package brotli import "math" /* 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 { /* TODO: generalize and move to platform.h */ var result uint32 = 0 for { n >>= 1 if n == 0 { break } result++ } return result } /* 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)) }