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Source file src/bytes/bytes_test.go

Documentation: bytes

  // Copyright 2009 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.
  
  package bytes_test
  
  import (
  	. "bytes"
  	"fmt"
  	"internal/testenv"
  	"math/rand"
  	"reflect"
  	"strings"
  	"testing"
  	"unicode"
  	"unicode/utf8"
  )
  
  func eq(a, b []string) bool {
  	if len(a) != len(b) {
  		return false
  	}
  	for i := 0; i < len(a); i++ {
  		if a[i] != b[i] {
  			return false
  		}
  	}
  	return true
  }
  
  func sliceOfString(s [][]byte) []string {
  	result := make([]string, len(s))
  	for i, v := range s {
  		result[i] = string(v)
  	}
  	return result
  }
  
  // For ease of reading, the test cases use strings that are converted to byte
  // slices before invoking the functions.
  
  var abcd = "abcd"
  var faces = "☺☻☹"
  var commas = "1,2,3,4"
  var dots = "1....2....3....4"
  
  type BinOpTest struct {
  	a string
  	b string
  	i int
  }
  
  func TestEqual(t *testing.T) {
  	for _, tt := range compareTests {
  		eql := Equal(tt.a, tt.b)
  		if eql != (tt.i == 0) {
  			t.Errorf(`Equal(%q, %q) = %v`, tt.a, tt.b, eql)
  		}
  		eql = EqualPortable(tt.a, tt.b)
  		if eql != (tt.i == 0) {
  			t.Errorf(`EqualPortable(%q, %q) = %v`, tt.a, tt.b, eql)
  		}
  	}
  }
  
  func TestEqualExhaustive(t *testing.T) {
  	var size = 128
  	if testing.Short() {
  		size = 32
  	}
  	a := make([]byte, size)
  	b := make([]byte, size)
  	b_init := make([]byte, size)
  	// randomish but deterministic data
  	for i := 0; i < size; i++ {
  		a[i] = byte(17 * i)
  		b_init[i] = byte(23*i + 100)
  	}
  
  	for len := 0; len <= size; len++ {
  		for x := 0; x <= size-len; x++ {
  			for y := 0; y <= size-len; y++ {
  				copy(b, b_init)
  				copy(b[y:y+len], a[x:x+len])
  				if !Equal(a[x:x+len], b[y:y+len]) || !Equal(b[y:y+len], a[x:x+len]) {
  					t.Errorf("Equal(%d, %d, %d) = false", len, x, y)
  				}
  			}
  		}
  	}
  }
  
  // make sure Equal returns false for minimally different strings. The data
  // is all zeros except for a single one in one location.
  func TestNotEqual(t *testing.T) {
  	var size = 128
  	if testing.Short() {
  		size = 32
  	}
  	a := make([]byte, size)
  	b := make([]byte, size)
  
  	for len := 0; len <= size; len++ {
  		for x := 0; x <= size-len; x++ {
  			for y := 0; y <= size-len; y++ {
  				for diffpos := x; diffpos < x+len; diffpos++ {
  					a[diffpos] = 1
  					if Equal(a[x:x+len], b[y:y+len]) || Equal(b[y:y+len], a[x:x+len]) {
  						t.Errorf("NotEqual(%d, %d, %d, %d) = true", len, x, y, diffpos)
  					}
  					a[diffpos] = 0
  				}
  			}
  		}
  	}
  }
  
  var indexTests = []BinOpTest{
  	{"", "", 0},
  	{"", "a", -1},
  	{"", "foo", -1},
  	{"fo", "foo", -1},
  	{"foo", "baz", -1},
  	{"foo", "foo", 0},
  	{"oofofoofooo", "f", 2},
  	{"oofofoofooo", "foo", 4},
  	{"barfoobarfoo", "foo", 3},
  	{"foo", "", 0},
  	{"foo", "o", 1},
  	{"abcABCabc", "A", 3},
  	// cases with one byte strings - test IndexByte and special case in Index()
  	{"", "a", -1},
  	{"x", "a", -1},
  	{"x", "x", 0},
  	{"abc", "a", 0},
  	{"abc", "b", 1},
  	{"abc", "c", 2},
  	{"abc", "x", -1},
  	{"barfoobarfooyyyzzzyyyzzzyyyzzzyyyxxxzzzyyy", "x", 33},
  	{"foofyfoobarfoobar", "y", 4},
  	{"oooooooooooooooooooooo", "r", -1},
  }
  
  var lastIndexTests = []BinOpTest{
  	{"", "", 0},
  	{"", "a", -1},
  	{"", "foo", -1},
  	{"fo", "foo", -1},
  	{"foo", "foo", 0},
  	{"foo", "f", 0},
  	{"oofofoofooo", "f", 7},
  	{"oofofoofooo", "foo", 7},
  	{"barfoobarfoo", "foo", 9},
  	{"foo", "", 3},
  	{"foo", "o", 2},
  	{"abcABCabc", "A", 3},
  	{"abcABCabc", "a", 6},
  }
  
  var indexAnyTests = []BinOpTest{
  	{"", "", -1},
  	{"", "a", -1},
  	{"", "abc", -1},
  	{"a", "", -1},
  	{"a", "a", 0},
  	{"aaa", "a", 0},
  	{"abc", "xyz", -1},
  	{"abc", "xcz", 2},
  	{"ab☺c", "x☺yz", 2},
  	{"a☺b☻c☹d", "cx", len("a☺b☻")},
  	{"a☺b☻c☹d", "uvw☻xyz", len("a☺b")},
  	{"aRegExp*", ".(|)*+?^$[]", 7},
  	{dots + dots + dots, " ", -1},
  	{"012abcba210", "\xffb", 4},
  	{"012\x80bcb\x80210", "\xffb", 3},
  }
  
  var lastIndexAnyTests = []BinOpTest{
  	{"", "", -1},
  	{"", "a", -1},
  	{"", "abc", -1},
  	{"a", "", -1},
  	{"a", "a", 0},
  	{"aaa", "a", 2},
  	{"abc", "xyz", -1},
  	{"abc", "ab", 1},
  	{"ab☺c", "x☺yz", 2},
  	{"a☺b☻c☹d", "cx", len("a☺b☻")},
  	{"a☺b☻c☹d", "uvw☻xyz", len("a☺b")},
  	{"a.RegExp*", ".(|)*+?^$[]", 8},
  	{dots + dots + dots, " ", -1},
  	{"012abcba210", "\xffb", 6},
  	{"012\x80bcb\x80210", "\xffb", 7},
  }
  
  // Execute f on each test case.  funcName should be the name of f; it's used
  // in failure reports.
  func runIndexTests(t *testing.T, f func(s, sep []byte) int, funcName string, testCases []BinOpTest) {
  	for _, test := range testCases {
  		a := []byte(test.a)
  		b := []byte(test.b)
  		actual := f(a, b)
  		if actual != test.i {
  			t.Errorf("%s(%q,%q) = %v; want %v", funcName, a, b, actual, test.i)
  		}
  	}
  }
  
  func runIndexAnyTests(t *testing.T, f func(s []byte, chars string) int, funcName string, testCases []BinOpTest) {
  	for _, test := range testCases {
  		a := []byte(test.a)
  		actual := f(a, test.b)
  		if actual != test.i {
  			t.Errorf("%s(%q,%q) = %v; want %v", funcName, a, test.b, actual, test.i)
  		}
  	}
  }
  
  func TestIndex(t *testing.T)     { runIndexTests(t, Index, "Index", indexTests) }
  func TestLastIndex(t *testing.T) { runIndexTests(t, LastIndex, "LastIndex", lastIndexTests) }
  func TestIndexAny(t *testing.T)  { runIndexAnyTests(t, IndexAny, "IndexAny", indexAnyTests) }
  func TestLastIndexAny(t *testing.T) {
  	runIndexAnyTests(t, LastIndexAny, "LastIndexAny", lastIndexAnyTests)
  }
  
  func TestIndexByte(t *testing.T) {
  	for _, tt := range indexTests {
  		if len(tt.b) != 1 {
  			continue
  		}
  		a := []byte(tt.a)
  		b := tt.b[0]
  		pos := IndexByte(a, b)
  		if pos != tt.i {
  			t.Errorf(`IndexByte(%q, '%c') = %v`, tt.a, b, pos)
  		}
  		posp := IndexBytePortable(a, b)
  		if posp != tt.i {
  			t.Errorf(`indexBytePortable(%q, '%c') = %v`, tt.a, b, posp)
  		}
  	}
  }
  
  func TestLastIndexByte(t *testing.T) {
  	testCases := []BinOpTest{
  		{"", "q", -1},
  		{"abcdef", "q", -1},
  		{"abcdefabcdef", "a", len("abcdef")},      // something in the middle
  		{"abcdefabcdef", "f", len("abcdefabcde")}, // last byte
  		{"zabcdefabcdef", "z", 0},                 // first byte
  		{"a☺b☻c☹d", "b", len("a☺")},               // non-ascii
  	}
  	for _, test := range testCases {
  		actual := LastIndexByte([]byte(test.a), test.b[0])
  		if actual != test.i {
  			t.Errorf("LastIndexByte(%q,%c) = %v; want %v", test.a, test.b[0], actual, test.i)
  		}
  	}
  }
  
  // test a larger buffer with different sizes and alignments
  func TestIndexByteBig(t *testing.T) {
  	var n = 1024
  	if testing.Short() {
  		n = 128
  	}
  	b := make([]byte, n)
  	for i := 0; i < n; i++ {
  		// different start alignments
  		b1 := b[i:]
  		for j := 0; j < len(b1); j++ {
  			b1[j] = 'x'
  			pos := IndexByte(b1, 'x')
  			if pos != j {
  				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
  			}
  			b1[j] = 0
  			pos = IndexByte(b1, 'x')
  			if pos != -1 {
  				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
  			}
  		}
  		// different end alignments
  		b1 = b[:i]
  		for j := 0; j < len(b1); j++ {
  			b1[j] = 'x'
  			pos := IndexByte(b1, 'x')
  			if pos != j {
  				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
  			}
  			b1[j] = 0
  			pos = IndexByte(b1, 'x')
  			if pos != -1 {
  				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
  			}
  		}
  		// different start and end alignments
  		b1 = b[i/2 : n-(i+1)/2]
  		for j := 0; j < len(b1); j++ {
  			b1[j] = 'x'
  			pos := IndexByte(b1, 'x')
  			if pos != j {
  				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
  			}
  			b1[j] = 0
  			pos = IndexByte(b1, 'x')
  			if pos != -1 {
  				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
  			}
  		}
  	}
  }
  
  // test a small index across all page offsets
  func TestIndexByteSmall(t *testing.T) {
  	b := make([]byte, 5015) // bigger than a page
  	// Make sure we find the correct byte even when straddling a page.
  	for i := 0; i <= len(b)-15; i++ {
  		for j := 0; j < 15; j++ {
  			b[i+j] = byte(100 + j)
  		}
  		for j := 0; j < 15; j++ {
  			p := IndexByte(b[i:i+15], byte(100+j))
  			if p != j {
  				t.Errorf("IndexByte(%q, %d) = %d", b[i:i+15], 100+j, p)
  			}
  		}
  		for j := 0; j < 15; j++ {
  			b[i+j] = 0
  		}
  	}
  	// Make sure matches outside the slice never trigger.
  	for i := 0; i <= len(b)-15; i++ {
  		for j := 0; j < 15; j++ {
  			b[i+j] = 1
  		}
  		for j := 0; j < 15; j++ {
  			p := IndexByte(b[i:i+15], byte(0))
  			if p != -1 {
  				t.Errorf("IndexByte(%q, %d) = %d", b[i:i+15], 0, p)
  			}
  		}
  		for j := 0; j < 15; j++ {
  			b[i+j] = 0
  		}
  	}
  }
  
  func TestIndexRune(t *testing.T) {
  	tests := []struct {
  		in   string
  		rune rune
  		want int
  	}{
  		{"", 'a', -1},
  		{"", '☺', -1},
  		{"foo", '☹', -1},
  		{"foo", 'o', 1},
  		{"foo☺bar", '☺', 3},
  		{"foo☺☻☹bar", '☹', 9},
  		{"a A x", 'A', 2},
  		{"some_text=some_value", '=', 9},
  		{"☺a", 'a', 3},
  		{"a☻☺b", '☺', 4},
  
  		// RuneError should match any invalid UTF-8 byte sequence.
  		{"�", '�', 0},
  		{"\xff", '�', 0},
  		{"☻x�", '�', len("☻x")},
  		{"☻x\xe2\x98", '�', len("☻x")},
  		{"☻x\xe2\x98�", '�', len("☻x")},
  		{"☻x\xe2\x98x", '�', len("☻x")},
  
  		// Invalid rune values should never match.
  		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", -1, -1},
  		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", 0xD800, -1}, // Surrogate pair
  		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", utf8.MaxRune + 1, -1},
  	}
  	for _, tt := range tests {
  		if got := IndexRune([]byte(tt.in), tt.rune); got != tt.want {
  			t.Errorf("IndexRune(%q, %d) = %v; want %v", tt.in, tt.rune, got, tt.want)
  		}
  	}
  
  	haystack := []byte("test世界")
  	allocs := testing.AllocsPerRun(1000, func() {
  		if i := IndexRune(haystack, 's'); i != 2 {
  			t.Fatalf("'s' at %d; want 2", i)
  		}
  		if i := IndexRune(haystack, '世'); i != 4 {
  			t.Fatalf("'世' at %d; want 4", i)
  		}
  	})
  	if allocs != 0 {
  		t.Errorf("expected no allocations, got %f", allocs)
  	}
  }
  
  // test count of a single byte across page offsets
  func TestCountByte(t *testing.T) {
  	b := make([]byte, 5015) // bigger than a page
  	windows := []int{1, 2, 3, 4, 15, 16, 17, 31, 32, 33, 63, 64, 65, 128}
  	testCountWindow := func(i, window int) {
  		for j := 0; j < window; j++ {
  			b[i+j] = byte(100)
  			p := Count(b[i:i+window], []byte{100})
  			if p != j+1 {
  				t.Errorf("TestCountByte.Count(%q, 100) = %d", b[i:i+window], p)
  			}
  			pGeneric := CountGeneric(b[i:i+window], []byte{100})
  			if pGeneric != j+1 {
  				t.Errorf("TestCountByte.CountGeneric(%q, 100) = %d", b[i:i+window], p)
  			}
  		}
  	}
  
  	maxWnd := windows[len(windows)-1]
  
  	for i := 0; i <= 2*maxWnd; i++ {
  		for _, window := range windows {
  			if window > len(b[i:]) {
  				window = len(b[i:])
  			}
  			testCountWindow(i, window)
  			for j := 0; j < window; j++ {
  				b[i+j] = byte(0)
  			}
  		}
  	}
  	for i := 4096 - (maxWnd + 1); i < len(b); i++ {
  		for _, window := range windows {
  			if window > len(b[i:]) {
  				window = len(b[i:])
  			}
  			testCountWindow(i, window)
  			for j := 0; j < window; j++ {
  				b[i+j] = byte(0)
  			}
  		}
  	}
  }
  
  // Make sure we don't count bytes outside our window
  func TestCountByteNoMatch(t *testing.T) {
  	b := make([]byte, 5015)
  	windows := []int{1, 2, 3, 4, 15, 16, 17, 31, 32, 33, 63, 64, 65, 128}
  	for i := 0; i <= len(b); i++ {
  		for _, window := range windows {
  			if window > len(b[i:]) {
  				window = len(b[i:])
  			}
  			// Fill the window with non-match
  			for j := 0; j < window; j++ {
  				b[i+j] = byte(100)
  			}
  			// Try to find something that doesn't exist
  			p := Count(b[i:i+window], []byte{0})
  			if p != 0 {
  				t.Errorf("TestCountByteNoMatch(%q, 0) = %d", b[i:i+window], p)
  			}
  			pGeneric := CountGeneric(b[i:i+window], []byte{0})
  			if pGeneric != 0 {
  				t.Errorf("TestCountByteNoMatch.CountGeneric(%q, 100) = %d", b[i:i+window], p)
  			}
  			for j := 0; j < window; j++ {
  				b[i+j] = byte(0)
  			}
  		}
  	}
  }
  
  var bmbuf []byte
  
  func valName(x int) string {
  	if s := x >> 20; s<<20 == x {
  		return fmt.Sprintf("%dM", s)
  	}
  	if s := x >> 10; s<<10 == x {
  		return fmt.Sprintf("%dK", s)
  	}
  	return fmt.Sprint(x)
  }
  
  func benchBytes(b *testing.B, sizes []int, f func(b *testing.B, n int)) {
  	for _, n := range sizes {
  		if isRaceBuilder && n > 4<<10 {
  			continue
  		}
  		b.Run(valName(n), func(b *testing.B) {
  			if len(bmbuf) < n {
  				bmbuf = make([]byte, n)
  			}
  			b.SetBytes(int64(n))
  			f(b, n)
  		})
  	}
  }
  
  var indexSizes = []int{10, 32, 4 << 10, 4 << 20, 64 << 20}
  
  var isRaceBuilder = strings.HasSuffix(testenv.Builder(), "-race")
  
  func BenchmarkIndexByte(b *testing.B) {
  	benchBytes(b, indexSizes, bmIndexByte(IndexByte))
  }
  
  func BenchmarkIndexBytePortable(b *testing.B) {
  	benchBytes(b, indexSizes, bmIndexByte(IndexBytePortable))
  }
  
  func bmIndexByte(index func([]byte, byte) int) func(b *testing.B, n int) {
  	return func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		buf[n-1] = 'x'
  		for i := 0; i < b.N; i++ {
  			j := index(buf, 'x')
  			if j != n-1 {
  				b.Fatal("bad index", j)
  			}
  		}
  		buf[n-1] = '\x00'
  	}
  }
  
  func BenchmarkIndexRune(b *testing.B) {
  	benchBytes(b, indexSizes, bmIndexRune(IndexRune))
  }
  
  func BenchmarkIndexRuneASCII(b *testing.B) {
  	benchBytes(b, indexSizes, bmIndexRuneASCII(IndexRune))
  }
  
  func bmIndexRuneASCII(index func([]byte, rune) int) func(b *testing.B, n int) {
  	return func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		buf[n-1] = 'x'
  		for i := 0; i < b.N; i++ {
  			j := index(buf, 'x')
  			if j != n-1 {
  				b.Fatal("bad index", j)
  			}
  		}
  		buf[n-1] = '\x00'
  	}
  }
  
  func bmIndexRune(index func([]byte, rune) int) func(b *testing.B, n int) {
  	return func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		utf8.EncodeRune(buf[n-3:], '世')
  		for i := 0; i < b.N; i++ {
  			j := index(buf, '世')
  			if j != n-3 {
  				b.Fatal("bad index", j)
  			}
  		}
  		buf[n-3] = '\x00'
  		buf[n-2] = '\x00'
  		buf[n-1] = '\x00'
  	}
  }
  
  func BenchmarkEqual(b *testing.B) {
  	b.Run("0", func(b *testing.B) {
  		var buf [4]byte
  		buf1 := buf[0:0]
  		buf2 := buf[1:1]
  		for i := 0; i < b.N; i++ {
  			eq := Equal(buf1, buf2)
  			if !eq {
  				b.Fatal("bad equal")
  			}
  		}
  	})
  
  	sizes := []int{1, 6, 9, 15, 16, 20, 32, 4 << 10, 4 << 20, 64 << 20}
  	benchBytes(b, sizes, bmEqual(Equal))
  }
  
  func BenchmarkEqualPort(b *testing.B) {
  	sizes := []int{1, 6, 32, 4 << 10, 4 << 20, 64 << 20}
  	benchBytes(b, sizes, bmEqual(EqualPortable))
  }
  
  func bmEqual(equal func([]byte, []byte) bool) func(b *testing.B, n int) {
  	return func(b *testing.B, n int) {
  		if len(bmbuf) < 2*n {
  			bmbuf = make([]byte, 2*n)
  		}
  		buf1 := bmbuf[0:n]
  		buf2 := bmbuf[n : 2*n]
  		buf1[n-1] = 'x'
  		buf2[n-1] = 'x'
  		for i := 0; i < b.N; i++ {
  			eq := equal(buf1, buf2)
  			if !eq {
  				b.Fatal("bad equal")
  			}
  		}
  		buf1[n-1] = '\x00'
  		buf2[n-1] = '\x00'
  	}
  }
  
  func BenchmarkIndex(b *testing.B) {
  	benchBytes(b, indexSizes, func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		buf[n-1] = 'x'
  		for i := 0; i < b.N; i++ {
  			j := Index(buf, buf[n-7:])
  			if j != n-7 {
  				b.Fatal("bad index", j)
  			}
  		}
  		buf[n-1] = '\x00'
  	})
  }
  
  func BenchmarkIndexEasy(b *testing.B) {
  	benchBytes(b, indexSizes, func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		buf[n-1] = 'x'
  		buf[n-7] = 'x'
  		for i := 0; i < b.N; i++ {
  			j := Index(buf, buf[n-7:])
  			if j != n-7 {
  				b.Fatal("bad index", j)
  			}
  		}
  		buf[n-1] = '\x00'
  		buf[n-7] = '\x00'
  	})
  }
  
  func BenchmarkCount(b *testing.B) {
  	benchBytes(b, indexSizes, func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		buf[n-1] = 'x'
  		for i := 0; i < b.N; i++ {
  			j := Count(buf, buf[n-7:])
  			if j != 1 {
  				b.Fatal("bad count", j)
  			}
  		}
  		buf[n-1] = '\x00'
  	})
  }
  
  func BenchmarkCountEasy(b *testing.B) {
  	benchBytes(b, indexSizes, func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		buf[n-1] = 'x'
  		buf[n-7] = 'x'
  		for i := 0; i < b.N; i++ {
  			j := Count(buf, buf[n-7:])
  			if j != 1 {
  				b.Fatal("bad count", j)
  			}
  		}
  		buf[n-1] = '\x00'
  		buf[n-7] = '\x00'
  	})
  }
  
  func BenchmarkCountSingle(b *testing.B) {
  	benchBytes(b, indexSizes, func(b *testing.B, n int) {
  		buf := bmbuf[0:n]
  		step := 8
  		for i := 0; i < len(buf); i += step {
  			buf[i] = 1
  		}
  		expect := (len(buf) + (step - 1)) / step
  		for i := 0; i < b.N; i++ {
  			j := Count(buf, []byte{1})
  			if j != expect {
  				b.Fatal("bad count", j, expect)
  			}
  		}
  		for i := 0; i < len(buf); i++ {
  			buf[i] = 0
  		}
  	})
  }
  
  type ExplodeTest struct {
  	s string
  	n int
  	a []string
  }
  
  var explodetests = []ExplodeTest{
  	{"", -1, []string{}},
  	{abcd, -1, []string{"a", "b", "c", "d"}},
  	{faces, -1, []string{"☺", "☻", "☹"}},
  	{abcd, 2, []string{"a", "bcd"}},
  }
  
  func TestExplode(t *testing.T) {
  	for _, tt := range explodetests {
  		a := SplitN([]byte(tt.s), nil, tt.n)
  		result := sliceOfString(a)
  		if !eq(result, tt.a) {
  			t.Errorf(`Explode("%s", %d) = %v; want %v`, tt.s, tt.n, result, tt.a)
  			continue
  		}
  		s := Join(a, []byte{})
  		if string(s) != tt.s {
  			t.Errorf(`Join(Explode("%s", %d), "") = "%s"`, tt.s, tt.n, s)
  		}
  	}
  }
  
  type SplitTest struct {
  	s   string
  	sep string
  	n   int
  	a   []string
  }
  
  var splittests = []SplitTest{
  	{abcd, "a", 0, nil},
  	{abcd, "a", -1, []string{"", "bcd"}},
  	{abcd, "z", -1, []string{"abcd"}},
  	{abcd, "", -1, []string{"a", "b", "c", "d"}},
  	{commas, ",", -1, []string{"1", "2", "3", "4"}},
  	{dots, "...", -1, []string{"1", ".2", ".3", ".4"}},
  	{faces, "☹", -1, []string{"☺☻", ""}},
  	{faces, "~", -1, []string{faces}},
  	{faces, "", -1, []string{"☺", "☻", "☹"}},
  	{"1 2 3 4", " ", 3, []string{"1", "2", "3 4"}},
  	{"1 2", " ", 3, []string{"1", "2"}},
  	{"123", "", 2, []string{"1", "23"}},
  	{"123", "", 17, []string{"1", "2", "3"}},
  }
  
  func TestSplit(t *testing.T) {
  	for _, tt := range splittests {
  		a := SplitN([]byte(tt.s), []byte(tt.sep), tt.n)
  		result := sliceOfString(a)
  		if !eq(result, tt.a) {
  			t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
  			continue
  		}
  		if tt.n == 0 {
  			continue
  		}
  		s := Join(a, []byte(tt.sep))
  		if string(s) != tt.s {
  			t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
  		}
  		if tt.n < 0 {
  			b := Split([]byte(tt.s), []byte(tt.sep))
  			if !reflect.DeepEqual(a, b) {
  				t.Errorf("Split disagrees withSplitN(%q, %q, %d) = %v; want %v", tt.s, tt.sep, tt.n, b, a)
  			}
  		}
  		if len(a) > 0 {
  			in, out := a[0], s
  			if cap(in) == cap(out) && &in[:1][0] == &out[:1][0] {
  				t.Errorf("Join(%#v, %q) didn't copy", a, tt.sep)
  			}
  		}
  	}
  }
  
  var splitaftertests = []SplitTest{
  	{abcd, "a", -1, []string{"a", "bcd"}},
  	{abcd, "z", -1, []string{"abcd"}},
  	{abcd, "", -1, []string{"a", "b", "c", "d"}},
  	{commas, ",", -1, []string{"1,", "2,", "3,", "4"}},
  	{dots, "...", -1, []string{"1...", ".2...", ".3...", ".4"}},
  	{faces, "☹", -1, []string{"☺☻☹", ""}},
  	{faces, "~", -1, []string{faces}},
  	{faces, "", -1, []string{"☺", "☻", "☹"}},
  	{"1 2 3 4", " ", 3, []string{"1 ", "2 ", "3 4"}},
  	{"1 2 3", " ", 3, []string{"1 ", "2 ", "3"}},
  	{"1 2", " ", 3, []string{"1 ", "2"}},
  	{"123", "", 2, []string{"1", "23"}},
  	{"123", "", 17, []string{"1", "2", "3"}},
  }
  
  func TestSplitAfter(t *testing.T) {
  	for _, tt := range splitaftertests {
  		a := SplitAfterN([]byte(tt.s), []byte(tt.sep), tt.n)
  		result := sliceOfString(a)
  		if !eq(result, tt.a) {
  			t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
  			continue
  		}
  		s := Join(a, nil)
  		if string(s) != tt.s {
  			t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
  		}
  		if tt.n < 0 {
  			b := SplitAfter([]byte(tt.s), []byte(tt.sep))
  			if !reflect.DeepEqual(a, b) {
  				t.Errorf("SplitAfter disagrees withSplitAfterN(%q, %q, %d) = %v; want %v", tt.s, tt.sep, tt.n, b, a)
  			}
  		}
  	}
  }
  
  type FieldsTest struct {
  	s string
  	a []string
  }
  
  var fieldstests = []FieldsTest{
  	{"", []string{}},
  	{" ", []string{}},
  	{" \t ", []string{}},
  	{"  abc  ", []string{"abc"}},
  	{"1 2 3 4", []string{"1", "2", "3", "4"}},
  	{"1  2  3  4", []string{"1", "2", "3", "4"}},
  	{"1\t\t2\t\t3\t4", []string{"1", "2", "3", "4"}},
  	{"1\u20002\u20013\u20024", []string{"1", "2", "3", "4"}},
  	{"\u2000\u2001\u2002", []string{}},
  	{"\n™\t™\n", []string{"™", "™"}},
  	{faces, []string{faces}},
  }
  
  func TestFields(t *testing.T) {
  	for _, tt := range fieldstests {
  		a := Fields([]byte(tt.s))
  		result := sliceOfString(a)
  		if !eq(result, tt.a) {
  			t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
  			continue
  		}
  	}
  }
  
  func TestFieldsFunc(t *testing.T) {
  	for _, tt := range fieldstests {
  		a := FieldsFunc([]byte(tt.s), unicode.IsSpace)
  		result := sliceOfString(a)
  		if !eq(result, tt.a) {
  			t.Errorf("FieldsFunc(%q, unicode.IsSpace) = %v; want %v", tt.s, a, tt.a)
  			continue
  		}
  	}
  	pred := func(c rune) bool { return c == 'X' }
  	var fieldsFuncTests = []FieldsTest{
  		{"", []string{}},
  		{"XX", []string{}},
  		{"XXhiXXX", []string{"hi"}},
  		{"aXXbXXXcX", []string{"a", "b", "c"}},
  	}
  	for _, tt := range fieldsFuncTests {
  		a := FieldsFunc([]byte(tt.s), pred)
  		result := sliceOfString(a)
  		if !eq(result, tt.a) {
  			t.Errorf("FieldsFunc(%q) = %v, want %v", tt.s, a, tt.a)
  		}
  	}
  }
  
  // Test case for any function which accepts and returns a byte slice.
  // For ease of creation, we write the byte slices as strings.
  type StringTest struct {
  	in, out string
  }
  
  var upperTests = []StringTest{
  	{"", ""},
  	{"abc", "ABC"},
  	{"AbC123", "ABC123"},
  	{"azAZ09_", "AZAZ09_"},
  	{"\u0250\u0250\u0250\u0250\u0250", "\u2C6F\u2C6F\u2C6F\u2C6F\u2C6F"}, // grows one byte per char
  }
  
  var lowerTests = []StringTest{
  	{"", ""},
  	{"abc", "abc"},
  	{"AbC123", "abc123"},
  	{"azAZ09_", "azaz09_"},
  	{"\u2C6D\u2C6D\u2C6D\u2C6D\u2C6D", "\u0251\u0251\u0251\u0251\u0251"}, // shrinks one byte per char
  }
  
  const space = "\t\v\r\f\n\u0085\u00a0\u2000\u3000"
  
  var trimSpaceTests = []StringTest{
  	{"", ""},
  	{"abc", "abc"},
  	{space + "abc" + space, "abc"},
  	{" ", ""},
  	{" \t\r\n \t\t\r\r\n\n ", ""},
  	{" \t\r\n x\t\t\r\r\n\n ", "x"},
  	{" \u2000\t\r\n x\t\t\r\r\ny\n \u3000", "x\t\t\r\r\ny"},
  	{"1 \t\r\n2", "1 \t\r\n2"},
  	{" x\x80", "x\x80"},
  	{" x\xc0", "x\xc0"},
  	{"x \xc0\xc0 ", "x \xc0\xc0"},
  	{"x \xc0", "x \xc0"},
  	{"x \xc0 ", "x \xc0"},
  	{"x \xc0\xc0 ", "x \xc0\xc0"},
  	{"x ☺\xc0\xc0 ", "x ☺\xc0\xc0"},
  	{"x ☺ ", "x ☺"},
  }
  
  // Execute f on each test case.  funcName should be the name of f; it's used
  // in failure reports.
  func runStringTests(t *testing.T, f func([]byte) []byte, funcName string, testCases []StringTest) {
  	for _, tc := range testCases {
  		actual := string(f([]byte(tc.in)))
  		if actual != tc.out {
  			t.Errorf("%s(%q) = %q; want %q", funcName, tc.in, actual, tc.out)
  		}
  	}
  }
  
  func tenRunes(r rune) string {
  	runes := make([]rune, 10)
  	for i := range runes {
  		runes[i] = r
  	}
  	return string(runes)
  }
  
  // User-defined self-inverse mapping function
  func rot13(r rune) rune {
  	const step = 13
  	if r >= 'a' && r <= 'z' {
  		return ((r - 'a' + step) % 26) + 'a'
  	}
  	if r >= 'A' && r <= 'Z' {
  		return ((r - 'A' + step) % 26) + 'A'
  	}
  	return r
  }
  
  func TestMap(t *testing.T) {
  	// Run a couple of awful growth/shrinkage tests
  	a := tenRunes('a')
  
  	// 1.  Grow. This triggers two reallocations in Map.
  	maxRune := func(r rune) rune { return unicode.MaxRune }
  	m := Map(maxRune, []byte(a))
  	expect := tenRunes(unicode.MaxRune)
  	if string(m) != expect {
  		t.Errorf("growing: expected %q got %q", expect, m)
  	}
  
  	// 2. Shrink
  	minRune := func(r rune) rune { return 'a' }
  	m = Map(minRune, []byte(tenRunes(unicode.MaxRune)))
  	expect = a
  	if string(m) != expect {
  		t.Errorf("shrinking: expected %q got %q", expect, m)
  	}
  
  	// 3. Rot13
  	m = Map(rot13, []byte("a to zed"))
  	expect = "n gb mrq"
  	if string(m) != expect {
  		t.Errorf("rot13: expected %q got %q", expect, m)
  	}
  
  	// 4. Rot13^2
  	m = Map(rot13, Map(rot13, []byte("a to zed")))
  	expect = "a to zed"
  	if string(m) != expect {
  		t.Errorf("rot13: expected %q got %q", expect, m)
  	}
  
  	// 5. Drop
  	dropNotLatin := func(r rune) rune {
  		if unicode.Is(unicode.Latin, r) {
  			return r
  		}
  		return -1
  	}
  	m = Map(dropNotLatin, []byte("Hello, 세계"))
  	expect = "Hello"
  	if string(m) != expect {
  		t.Errorf("drop: expected %q got %q", expect, m)
  	}
  
  	// 6. Invalid rune
  	invalidRune := func(r rune) rune {
  		return utf8.MaxRune + 1
  	}
  	m = Map(invalidRune, []byte("x"))
  	expect = "\uFFFD"
  	if string(m) != expect {
  		t.Errorf("invalidRune: expected %q got %q", expect, m)
  	}
  }
  
  func TestToUpper(t *testing.T) { runStringTests(t, ToUpper, "ToUpper", upperTests) }
  
  func TestToLower(t *testing.T) { runStringTests(t, ToLower, "ToLower", lowerTests) }
  
  func TestTrimSpace(t *testing.T) { runStringTests(t, TrimSpace, "TrimSpace", trimSpaceTests) }
  
  type RepeatTest struct {
  	in, out string
  	count   int
  }
  
  var RepeatTests = []RepeatTest{
  	{"", "", 0},
  	{"", "", 1},
  	{"", "", 2},
  	{"-", "", 0},
  	{"-", "-", 1},
  	{"-", "----------", 10},
  	{"abc ", "abc abc abc ", 3},
  }
  
  func TestRepeat(t *testing.T) {
  	for _, tt := range RepeatTests {
  		tin := []byte(tt.in)
  		tout := []byte(tt.out)
  		a := Repeat(tin, tt.count)
  		if !Equal(a, tout) {
  			t.Errorf("Repeat(%q, %d) = %q; want %q", tin, tt.count, a, tout)
  			continue
  		}
  	}
  }
  
  func repeat(b []byte, count int) (err error) {
  	defer func() {
  		if r := recover(); r != nil {
  			switch v := r.(type) {
  			case error:
  				err = v
  			default:
  				err = fmt.Errorf("%s", v)
  			}
  		}
  	}()
  
  	Repeat(b, count)
  
  	return
  }
  
  // See Issue golang.org/issue/16237
  func TestRepeatCatchesOverflow(t *testing.T) {
  	tests := [...]struct {
  		s      string
  		count  int
  		errStr string
  	}{
  		0: {"--", -2147483647, "negative"},
  		1: {"", int(^uint(0) >> 1), ""},
  		2: {"-", 10, ""},
  		3: {"gopher", 0, ""},
  		4: {"-", -1, "negative"},
  		5: {"--", -102, "negative"},
  		6: {string(make([]byte, 255)), int((^uint(0))/255 + 1), "overflow"},
  	}
  
  	for i, tt := range tests {
  		err := repeat([]byte(tt.s), tt.count)
  		if tt.errStr == "" {
  			if err != nil {
  				t.Errorf("#%d panicked %v", i, err)
  			}
  			continue
  		}
  
  		if err == nil || !strings.Contains(err.Error(), tt.errStr) {
  			t.Errorf("#%d expected %q got %q", i, tt.errStr, err)
  		}
  	}
  }
  
  func runesEqual(a, b []rune) bool {
  	if len(a) != len(b) {
  		return false
  	}
  	for i, r := range a {
  		if r != b[i] {
  			return false
  		}
  	}
  	return true
  }
  
  type RunesTest struct {
  	in    string
  	out   []rune
  	lossy bool
  }
  
  var RunesTests = []RunesTest{
  	{"", []rune{}, false},
  	{" ", []rune{32}, false},
  	{"ABC", []rune{65, 66, 67}, false},
  	{"abc", []rune{97, 98, 99}, false},
  	{"\u65e5\u672c\u8a9e", []rune{26085, 26412, 35486}, false},
  	{"ab\x80c", []rune{97, 98, 0xFFFD, 99}, true},
  	{"ab\xc0c", []rune{97, 98, 0xFFFD, 99}, true},
  }
  
  func TestRunes(t *testing.T) {
  	for _, tt := range RunesTests {
  		tin := []byte(tt.in)
  		a := Runes(tin)
  		if !runesEqual(a, tt.out) {
  			t.Errorf("Runes(%q) = %v; want %v", tin, a, tt.out)
  			continue
  		}
  		if !tt.lossy {
  			// can only test reassembly if we didn't lose information
  			s := string(a)
  			if s != tt.in {
  				t.Errorf("string(Runes(%q)) = %x; want %x", tin, s, tin)
  			}
  		}
  	}
  }
  
  type TrimTest struct {
  	f            string
  	in, arg, out string
  }
  
  var trimTests = []TrimTest{
  	{"Trim", "abba", "a", "bb"},
  	{"Trim", "abba", "ab", ""},
  	{"TrimLeft", "abba", "ab", ""},
  	{"TrimRight", "abba", "ab", ""},
  	{"TrimLeft", "abba", "a", "bba"},
  	{"TrimRight", "abba", "a", "abb"},
  	{"Trim", "<tag>", "<>", "tag"},
  	{"Trim", "* listitem", " *", "listitem"},
  	{"Trim", `"quote"`, `"`, "quote"},
  	{"Trim", "\u2C6F\u2C6F\u0250\u0250\u2C6F\u2C6F", "\u2C6F", "\u0250\u0250"},
  	{"Trim", "\x80test\xff", "\xff", "test"},
  	{"Trim", " Ġ ", " ", "Ġ"},
  	{"Trim", " Ġİ0", "0 ", "Ġİ"},
  	//empty string tests
  	{"Trim", "abba", "", "abba"},
  	{"Trim", "", "123", ""},
  	{"Trim", "", "", ""},
  	{"TrimLeft", "abba", "", "abba"},
  	{"TrimLeft", "", "123", ""},
  	{"TrimLeft", "", "", ""},
  	{"TrimRight", "abba", "", "abba"},
  	{"TrimRight", "", "123", ""},
  	{"TrimRight", "", "", ""},
  	{"TrimRight", "☺\xc0", "☺", "☺\xc0"},
  	{"TrimPrefix", "aabb", "a", "abb"},
  	{"TrimPrefix", "aabb", "b", "aabb"},
  	{"TrimSuffix", "aabb", "a", "aabb"},
  	{"TrimSuffix", "aabb", "b", "aab"},
  }
  
  func TestTrim(t *testing.T) {
  	for _, tc := range trimTests {
  		name := tc.f
  		var f func([]byte, string) []byte
  		var fb func([]byte, []byte) []byte
  		switch name {
  		case "Trim":
  			f = Trim
  		case "TrimLeft":
  			f = TrimLeft
  		case "TrimRight":
  			f = TrimRight
  		case "TrimPrefix":
  			fb = TrimPrefix
  		case "TrimSuffix":
  			fb = TrimSuffix
  		default:
  			t.Errorf("Undefined trim function %s", name)
  		}
  		var actual string
  		if f != nil {
  			actual = string(f([]byte(tc.in), tc.arg))
  		} else {
  			actual = string(fb([]byte(tc.in), []byte(tc.arg)))
  		}
  		if actual != tc.out {
  			t.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.arg, actual, tc.out)
  		}
  	}
  }
  
  type predicate struct {
  	f    func(r rune) bool
  	name string
  }
  
  var isSpace = predicate{unicode.IsSpace, "IsSpace"}
  var isDigit = predicate{unicode.IsDigit, "IsDigit"}
  var isUpper = predicate{unicode.IsUpper, "IsUpper"}
  var isValidRune = predicate{
  	func(r rune) bool {
  		return r != utf8.RuneError
  	},
  	"IsValidRune",
  }
  
  type TrimFuncTest struct {
  	f       predicate
  	in, out string
  }
  
  func not(p predicate) predicate {
  	return predicate{
  		func(r rune) bool {
  			return !p.f(r)
  		},
  		"not " + p.name,
  	}
  }
  
  var trimFuncTests = []TrimFuncTest{
  	{isSpace, space + " hello " + space, "hello"},
  	{isDigit, "\u0e50\u0e5212hello34\u0e50\u0e51", "hello"},
  	{isUpper, "\u2C6F\u2C6F\u2C6F\u2C6FABCDhelloEF\u2C6F\u2C6FGH\u2C6F\u2C6F", "hello"},
  	{not(isSpace), "hello" + space + "hello", space},
  	{not(isDigit), "hello\u0e50\u0e521234\u0e50\u0e51helo", "\u0e50\u0e521234\u0e50\u0e51"},
  	{isValidRune, "ab\xc0a\xc0cd", "\xc0a\xc0"},
  	{not(isValidRune), "\xc0a\xc0", "a"},
  }
  
  func TestTrimFunc(t *testing.T) {
  	for _, tc := range trimFuncTests {
  		actual := string(TrimFunc([]byte(tc.in), tc.f.f))
  		if actual != tc.out {
  			t.Errorf("TrimFunc(%q, %q) = %q; want %q", tc.in, tc.f.name, actual, tc.out)
  		}
  	}
  }
  
  type IndexFuncTest struct {
  	in          string
  	f           predicate
  	first, last int
  }
  
  var indexFuncTests = []IndexFuncTest{
  	{"", isValidRune, -1, -1},
  	{"abc", isDigit, -1, -1},
  	{"0123", isDigit, 0, 3},
  	{"a1b", isDigit, 1, 1},
  	{space, isSpace, 0, len(space) - 3}, // last rune in space is 3 bytes
  	{"\u0e50\u0e5212hello34\u0e50\u0e51", isDigit, 0, 18},
  	{"\u2C6F\u2C6F\u2C6F\u2C6FABCDhelloEF\u2C6F\u2C6FGH\u2C6F\u2C6F", isUpper, 0, 34},
  	{"12\u0e50\u0e52hello34\u0e50\u0e51", not(isDigit), 8, 12},
  
  	// tests of invalid UTF-8
  	{"\x801", isDigit, 1, 1},
  	{"\x80abc", isDigit, -1, -1},
  	{"\xc0a\xc0", isValidRune, 1, 1},
  	{"\xc0a\xc0", not(isValidRune), 0, 2},
  	{"\xc0☺\xc0", not(isValidRune), 0, 4},
  	{"\xc0☺\xc0\xc0", not(isValidRune), 0, 5},
  	{"ab\xc0a\xc0cd", not(isValidRune), 2, 4},
  	{"a\xe0\x80cd", not(isValidRune), 1, 2},
  }
  
  func TestIndexFunc(t *testing.T) {
  	for _, tc := range indexFuncTests {
  		first := IndexFunc([]byte(tc.in), tc.f.f)
  		if first != tc.first {
  			t.Errorf("IndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, first, tc.first)
  		}
  		last := LastIndexFunc([]byte(tc.in), tc.f.f)
  		if last != tc.last {
  			t.Errorf("LastIndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, last, tc.last)
  		}
  	}
  }
  
  type ReplaceTest struct {
  	in       string
  	old, new string
  	n        int
  	out      string
  }
  
  var ReplaceTests = []ReplaceTest{
  	{"hello", "l", "L", 0, "hello"},
  	{"hello", "l", "L", -1, "heLLo"},
  	{"hello", "x", "X", -1, "hello"},
  	{"", "x", "X", -1, ""},
  	{"radar", "r", "<r>", -1, "<r>ada<r>"},
  	{"", "", "<>", -1, "<>"},
  	{"banana", "a", "<>", -1, "b<>n<>n<>"},
  	{"banana", "a", "<>", 1, "b<>nana"},
  	{"banana", "a", "<>", 1000, "b<>n<>n<>"},
  	{"banana", "an", "<>", -1, "b<><>a"},
  	{"banana", "ana", "<>", -1, "b<>na"},
  	{"banana", "", "<>", -1, "<>b<>a<>n<>a<>n<>a<>"},
  	{"banana", "", "<>", 10, "<>b<>a<>n<>a<>n<>a<>"},
  	{"banana", "", "<>", 6, "<>b<>a<>n<>a<>n<>a"},
  	{"banana", "", "<>", 5, "<>b<>a<>n<>a<>na"},
  	{"banana", "", "<>", 1, "<>banana"},
  	{"banana", "a", "a", -1, "banana"},
  	{"banana", "a", "a", 1, "banana"},
  	{"☺☻☹", "", "<>", -1, "<>☺<>☻<>☹<>"},
  }
  
  func TestReplace(t *testing.T) {
  	for _, tt := range ReplaceTests {
  		in := append([]byte(tt.in), "<spare>"...)
  		in = in[:len(tt.in)]
  		out := Replace(in, []byte(tt.old), []byte(tt.new), tt.n)
  		if s := string(out); s != tt.out {
  			t.Errorf("Replace(%q, %q, %q, %d) = %q, want %q", tt.in, tt.old, tt.new, tt.n, s, tt.out)
  		}
  		if cap(in) == cap(out) && &in[:1][0] == &out[:1][0] {
  			t.Errorf("Replace(%q, %q, %q, %d) didn't copy", tt.in, tt.old, tt.new, tt.n)
  		}
  	}
  }
  
  type TitleTest struct {
  	in, out string
  }
  
  var TitleTests = []TitleTest{
  	{"", ""},
  	{"a", "A"},
  	{" aaa aaa aaa ", " Aaa Aaa Aaa "},
  	{" Aaa Aaa Aaa ", " Aaa Aaa Aaa "},
  	{"123a456", "123a456"},
  	{"double-blind", "Double-Blind"},
  	{"ÿøû", "Ÿøû"},
  	{"with_underscore", "With_underscore"},
  	{"unicode \xe2\x80\xa8 line separator", "Unicode \xe2\x80\xa8 Line Separator"},
  }
  
  func TestTitle(t *testing.T) {
  	for _, tt := range TitleTests {
  		if s := string(Title([]byte(tt.in))); s != tt.out {
  			t.Errorf("Title(%q) = %q, want %q", tt.in, s, tt.out)
  		}
  	}
  }
  
  var ToTitleTests = []TitleTest{
  	{"", ""},
  	{"a", "A"},
  	{" aaa aaa aaa ", " AAA AAA AAA "},
  	{" Aaa Aaa Aaa ", " AAA AAA AAA "},
  	{"123a456", "123A456"},
  	{"double-blind", "DOUBLE-BLIND"},
  	{"ÿøû", "ŸØÛ"},
  }
  
  func TestToTitle(t *testing.T) {
  	for _, tt := range ToTitleTests {
  		if s := string(ToTitle([]byte(tt.in))); s != tt.out {
  			t.Errorf("ToTitle(%q) = %q, want %q", tt.in, s, tt.out)
  		}
  	}
  }
  
  var EqualFoldTests = []struct {
  	s, t string
  	out  bool
  }{
  	{"abc", "abc", true},
  	{"ABcd", "ABcd", true},
  	{"123abc", "123ABC", true},
  	{"αβδ", "ΑΒΔ", true},
  	{"abc", "xyz", false},
  	{"abc", "XYZ", false},
  	{"abcdefghijk", "abcdefghijX", false},
  	{"abcdefghijk", "abcdefghij\u212A", true},
  	{"abcdefghijK", "abcdefghij\u212A", true},
  	{"abcdefghijkz", "abcdefghij\u212Ay", false},
  	{"abcdefghijKz", "abcdefghij\u212Ay", false},
  }
  
  func TestEqualFold(t *testing.T) {
  	for _, tt := range EqualFoldTests {
  		if out := EqualFold([]byte(tt.s), []byte(tt.t)); out != tt.out {
  			t.Errorf("EqualFold(%#q, %#q) = %v, want %v", tt.s, tt.t, out, tt.out)
  		}
  		if out := EqualFold([]byte(tt.t), []byte(tt.s)); out != tt.out {
  			t.Errorf("EqualFold(%#q, %#q) = %v, want %v", tt.t, tt.s, out, tt.out)
  		}
  	}
  }
  
  func TestBufferGrowNegative(t *testing.T) {
  	defer func() {
  		if err := recover(); err == nil {
  			t.Fatal("Grow(-1) should have panicked")
  		}
  	}()
  	var b Buffer
  	b.Grow(-1)
  }
  
  func TestBufferTruncateNegative(t *testing.T) {
  	defer func() {
  		if err := recover(); err == nil {
  			t.Fatal("Truncate(-1) should have panicked")
  		}
  	}()
  	var b Buffer
  	b.Truncate(-1)
  }
  
  func TestBufferTruncateOutOfRange(t *testing.T) {
  	defer func() {
  		if err := recover(); err == nil {
  			t.Fatal("Truncate(20) should have panicked")
  		}
  	}()
  	var b Buffer
  	b.Write(make([]byte, 10))
  	b.Truncate(20)
  }
  
  var containsTests = []struct {
  	b, subslice []byte
  	want        bool
  }{
  	{[]byte("hello"), []byte("hel"), true},
  	{[]byte("日本語"), []byte("日本"), true},
  	{[]byte("hello"), []byte("Hello, world"), false},
  	{[]byte("東京"), []byte("京東"), false},
  }
  
  func TestContains(t *testing.T) {
  	for _, tt := range containsTests {
  		if got := Contains(tt.b, tt.subslice); got != tt.want {
  			t.Errorf("Contains(%q, %q) = %v, want %v", tt.b, tt.subslice, got, tt.want)
  		}
  	}
  }
  
  var ContainsAnyTests = []struct {
  	b        []byte
  	substr   string
  	expected bool
  }{
  	{[]byte(""), "", false},
  	{[]byte(""), "a", false},
  	{[]byte(""), "abc", false},
  	{[]byte("a"), "", false},
  	{[]byte("a"), "a", true},
  	{[]byte("aaa"), "a", true},
  	{[]byte("abc"), "xyz", false},
  	{[]byte("abc"), "xcz", true},
  	{[]byte("a☺b☻c☹d"), "uvw☻xyz", true},
  	{[]byte("aRegExp*"), ".(|)*+?^$[]", true},
  	{[]byte(dots + dots + dots), " ", false},
  }
  
  func TestContainsAny(t *testing.T) {
  	for _, ct := range ContainsAnyTests {
  		if ContainsAny(ct.b, ct.substr) != ct.expected {
  			t.Errorf("ContainsAny(%s, %s) = %v, want %v",
  				ct.b, ct.substr, !ct.expected, ct.expected)
  		}
  	}
  }
  
  var ContainsRuneTests = []struct {
  	b        []byte
  	r        rune
  	expected bool
  }{
  	{[]byte(""), 'a', false},
  	{[]byte("a"), 'a', true},
  	{[]byte("aaa"), 'a', true},
  	{[]byte("abc"), 'y', false},
  	{[]byte("abc"), 'c', true},
  	{[]byte("a☺b☻c☹d"), 'x', false},
  	{[]byte("a☺b☻c☹d"), '☻', true},
  	{[]byte("aRegExp*"), '*', true},
  }
  
  func TestContainsRune(t *testing.T) {
  	for _, ct := range ContainsRuneTests {
  		if ContainsRune(ct.b, ct.r) != ct.expected {
  			t.Errorf("ContainsRune(%q, %q) = %v, want %v",
  				ct.b, ct.r, !ct.expected, ct.expected)
  		}
  	}
  }
  
  var makeFieldsInput = func() []byte {
  	x := make([]byte, 1<<20)
  	// Input is ~10% space, ~10% 2-byte UTF-8, rest ASCII non-space.
  	for i := range x {
  		switch rand.Intn(10) {
  		case 0:
  			x[i] = ' '
  		case 1:
  			if i > 0 && x[i-1] == 'x' {
  				copy(x[i-1:], "χ")
  				break
  			}
  			fallthrough
  		default:
  			x[i] = 'x'
  		}
  	}
  	return x
  }
  
  var fieldsInput = makeFieldsInput()
  
  func BenchmarkFields(b *testing.B) {
  	b.SetBytes(int64(len(fieldsInput)))
  	for i := 0; i < b.N; i++ {
  		Fields(fieldsInput)
  	}
  }
  
  func BenchmarkFieldsFunc(b *testing.B) {
  	b.SetBytes(int64(len(fieldsInput)))
  	for i := 0; i < b.N; i++ {
  		FieldsFunc(fieldsInput, unicode.IsSpace)
  	}
  }
  
  func BenchmarkTrimSpace(b *testing.B) {
  	s := []byte("  Some text.  \n")
  	for i := 0; i < b.N; i++ {
  		TrimSpace(s)
  	}
  }
  
  func makeBenchInputHard() []byte {
  	tokens := [...]string{
  		"<a>", "<p>", "<b>", "<strong>",
  		"</a>", "</p>", "</b>", "</strong>",
  		"hello", "world",
  	}
  	x := make([]byte, 0, 1<<20)
  	for {
  		i := rand.Intn(len(tokens))
  		if len(x)+len(tokens[i]) >= 1<<20 {
  			break
  		}
  		x = append(x, tokens[i]...)
  	}
  	return x
  }
  
  var benchInputHard = makeBenchInputHard()
  
  func BenchmarkSplitEmptySeparator(b *testing.B) {
  	for i := 0; i < b.N; i++ {
  		Split(benchInputHard, nil)
  	}
  }
  
  func BenchmarkSplitSingleByteSeparator(b *testing.B) {
  	sep := []byte("/")
  	for i := 0; i < b.N; i++ {
  		Split(benchInputHard, sep)
  	}
  }
  
  func BenchmarkSplitMultiByteSeparator(b *testing.B) {
  	sep := []byte("hello")
  	for i := 0; i < b.N; i++ {
  		Split(benchInputHard, sep)
  	}
  }
  
  func BenchmarkSplitNSingleByteSeparator(b *testing.B) {
  	sep := []byte("/")
  	for i := 0; i < b.N; i++ {
  		SplitN(benchInputHard, sep, 10)
  	}
  }
  
  func BenchmarkSplitNMultiByteSeparator(b *testing.B) {
  	sep := []byte("hello")
  	for i := 0; i < b.N; i++ {
  		SplitN(benchInputHard, sep, 10)
  	}
  }
  
  func BenchmarkRepeat(b *testing.B) {
  	for i := 0; i < b.N; i++ {
  		Repeat([]byte("-"), 80)
  	}
  }
  
  func BenchmarkBytesCompare(b *testing.B) {
  	for n := 1; n <= 2048; n <<= 1 {
  		b.Run(fmt.Sprint(n), func(b *testing.B) {
  			var x = make([]byte, n)
  			var y = make([]byte, n)
  
  			for i := 0; i < n; i++ {
  				x[i] = 'a'
  			}
  
  			for i := 0; i < n; i++ {
  				y[i] = 'a'
  			}
  
  			b.ResetTimer()
  			for i := 0; i < b.N; i++ {
  				Compare(x, y)
  			}
  		})
  	}
  }
  
  func BenchmarkIndexAnyASCII(b *testing.B) {
  	x := Repeat([]byte{'#'}, 4096) // Never matches set
  	cs := "0123456789abcdef"
  	for k := 1; k <= 4096; k <<= 4 {
  		for j := 1; j <= 16; j <<= 1 {
  			b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
  				for i := 0; i < b.N; i++ {
  					IndexAny(x[:k], cs[:j])
  				}
  			})
  		}
  	}
  }
  
  func BenchmarkTrimASCII(b *testing.B) {
  	cs := "0123456789abcdef"
  	for k := 1; k <= 4096; k <<= 4 {
  		for j := 1; j <= 16; j <<= 1 {
  			b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
  				x := Repeat([]byte(cs[:j]), k) // Always matches set
  				for i := 0; i < b.N; i++ {
  					Trim(x[:k], cs[:j])
  				}
  			})
  		}
  	}
  }
  

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