Question

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Explanation of an algorithm to set, clear and test a single bit

I have an unsigned char. I would like to have bits 2 through 4 (counting from the least significant bit as 0) copied to another unsigned char as the first three bits. For example, in

abcdefgh // a,b,c,d,e,f,g,h are 0 or 1

becomes

00000def

I have tried

unsigned char input, output;
output = (input << 3) >> 5;

which does not work, but

output = (input << 3)
output >>= 5;

does work.

Is there a way in C to accomplish this in one line?

Answer 1

shift it, then mask the rest off:

output = ( input >> 2 ) & 0x07;