Re: Naive implementation of strverscmp(3)

[Ulrich Spoerlein]

Peter Jeremy wrote:

>Is there a chance this might get included into libc? Or is it considered >bloat?

I don't think it belongs in libc.  Maybe libutil.

This would require patching the gqview configure script, but I can live with that.

For the first point, consider
  strverscmp("jan25", "janx25");

strverscmp("foo.009", "foo.0") > 0





Ulrich Spoerlein
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#ifdef __FreeBSD__
int
strverscmp(const char *s1, const char *s2);

int
strverscmp(const char *s1, const char *s2)
{
  static const char *digits = "0123456789";
  char *t1, *t2;
  int ret;
  long n1, n2;
  size_t p1, p2;

  p1 = strcspn(s1, digits);
  p2 = strcspn(s2, digits);
  //while ((p1=strcspn(s1, digits)) != 0 && p1 == (p2=strcspn(s2, digits))) {
  while (p1 == p2 && p1 != 0) {
  
    /* Different prefix */
    if ((ret = strncmp(s1, s2, p1)) != 0)
      return ret;

    s1 += p1;
    s2 += p2;
    n1 = strtol(s1, &t1, 10);
    n2 = strtol(s2, &t2, 10);
    
    if (n1 < n2)
      return -1;
    else if (n1 > n2)
      return 1;

    /* One number is "shorter", e.g., "07" vs "007" */
    if (t1-s1 < t2-s2)
      return 1;
    else if (t1-s1 > t2-s2)
      return -1;

    /* Numbers are equal or not present, try with next ones. */
    s1 = t1;
    s2 = t2;
    p1 = strcspn(s1, digits);
    p2 = strcspn(s2, digits);
  }
  
  return strcmp(s1, s2);
}
#endif

int
main(int argc, char **argv)
{
  char **array, *temp;
  int i, j, n = 10;

  array = (char **) calloc(n, sizeof(char *));
  array[0] = strdup("jan009");
  array[1] = strdup("jan10");
  array[2] = strdup("jan09");
  array[3] = strdup("jan0a");
  array[4] = strdup("jan17b");
  array[5] = strdup("jan17a");
  array[6] = strdup("janx25");
  array[7] = strdup("jan25");
  array[8] = strdup("jan17x");
  array[9] = strdup("jan9");

  /* Bubble sort */
  for (i=0; i<n; ++i) {
    for (j=i; j<n; ++j) {
      if (strverscmp(array[i], array[j]) > 0) {
        temp = array[j];
        array[j] = array[i];
        array[i] = temp;
      }
    }
  }

  for (i=0; i<n; ++i) {
    printf("%s\n", array[i]);
  }

  printf("%d = 0\n", strverscmp("a", "a"));
  printf("%d < 0\n", strverscmp("item#99", "item#100"));
  printf("%d > 0\n", strverscmp("alpha1", "alpha001"));
  printf("%d > 0\n", strverscmp("part1_f012", "part1_f01"));
  printf("%d < 0\n", strverscmp("foo.009", "foo.0"));
  printf("%d\n", strcmp("jan25", "janx25"));
  printf("%d\n", strverscmp("jan25", "janx25"));

  return 0;
}

This fell victim to a rearranging of the while loop. Thanks for pointing that out! Attached is an updated version, which now also takes leading zeros into account. It still differs from the GNU version, because In my book, '009' is just greater than zero, no matter what. If someone could explain to me, why the GNU folks do it the other way round, I could try implementing that too. Also, what do people think about the commented out while construct? It saves a call to strcspn(s2) if s1 has no digits, but it's rather ugly.

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