This is the method used to sort the filenames of pages inside an archive for iComics v1.1.

ICComicLoader+PageOrdering.m

- (NSComparisonResult)sortedArchiveEntryIndex:(NSString *)firstName againstIndex:(NSString *)secondName
{
    //if first name is empty, assume ascending
    if ([firstName length] == 0)
        return NSOrderedAscending;
  
    if ([secondName length] == 0)
        return NSOrderedDescending;
    
    //convert the names to raw bytes so they can be manually compared on a numerical basis
    const char *firstString     = [[firstName uppercaseString] cStringUsingEncoding:NSASCIIStringEncoding];
    const char *secondString    = [[secondName uppercaseString] cStringUsingEncoding:NSASCIIStringEncoding];
    
    if (!firstString)
        return NSOrderedAscending;
    
    if (!secondString)
        return NSOrderedDescending;
    
    //loop through each character in the first name byte array
    NSInteger i = 0;
    for (i = 0; i < strlen(firstString); i++)
    {
        //if there are no more characters in the second string, assume 
        if (i >= strlen(secondString))
            return NSOrderedDescending;
        
        char j = firstString[i];
        char k = secondString[i];
        
        //if first character is '_' (eg it's a notice), send it to the back
        if (i == 0 && j == '_') { return NSOrderedDescending; }
        if (i == 0 && k == '_') { return NSOrderedAscending;  }
        
        //if they're both numbers, collect the lot and compare both
        if (isdigit(j) && isdigit(k)) {
            NSInteger firstNumber=0, secondNumber=0, index = i;
            
            char p, q;
            do {
                p = firstString[index];
                q = secondString[index];
                
                if (isdigit(p))
                    firstNumber = (firstNumber * 10) + (p - '0');
                
                if (isdigit(q))
                    secondNumber = (secondNumber * 10) + (q - '0');
                
                index++;
            } while (isdigit(p) || isdigit(q));
            
            if (firstNumber < secondNumber)
                return NSOrderedAscending;
            else if (firstNumber > secondNumber)
                return NSOrderedDescending;
            
            //if the numbers turned out to be equal, skip what we just did, and continue
            i = index-2; // (-2 -> Undoes both loops)
            continue;
        }
        
        if (j == k)
            continue;
        
        //give priority to filenames with preceeding periods
        if (j == '.' && k != '.')
            return NSOrderedAscending;
        
        if (j != '.' && k == '.')
            return NSOrderedDescending;
        
        //byte-compare the two letters
        if (j > k) {
            //if there are no more slashes in the firstString (and more in the second string), assume firstString is in its final
            //path component and give priority
            if (strchr(firstString+i, '/') == NULL && strchr(secondString+i, '/') != NULL)
                return NSOrderedAscending;
            
            return NSOrderedDescending;
        }
        else
        {
            if (strchr(secondString+i, '/') == NULL && strchr(firstString+i, '/') != NULL)
                return NSOrderedDescending;
            
            return NSOrderedAscending;
        }
    }
    
    if (i < strlen(secondString))
        return NSOrderedAscending;
    
    return NSOrderedSame;
}