[游戏开发]Android_NDK C结构体和枚举（D5）

Android_NDK C结构体和枚举

结构体定义和使用

struct Worker{
    char name[10];
    int age;
    double salary;
};

//不初始化，有默认值
struct Worker1{
    char name[10];
    int age;
    double salary;
}jack = {"jack",18,200},darry;


struct Name{
    char fisrtName[10];
    char name[10];
}
struct Worker2{
    //可以声明内部类
    Name name;
    int age;
    double salary;
};

void main(){
    //不初始化，没有默认值
    struct Worker worker = {"awewe",18,1000};
    
    char * name = worker.name;
    int age = worker.age;
    double salary = worker.salary;


}

结构体指针和动态内存开辟

不推荐

struct Worker{
    char name[10];
    int age;
    double salary;
};

void main(){
    //不初始化，没有默认值
    struct Worker worker = {"awewe",18,1000};
    
    Worker * wp = &worker;
    wp->age = 22;

}

推荐

struct Worker{
    char name[10];
    int age;
    double salary;
};

void main(){
    Worker * worker = (Worker *)malloc(sizeof(Worker));
    worker-> age = 90;


    if(worker){
        free(worker);
    }
}

结构体数组

struct Worker{
    char name[10];
    int age;
    double salary;
};

void main(){
    Worker worker[2] = {{"123",12,123},{}};

    Worker * wp = (Worker*) malloc(sizeof(Worker)*3);

    //对第一个操作
    strcpy(wp->name,"31231");
    wp->age = 12;

    wp += 1;
    //对第二个操作
    strcpy(wp->name,"31231");
    wp->age = 12;
}

字节对齐和结构体大小计算

计算规则

1. 按照最大的字节去计算
2. 按照基本数据类型来
3. 首先会把所有的加起来，是否能整除最大字节数，不够则累加，一直加到可以整除为止
4. 结构体嵌套按照把第一个成员看成结构体中最大的成员

struct Worker{
    char name[10];
    int age;
    double salary;
    //10 + 4 +8 = 22
    //3 * 8 = 24
    //可以整除，则是24
};

struct Worker1{
    char name[18];
    int age;
    double salary;
    //18 + 4 +8 = 30
    //3 * 8 = 24
    //不可以可以整除，则是24 + 8 = 32
};

struct Birth{
    int y;
    int m;
    int d;
    //4 + 4 +4 = 12
    //可以整除，则是12
};

struct Worker{
    int num;
    char sex;
    int age;
    char name[10];
    double salary;

    struct Birth b;

    //4 + 1 +4 + 10 + 12 = 32
    //3 * 12 = 36
    //可以整除，则是36
};

结构体别名

struct Birth{
    int y;
    int m;
    int d;
};

//取别名
typedef Worker Worker_;
//取别名
typedef Worker * Worker_p;

void main(){
    Worker_ worker = {"123",23,23};

    Worker_p p = (Worker*)malloc(sizeof(Worker));
}

• 使用typedef可以取多个别名。
• 也可以对结构体指针取别名。
• 也可以不加struct关键字。

联合体

union Person{
    char name[10];
    int age;
    //大小12 
}

void main(){
    Person p;
    //只能拿到age
    strcpy(p.name , "DDDDD");
    p.age = 12;
    //只能拿到name
    p.age = 12;
    strcpy(p.name , "DDDDD");
}

联合体只能存在一个，要么是name，要么是age。所以构造方法也只能穿一个值。
大小计算就是最大值。被最大值整除即可

枚举

enum ContentType{
    TEXT,IMAGE,VOICE
}

void main(){
    ContentType ct = TEXT;
    ContentType ct1 = VOICE;
    //enum类似int
}

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