compare_test.go

Documentation: strings

		 1  // Copyright 2013 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  package strings_test
		 6  
		 7  // Derived from bytes/compare_test.go.
		 8  // Benchmarks omitted since the underlying implementation is identical.
		 9  
		10  import (
		11  	"internal/testenv"
		12  	. "strings"
		13  	"testing"
		14  	"unsafe"
		15  )
		16  
		17  var compareTests = []struct {
		18  	a, b string
		19  	i		int
		20  }{
		21  	{"", "", 0},
		22  	{"a", "", 1},
		23  	{"", "a", -1},
		24  	{"abc", "abc", 0},
		25  	{"ab", "abc", -1},
		26  	{"abc", "ab", 1},
		27  	{"x", "ab", 1},
		28  	{"ab", "x", -1},
		29  	{"x", "a", 1},
		30  	{"b", "x", -1},
		31  	// test runtime·memeq's chunked implementation
		32  	{"abcdefgh", "abcdefgh", 0},
		33  	{"abcdefghi", "abcdefghi", 0},
		34  	{"abcdefghi", "abcdefghj", -1},
		35  }
		36  
		37  func TestCompare(t *testing.T) {
		38  	for _, tt := range compareTests {
		39  		cmp := Compare(tt.a, tt.b)
		40  		if cmp != tt.i {
		41  			t.Errorf(`Compare(%q, %q) = %v`, tt.a, tt.b, cmp)
		42  		}
		43  	}
		44  }
		45  
		46  func TestCompareIdenticalString(t *testing.T) {
		47  	var s = "Hello Gophers!"
		48  	if Compare(s, s) != 0 {
		49  		t.Error("s != s")
		50  	}
		51  	if Compare(s, s[:1]) != 1 {
		52  		t.Error("s > s[:1] failed")
		53  	}
		54  }
		55  
		56  func TestCompareStrings(t *testing.T) {
		57  	// unsafeString converts a []byte to a string with no allocation.
		58  	// The caller must not modify b while the result string is in use.
		59  	unsafeString := func(b []byte) string {
		60  		return *(*string)(unsafe.Pointer(&b))
		61  	}
		62  
		63  	lengths := make([]int, 0) // lengths to test in ascending order
		64  	for i := 0; i <= 128; i++ {
		65  		lengths = append(lengths, i)
		66  	}
		67  	lengths = append(lengths, 256, 512, 1024, 1333, 4095, 4096, 4097)
		68  
		69  	if !testing.Short() || testenv.Builder() != "" {
		70  		lengths = append(lengths, 65535, 65536, 65537, 99999)
		71  	}
		72  
		73  	n := lengths[len(lengths)-1]
		74  	a := make([]byte, n+1)
		75  	b := make([]byte, n+1)
		76  	lastLen := 0
		77  	for _, len := range lengths {
		78  		// randomish but deterministic data. No 0 or 255.
		79  		for i := 0; i < len; i++ {
		80  			a[i] = byte(1 + 31*i%254)
		81  			b[i] = byte(1 + 31*i%254)
		82  		}
		83  		// data past the end is different
		84  		for i := len; i <= n; i++ {
		85  			a[i] = 8
		86  			b[i] = 9
		87  		}
		88  
		89  		sa, sb := unsafeString(a), unsafeString(b)
		90  		cmp := Compare(sa[:len], sb[:len])
		91  		if cmp != 0 {
		92  			t.Errorf(`CompareIdentical(%d) = %d`, len, cmp)
		93  		}
		94  		if len > 0 {
		95  			cmp = Compare(sa[:len-1], sb[:len])
		96  			if cmp != -1 {
		97  				t.Errorf(`CompareAshorter(%d) = %d`, len, cmp)
		98  			}
		99  			cmp = Compare(sa[:len], sb[:len-1])
	 100  			if cmp != 1 {
	 101  				t.Errorf(`CompareBshorter(%d) = %d`, len, cmp)
	 102  			}
	 103  		}
	 104  		for k := lastLen; k < len; k++ {
	 105  			b[k] = a[k] - 1
	 106  			cmp = Compare(unsafeString(a[:len]), unsafeString(b[:len]))
	 107  			if cmp != 1 {
	 108  				t.Errorf(`CompareAbigger(%d,%d) = %d`, len, k, cmp)
	 109  			}
	 110  			b[k] = a[k] + 1
	 111  			cmp = Compare(unsafeString(a[:len]), unsafeString(b[:len]))
	 112  			if cmp != -1 {
	 113  				t.Errorf(`CompareBbigger(%d,%d) = %d`, len, k, cmp)
	 114  			}
	 115  			b[k] = a[k]
	 116  		}
	 117  		lastLen = len
	 118  	}
	 119  }
	 120
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