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go-切片的追加

• 技术杂谈 • 阅读 81 
// The append built-in function appends elements to the end of a slice. If
// it has sufficient capacity, the destination is resliced to accommodate the
// new elements. If it does not, a new underlying array will be allocated.

// Append returns the updated slice. It is therefore necessary to store the
// result of append, often in the variable holding the slice itself:
//  slice = append(slice, elem1, elem2)
//  slice = append(slice, anotherSlice...)
// As a special case, it is legal to append a string to a byte slice, like this:
//  slice = append([]byte("hello "), "world"...)
func append(slice []Type, elems ...Type) []Type
  • 该函数的作用是追加元素到切片slice的末尾。
  • 如果slice还有剩余的容量，则该切片被允许容纳新的元素；如果没有剩余容量，一个新的底层数组将会创建。
  • 该函数返回更新的切片，因此新的切片必须存储追加结果，通常更新的切片也包含原切片本身。
package test

import (
    "fmt"
    "testing"
)

func TestSize(t *testing.T) {
    a := []int{1, 2, 3, 4, 5, 6}
    fmt.Printf("aaaa 的地址: %p ,长度 :%d %#v\n", a, len(a), a)
    for i := 0; i < len(a); i++ {
        fmt.Printf("a[%d] 的地址: %p \n", i, &a[i])
    }
  // b 引用a索引为 2的元素
    b := a[2:3]
    fmt.Printf("bbbb 的地址: %p ,长度 :%d %#v\n", b, len(b), b)
    for i := 0; i < 16; i++ {
        b = append(b, 30)
        fmt.Printf("b----b 的地址: %p ,长度 :%d %#v\n", b, len(b), b)
        //fmt.Printf("a----a 的地址: %p ,长度 :%d %#v\n", a, len(a), a)
    }
}

`plain_text
=== RUN TestSize
aaaa 的地址: 0xc000020420 ,长度 :6 []int{1, 2, 3, 4, 5, 6}
a[0] 的地址: 0xc000020420
a[1] 的地址: 0xc000020428
a[2] 的地址: 0xc000020430 // b 的引用地址
a[3] 的地址: 0xc000020438
a[4] 的地址: 0xc000020440
a[5] 的地址: 0xc000020448
b 的地址: 0xc000020430 ,容量： 4,长度 :1 []int{3}
b 的地址: 0xc000020430 ,容量： 4,长度 :2 []int{3, 30}
b 的地址: 0xc000020430 ,容量： 4,长度 :3 []int{3, 30, 30}
b 的地址: 0xc000020430 ,容量： 4,长度 :4 []int{3, 30, 30, 30}

//扩容后,地址改变
b 的地址: 0xc00001a280 ,容量： 8,长度 :5 []int{3, 30, 30, 30, 30}
b 的地址: 0xc00001a280 ,容量： 8,长度 :6 []int{3, 30, 30, 30, 30, 30}
b 的地址: 0xc00001a280 ,容量： 8,长度 :7 []int{3, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00001a280 ,容量： 8,长度 :8 []int{3, 30, 30, 30, 30, 30, 30, 30}
//扩容后,地址改变
b 的地址: 0xc000116180 ,容量： 16,长度 :9 []int{3, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :10 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :11 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :12 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :13 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :14 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :15 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc000116180 ,容量： 16,长度 :16 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
//扩容后,地址改变
b 的地址: 0xc00000a700 ,容量： 32,长度 :17 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :18 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :19 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :20 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :21 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :22 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :23 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :24 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :25 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :26 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :27 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :28 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :29 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :30 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :31 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00000a700 ,容量： 32,长度 :32 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}

//扩容后,地址改变

b 的地址: 0xc00014e000 ,容量： 64,长度 :33 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :34 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :35 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :36 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :37 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :38 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :39 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :40 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}
b 的地址: 0xc00014e000 ,容量： 64,长度 :41 []int{3, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}

Original: https://www.cnblogs.com/burner/p/01qie-pian-de-zhui-jia.html
Author: 浪客禅心
Title: go-切片的追加

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