Question

How to extract N bits from a given position in a number with C

Answer 1

#include <stdio.h>
 
void print_bits(unsigned int n, int size) {
    for (unsigned int i = 1 << (size - 1); i > 0; i = i / 2) {
        (n & i) ? printf("1") : printf("0");
    }
}
 
int extract_bits(int number, int N, int pos) {
    return ( ((1 << N) - 1) & (number >> (pos - 1)) );
}
 
 
int main()
{
    unsigned int number = 441; // 000000-011011-1001
    int N = 6, pos = 5;
    
    print_bits(number, 16);
    printf("\n");
    
    int extracted_bits = extract_bits(number, N, pos);
    
    print_bits(extracted_bits, 16);

    return 0;
}
 
 
 
   
/*
run:
   
0000000110111001
0000000000011011
   
*/

 

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