compare_test.go

     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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