It is not used as a parameter, you cannot use global variables, and you cannot use it as a return value. How to use this

jinyuyi

That's it. This is the structure to be used
typedef struct
{
char name [256]; // filename
uint32_t size; // file size
uint8_t * buffer; // buffer
uint8_t ver; // version
} file_t;
My file open function has a file descriptor fd. The file open function is used for read and write operations. The file open function returns the file_t pointer as a parameter to the read and write function. How can the fd value in the file open function be used? Used in read and write functions? fd is not used as a parameter and cannot be used as a return value. If global variables are used, the value of fd in two consecutive files becomes the descriptor of the second file, which is not enough?

suizbs

Looks messy

orangedj

You bull, write it in main

suizbs

Why can't you pass in parameters

zxc123456789

It can only be said that it is a perverted request.

jinyuyi

I can't help it? I don't want to do that either. But the requirement is that the function parameters and return value (that structure) cannot be changed. Everyone help

珈蓝易拉罐

Implement a global registry, open one, put it in, and then use the person to find it by name. . . --b

珈蓝易拉罐

What does it matter that the return value (that structure) cannot be tampered with?

jinyuyi

Implement a global registry, open one, put it in, and then use the person to find it by name. . . --b
The registry is not needed, the system is linux.
What does it matter that the return value (that structure) cannot be tampered with?
This means that the file descriptor I want cannot be passed as a parameter to the next function to use this file description server.

珈蓝易拉罐

It's not that the "register" of the system is your own implementation of a "registration information table", such as through std :: map.

Will it be modified if you pass it? Then you can pass the value instead of the pointer. If you have to modify it, you ca n’t change the actual parameter.