What are go types and dot syntax?

php editor Strawberry will introduce you to the types and dot syntax in Go language. In Go language, type is an attribute of a variable and is used to define the data type of the variable. Types in the Go language include basic types (such as integers, floating point types, Boolean types, etc.) and composite types (such as arrays, slices, maps, etc.). The dot syntax is the syntax used to access the properties and methods of structures and objects. By using dot syntax, we can directly use the properties of an object or structure or call its methods to operate and process data. This concise and intuitive syntax makes Go language more convenient and efficient in programming.

Question content

dmeo code

package listing12_9

import (
    "runtime"
    "sync"
    "sync/atomic"
)

type SpinLock int32

func (s *SpinLock) Lock() {
    for !atomic.CompareAndSwapInt32((*int32)(s), 0, 1) {
        runtime.Gosched()
    }
}

func (s *SpinLock) Unlock() {
    atomic.StoreInt32((*int32)(s), 0)
}

func NewSpinLock() sync.Locker {
    var lock SpinLock
    return &lock
}

atomic.CompareAndSwapInt32((*int32)(s), 0, 1) What is the syntax and what do (*int) and (s) mean?

Solution

You have defined the type here:

type SpinLock int32

But you will call methods in the atomic package using the following specification:

func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)

So, to send a variable s of type SpinLock to the CompareAndSwapInt32 method, you must tell the compiler that s can Used as int32, this is called type conversion, in golang we do this:

convertedValue := TargetType(variable)

But in Learn Go Concurrent Programming book, it uses converting variable s from type *SpinLock to *int32, a more modern approach might be:

type SpinLock int32

func (s SpinLock) Lock() {
    castedS := int32(s)
    for !atomic.CompareAndSwapInt32(&castedS, 0, 1) {
        runtime.Gosched()
    }
}

func (s SpinLock) Unlock() {
    castedS := int32(s)
    atomic.StoreInt32(&castedS, 0)
    atomic.StoreInt32(&castedS, 0)
}

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