CODEWITHSUNDEEP
cbit-manipulation
Nanomurf
Nanomurf

Reputation: 759

More elegant solution for multiple bit shifts

Let's take an array of bit-masked status bytes:

char status[10];

Now, let's say we want to pull the 3rd bit out of each status byte and put them into an int, where the LSB of the int is status[0] bit 3, next is status[1] bit 3, etc.

int foobits = 0;
for( i = 0; i < 10; i++ )
{
    foobits |= (( status[i] & 0x04 ) >> 2) << i;
}

My question is: is there an alternative way to accomplish this that involves only one shift?

Edit: I'm trying to use foobits to contain the bit array of status[i] bit #3s.

Upvotes: 2

Views: 2388

Answers (1)

Jim Balter
Jim Balter

Reputation: 16406

You could do this

int foobits = 0;
for( i = 0; i < 10; i++ )
{
    foobits |= (status[i] & 0x04) << i;
}
foobits >>= 2;

but why bother?

"Premature optimization is the root of all evil." -- Donald Knuth

Upvotes: 3

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