Detailed introduction to the implementation principles and common usage of golang slice

Slice in Go language is a dynamic sequence based on array implementation, which can dynamically increase or decrease its size at runtime, and supports common operations on sliced ​​data, such as append, insert, splice, copy, and slice operations. . This article will introduce the implementation principles and common usage of slice in detail.

1. Slice data structure

In the Go language, the slice data structure consists of three parts: a pointer to the underlying array, slice length and slice capacity. The specific definition is as follows:

type slice struct {

ptr *int  // 指向 slice 引用的底层数组
len int   // slice 的长度
cap int   // slice 的容量

}

Among them, the pointer ptr points to the starting position of the underlying array, len represents the length of the slice, and cap represents the slice. capacity. The length of the slice represents the number of elements currently stored in the slice, and the capacity of the slice represents the number of elements that can be stored in the current underlying array.

2. Initialization of slice

In the Go language, there are two ways to create a slice: use the built-in function make() to create a slice, or use a slice literal to directly declare and initialize a slice. .

Use the built-in function make() to create a slice:

slice := make([]type, length, capacity)

The make() function will create an underlying array , and returns a slice pointing to the array, whose parameters respectively represent the type of the slice element, the length of the slice, and the capacity of the slice. Among them, the slice capacity can be omitted. If it is omitted, it will default to the same length, indicating that the slice has no free space.

Use slice literals to declare and initialize slices:

slice := []type{elements}

Slices created by slice literals do not need to specify the length and capacity, Go The language automatically calculates the length and capacity of the slice based on the number of elements in the slice.

3. Basic operations of slice

1. Get the elements in the slice

Use the subscript operator [] to get the element with the specified subscript in the slice. The subscript is from Starting from 0, the maximum value can be len-1. For example:

slice := []int{1, 2, 3}
fmt.Println(slice[0]) // Output: 1

2. Slice traversal

You can use the for loop and range keyword to traverse the elements in the slice. For example:

slice := []int{1, 2, 3}
for index, value := range slice {

fmt.Printf("index:%d value:%d\n", index, value)

}

3. Append Elements to slice

Use the built-in function append() to append elements to the slice. The append() function returns a new slice, and the original slice will not be modified. For example:

slice1 := []int{1, 2, 3}
slice2 := append(slice1, 4, 5)
fmt.Println(slice1) // Output: [1 2 3]
fmt.Println(slice2) //Output: [1 2 3 4 5]

4. Copy slice

Use the built-in function copy() to copy a slice Copy to another slice. For example:

slice1 := []int{1, 2, 3}
slice2 := make([]int, len(slice1))
copy(slice2, slice1)
fmt.Println(slice2) //Output: [1 2 3]

5. Slice slice

Use the slice operator [:] to slice the slice starting from the specified index. The result of slicing is a new slice, and the original slice will not be modified. For example:

slice1 := []int{1, 2, 3}
slice2 := slice1[1:]
fmt.Println(slice2) // Output: [2 3]

4. Implementation principle of slice

Slice in Go language is a dynamic sequence implemented based on arrays. When a slice is created, the Go language creates an array and points the slice's ptr to the starting position of the array. Initially, the length of the slice is 0 and the capacity is the length of the underlying array. When append() is called to append an element, the Go language will check whether the current slice has enough capacity to store the new element. If it is enough, it will add the new element directly to the end of the current slice; if it is insufficient, it will reallocate a larger array. And copy the elements in the current slice to the new array, and then append the new elements. Therefore, if the capacity of the slice is insufficient, the underlying array will change, which will affect all slices that reference the array.

When slicing a slice, the Go language will create a new slice and point ptr to the starting position of the slice in the original array. The length and capacity of the slice are determined by the slice operator [:] and the parameters when creating the slice. Therefore, no new array is created when slicing, but the original array is reused.

5. Summary

This article introduces the implementation principle and common usage of slice in Go language. Slice is an important data structure for realizing dynamic sequences in Go language. Its use is flexible and efficient. For It is especially convenient for processing variable-length data. Proficient in the usage skills and implementation principles of slice, you can write Go programs more efficiently and optimize code performance.

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