《jdk8u源码分析》5.2.JLI_ValidVersionString

src/share/bin/version_comp.c::JLI_ValidVersionString

/*
 *      Validates a version string by the extended JSR 56 grammar.
 */
int
JLI_ValidVersionString(char *version_string)
{
    char        *vs;
    char        *m1;
    char        *end;
    if ((version_string == NULL) || (JLI_StrLen(version_string) == 0))
        return (0);
    //拷贝一份版本号副本
    m1 = vs = JLI_StringDup(version_string);
    do {
    	//搜索vs中第一次出现' '的位置，如果未找到返回NULL
    	//如果找到，将vs从空格前截断，end指针指向剩余部分（包含空格）
        if ((end = JLI_StrChr(vs, ' ')) != NULL)
            *end = '\0';//end首地址赋值为'\0'
        //校验元素vs，如果vs包含空格，仅判断空格前的部分
        //如果元素无效直接释放内存并返回
        if (!valid_element(vs)) {
            JLI_MemFree(m1);
            return (0);
        }
        //如果vs包含空格，重新将vs赋值指向空格后的字符串，继续循环判断
        if (end != NULL)
            vs = end + 1;
    } while (end != NULL);
    JLI_MemFree(m1);
    return (1);
}

src/share/bin/version_comp.c::valid_element

/*
 *      Return true if this is a valid element (as defined in JSR 56).
 *      An element is the intersection (and) of multiple simple-elements.
 */
static int
valid_element(char *element)
{
    char        *end;
    if ((element == NULL) || (JLI_StrLen(element) == 0))
        return (0);
    do {
    	//搜索vs中第一次出现'&'的位置，如果未找到返回NULL
    	//如果找到，将element从空格前截断，end指针指向剩余部分（包含空格）
        if ((end = JLI_StrChr(element, '&')) != NULL)
            *end = '\0';//end首地址赋值为'\0'
        //校验元素element，如果vs包含空格，仅判断空格前的部分
        //如果元素无效直接释放内存并返回
        if (!valid_simple_element(element))
            return (0);
        //如果vs包含空格，重新将element赋值指向空格后的字符串，继续循环判断
        if (end != NULL)
            element = end + 1;
    } while (end != NULL);
    return (1);
}

src/share/bin/version_comp.c::valid_simple_element

/*
 *      Return true if this is a valid simple-element (as defined in JSR 56).
 *
 *      The official grammar for a simple-element is:
 *
 *              simple-element  ::= version-id | version-id modifier
 *              modifier        ::= '+' | '*'
 *              version-id      ::= string ( separator  string )*
 *              string          ::= char ( char )*
 *              char            ::= Any ASCII character except a space, an
 *                                  ampersand, a separator or a modifier
 *              separator       ::= '.' | '-' | '_'
 *
 *      However, for efficiency, it is time to abandon the top down parser
 *      implementation.  After deleting the potential trailing modifier, we
 *      are left with a version-id.
 *
 *      Note that a valid version-id has three simple properties:
 *
 *      1) Doesn't contain a space, an ampersand or a modifier.
 *
 *      2) Doesn't begin or end with a separator.
 *
 *      3) Doesn't contain two adjacent separators.
 *
 *      Any other line noise constitutes a valid version-id.
 */
static int
valid_simple_element(char *simple_element)
{
    char        *last;
    size_t      len;

	//如果验证字符串为NULL或空串，直接返回0
    if ((simple_element == NULL) || ((len = JLI_StrLen(simple_element)) == 0))
        return (0);
    //字符串最后一个字符为 '*' | '+'
    last = simple_element + len - 1;
    if (*last == '*' || *last == '+') {
    	//字符串长度为1，直接返回0
        if (--len == 0)
            return (0);
        //先执行--,即last字符指针向前移动一个单位，再设置对应内存的值为'\0'
        //参考C语言运算符优先级：http://c.biancheng.net/view/161.html
        //意图应该是删除最后的 '*' | '+'
        *last-- = '\0';
    }
    //判断是否包含：' ' | '+' | '*'，如果是，版本号无效
    if (JLI_StrPBrk(simple_element, " &+*") != NULL)    /* Property #1 */
        return (0);
    //判断是否以分隔符开始或结束：'.' | '-' | '_'，如果是，版本号无效
    if ((JLI_StrChr(".-_", *simple_element) != NULL) || /* Property #2 */
      (JLI_StrChr(".-_", *last) != NULL))
        return (0);
    //判断是否包含两个连续的分隔符：'.' | '-' | '_'，如果是，版本号无效
    for (; simple_element != last; simple_element++)    /* Property #3 */
        if ((JLI_StrChr(".-_", *simple_element) != NULL) &&
          (JLI_StrChr(".-_", *(simple_element + 1)) != NULL))
            return (0);
    return (1);
}

标签：5.2,end,version,simple,element,源码,jdk8u,NULL,JLI
来源： https://blog.csdn.net/weixin_37477523/article/details/88130054