c - 了解 Tokyo Cabinet 中的 tchdbfwmkeys 方法(在数据库中获取前向匹配键)

Question

我很难理解 Tokyo Cabinet 中的 tchdbfwmkeys 方法。

文档如下:

The function tchdbfwmkeys is used in order to get forward matching keys in a hash database object.

TCLIST *tchdbfwmkeys(TCHDB *hdb, const void *pbuf, int psiz, int max);

    `hdb' specifies the hash database object. 

    `pbuf' specifies the pointer to the region of the prefix. 

    `psiz' specifies the size of the region of the prefix. 

    `max' specifies the maximum number of keys to be fetched. If it is negative, no limit is specified. 

    The return value is a list object of the corresponding keys. This function does never fail. It returns an empty list even if no key corresponds. 

    Because the object of the return value is created with the function `tclistnew', it should be deleted with the function `tclistdel' when it is no longer in use. Note that this function may be very slow because every key in the database is scanned. 

我对它的含义有一个模糊的理解:你传递一个键的前缀，它返回所有具有这个前缀的键。例如，您传递前缀 data_ 并获得数据库中以 data_ 开头的所有键。

不过，我不确定这是否正确，即使是这样，我也不理解 pbuf 和 psiz 参数。您究竟应该传递给他们什么？

Answer 1

你的理解是正确的。

pbuf 和 psiz:这是 Toyko Cabinet 中的常见模式。为了允许任意键，键(或键子字符串)不作为字符串传递，而是作为指向区域及其大小的指针传递。