php natsort內核函數淺析第1/2頁

官方手冊（http://us.php.net/manual/en/function.natsort.php）
復制代碼 代碼如下:
bool natsort ( array &$array )
This function implements a sort algorithm that orders alphanumeric strings in the way a human being would while maintaining key/value associations. This is described as a "natural ordering". An example of the difference between this algorithm and the regular computer string sorting algorithms (used in sort()) can be seen in the example below.

據官方手冊還可以得到這樣的結果：

img1.png img2.png img10.png img12.png

顯然這很適合對類似文件名的排序。從結果看這種自然算法應該是去掉頭和尾的非數字部分，然後對留下來的數字部分進行排序，究竟是不是，還是看一下php源碼吧。
復制代碼 代碼如下:
//從ext/standard/array.c抽取的相關代碼如下
static int php_array_natural_general_compare(const void *a, const void *b, int fold_case) /* {{{ */
{
    Bucket *f, *s;
    zval *fval, *sval;
    zval first, second;
    int result;
    f = *((Bucket **) a);
    s = *((Bucket **) b);
    fval = *((zval **) f->pData);
    sval = *((zval **) s->pData);
    first = *fval;
    second = *sval;
    if (Z_TYPE_P(fval) != IS_STRING) {
        zval_copy_ctor(&first);
        convert_to_string(&first);
    }
    if (Z_TYPE_P(sval) != IS_STRING) {
        zval_copy_ctor(&second);
        convert_to_string(&second);
    }
    result = strnatcmp_ex(Z_STRVAL(first), Z_STRLEN(first), Z_STRVAL(second), Z_STRLEN(second), fold_case);
    if (Z_TYPE_P(fval) != IS_STRING) {
        zval_dtor(&first);
    }
    if (Z_TYPE_P(sval) != IS_STRING) {
        zval_dtor(&second);
    }
    return result;
}
/* }}} */
static int php_array_natural_compare(const void *a, const void *b TSRMLS_DC) /* {{{ */
{
    return php_array_natural_general_compare(a, b, 0);
}
/* }}} */
static void php_natsort(INTERNAL_FUNCTION_PARAMETERS, int fold_case) /* {{{ */
{
    zval *array;
    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &array) == FAILURE) {
        return;
    }
    if (fold_case) {
        if (zend_hash_sort(Z_ARRVAL_P(array), zend_qsort, php_array_natural_case_compare, 0 TSRMLS_CC) == FAILURE) {
            return;
        }
    } else {
        if (zend_hash_sort(Z_ARRVAL_P(array), zend_qsort, php_array_natural_compare, 0 TSRMLS_CC) == FAILURE) {
            return;
        }
    }
    RETURN_TRUE;
}
/* }}} */
/* {{{ proto void natsort(array &array_arg)
Sort an array using natural sort */
PHP_FUNCTION(natsort)
{
    php_natsort(INTERNAL_FUNCTION_PARAM_PASSTHRU, 0);
}
/* }}} */

雖然是第一次查看php的內核代碼，不過憑借多年看代碼的經驗，還是很容易找到這個自然排序算法的核心就是函數：strnatcmp_ex（位於ext/standard/strnatcmp.c文件中）。