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# Source file src/math/big/natconv_test.go

## Documentation: math/big

// Use of this source code is governed by a BSD-style

package big

import (
"bytes"
"fmt"
"io"
"math/bits"
"strings"
"testing"
)

func TestMaxBase(t *testing.T) {
if MaxBase != len(digits) {
t.Fatalf("%d != %d", MaxBase, len(digits))
}
}

// log2 computes the integer binary logarithm of x.
// The result is the integer n for which 2^n <= x < 2^(n+1).
// If x == 0, the result is -1.
func log2(x Word) int {
return bits.Len(uint(x)) - 1
}

func itoa(x nat, base int) []byte {
// special cases
switch {
case base < 2:
panic("illegal base")
case len(x) == 0:
return []byte("0")
}

// allocate buffer for conversion
i := x.bitLen()/log2(Word(base)) + 1 // +1: round up
s := make([]byte, i)

// don't destroy x
q := nat(nil).set(x)

// convert
for len(q) > 0 {
i--
var r Word
q, r = q.divW(q, Word(base))
s[i] = digits[r]
}

return s[i:]
}

var strTests = []struct {
x nat    // nat value to be converted
b int    // conversion base
s string // expected result
}{
{nil, 2, "0"},
{nat{1}, 2, "1"},
{nat{0xc5}, 2, "11000101"},
{nat{03271}, 8, "3271"},
{nat{10}, 10, "10"},
{nat{1234567890}, 10, "1234567890"},
{nat{0x229be7}, 17, "1a2b3c"},
{nat{0x309663e6}, 32, "o9cov6"},
{nat{0x309663e6}, 62, "TakXI"},
}

func TestString(t *testing.T) {
// test invalid base explicitly
var panicStr string
func() {
defer func() {
panicStr = recover().(string)
}()
natOne.utoa(1)
}()
if panicStr != "invalid base" {
t.Errorf("expected panic for invalid base")
}

for _, a := range strTests {
s := string(a.x.utoa(a.b))
if s != a.s {
t.Errorf("string%+v\n\tgot s = %s; want %s", a, s, a.s)
}

x, b, _, err := nat(nil).scan(strings.NewReader(a.s), a.b, false)
if x.cmp(a.x) != 0 {
t.Errorf("scan%+v\n\tgot z = %v; want %v", a, x, a.x)
}
if b != a.b {
t.Errorf("scan%+v\n\tgot b = %d; want %d", a, b, a.b)
}
if err != nil {
t.Errorf("scan%+v\n\tgot error = %s", a, err)
}
}
}

var natScanTests = []struct {
s     string // string to be scanned
base  int    // input base
frac  bool   // fraction ok
x     nat    // expected nat
b     int    // expected base
count int    // expected digit count
ok    bool   // expected success
next  rune   // next character (or 0, if at EOF)
}{
// error: no mantissa
{},
{s: "?"},
{base: 10},
{base: 36},
{base: 62},
{s: "?", base: 10},
{s: "0x"},
{s: "345", base: 2},

// error: incorrect use of decimal point
{s: ".0"},
{s: ".0", base: 10},
{s: ".", base: 0},
{s: "0x.0"},

// no errors
{"0", 0, false, nil, 10, 1, true, 0},
{"0", 10, false, nil, 10, 1, true, 0},
{"0", 36, false, nil, 36, 1, true, 0},
{"0", 62, false, nil, 62, 1, true, 0},
{"1", 0, false, nat{1}, 10, 1, true, 0},
{"1", 10, false, nat{1}, 10, 1, true, 0},
{"0 ", 0, false, nil, 10, 1, true, ' '},
{"08", 0, false, nil, 10, 1, true, '8'},
{"08", 10, false, nat{8}, 10, 2, true, 0},
{"018", 0, false, nat{1}, 8, 1, true, '8'},
{"0b1", 0, false, nat{1}, 2, 1, true, 0},
{"0b11000101", 0, false, nat{0xc5}, 2, 8, true, 0},
{"03271", 0, false, nat{03271}, 8, 4, true, 0},
{"10ab", 0, false, nat{10}, 10, 2, true, 'a'},
{"1234567890", 0, false, nat{1234567890}, 10, 10, true, 0},
{"A", 36, false, nat{10}, 36, 1, true, 0},
{"A", 37, false, nat{36}, 37, 1, true, 0},
{"xyz", 36, false, nat{(33*36+34)*36 + 35}, 36, 3, true, 0},
{"XYZ?", 36, false, nat{(33*36+34)*36 + 35}, 36, 3, true, '?'},
{"XYZ?", 62, false, nat{(59*62+60)*62 + 61}, 62, 3, true, '?'},
{"0x", 16, false, nil, 16, 1, true, 'x'},

// no errors, decimal point
{"0.", 0, false, nil, 10, 1, true, '.'},
{"0.", 10, true, nil, 10, 0, true, 0},
{"0.1.2", 10, true, nat{1}, 10, -1, true, '.'},
{".000", 10, true, nil, 10, -3, true, 0},
{"12.3", 10, true, nat{123}, 10, -1, true, 0},
{"012.345", 10, true, nat{12345}, 10, -3, true, 0},
}

func TestScanBase(t *testing.T) {
for _, a := range natScanTests {
x, b, count, err := nat(nil).scan(r, a.base, a.frac)
if err == nil && !a.ok {
t.Errorf("scan%+v\n\texpected error", a)
}
if err != nil {
if a.ok {
t.Errorf("scan%+v\n\tgot error = %s", a, err)
}
continue
}
if x.cmp(a.x) != 0 {
t.Errorf("scan%+v\n\tgot z = %v; want %v", a, x, a.x)
}
if b != a.b {
t.Errorf("scan%+v\n\tgot b = %d; want %d", a, b, a.base)
}
if count != a.count {
t.Errorf("scan%+v\n\tgot count = %d; want %d", a, count, a.count)
}
if err == io.EOF {
next = 0
err = nil
}
if err == nil && next != a.next {
t.Errorf("scan%+v\n\tgot next = %q; want %q", a, next, a.next)
}
}
}

var pi = "3" +
"14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651" +
"32823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461" +
"28475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920" +
"96282925409171536436789259036001133053054882046652138414695194151160943305727036575959195309218611738193261179" +
"31051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798" +
"60943702770539217176293176752384674818467669405132000568127145263560827785771342757789609173637178721468440901" +
"22495343014654958537105079227968925892354201995611212902196086403441815981362977477130996051870721134999999837" +
"29780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083" +
"81420617177669147303598253490428755468731159562863882353787593751957781857780532171226806613001927876611195909" +
"21642019893809525720106548586327886593615338182796823030195203530185296899577362259941389124972177528347913151" +
"55748572424541506959508295331168617278558890750983817546374649393192550604009277016711390098488240128583616035" +
"63707660104710181942955596198946767837449448255379774726847104047534646208046684259069491293313677028989152104" +
"75216205696602405803815019351125338243003558764024749647326391419927260426992279678235478163600934172164121992" +
"45863150302861829745557067498385054945885869269956909272107975093029553211653449872027559602364806654991198818" +
"34797753566369807426542527862551818417574672890977772793800081647060016145249192173217214772350141441973568548" +
"16136115735255213347574184946843852332390739414333454776241686251898356948556209921922218427255025425688767179" +
"04946016534668049886272327917860857843838279679766814541009538837863609506800642251252051173929848960841284886" +
"26945604241965285022210661186306744278622039194945047123713786960956364371917287467764657573962413890865832645" +
"99581339047802759009946576407895126946839835259570982582262052248940772671947826848260147699090264013639443745" +
"53050682034962524517493996514314298091906592509372216964615157098583874105978859597729754989301617539284681382" +
"68683868942774155991855925245953959431049972524680845987273644695848653836736222626099124608051243884390451244" +
"13654976278079771569143599770012961608944169486855584840635342207222582848864815845602850601684273945226746767" +
"88952521385225499546667278239864565961163548862305774564980355936345681743241125150760694794510965960940252288" +
"79710893145669136867228748940560101503308617928680920874760917824938589009714909675985261365549781893129784821" +
"68299894872265880485756401427047755513237964145152374623436454285844479526586782105114135473573952311342716610" +
"21359695362314429524849371871101457654035902799344037420073105785390621983874478084784896833214457138687519435" +
"06430218453191048481005370614680674919278191197939952061419663428754440643745123718192179998391015919561814675" +
"14269123974894090718649423196156794520809514655022523160388193014209376213785595663893778708303906979207734672" +
"21825625996615014215030680384477345492026054146659252014974428507325186660021324340881907104863317346496514539" +
"05796268561005508106658796998163574736384052571459102897064140110971206280439039759515677157700420337869936007" +
"23055876317635942187312514712053292819182618612586732157919841484882916447060957527069572209175671167229109816" +
"90915280173506712748583222871835209353965725121083579151369882091444210067510334671103141267111369908658516398" +
"31501970165151168517143765761835155650884909989859982387345528331635507647918535893226185489632132933089857064" +
"20467525907091548141654985946163718027098199430992448895757128289059232332609729971208443357326548938239119325" +
"97463667305836041428138830320382490375898524374417029132765618093773444030707469211201913020330380197621101100" +
"44929321516084244485963766983895228684783123552658213144957685726243344189303968642624341077322697802807318915" +
"44110104468232527162010526522721116603966655730925471105578537634668206531098965269186205647693125705863566201" +
"85581007293606598764861179104533488503461136576867532494416680396265797877185560845529654126654085306143444318" +
"58676975145661406800700237877659134401712749470420562230538994561314071127000407854733269939081454664645880797" +
"27082668306343285878569830523580893306575740679545716377525420211495576158140025012622859413021647155097925923" +
"09907965473761255176567513575178296664547791745011299614890304639947132962107340437518957359614589019389713111" +
"79042978285647503203198691514028708085990480109412147221317947647772622414254854540332157185306142288137585043" +
"06332175182979866223717215916077166925474873898665494945011465406284336639379003976926567214638530673609657120" +
"91807638327166416274888800786925602902284721040317211860820419000422966171196377921337575114959501566049631862" +
"94726547364252308177036751590673502350728354056704038674351362222477158915049530984448933309634087807693259939" +
"78054193414473774418426312986080998886874132604721569516239658645730216315981931951673538129741677294786724229" +
"24654366800980676928238280689964004824354037014163149658979409243237896907069779422362508221688957383798623001" +
"59377647165122893578601588161755782973523344604281512627203734314653197777416031990665541876397929334419521541" +
"34189948544473456738316249934191318148092777710386387734317720754565453220777092120190516609628049092636019759" +
"88281613323166636528619326686336062735676303544776280350450777235547105859548702790814356240145171806246436267" +
"94561275318134078330336254232783944975382437205835311477119926063813346776879695970309833913077109870408591337"

// Test case for BenchmarkScanPi.
func TestScanPi(t *testing.T) {
var x nat
z, _, _, err := x.scan(strings.NewReader(pi), 10, false)
if err != nil {
t.Errorf("scanning pi: %s", err)
}
if s := string(z.utoa(10)); s != pi {
t.Errorf("scanning pi: got %s", s)
}
}

func TestScanPiParallel(t *testing.T) {
const n = 2
c := make(chan int)
for i := 0; i < n; i++ {
go func() {
TestScanPi(t)
c <- 0
}()
}
for i := 0; i < n; i++ {
<-c
}
}

func BenchmarkScanPi(b *testing.B) {
for i := 0; i < b.N; i++ {
var x nat
}
}

func BenchmarkStringPiParallel(b *testing.B) {
var x nat
x, _, _, _ = x.scan(strings.NewReader(pi), 0, false)
if string(x.utoa(10)) != pi {
panic("benchmark incorrect: conversion failed")
}
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
x.utoa(10)
}
})
}

func BenchmarkScan(b *testing.B) {
const x = 10
for _, base := range []int{2, 8, 10, 16} {
for _, y := range []Word{10, 100, 1000, 10000, 100000} {
if isRaceBuilder && y > 1000 {
continue
}
b.Run(fmt.Sprintf("%d/Base%d", y, base), func(b *testing.B) {
b.StopTimer()
var z nat
z = z.expWW(x, y)

s := z.utoa(base)
if t := itoa(z, base); !bytes.Equal(s, t) {
b.Fatalf("scanning: got %s; want %s", s, t)
}
b.StartTimer()

for i := 0; i < b.N; i++ {
}
})
}
}
}

func BenchmarkString(b *testing.B) {
const x = 10
for _, base := range []int{2, 8, 10, 16} {
for _, y := range []Word{10, 100, 1000, 10000, 100000} {
if isRaceBuilder && y > 1000 {
continue
}
b.Run(fmt.Sprintf("%d/Base%d", y, base), func(b *testing.B) {
b.StopTimer()
var z nat
z = z.expWW(x, y)
z.utoa(base) // warm divisor cache
b.StartTimer()

for i := 0; i < b.N; i++ {
_ = z.utoa(base)
}
})
}
}
}

func BenchmarkLeafSize(b *testing.B) {
for n := 0; n <= 16; n++ {
b.Run(fmt.Sprint(n), func(b *testing.B) { LeafSizeHelper(b, 10, n) })
}
// Try some large lengths
for _, n := range []int{32, 64} {
b.Run(fmt.Sprint(n), func(b *testing.B) { LeafSizeHelper(b, 10, n) })
}
}

func LeafSizeHelper(b *testing.B, base, size int) {
b.StopTimer()
originalLeafSize := leafSize
resetTable(cacheBase10.table[:])
leafSize = size
b.StartTimer()

for d := 1; d <= 10000; d *= 10 {
b.StopTimer()
var z nat
z = z.expWW(Word(base), Word(d)) // build target number
_ = z.utoa(base)                 // warm divisor cache
b.StartTimer()

for i := 0; i < b.N; i++ {
_ = z.utoa(base)
}
}

b.StopTimer()
resetTable(cacheBase10.table[:])
leafSize = originalLeafSize
b.StartTimer()
}

func resetTable(table []divisor) {
if table != nil && table[0].bbb != nil {
for i := 0; i < len(table); i++ {
table[i].bbb = nil
table[i].nbits = 0
table[i].ndigits = 0
}
}
}

func TestStringPowers(t *testing.T) {
var p Word
for b := 2; b <= 16; b++ {
for p = 0; p <= 512; p++ {
x := nat(nil).expWW(Word(b), p)
xs := x.utoa(b)
xs2 := itoa(x, b)
if !bytes.Equal(xs, xs2) {
t.Errorf("failed at %d ** %d in base %d: %s != %s", b, p, b, xs, xs2)
}
}
if b >= 3 && testing.Short() {
break
}
}
}

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