php内置函数分析之strtoupper()、strtolower()

 1 PHP_FUNCTION(strtoupper) 2 { 3 ????zend_string *str; 4 ?5 ????ZEND_PARSE_PARAMETERS_START(1, 1) 6 ????????Z_PARAM_STR(str) 7 ????ZEND_PARSE_PARAMETERS_END(); 8 ?9 ????RETURN_STR(php_string_toupper(str));10 }

 1 PHPAPI zend_string *php_string_toupper(zend_string *s) 2 { 3 ????unsigned char *c, *e; 4 ?5 ????c = (unsigned char *)ZSTR_VAL(s); //字符串首地址 6 ????e = c + ZSTR_LEN(s); // 字符串末尾之后的地址，指向字符串结束标志"\0" 7 ?8 ????while (c < e) { 9 ????????if (islower(*c)) { //遇到第一个小写字符，则进入此if分支，对之后字符的操作都将在此if中完成10 ????????????register unsigned char *r;11 ????????????zend_string *res = zend_string_alloc(ZSTR_LEN(s), 0); //开辟内存存放zend_string类型数据12 13 ????????????if (c != (unsigned char*)ZSTR_VAL(s)) { //c不是字符串首地址时，执行此if14 ????????????????memcpy(ZSTR_VAL(res), ZSTR_VAL(s), c - (unsigned char*)ZSTR_VAL(s)); //将c位置之前的字符数据复制给res15 ????????????}16 ????????????r = c + (ZSTR_VAL(res) - ZSTR_VAL(s)); // 开始进行转换的位置17 ????????????// 下面的while中对每个字符都执行大写转换操作18 ????????????while (c < e) {19 ????????????????*r = toupper(*c);20 ????????????????r++;21 ????????????????c++;22 ????????????}23 ????????????*r = ‘\0‘; //为字符串添加结束标志24 ????????????return res; //返回新字符串25 ????????}26 ????????c++;27 ????}28 ????return zend_string_copy(s); //原始字符串没有被操作，则返回原始字符串，并将引用+1 29 }