Subversion Repositories pcounter

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <ctype.h>

typedef unsigned long count_t;

count_t pcount_decode(unsigned n, count_t b) {

  count_t y = b;

  unsigned k;

  for (k = 1; k < n; k++)

    if ((y & ((1<<k)-1)) < k)

      y = y ^ (1<<k);

  return y;

}

count_t pcount_encode(unsigned n, count_t y) {

  count_t b = y;

  unsigned k;

  for (k = n-1; k > 0; k--)

    if ((b & ((1<<k)-1)) < k)

      b = b ^ (1<<k);

  return b;

}

int main() {

  char s[256], *c;

  count_t b, y, z;

  for (;;) {

    if (!fgets(s, sizeof(s), stdin))

      break;

    for (c = s + strlen(s) - 1; isspace(*c); c--)

      *c = '\0';

    b = strtoul(s, NULL, 2);

    y = pcount_decode(strlen(s), b);

    z = pcount_encode(strlen(s), y);

    printf("%08lx -> %08lx -> %08lx\n", b, y, z);

  }

  return 0;

}