133 lines
4.1 KiB
Go
133 lines
4.1 KiB
Go
package code
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import (
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"fmt"
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"reflect"
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"testing"
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"unsafe"
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"github.com/stretchr/testify/assert"
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)
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func TestSliceArray(t *testing.T) {
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var arr = [...]int{1, 2, 3}
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var slice = []int{1, 2, 3}
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ModifyArray(arr)
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ModifySlice(slice)
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t.Logf("%v %v\n", arr, slice)
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assert.NotEqual(t, arr[2], 1)
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assert.Equal(t, slice[2], 1)
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}
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func ModifyArray(arr [3]int) {
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fmt.Println(arr)
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arr[2] = 1
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}
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func ModifySlice(slice []int) {
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fmt.Println(slice)
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slice[2] = 1
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}
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func TestSlice(t *testing.T) {
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slice := []int{1, 2, 3}
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arr := [...]int{1, 2, 3}
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fmt.Printf("切片：底层数组指针：%d 切片：指针%v reflect.SliceHeader: %+v\n",
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unsafe.SliceData(slice), unsafe.Pointer(&slice), (*reflect.SliceHeader)(unsafe.Pointer(&slice)))
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SlicePointer(slice)
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fmt.Printf("数组：底层数组指针：%d 数组指针：%d\n", unsafe.Pointer(&arr), unsafe.Pointer(&arr[0]))
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ArrayPointer(arr)
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}
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func SlicePointer(slice []int) {
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fmt.Printf("切片：底层数组指针：%d 切片：指针%v reflect.SliceHeader: %+v\n",
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unsafe.SliceData(slice), unsafe.Pointer(&slice), (*reflect.SliceHeader)(unsafe.Pointer(&slice)))
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}
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func ArrayPointer(arr [3]int) {
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fmt.Printf("数组：底层数组指针：%d 数组指针：%d\n", unsafe.Pointer(&arr), unsafe.Pointer(&arr[0]))
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}
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func TestModify(t *testing.T) {
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arr := [...]int{1, 2, 3, 4, 5, 6, 7}
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slice := arr[:]
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slice[4] = 8
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t.Logf("arr[4]=%v,slice[4]=%v\n", arr[4], slice[4])
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assert.Equal(t, slice[4], arr[4])
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slice = append(slice, 9)
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slice[5] = 10
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t.Logf("arr[4]=%v,slice[4]=%v\n", arr[4], slice[4])
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assert.Equal(t, slice[4], arr[4])
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t.Logf("arr[5]=%v,slice[5]=%v\n", arr[5], slice[5])
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assert.NotEqual(t, slice[5], arr[5])
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}
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func TestModifyTwoSlice(t *testing.T) {
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arr := [...]int{1, 2, 3, 4, 5, 6, 7, 8, 9}
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slice1 := arr[1:5]
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slice2 := arr[3:8]
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slice1[2] = 8
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t.Logf("%v %v %v\n", arr, slice1, slice2)
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assert.Equal(t, slice1[2], slice2[0], arr[3])
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}
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func TestCap(t *testing.T) {
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slice := []int{1, 2, 3, 4}
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fmt.Printf("len:%d cap: %d\n", len(slice), cap(slice))
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slice = append(slice, make([]int, 11)...)
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fmt.Printf("len:%d cap: %d\n", len(slice), cap(slice)) // oldcap<256，直接使用新切片容量
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slice = append(slice, make([]int, 260)...)
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fmt.Printf("len:%d cap: %d\n", len(slice), cap(slice)) // oldcap<256，直接使用新切片容量
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slice = append(slice, make([]int, 250)...)
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fmt.Printf("len:%d cap: %d\n", len(slice), cap(slice)) // 1.25倍循环扩容
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}
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func TestString(t *testing.T) {
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str := "hello"
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fmt.Printf("%d %+v\n", &str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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str = "world"
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fmt.Printf("%d %+v\n", &str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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str = str[:3]
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fmt.Printf("%d %+v\n", &str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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}
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func TestStringAsSlice(t *testing.T) {
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str := "hello,world"
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hello := str[:5]
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world := str[6:]
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fmt.Printf("%d %+v\n", &str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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fmt.Printf("%d %+v\n", &hello, (*reflect.StringHeader)(unsafe.Pointer(&hello)))
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fmt.Printf("%d %+v\n", &world, (*reflect.StringHeader)(unsafe.Pointer(&world)))
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}
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func TestCopy(t *testing.T) {
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str := "hello,world"
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fmt.Printf("%d %+v\n", &str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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b := []byte(str)
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fmt.Printf("%d %+v\n", unsafe.Pointer(&b), (*reflect.SliceHeader)(unsafe.Pointer(&b)))
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}
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func TestZeroCopy(t *testing.T) {
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str := "hello,world"
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fmt.Printf("%d %+v\n", &str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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b := unsafe.Slice(unsafe.StringData(str), len(str))
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fmt.Printf("%s %+v\n", b, (*reflect.SliceHeader)(unsafe.Pointer(&b)))
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}
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func TestConvertZeroCopy(t *testing.T) {
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n := []int64{1, 2, 3, 4}
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// 注意精度问题
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fmt.Printf("%+v\n", (*reflect.SliceHeader)(unsafe.Pointer(&n)))
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f := unsafe.Slice(unsafe.SliceData(n), len(n))
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fmt.Printf("%v %+v\n", f, (*reflect.SliceHeader)(unsafe.Pointer(&f)))
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}
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func TestReplace(t *testing.T) {
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str := "hello,world"
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fmt.Printf("%v %+v\n", str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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b := []byte(str)
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b[1] = 'a'
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str = unsafe.String(unsafe.SliceData(b), len(b))
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fmt.Printf("%v %+v\n", str, (*reflect.StringHeader)(unsafe.Pointer(&str)))
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}
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