读书笔记:跟涛哥一起学嵌入式_note

本文链接：https://blog.youkuaiyun.com/u011559046/article/details/87933567

本文深入探讨C语言的高级特性，包括指定初始化、数组、switch-case、结构体及container_of宏的使用。从标准C到C99/GNUC标准，详细讲解不同初始化方式，并通过实例说明结构体成员的灵活指定。同时，介绍container_of宏在复杂数据结构操作中的应用。

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跟涛哥一起学嵌入式:https://zhuanlan.zhihu.com/wanglitao

指定初始化

数组

标准 C 中

int a[10] = {0,1,2,3,4,5,6,7,8};

C99 /GNU C 标准

int b[100] ={ [10] = 1, [30] = 2};
int b[100] = { [10 ... 30] = 1, [50 ... 60] = 2 }；

switch-case

... 和其两端的数据范围2和8之间也要空格，不能写成2...8的形式，否则编译就会通不过。

    switch(i)
    {
        case 1:
            printf("1\n");
            break;
        case 2 ... 8:
            printf("%d\n",i);
            break;
        case 9:
            printf("9\n");
            break;
        default:
            printf("default!\n");
            break;
    }

结构体

struct student{
    char name[20];
    int age;
};

标准 C 中

struct student stu1={ "wit",20 };

C99 /GNU C 标准

    struct student stu2=
    {
        .name = "wanglitao",
        .age  = 28
    };

举例

struct file_operations {
        struct module *owner;
        loff_t (*llseek) (struct file *, loff_t, int);
        ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
        ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
        ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
        ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
        int (*iterate) (struct file *, struct dir_context *);
        unsigned int (*poll) (struct file *, struct poll_table_struct *);
        long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
        long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
        int (*mmap) (struct file *, struct vm_area_struct *);
        int (*open) (struct inode *, struct file *);
        int (*flush) (struct file *, fl_owner_t id);
        int (*release) (struct inode *, struct file *);
        int (*fsync) (struct file *, loff_t, loff_t, int datasync);
        int (*aio_fsync) (struct kiocb *, int datasync);
        int (*fasync) (int, struct file *, int);
        int (*lock) (struct file *, int, struct file_lock *);
        ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
        unsigned long (*get_unmapped_area)(struct file *,
               unsigned long, unsigned long, unsigned long, unsigned long);
        int (*check_flags)(int);
        int (*flock) (struct file *, int, struct file_lock *);
        ssize_t (*splice_write)(struct pipe_inode_info *, 
            struct file *, loff_t *, size_t, unsigned int);
        ssize_t (*splice_read)(struct file *, loff_t *, 
            struct pipe_inode_info *, size_t, unsigned int);
        int (*setlease)(struct file *, long, struct file_lock **, void **);
        long (*fallocate)(struct file *file, int mode, loff_t offset,
                  loff_t len);
        void (*show_fdinfo)(struct seq_file *m, struct file *f);
        #ifndef CONFIG_MMU
        unsigned (*mmap_capabilities)(struct file *);
        #endif
    };

static const struct file_operations ab3100_otp_operations = {
.open        = ab3100_otp_open,
.read        = seq_read,
.llseek        = seq_lseek,
.release    = single_release,
};

指定声明了部分变量，结构体类型发生改变时，如添加成员、减少成员、调整成员顺序，声明的变量不需要改变。

container_of 宏

#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#define  container_of(ptr, type, member) ({    \
         const typeof( ((type *)0)->member ) *__mptr = (ptr); \
         (type *)( (char *)__mptr - offsetof(type,member) );})