php natsort内核函数浅析

/* {{{ compare_right
*/
static int
compare_right(char const **a, char const *aend, char const **b, char const *bend)
{
    int bias = 0;
    /* The longest run of digits wins. That aside, the greatest
     value wins, but we can't know that it will until we've scanned
     both numbers to know that they have the same magnitude, so we
     remember it in BIAS. */
    for(;; (*a)++, (*b)++) {
        if ((*a == aend || !isdigit((int)(unsigned char)**a)) &&
            (*b == bend || !isdigit((int)(unsigned char)**b)))
            return bias;
        else if (*a == aend || !isdigit((int)(unsigned char)**a))
            return -1;
        else if (*b == bend || !isdigit((int)(unsigned char)**b))
            return +1;
        else if (**a < **b) {
            if (!bias)
                bias = -1;
        } else if (**a > **b) {
            if (!bias)
                bias = +1;
        }
}
return 0;
}
/* }}} */
/* {{{ compare_left
*/
static int
compare_left(char const **a, char const *aend, char const **b, char const *bend)
{
/* Compare two left-aligned numbers: the first to have a
different value wins. */
    for(;; (*a)++, (*b)++) {
        if ((*a == aend || !isdigit((int)(unsigned char)**a)) &&
            (*b == bend || !isdigit((int)(unsigned char)**b)))
            return 0;
        else if (*a == aend || !isdigit((int)(unsigned char)**a))
            return -1;
        else if (*b == bend || !isdigit((int)(unsigned char)**b))
            return +1;
         else if (**a < **b)
             return -1;
         else if (**a > **b)
             return +1;
}

return 0;
}
/* }}} */
/* {{{ strnatcmp_ex
* call in array.c: strnatcmp_ex(Z_STRVAL(first), Z_STRLEN(first), Z_STRVAL(second), Z_STRLEN(second), fold_case);
*/
PHPAPI int strnatcmp_ex(char const *a, size_t a_len, char const *b, size_t b_len, int fold_case)
{
    char ca, cb;
    char const *ap, *bp;
    char const *aend = a + a_len,
             *bend = b + b_len;
    int fractional, result;
    if (a_len == 0 || b_len == 0)
        return a_len - b_len;
    ap = a;
    bp = b;
    while (1) {
        ca = *ap; cb = *bp;
        /* skip over leading spaces or zeros */
        while (isspace((int)(unsigned char)ca) || (ca == '0' && (ap+1 < aend) && (*(ap+1)!='.')))
            ca = *++ap;
        while (isspace((int)(unsigned char)cb) || (cb == '0' && (bp+1 < bend) && (*(bp+1)!='.')))
            cb = *++bp;
        /* process run of digits */
        if (isdigit((int)(unsigned char)ca) && isdigit((int)(unsigned char)cb)) {
            fractional = (ca == '0' || cb == '0');
            if (fractional)
                result = compare_left(&ap, aend, &bp, bend);
            else
                result = compare_right(&ap, aend, &bp, bend);
            if (result != 0)
                return result;
            else if (ap == aend && bp == bend)
                /* End of the strings. Let caller sort them out. */
                return 0;
            else {
                /* Keep on comparing from the current point. */
                ca = *ap; cb = *bp;
            }
        }
        if (fold_case) {
            ca = toupper((int)(unsigned char)ca);
            cb = toupper((int)(unsigned char)cb);
        }
        if (ca < cb)
            return -1;
        else if (ca > cb)
            return +1;
        ++ap; ++bp;
        if (ap >= aend && bp >= bend)
            /* The strings compare the same. Perhaps the caller
             will want to call strcmp to break the tie. */
            return 0;
        else if (ap >= aend)
            return -1;
        else if (bp >= bend)
            return 1;
    }
}
/* }}} */

while (isspace((int)(unsigned char)ca) || (ca == '0' && (ap+1 < aend) && (*(ap+1)!='.')))
    ca = *++ap;
while (isspace((int)(unsigned char)cb) || (cb == '0' && (bp+1 < bend) && (*(bp+1)!='.')))
    cb = *++bp;