typedef fixed length array?

Question

I have to define a 24-bit data type.I am using `char[3]` to represent the type. Can I typedef `char[3]` to `type24`? I tried it in a code sample. I put `typedef char[3] type24;` in my header file. The compiler did not complain about it. But when I defined a function `void foo(type24 val) {}` in my C file, it did complain. I would like to be able to define functions like `type24_to_int32(type24 val)` instead of `type24_to_int32(char value[3])`.

Answer 1

You cannot do this directly. In C, you cannot accept raw arrays by value (it decays to a pointer). However, in this case, the typedef is unable to decay to a pointer, and so you get an error. The way to get around this limitation is to use a struct.

typedef struct {

char data[3];

} type24;

int32_t type24_to_int32(type24 val) {

// Access bytes using val.data[0], val.data[1], etc.

}

void foo(type24 val) {

// Passed by value safely

}