golang address conversion

In golang, there are two storage methods for variables, one is that value types are stored on the stack, and the other is that reference types are stored on the heap. When we need to convert an address into a value, we need to pay attention to whether it is a value type or a reference type.

For value types, you can use the "*address" operator to convert the address into a value, for example:

a := 10
p := &a         // 取变量 a 的地址
b := *p         // *p 表示取出 a 的值
fmt.Println(b)  // 输出：10

At this time, the type of variable b is int, and its value is equal to the value of variable a , because *p means taking out the value of the variable pointed to by p.

For reference types, the address can also be converted into a value through the "*address" operator, for example:

var s []int          // 定义一个切片 s
s = append(s, 1, 2)  // 为 s 添加元素
p := &s              // 取切片 s 的地址
v := *p              // *p 表示取出 s 的值，即切片本身
fmt.Println(v)       // 输出：[1 2]

At this time, the type of variable v is []int, and its value is equal to the variable The value of s, because *p means taking out the value of the variable pointed to by p, that is, the slice s itself. In some cases, you need to copy the value of the reference type, and you need to use the "value copy" method:

s1 := []int{1, 2}
s2 := make([]int, len(s1))
copy(s2, s1)        // 将 s1 拷贝到 s2
fmt.Println(s2)     // 输出：[1 2]
p1 := &s1           // 取切片 s1 的地址
p2 := &s2           // 取切片 s2 的地址
fmt.Println(*p1 == *p2)  // 输出：false，因为 s1 和 s2 的地址不同

In the above code, the value of s1 is copied to s2 through the copy function, so that s2 It is a new slice with a different address than s1. Therefore, the values ​​of p1 and p2 are also different.

It should be noted that in golang, pointers do not support arithmetic operations on pointer variables, that is, p, p-- such operations are wrong. When adding and subtracting pointers, we need to use variables to store addresses, for example:

a := []int{1, 2, 3}
p := &a[0]       // 取数组 a 的第一个元素的地址
p = p + 2        // 将 p 指向数组 a 的第三个元素
fmt.Println(*p)  // 输出：3

At this time, the value of p is the address of a[2], because the address of the third element is equal to the first The address of the element plus the size of 2 elements.

In golang, pointers are a powerful tool, but they need to be used with caution to avoid problems caused by pointers. When using pointers, you need to follow the following points:

1. Pointer variables must be initialized, otherwise a null pointer exception will be thrown.
2. You cannot assign a value to a pointer variable beyond the scope of the variable it points to.
3. Do not confuse pointer type and non-pointer type variables.
4. Avoid circular references, which can lead to memory leaks.

In short, pointers are advanced tools used to improve program efficiency and deal with special problems. As a developer, you need to have an in-depth understanding and application of pointers.

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