I was pondering (and therefore am looking for a way to learn this, and not a better solution) if it is possible to get an array of bits in a structure.
Let me demonstrate by an example. Imagine such a code:
#include <stdio.h>
struct A
{
unsigned int bit0:1;
unsigned int bit1:1;
unsigned int bit2:1;
unsigned int bit3:1;
};
int main()
{
struct A a = {1, 0, 1, 1};
printf("%u
", a.bit0);
printf("%u
", a.bit1);
printf("%u
", a.bit2);
printf("%u
", a.bit3);
return 0;
}
In this code, we have 4 individual bits packed in a struct. They can be accessed individually, leaving the job of bit manipulation to the compiler. What I was wondering is if such a thing is possible:
#include <stdio.h>
typedef unsigned int bit:1;
struct B
{
bit bits[4];
};
int main()
{
struct B b = {{1, 0, 1, 1}};
for (i = 0; i < 4; ++i)
printf("%u
", b.bits[i]);
return 0;
}
I tried declaring bits
in struct B
as unsigned int bits[4]:1
or unsigned int bits:1[4]
or similar things to no avail. My best guess was to typedef unsigned int bit:1;
and use bit
as the type, yet still doesn't work.
My question is, is such a thing possible? If yes, how? If not, why not? The 1 bit unsigned int is a valid type, so why shouldn't you be able to get an array of it?
Again, I don't want a replacement for this, I am just wondering how such a thing is possible.
P.S. I am tagging this as C++, although the code is written in C, because I assume the method would be existent in both languages. If there is a C++ specific way to do it (by using the language constructs, not the libraries) I would also be interested to know.
UPDATE: I am completely aware that I can do the bit operations myself. I have done it a thousand times in the past. I am NOT interested in an answer that says use an array/vector instead and do bit manipulation. I am only thinking if THIS CONSTRUCT is possible or not, NOT an alternative.
Update: Answer for the impatient (thanks to neagoegab):
Instead of
typedef unsigned int bit:1;
I could use
typedef struct
{
unsigned int value:1;
} bit;
properly using #pragma pack
See Question&Answers more detail:
os