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If condition could not understood

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faisaldj

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Can somebody elaborate the If condition in this sample code
I try to debug it and everytime getting

00000000
or
00000001

but could not interpret the logic.


////////////////////////////// Code ////////////////////////

phase _buff is 8 bit.
unsigned char phase_buff=0x60;

for (b = 0; b < 9; b++)

{

if ( ( phase_buff[a] >> (7 - b) ) & 1 ) {
{
do_something;
}
}

regards,
faisal.
 

inside the if statement you shift right (7-b) bits and then check if the lsb is 1 (the other bits are masked)

Alex
 
yes, this code for (b = 0; b < 9; b++) executes from b=0 to b=8
so if phase_buff[a] is 8 bit , b should be 0 to 7.

There are also 2 ways to do the masking inside the if,
the first is to shift right the variable and mask the 7 bits using 1 as you are doing
or you can shift the 1 to the left, I'm not sure which is faster, the result will be the same, i think this is easier to read.
if ( phase_buff[a] & (1<<b) )
so you are masking with 00000001 00000010 00000100 etc

Alex
 
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