repo_description: The Go programming language
repo_topics: go golang language programming-language
code: // Copyright 2013 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"
  	"testing"
  )
  
  var compareTests = []struct {
  	a, b []byte
  	i    int
  }{
  	{[]byte(""), []byte(""), 0},
  	{[]byte("a"), []byte(""), 1},
  	{[]byte(""), []byte("a"), -1},
  	{[]byte("abc"), []byte("abc"), 0},
  	{[]byte("abd"), []byte("abc"), 1},
  	{[]byte("abc"), []byte("abd"), -1},
  	{[]byte("ab"), []byte("abc"), -1},
  	{[]byte("abc"), []byte("ab"), 1},
  	{[]byte("x"), []byte("ab"), 1},
  	{[]byte("ab"), []byte("x"), -1},
  	{[]byte("x"), []byte("a"), 1},
  	{[]byte("b"), []byte("x"), -1},
  	// test runtime·memeq's chunked implementation
  	{[]byte("abcdefgh"), []byte("abcdefgh"), 0},
  	{[]byte("abcdefghi"), []byte("abcdefghi"), 0},
  	{[]byte("abcdefghi"), []byte("abcdefghj"), -1},
  	{[]byte("abcdefghj"), []byte("abcdefghi"), 1},
  	// nil tests
  	{nil, nil, 0},
  	{[]byte(""), nil, 0},
  	{nil, []byte(""), 0},
  	{[]byte("a"), nil, 1},
  	{nil, []byte("a"), -1},
  }
  
  func TestCompare(t *testing.T) {
  	for _, tt := range compareTests {
  		numShifts := 16
  		buffer := make([]byte, len(tt.b)+numShifts)
  		// vary the input alignment of tt.b
  		for offset := 0; offset <= numShifts; offset++ {
  			shiftedB := buffer[offset : len(tt.b)+offset]
  			copy(shiftedB, tt.b)
  			cmp := Compare(tt.a, shiftedB)
  			if cmp != tt.i {
  				t.Errorf(`Compare(%q, %q), offset %d = %v; want %v`, tt.a, tt.b, offset, cmp, tt.i)
  			}
  		}
  	}
  }
  
  func TestCompareIdenticalSlice(t *testing.T) {
  	var b = []byte("Hello Gophers!")
  	if Compare(b, b) != 0 {
  		t.Error("b != b")
  	}
  	if Compare(b, b[:1]) != 1 {
  		t.Error("b > b[:1] failed")
  	}
  }
  
  func TestCompareBytes(t *testing.T) {
  	lengths := make([]int, 0) // lengths to test in ascending order
  	for i := 0; i <= 128; i++ {
  		lengths = append(lengths, i)
  	}
  	lengths = append(lengths, 256, 512, 1024, 1333, 4095, 4096, 4097)
  
  	if !testing.Short() {
  		lengths = append(lengths, 65535, 65536, 65537, 99999)
  	}
  
  	n := lengths[len(lengths)-1]
  	a := make([]byte, n+1)
  	b := make([]byte, n+1)
  	for _, len := range lengths {
  		// randomish but deterministic data. No 0 or 255.
  		for i := 0; i < len; i++ {
  			a[i] = byte(1 + 31*i%254)
  			b[i] = byte(1 + 31*i%254)
  		}
  		// data past the end is different
  		for i := len; i <= n; i++ {
  			a[i] = 8
  			b[i] = 9
  		}
  		cmp := Compare(a[:len], b[:len])
  		if cmp != 0 {
  			t.Errorf(`CompareIdentical(%d) = %d`, len, cmp)
  		}
  		if len > 0 {
  			cmp = Compare(a[:len-1], b[:len])
  			if cmp != -1 {
  				t.Errorf(`CompareAshorter(%d) = %d`, len, cmp)
  			}
  			cmp = Compare(a[:len], b[:len-1])
  			if cmp != 1 {
  				t.Errorf(`CompareBshorter(%d) = %d`, len, cmp)
  			}
  		}
  		for k := 0; k < len; k++ {
  			b[k] = a[k] - 1
  			cmp = Compare(a[:len], b[:len])
  			if cmp != 1 {
  				t.Errorf(`CompareAbigger(%d,%d) = %d`, len, k, cmp)
  			}
  			b[k] = a[k] + 1
  			cmp = Compare(a[:len], b[:len])
  			if cmp != -1 {
  				t.Errorf(`CompareBbigger(%d,%d) = %d`, len, k, cmp)
  			}
  			b[k] = a[k]
  		}
  	}
  }
  
  func TestEndianBaseCompare(t *testing.T) {
  	// This test compares byte slices that are almost identical, except one
  	// difference that for some j, a[j]>b[j] and a[j+1]<b[j+1]. If the implementation
  	// compares large chunks with wrong endianness, it gets wrong result.
  	// no vector register is larger than 512 bytes for now
  	const maxLength = 512
  	a := make([]byte, maxLength)
  	b := make([]byte, maxLength)
  	// randomish but deterministic data. No 0 or 255.
  	for i := 0; i < maxLength; i++ {
  		a[i] = byte(1 + 31*i%254)
  		b[i] = byte(1 + 31*i%254)
  	}
  	for i := 2; i <= maxLength; i <<= 1 {
  		for j := 0; j < i-1; j++ {
  			a[j] = b[j] - 1
  			a[j+1] = b[j+1] + 1
  			cmp := Compare(a[:i], b[:i])
  			if cmp != -1 {
  				t.Errorf(`CompareBbigger(%d,%d) = %d`, i, j, cmp)
  			}
  			a[j] = b[j] + 1
  			a[j+1] = b[j+1] - 1
  			cmp = Compare(a[:i], b[:i])
  			if cmp != 1 {
  				t.Errorf(`CompareAbigger(%d,%d) = %d`, i, j, cmp)
  			}
  			a[j] = b[j]
  			a[j+1] = b[j+1]
  		}
  	}
  }
  
  func BenchmarkCompareBytesEqual(b *testing.B) {
  	b1 := []byte("Hello Gophers!")
  	b2 := []byte("Hello Gophers!")
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  }
  
  func BenchmarkCompareBytesToNil(b *testing.B) {
  	b1 := []byte("Hello Gophers!")
  	var b2 []byte
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != 1 {
  			b.Fatal("b1 > b2 failed")
  		}
  	}
  }
  
  func BenchmarkCompareBytesEmpty(b *testing.B) {
  	b1 := []byte("")
  	b2 := b1
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  }
  
  func BenchmarkCompareBytesIdentical(b *testing.B) {
  	b1 := []byte("Hello Gophers!")
  	b2 := b1
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  }
  
  func BenchmarkCompareBytesSameLength(b *testing.B) {
  	b1 := []byte("Hello Gophers!")
  	b2 := []byte("Hello, Gophers")
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != -1 {
  			b.Fatal("b1 < b2 failed")
  		}
  	}
  }
  
  func BenchmarkCompareBytesDifferentLength(b *testing.B) {
  	b1 := []byte("Hello Gophers!")
  	b2 := []byte("Hello, Gophers!")
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != -1 {
  			b.Fatal("b1 < b2 failed")
  		}
  	}
  }
  
  func benchmarkCompareBytesBigUnaligned(b *testing.B, offset int) {
  	b.StopTimer()
  	b1 := make([]byte, 0, 1<<20)
  	for len(b1) < 1<<20 {
  		b1 = append(b1, "Hello Gophers!"...)
  	}
  	b2 := append([]byte("12345678")[:offset], b1...)
  	b.StartTimer()
  	for j := 0; j < b.N; j++ {
  		if Compare(b1, b2[offset:]) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  	b.SetBytes(int64(len(b1)))
  }
  
  func BenchmarkCompareBytesBigUnaligned(b *testing.B) {
  	for i := 1; i < 8; i++ {
  		b.Run(fmt.Sprintf("offset=%d", i), func(b *testing.B) {
  			benchmarkCompareBytesBigUnaligned(b, i)
  		})
  	}
  }
  
  func benchmarkCompareBytesBigBothUnaligned(b *testing.B, offset int) {
  	b.StopTimer()
  	pattern := []byte("Hello Gophers!")
  	b1 := make([]byte, 0, 1<<20+len(pattern))
  	for len(b1) < 1<<20 {
  		b1 = append(b1, pattern...)
  	}
  	b2 := make([]byte, len(b1))
  	copy(b2, b1)
  	b.StartTimer()
  	for j := 0; j < b.N; j++ {
  		if Compare(b1[offset:], b2[offset:]) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  	b.SetBytes(int64(len(b1[offset:])))
  }
  
  func BenchmarkCompareBytesBigBothUnaligned(b *testing.B) {
  	for i := 0; i < 8; i++ {
  		b.Run(fmt.Sprintf("offset=%d", i), func(b *testing.B) {
  			benchmarkCompareBytesBigBothUnaligned(b, i)
  		})
  	}
  }
  
  func BenchmarkCompareBytesBig(b *testing.B) {
  	b.StopTimer()
  	b1 := make([]byte, 0, 1<<20)
  	for len(b1) < 1<<20 {
  		b1 = append(b1, "Hello Gophers!"...)
  	}
  	b2 := append([]byte{}, b1...)
  	b.StartTimer()
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  	b.SetBytes(int64(len(b1)))
  }
  
  func BenchmarkCompareBytesBigIdentical(b *testing.B) {
  	b.StopTimer()
  	b1 := make([]byte, 0, 1<<20)
  	for len(b1) < 1<<20 {
  		b1 = append(b1, "Hello Gophers!"...)
  	}
  	b2 := b1
  	b.StartTimer()
  	for i := 0; i < b.N; i++ {
  		if Compare(b1, b2) != 0 {
  			b.Fatal("b1 != b2")
  		}
  	}
  	b.SetBytes(int64(len(b1)))
  }
  