github.com/xushiwei/go@v0.0.0-20130601165731-2b9d83f45bc9/src/pkg/runtime/append_test.go (about)

     1  // Copyright 2011 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  package runtime_test
     5  
     6  import "testing"
     7  
     8  const N = 20
     9  
    10  func BenchmarkAppend(b *testing.B) {
    11  	b.StopTimer()
    12  	x := make([]int, 0, N)
    13  	b.StartTimer()
    14  	for i := 0; i < b.N; i++ {
    15  		x = x[0:0]
    16  		for j := 0; j < N; j++ {
    17  			x = append(x, j)
    18  		}
    19  	}
    20  }
    21  
    22  func benchmarkAppendBytes(b *testing.B, length int) {
    23  	b.StopTimer()
    24  	x := make([]byte, 0, N)
    25  	y := make([]byte, length)
    26  	b.StartTimer()
    27  	for i := 0; i < b.N; i++ {
    28  		x = x[0:0]
    29  		x = append(x, y...)
    30  	}
    31  }
    32  
    33  func BenchmarkAppend1Byte(b *testing.B) {
    34  	benchmarkAppendBytes(b, 1)
    35  }
    36  
    37  func BenchmarkAppend4Bytes(b *testing.B) {
    38  	benchmarkAppendBytes(b, 4)
    39  }
    40  
    41  func BenchmarkAppend8Bytes(b *testing.B) {
    42  	benchmarkAppendBytes(b, 8)
    43  }
    44  
    45  func BenchmarkAppend16Bytes(b *testing.B) {
    46  	benchmarkAppendBytes(b, 16)
    47  }
    48  
    49  func BenchmarkAppend32Bytes(b *testing.B) {
    50  	benchmarkAppendBytes(b, 32)
    51  }
    52  
    53  func benchmarkAppendStr(b *testing.B, str string) {
    54  	b.StopTimer()
    55  	x := make([]byte, 0, N)
    56  	b.StartTimer()
    57  	for i := 0; i < b.N; i++ {
    58  		x = x[0:0]
    59  		x = append(x, str...)
    60  	}
    61  }
    62  
    63  func BenchmarkAppendStr1Byte(b *testing.B) {
    64  	benchmarkAppendStr(b, "1")
    65  }
    66  
    67  func BenchmarkAppendStr4Bytes(b *testing.B) {
    68  	benchmarkAppendStr(b, "1234")
    69  }
    70  
    71  func BenchmarkAppendStr8Bytes(b *testing.B) {
    72  	benchmarkAppendStr(b, "12345678")
    73  }
    74  
    75  func BenchmarkAppendStr16Bytes(b *testing.B) {
    76  	benchmarkAppendStr(b, "1234567890123456")
    77  }
    78  
    79  func BenchmarkAppendStr32Bytes(b *testing.B) {
    80  	benchmarkAppendStr(b, "12345678901234567890123456789012")
    81  }
    82  
    83  func BenchmarkAppendSpecialCase(b *testing.B) {
    84  	b.StopTimer()
    85  	x := make([]int, 0, N)
    86  	b.StartTimer()
    87  	for i := 0; i < b.N; i++ {
    88  		x = x[0:0]
    89  		for j := 0; j < N; j++ {
    90  			if len(x) < cap(x) {
    91  				x = x[:len(x)+1]
    92  				x[len(x)-1] = j
    93  			} else {
    94  				x = append(x, j)
    95  			}
    96  		}
    97  	}
    98  }
    99  
   100  var x []int
   101  
   102  func f() int {
   103  	x[:1][0] = 3
   104  	return 2
   105  }
   106  
   107  func TestSideEffectOrder(t *testing.T) {
   108  	x = make([]int, 0, 10)
   109  	x = append(x, 1, f())
   110  	if x[0] != 1 || x[1] != 2 {
   111  		t.Error("append failed: ", x[0], x[1])
   112  	}
   113  }
   114  
   115  func TestAppendOverlap(t *testing.T) {
   116  	x := []byte("1234")
   117  	x = append(x[1:], x...) // p > q in runtime·appendslice.
   118  	got := string(x)
   119  	want := "2341234"
   120  	if got != want {
   121  		t.Errorf("overlap failed: got %q want %q", got, want)
   122  	}
   123  }