Detailed explanation of the implementation and usage details of golang slicing

Golang is a rapidly growing programming language with memory safety and high concurrent computing capabilities. In Golang, slicing is a very commonly used data structure, which allows dynamic expansion and contraction. It is one of the commonly used data structures in the Golang language. This article will introduce the concept, implementation and usage details of slicing.

1. The concept of slicing

In Golang, slicing is a layer of encapsulation of arrays, which has the function of dynamic expansion. The definition format of slice is as follows:

var slice []type

where type is the data type and slice is the name of the slice. We can also create a new slice through the make function. The make function is defined as follows:

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

where type is the data type, length is the length of the slice, and capacity is the capacity of the slice. The length of the slice represents the number of elements in the slice, and the capacity of the slice represents the maximum number of elements that the slice can expand again.

2. Implementation of Slicing

In Golang, slice is a reference type, and its value is a structure containing a pointer to the underlying array, length and capacity. A slice can be understood as a dynamic array, which can increase or decrease the length of the array in time.

type slice struct {
    ptr *[2]int
    len int
    cap int
}

Among them, ptr points to the pointer of the underlying array, len represents the length of the slice, and cap represents the capacity of the slice. The following figure shows the internal structure of the slice:

          +-----+-----+-----+-----+-----+-----+-----+-----+
          |  0  |  1  |  2  |  3  |  4  |  5  |  6  |  7  |
          +-----+-----+-----+-----+-----+-----+-----+-----+
          |  a  |  b  |  c  |  d  |  e  |  f  |  g  |  h  |
          +-----+-----+-----+-----+-----+-----+-----+-----+
            |                      |         |
            ptr                    len       cap

In the above example, ptr points to the beginning of the underlying array. In Golang, we can use slices to perform slicing operations. The syntax of slicing operations is as follows:

slice[begin:end]

where begin is the starting position of the slice and end is the end position of the slice. If begin is not specified, the default is 0; if end is not specified, the default is the capacity of the slice.

3. Details of using slices

1. Slice length and capacity

The length and capacity of slices can be obtained through the len and cap functions. The length of the slice represents the number of elements stored in the slice, and the capacity of the slice represents the maximum number of elements that the slice can expand. For example:

slice := make([]int, 5, 10)
fmt.Println(len(slice)) // 输出5
fmt.Println(cap(slice)) // 输出10

In this example, the length of slice is 5 and the capacity is 10.

2. Automatic expansion of slices

When the length of a slice exceeds its capacity, the slice will automatically expand. When a slice is expanded, the capacity is doubled until the capacity reaches a specified maximum value. Automatic expansion will cause the underlying array to reallocate memory and copy the original elements to the new underlying array. The automatic expansion of the slice can be demonstrated by the following code:

slice := make([]int, 5, 10)
fmt.Println(len(slice)) // 输出5
fmt.Println(cap(slice)) // 输出10
for i := 0; i < 10; i++ {
    slice = append(slice, i)
    fmt.Println("Length:", len(slice), "Capacity:", cap(slice))
}

In this example, we extend the length of the slice to 10 by appending elements. When the capacity is insufficient, the slice will automatically expand and the capacity will double until it reaches the maximum value.

3. Value transfer of slices

Slices in Golang are reference types, so when passing a slice to a function, a pointer to the underlying array is passed. Modifying elements in a slice affects elements in the original slice. For example:

func modify(slice []int) {
    for i := range slice {
        slice[i] += 2
    }
    fmt.Println(slice)
}
func main() {
    slice := []int{1, 2, 3}
    modify(slice)
    fmt.Println(slice)
}

Run the above code, the output result is as follows:

[3 4 5]
[3 4 5]

In this example, we define a modify function, which modifies the elements in the slice and will affect the original slice Elements.

4. Summary

Slicing is a very important data structure in the Golang language and can be dynamically expanded and contracted. The implementation and use of slicing is very convenient, but there are some things that need to be paid attention to, such as value transfer and automatic expansion of slicing. I hope this article can help you gain an in-depth understanding of the implementation and application of slicing in Golang.

The above is the detailed content of Detailed explanation of the implementation and usage details of golang slicing. For more information, please follow other related articles on the PHP Chinese website!