apache 源码 的apr包中 *APR_POOL_DECLARE_ACCESSOR() 的含义是什么

dangyadang

apr的apr_pool.h中，关于宏   APR_POOL_DECLARE_ACCESSOR()  的含义是什么？
看了给的说明，也没弄明白到底什么意思？各位大侠指点下好么？
/*
* APR_POOL_DECLARE_ACCESSOR() is used in a header file to declare the
* accessor function. A typical usage and result would be:
* <pre>
*    APR_POOL_DECLARE_ACCESSOR(file);
* becomes:
*    APR_DECLARE(apr_pool_t *) apr_file_pool_get(apr_file_t *ob);
* </pre>
* @remark Doxygen unwraps this macro (via doxygen.conf) to provide
* actual help for each specific occurance of apr_foo_pool_get.
* @remark the linkage is specified for APR. It would be possible to expand
*       the macros to support other linkages.
*/
#define APR_POOL_DECLARE_ACCESSOR(type) \
    APR_DECLARE(apr_pool_t *) apr_##type##_pool_get \
        (const apr_##type##_t *the##type)