- PHP_FUNCTION(str_pad)
- {
- /* Input arguments */
- zend_string *input; /* Input string 输入字符串 */
- zend_long pad_length; /* Length to pad to 填充到多长.*/
- /* Helper variables */
- size_t num_pad_chars; /* Number of padding characters (total - input size) 要填充进去的字符个数 */
- char *pad_str = " "; /* Pointer to padding string */
- size_t pad_str_len = 1; // 填充字符的个数
- zend_long pad_type_val = STR_PAD_RIGHT; /* The padding type value 填充类型, 左填充, 右填充, 左右填充. 默认右填充 */
- size_t i, left_pad=0, right_pad=0;
- zend_string *result = NULL; /* Resulting string 返回值 */
- if (zend_parse_parameters(ZEND_NUM_ARGS(), "Sl|sl", &input, &pad_length, &pad_str, &pad_str_len, &pad_type_val) == FAILURE) {
- return;
- }
- /* If resulting string turns out to be shorter than input string,
- we simply copy the input and return. */
- /* 如果 pad_length(参数 2) 小于等于输入字符串的长度, 则返回原始的输入字符串.*/
- if (pad_length <0 || (size_t)pad_length <= ZSTR_LEN(input)) {
- RETURN_STRINGL(ZSTR_VAL(input), ZSTR_LEN(input));
- }
- /* 填充字符串长度为 0, 如: str_pad("abc", 10, ""), 则 Warning 级别的错误.
- 填充字符串的默认长度为 1, 即 str_pad("abc", 10), 的情况下 pad_str_len=1.*/
- if (pad_str_len == 0) {
- php_error_docref(NULL, E_WARNING, "Padding string cannot be empty");
- return;
- }
- /*pad_type 只能为 STR_PAD_LEFT, STR_PAD_RIGHT, or STR_PAD_BOTH 或 0, 1, 2*/
- if (pad_type_val < STR_PAD_LEFT || pad_type_val> STR_PAD_BOTH) {
- php_error_docref(NULL, E_WARNING, "Padding type has to be STR_PAD_LEFT, STR_PAD_RIGHT, or STR_PAD_BOTH");
- return;
- }
- num_pad_chars = pad_length - ZSTR_LEN(input); // 需要被填充进去的字符的数量
- if (num_pad_chars>= INT_MAX) { // num_pad_chars 的最大值是 2147483647.#define INT_MAX 2147483647
- php_error_docref(NULL, E_WARNING, "Padding length is too long");
- return;
- }
- result = zend_string_safe_alloc(1, ZSTR_LEN(input), num_pad_chars, 0);
- ZSTR_LEN(result) = 0;
- /* We need to figure out the left/right padding lengths. */
- switch (pad_type_val) {
- case STR_PAD_RIGHT:
- left_pad = 0;
- right_pad = num_pad_chars;
- break;
- case STR_PAD_LEFT:
- left_pad = num_pad_chars;
- right_pad = 0;
- break;
- // 左填充数量小于右, left_pad <= right_pad
- case STR_PAD_BOTH:
- left_pad = num_pad_chars / 2;
- right_pad = num_pad_chars - left_pad;
- break;
- }
- /* First we pad on the left. */
- /* 左填充: 循环添加字符 */
- for (i = 0; i < left_pad; i++)
- ZSTR_VAL(result)[ZSTR_LEN(result)++] = pad_str[i % pad_str_len];
- /* Then we copy the input string. */
- /* 左填充完成后, 附加输入字符串 */
- memcpy(ZSTR_VAL(result) + ZSTR_LEN(result), ZSTR_VAL(input), ZSTR_LEN(input));
- ZSTR_LEN(result) += ZSTR_LEN(input);
- /* Finally, we pad on the right. */
- /* 右填充: 循环添加字符串 */
- for (i = 0; i < right_pad; i++)
- ZSTR_VAL(result)[ZSTR_LEN(result)++] = pad_str[i % pad_str_len];
- // 添加字符串结束标志'\0'
- ZSTR_VAL(result)[ZSTR_LEN(result)] = '\0';
- // 返回新字符串
- RETURN_NEW_STR(result);
- }
来源: http://www.bubuko.com/infodetail-2619110.html