src/strings/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 unsafe.String(unsafe.SliceData(b), len(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 }