Re: Fix strverscmp

[Isaac Dunham <idunham@lavabit.com>]

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On Wed, 5 Dec 2012 23:14:56 -0500
Rich Felker <dalias@aerifal.cx> wrote:

> All that means is that you missed testing any case where it differs.
> 
> ./a.out s10212 s102102
> 2
> -1

I realized what you meant just after sending the last email...
Anyhow, after working out how the state should change and a little bit of testing, I arrived at the attached version.

Logic for the upper part:
Start, assuming a non-numeric char (1)
--if initialized to 0, it will break the case where the first 2 characters are differing digits!
while walking down to the difference, 
-record 0 if char was last
-record 2 for any other digit if char was last
-Reset to 1 if a non-digit is found.
This records the leading digit of a sequence.
When the difference is reached, record 0 if one branch contains a leading zero.


-- 
Isaac Dunham <idunham@lavabit.com>

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#define _GNU_SOURCE
#define _XOPEN_SOURCE	700
#include <stdio.h>
#include <string.h>
#include <ctype.h>


int str_vers_cmp(const char *l, const char *r){
	int haszero=1;
	while (*l && *r && l[0]==r[0]){
		if (l[0]=='0'){
			if (haszero==1) {
				haszero=0;
			}
		} else if (isdigit(l[0])) {
			if (haszero==1) {
				haszero=2;
			}
		} else {
			haszero=1;
		}
		l++; r++;
	}
	if (haszero==1 && (l[0]=='0' || r[0]=='0')) {
		haszero=0;
	}
	if ((isdigit(l[0]) && isdigit(r[0]) ) && haszero) {
	//return the one with the longer substring of numbers
		int lenl=0, lenr=0, firstl=l[0], firstr=r[0];
		while (isdigit(l++[0]) ) {
			lenl++;
		}
		while (isdigit(r++[0]) ) {
			lenr++;
		}
		if (lenl==lenr) {
			return (firstl -  firstr);
		} else {
			return (lenl - lenr);
		}
	} else {
		return (l[0] -  r[0]);
	}
} 

int main(int argc, char **argv){
	printf("%d\n%d\n",str_vers_cmp(argv[1], argv[2]), strverscmp(argv[1], argv[2]));
}