Analyze golang pointer conversion

Go language (Golang) is a statically typed programming language. It originated as an internal project of the search engine giant Google, debuted in 2009, and was released as open source in 2012. With the changes of the times, Go language has gradually become a highly respected programming language. One of its characteristics is that it handles pointers very clearly and concisely. This article will introduce in detail the use of Golang pointers and pointer conversion.

1. Basic use of pointers

In Golang, a pointer is a type that stores the memory address of a variable. The pointer can directly access the variable corresponding to the address, not the variable itself. We can use the symbol "&" to get the address of a variable and the symbol "*" to get the value of the variable pointed to by the pointer. The sample code is as follows:

func main() {
    var a int = 10
    var pa *int = &a
    fmt.Printf("a=%v, pa=%v\n", a, pa) // a=10, pa=0x123456
    *pa = 20
    fmt.Printf("a=%v, pa=%v\n", a, pa) // a=20, pa=0x123456
}

In the above code, pa is a pointer to a, &a can obtain a address, *pa can obtain the value pointed to by a, and modifications to *pa directly affect the value of a.

2. Pointer conversion

Pointer conversion refers to converting a value of one pointer type into a value of another pointer type. In Golang, pointer conversion is a technology that is gradually gaining attention.

In Go language, all pointers are strongly typed, that is to say, we cannot convert a pointer pointing to type int into type pointing to string pointer. However, we can achieve the versatility of pointers through unsafe.Pointer. unsafe.Pointer is a pointer to any type, which can convert any type of pointer into a unsafe.Pointer type pointer. The sample code is as follows:

func main() {
    var a int = 10
    var pa *int = &a
    fmt.Printf("a=%v, pa=%v\n", a, pa) // a=10, pa=0x123456
    
    var pb *string = (*string)(unsafe.Pointer(pa))
    // 将pa指向的int类型转换为string类型
    *pb = "hello"
    fmt.Printf("a=%v, pb=%v\n", a, pb) // a=1869375336, pb=0x123456
    
    var pc *int = (*int)(unsafe.Pointer(pb))
    // 将pb指向的string类型转换为int类型
    *pc = 20
    fmt.Printf("a=%v, pc=%v\n", a, pc) // a=20, pc=0x123456
}

In the above code, we first define the type of pa as *int and assign it as &a. At this time, pa points to the memory address of a. Next, we convert pa to a pointer of type *string and assign it to pb. At this time, pb points to the memory address of a, but its data type changes to string. After calling *pb="hello", the data saved in the corresponding memory address becomes the string "hello". Finally, we convert pb to a pointer of type *int and assign it to pc. At this time, pc still points to the memory address of a, but its data type changes back to int, calling *pc=20 After that, the value of a also became 20.

It should be noted that using unsafe.Pointer for pointer conversion is a highly dangerous behavior, which may have very serious consequences. Because unsafe.Pointer can point to any type of pointer, we must be extra careful when performing pointer conversion to avoid memory errors caused by data type mismatch.

3. Conclusion

Pointers are a very important concept in Golang, which can improve the efficiency of the code and reduce memory usage. The use of pointers requires us to have a certain understanding of the concept of memory, and it also requires us to carefully handle the issue of pointer conversion. Pointer conversion may bring many risks and problems. We need to carefully analyze every possible problem and handle it with caution to avoid unnecessary errors and failures.

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