6.0874628412503400,
6.1085244567781700,
6.1292830169449672,
6.1497471195046822,
6.1699250014423122,
6.1898245588800176,
6.2094533656289510,
6.2288186904958804,
6.2479275134435861,
6.2667865406949019,
6.2854022188622487,
6.3037807481771031,
6.3219280948873617,
6.3398500028846252,
6.3575520046180847,
6.3750394313469254,
6.3923174227787598,
6.4093909361377026,
6.4262647547020979,
6.4429434958487288,
6.4594316186372982,
6.4757334309663976,
6.4918530963296748,
6.5077946401986964,
6.5235619560570131,
6.5391588111080319,
6.5545888516776376,
6.5698556083309478,
6.5849625007211561,
6.5999128421871278,
6.6147098441152092,
6.6293566200796095,
6.6438561897747253,
6.6582114827517955,
6.6724253419714952,
6.6865005271832185,
6.7004397181410917,
6.7142455176661224,
6.7279204545631988,
6.7414669864011465,
6.7548875021634691,
6.7681843247769260,
6.7813597135246599,
6.7944158663501062,
6.8073549220576037,
6.8201789624151887,
6.8328900141647422,
6.8454900509443757,
6.8579809951275719,
6.8703647195834048,
6.8826430493618416,
6.8948177633079437,
6.9068905956085187,
6.9188632372745955,
6.9307373375628867,
6.9425145053392399,
6.9541963103868758,
6.9657842846620879,
6.9772799234999168,
6.9886846867721664,
7.0000000000000000,
7.0112272554232540,
7.0223678130284544,
7.0334230015374501,
7.0443941193584534,
7.0552824355011898,
7.0660891904577721,
7.0768155970508317,
7.0874628412503400,
7.0980320829605272,
7.1085244567781700,
7.1189410727235076,
7.1292830169449664,
7.1395513523987937,
7.1497471195046822,
7.1598713367783891,
7.1699250014423130,
7.1799090900149345,
7.1898245588800176,
7.1996723448363644,
7.2094533656289492,
7.2191685204621621,
7.2288186904958804,
7.2384047393250794,
7.2479275134435861,
7.2573878426926521,
7.2667865406949019,
7.2761244052742384,
7.2854022188622487,
7.2946207488916270,
7.3037807481771031,
7.3128829552843557,
7.3219280948873617,
7.3309168781146177,
7.3398500028846243,
7.3487281542310781,
7.3575520046180847,
7.3663222142458151,
7.3750394313469254,
7.3837042924740528,
7.3923174227787607,
7.4008794362821844,
7.4093909361377026,
7.4178525148858991,
7.4262647547020979,
7.4346282276367255,
7.4429434958487288,
7.4512111118323299,
7.4594316186372973,
7.4676055500829976,
7.4757334309663976,
7.4838157772642564,
7.4918530963296748,
7.4998458870832057,
7.5077946401986964,
7.5156998382840436,
7.5235619560570131,
7.5313814605163119,
7.5391588111080319,
7.5468944598876373,
7.5545888516776376,
7.5622424242210728,
7.5698556083309478,
7.5774288280357487,
7.5849625007211561,
7.5924570372680806,
7.5999128421871278,
7.6073303137496113,
7.6147098441152075,
7.6220518194563764,
7.6293566200796095,
7.6366246205436488,
7.6438561897747244,
7.6510516911789290,
7.6582114827517955,
7.6653359171851765,
7.6724253419714952,
7.6794800995054464,
7.6865005271832185,
7.6934869574993252,
7.7004397181410926,
7.7073591320808825,
7.7142455176661224,
7.7210991887071856,
7.7279204545631996,
7.7347096202258392,
7.7414669864011465,
7.7481928495894596,
7.7548875021634691,
7.7615512324444795,
7.7681843247769260,
7.7747870596011737,
7.7813597135246608,
7.7879025593914317,
7.7944158663501062,
7.8008998999203047,
7.8073549220576037,
7.8137811912170374,
7.8201789624151887,
7.8265484872909159,
7.8328900141647422,
7.8392037880969445,
7.8454900509443757,
7.8517490414160571,
7.8579809951275719,
7.8641861446542798,
7.8703647195834048,
7.8765169465650002,
7.8826430493618425,
7.8887432488982601,
7.8948177633079446,
7.9008668079807496,
7.9068905956085187,
7.9128893362299619,
7.9188632372745955,
7.9248125036057813,
7.9307373375628867,
7.9366379390025719,
7.9425145053392399,
7.9483672315846778,
7.9541963103868758,
7.9600019320680806,
7.9657842846620870,
7.9715435539507720,
7.9772799234999168,
7.9829935746943104,
7.9886846867721664,
7.9943534368588578,
}
/* Faster logarithm for small integers, with the property of log2(0) == 0. */
func fastLog2(v uint) float64 {
if v < uint(len(kLog2Table)) {
return float64(kLog2Table[v])
}
return math.Log2(float64(v))
}