buidler.go

// +build go1.10

package strutil

type Builder -> strings.Builder

builder1.9.go

// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Please see the license file inline:
//
// Copyright (c) 2009 The Go Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// +build !go1.10

package strutil

import (
	"unicode/utf8"
	"unsafe"
)

// A Builder is used to efficiently build a string using Write methods.
// It minimizes memory copying. The zero value is ready to use.
// Do not copy a non-zero Builder.
type Builder struct {
	addr *Builder // of receiver, to detect copies by value
	buf  []byte
}

// noescape hides a pointer from escape analysis.  noescape is
// the identity function but escape analysis doesn't think the
// output depends on the input. noescape is inlined and currently
// compiles down to zero instructions.
// USE CAREFULLY!
// This was copied from the runtime; see issues 23382 and 7921.
//go:nosplit
func noescape(p unsafe.Pointer) unsafe.Pointer {
	x := uintptr(p)
	return unsafe.Pointer(x ^ 0)
}

func (b *Builder) copyCheck() {
	if b.addr == nil {
		// This hack works around a failing of Go's escape analysis
		// that was causing b to escape and be heap allocated.
		// See issue 23382.
		// TODO: once issue 7921 is fixed, this should be reverted to
		// just "b.addr = b".
		b.addr = (*Builder)(noescape(unsafe.Pointer(b)))
	} else if b.addr != b {
		panic("strings: illegal use of non-zero Builder copied by value")
	}
}

// String returns the accumulated string.
func (b *Builder) String() string {
	return *(*string)(unsafe.Pointer(&b.buf))
}

// Len returns the number of accumulated bytes; b.Len() == len(b.String()).
func (b *Builder) Len() int { return len(b.buf) }

// Reset resets the Builder to be empty.
func (b *Builder) Reset() {
	b.addr = nil
	b.buf = nil
}

// grow copies the buffer to a new, larger buffer so that there are at least n
// bytes of capacity beyond len(b.buf).
func (b *Builder) grow(n int) {
	buf := make([]byte, len(b.buf), 2*cap(b.buf)+n)
	copy(buf, b.buf)
	b.buf = buf
}

// Grow grows b's capacity, if necessary, to guarantee space for
// another n bytes. After Grow(n), at least n bytes can be written to b
// without another allocation. If n is negative, Grow panics.
func (b *Builder) Grow(n int) {
	b.copyCheck()
	if n < 0 {
		panic("strings.Builder.Grow: negative count")
	}
	if cap(b.buf)-len(b.buf) < n {
		b.grow(n)
	}
}

// Write appends the contents of p to b's buffer.
// Write always returns len(p), nil.
func (b *Builder) Write(p []byte) (int, error) {
	b.copyCheck()
	b.buf = append(b.buf, p...)
	return len(p), nil
}

// WriteByte appends the byte c to b's buffer.
// The returned error is always nil.
func (b *Builder) WriteByte(c byte) error {
	b.copyCheck()
	b.buf = append(b.buf, c)
	return nil
}

// WriteRune appends the UTF-8 encoding of Unicode code point r to b's buffer.
// It returns the length of r and a nil error.
func (b *Builder) WriteRune(r rune) (int, error) {
	b.copyCheck()
	if r < utf8.RuneSelf {
		b.buf = append(b.buf, byte(r))
		return 1, nil
	}
	l := len(b.buf)
	if cap(b.buf)-l < utf8.UTFMax {
		b.grow(utf8.UTFMax)
	}
	n := utf8.EncodeRune(b.buf[l:l+utf8.UTFMax], r)
	b.buf = b.buf[:l+n]
	return n, nil
}

// WriteString appends the contents of s to b's buffer.
// It returns the length of s and a nil error.
func (b *Builder) WriteString(s string) (int, error) {
	b.copyCheck()
	b.buf = append(b.buf, s...)
	return len(s), nil
}

er.go

// experiment with cheaper stack traces.

type errorStackLazy struct {
	err error
	n   int
	pcs [32]uintptr
}

func newStackLazy(skip int, err error) error {
	esl := new(errorStackLazy)
	n := runtime.Callers(1+skip, esl.pcs[:])
	if n == 0 {
		return &emptyStack{err: err}
	}
	esl.n = n
	return esl
}

func (e *errorStackLazy) Error() string {
	return e.err.Error()
}

func (e *errorStackLazy) Format(st fmt.State, verb rune) {
	frs := make([]runtime.Frame, 0, e.n)
	cf := runtime.CallersFrames(e.pcs[:e.n])
	for {
		fr, ok := cf.Next()
		if !ok {
			break
		}
		if fr.Function == `` {
			fr.Function = `unknown`
		}
		frs = append(frs, fr)
	}
	formatFrames(frs, st, verb)
}

func formatFrames(frs []runtime.Frame, st fmt.State, verb rune) {
	var (
		b strutil.Builder
		n int
	)
	for _, l := range frs {
		n += len(l.File)
	}
	b.Grow(n * 2)

	switch {
	case verb == 's':
		for _, fr := range frs {
			b.WriteByte('\n')
			formatFrame(fr, &b, st, verb)
		}
	case verb == 'v':
		switch {
		case st.Flag('+'):
			for _, fr := range frs {
				b.WriteByte('\n')
				formatFrame(fr, &b, st, verb)
			}
		}
	}
	fmt.Fprint(st, b.String())
}

func formatFrame(fr runtime.Frame, b *strutil.Builder, s fmt.State, verb rune) {
	switch verb {
	case 's':
		switch {
		case s.Flag('+'):
			b.WriteString(fr.Function)
			b.WriteString("\n\t")
			b.WriteString(fr.File)
		default:
			b.WriteString(path.Base(fr.File))
		}
	case 'd':
		b.WriteString(strutil.Itoa(fr.Line))
	case 'n':
		b.WriteString(fr.Function)
	case 'v':
		b.WriteString(fr.Function)
		b.WriteString("\n\t")
		b.WriteString(fr.File)
		b.WriteByte(':')
		b.WriteString(strutil.Itoa(fr.Line))
	}
} 

itoa.go

package strutil

import (
	"strconv"
)

// Itoa is for zero-allocation Itoa for numbers under 10k, useful when it comes
// to formatting stack traces which may have many line numbers under 10k.
func Itoa(n int) string {
	switch {
	case n < 0:
		fallthrough
	default:
		return strconv.Itoa(n)
	case n < 10:
		n = n * 2
		return intStrLut2[n+1 : n+2]
	case n < 100:
		n = n % 100 * 2
		return intStrLut2[n : n+2]
	case n < 1000:
		n = (n - 100) * 3
		return intStrLut3[n : n+3]
	case n < 10000:
		n = (n - 1000) * 4
		return intStrLut4[n : n+4]
	}
}

var (
	intStrLut2 = "00010203040506070809101112131415161718192021" +
		"22232425262728293031323334353637383940414243444546474849" +
		"50515253545556575859606162636465666768697071727374757677" +
		"78798081828384858687888990919293949596979899"

	intStrLut3 = "100101102103104105106107108109110111112113114115116" +
		"117118119120121122123124125126127128129130131132133134135136137" +
		"138139140141142143144145146147148149150151152153154155156157158" +
		"159160161162163164165166167168169170171172173174175176177178179" +
		"180181182183184185186187188189190191192193194195196197198199200" +
		"201202203204205206207208209210211212213214215216217218219220221" +
		"222223224225226227228229230231232233234235236237238239240241242" +
		"243244245246247248249250251252253254255256257258259260261262263" +
		"264265266267268269270271272273274275276277278279280281282283284" +
		"285286287288289290291292293294295296297298299300301302303304305" +
		"306307308309310311312313314315316317318319320321322323324325326" +
		"327328329330331332333334335336337338339340341342343344345346347" +
		"348349350351352353354355356357358359360361362363364365366367368" +
		"369370371372373374375376377378379380381382383384385386387388389" +
		"390391392393394395396397398399400401402403404405406407408409410" +
		"411412413414415416417418419420421422423424425426427428429430431" +
		"432433434435436437438439440441442443444445446447448449450451452" +
		"453454455456457458459460461462463464465466467468469470471472473" +
		"474475476477478479480481482483484485486487488489490491492493494" +
		"495496497498499500501502503504505506507508509510511512513514515" +
		"516517518519520521522523524525526527528529530531532533534535536" +
		"537538539540541542543544545546547548549550551552553554555556557" +
		"558559560561562563564565566567568569570571572573574575576577578" +
		"579580581582583584585586587588589590591592593594595596597598599" +
		"600601602603604605606607608609610611612613614615616617618619620" +
		"621622623624625626627628629630631632633634635636637638639640641" +
		"642643644645646647648649650651652653654655656657658659660661662" +
		"663664665666667668669670671672673674675676677678679680681682683" +
		"684685686687688689690691692693694695696697698699700701702703704" +
		"705706707708709710711712713714715716717718719720721722723724725" +
		"726727728729730731732733734735736737738739740741742743744745746" +
		"747748749750751752753754755756757758759760761762763764765766767" +
		"768769770771772773774775776777778779780781782783784785786787788" +
		"789790791792793794795796797798799800801802803804805806807808809" +
		"810811812813814815816817818819820821822823824825826827828829830" +
		"831832833834835836837838839840841842843844845846847848849850851" +
		"852853854855856857858859860861862863864865866867868869870871872" +
		"873874875876877878879880881882883884885886887888889890891892893" +
		"894895896897898899900901902903904905906907908909910911912913914" +
		"915916917918919920921922923924925926927928929930931932933934935" +
		"936937938939940941942943944945946947948949950951952953954955956" +
		"957958959960961962963964965966967968969970971972973974975976977" +
		"978979980981982983984985986987988989990991992993994995996997998999"

	intStrLut4 = "1000100110021003100410051006100710081009101010111012" +
		"10131014101510161017101810191020102110221023102410251026102710281029" +
		"10301031103210331034103510361037103810391040104110421043104410451046" +
		"10471048104910501051105210531054105510561057105810591060106110621063" +
		"10641065106610671068106910701071107210731074107510761077107810791080" +
		"10811082108310841085108610871088108910901091109210931094109510961097" +
		"10981099110011011102110311041105110611071108110911101111111211131114" +
		"11151116111711181119112011211122112311241125112611271128112911301131" +
		"11321133113411351136113711381139114011411142114311441145114611471148" +
		"11491150115111521153115411551156115711581159116011611162116311641165" +
		"11661167116811691170117111721173117411751176117711781179118011811182" +
		"11831184118511861187118811891190119111921193119411951196119711981199" +
		"12001201120212031204120512061207120812091210121112121213121412151216" +
		"12171218121912201221122212231224122512261227122812291230123112321233" +
		"12341235123612371238123912401241124212431244124512461247124812491250" +
		"12511252125312541255125612571258125912601261126212631264126512661267" +
		"12681269127012711272127312741275127612771278127912801281128212831284" +
		"12851286128712881289129012911292129312941295129612971298129913001301" +
		"13021303130413051306130713081309131013111312131313141315131613171318" +
		"13191320132113221323132413251326132713281329133013311332133313341335" +
		"13361337133813391340134113421343134413451346134713481349135013511352" +
		"13531354135513561357135813591360136113621363136413651366136713681369" +
		"13701371137213731374137513761377137813791380138113821383138413851386" +
		"13871388138913901391139213931394139513961397139813991400140114021403" +
		"14041405140614071408140914101411141214131414141514161417141814191420" +
		"14211422142314241425142614271428142914301431143214331434143514361437" +
		"14381439144014411442144314441445144614471448144914501451145214531454" +
		"14551456145714581459146014611462146314641465146614671468146914701471" +
		"14721473147414751476147714781479148014811482148314841485148614871488" +
		"14891490149114921493149414951496149714981499150015011502150315041505" +
		"15061507150815091510151115121513151415151516151715181519152015211522" +
		"15231524152515261527152815291530153115321533153415351536153715381539" +
		"15401541154215431544154515461547154815491550155115521553155415551556" +
		"15571558155915601561156215631564156515661567156815691570157115721573" +
		"15741575157615771578157915801581158215831584158515861587158815891590" +
		"15911592159315941595159615971598159916001601160216031604160516061607" +
		"16081609161016111612161316141615161616171618161916201621162216231624" +
		"16251626162716281629163016311632163316341635163616371638163916401641" +
		"16421643164416451646164716481649165016511652165316541655165616571658" +
		"16591660166116621663166416651666166716681669167016711672167316741675" +
		"16761677167816791680168116821683168416851686168716881689169016911692" +
		"16931694169516961697169816991700170117021703170417051706170717081709" +
		"17101711171217131714171517161717171817191720172117221723172417251726" +
		"17271728172917301731173217331734173517361737173817391740174117421743" +
		"17441745174617471748174917501751175217531754175517561757175817591760" +
		"17611762176317641765176617671768176917701771177217731774177517761777" +
		"17781779178017811782178317841785178617871788178917901791179217931794" +
		"17951796179717981799180018011802180318041805180618071808180918101811" +
		"18121813181418151816181718181819182018211822182318241825182618271828" +
		"18291830183118321833183418351836183718381839184018411842184318441845" +
		"18461847184818491850185118521853185418551856185718581859186018611862" +
		"18631864186518661867186818691870187118721873187418751876187718781879" +
		"18801881188218831884188518861887188818891890189118921893189418951896" +
		"18971898189919001901190219031904190519061907190819091910191119121913" +
		"19141915191619171918191919201921192219231924192519261927192819291930" +
		"19311932193319341935193619371938193919401941194219431944194519461947" +
		"19481949195019511952195319541955195619571958195919601961196219631964" +
		"19651966196719681969197019711972197319741975197619771978197919801981" +
		"19821983198419851986198719881989199019911992199319941995199619971998" +
		"19992000200120022003200420052006200720082009201020112012201320142015" +
		"20162017201820192020202120222023202420252026202720282029203020312032" +
		"20332034203520362037203820392040204120422043204420452046204720482049" +
		"20502051205220532054205520562057205820592060206120622063206420652066" +
		"20672068206920702071207220732074207520762077207820792080208120822083" +
		"20842085208620872088208920902091209220932094209520962097209820992100" +
		"21012102210321042105210621072108210921102111211221132114211521162117" +
		"21182119212021212122212321242125212621272128212921302131213221332134" +
		"21352136213721382139214021412142214321442145214621472148214921502151" +
		"21522153215421552156215721582159216021612162216321642165216621672168" +
		"21692170217121722173217421752176217721782179218021812182218321842185" +
		"21862187218821892190219121922193219421952196219721982199220022012202" +
		"22032204220522062207220822092210221122122213221422152216221722182219" +
		"22202221222222232224222522262227222822292230223122322233223422352236" +
		"22372238223922402241224222432244224522462247224822492250225122522253" +
		"22542255225622572258225922602261226222632264226522662267226822692270" +
		"22712272227322742275227622772278227922802281228222832284228522862287" +
		"22882289229022912292229322942295229622972298229923002301230223032304" +
		"23052306230723082309231023112312231323142315231623172318231923202321" +
		"23222323232423252326232723282329233023312332233323342335233623372338" +
		"23392340234123422343234423452346234723482349235023512352235323542355" +
		"23562357235823592360236123622363236423652366236723682369237023712372" +
		"23732374237523762377237823792380238123822383238423852386238723882389" +
		"23902391239223932394239523962397239823992400240124022403240424052406" +
		"24072408240924102411241224132414241524162417241824192420242124222423" +
		"24242425242624272428242924302431243224332434243524362437243824392440" +
		"24412442244324442445244624472448244924502451245224532454245524562457" +
		"24582459246024612462246324642465246624672468246924702471247224732474" +
		"24752476247724782479248024812482248324842485248624872488248924902491" +
		"24922493249424952496249724982499250025012502250325042505250625072508" +
		"25092510251125122513251425152516251725182519252025212522252325242525" +
		"25262527252825292530253125322533253425352536253725382539254025412542" +
		"25432544254525462547254825492550255125522553255425552556255725582559" +
		"25602561256225632564256525662567256825692570257125722573257425752576" +
		"25772578257925802581258225832584258525862587258825892590259125922593" +
		"25942595259625972598259926002601260226032604260526062607260826092610" +
		"26112612261326142615261626172618261926202621262226232624262526262627" +
		"26282629263026312632263326342635263626372638263926402641264226432644" +
		"26452646264726482649265026512652265326542655265626572658265926602661" +
		"26622663266426652666266726682669267026712672267326742675267626772678" +
		"26792680268126822683268426852686268726882689269026912692269326942695" +
		"26962697269826992700270127022703270427052706270727082709271027112712" +
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		"99049905990699079908990999109911991299139914991599169917991899199920" +
		"99219922992399249925992699279928992999309931993299339934993599369937" +
		"99389939994099419942994399449945994699479948994999509951995299539954" +
		"99559956995799589959996099619962996399649965996699679968996999709971" +
		"99729973997499759976997799789979998099819982998399849985998699879988" +
		"99899990999199929993999499959996999799989999"
)

itoa_test.go

package strutil

import (
	"bytes"
	"fmt"
	"strconv"
	"testing"
)

func TestItoa(t *testing.T) {
	tests := []struct {
		from int
		exp  string
	}{
		{0, `0`}, {1, `1`}, {8, `8`}, {9, `9`},
		{10, `10`}, {11, `11`}, {98, `98`}, {99, `99`},
		{100, `100`}, {101, `101`}, {998, `998`}, {999, `999`},
		{1000, `1000`}, {1001, `1001`}, {9998, `9998`}, {9999, `9999`},
	}
	for idx, test := range tests {
		t.Logf(`test #%v from %v exp %v`, idx, test.from, test.exp)

		if exp, got := test.exp, Itoa(test.from); exp != got {
			t.Fatalf(`exp %v; got %v`, exp, got)
		}
	}
	for i := 0; i < 10010; i++ {
		if exp, got := strconv.Itoa(i), Itoa(i); exp != got {
			t.Fatalf(`from %v exp %v; got %v`, i, exp, got)
		}
	}
}

func BenchmarkItoa(b *testing.B) {
	for _, y := range []int{100, 500, 1000, 9999} {
		str := fmt.Sprint(y)
		b.Run(`From`+str, func(b *testing.B) {
			b.Run(`Std`, func(b *testing.B) {
				b.ReportAllocs()
				for i := 0; i < b.N; i++ {
					if s := strconv.Itoa(y); s != str {
						b.Fatalf(`exp %v; got %v`, str, s)
					}
				}
			})
			b.Run(`Itoa`, func(b *testing.B) {
				b.ReportAllocs()
				for i := 0; i < b.N; i++ {
					if s := Itoa(y); s != str {
						b.Fatalf(`exp %v; got %v`, str, s)
					}
				}
			})
		})
	}
}

func makeLut3() {
	var (
		buf bytes.Buffer
		y   = 4
	)
	fmt.Fprintf(&buf, `var intStrLut3 = "`)
	for i := 100; i <= 999; i++ {
		fmt.Fprintf(&buf, "%03d", i)
		if y++; y > 20 {
			fmt.Fprintf(&buf, "\" +\n\"")
			y = 0
		}
	}
	fmt.Fprintf(&buf, `"`)
	fmt.Println(buf.String())
}

func makeLut4() {
	var (
		buf bytes.Buffer
		y   = 4
	)
	fmt.Fprintf(&buf, `var intStrLut4 = "`)
	for i := 1000; i <= 9999; i++ {
		fmt.Fprintf(&buf, "%04d", i)
		if y++; y > 16 {
			fmt.Fprintf(&buf, "\" +\n\"")
			y = 0
		}
	}
	fmt.Fprintf(&buf, `"`)
	fmt.Println(buf.String())
}