C项目中头文件的组织方法

zhoubug

#ifdef __cplusplus                                                                              extern "C" {                                                                                    #endif /* __cplusplus */   typedef struct data_t data_t; int func(data_t *data,int n); #ifdef __cplusplus } #endif

上面是头文件的，然后在c文件定义data_t的结构。
这种黑盒子的方式提供接口在c的很多开源库里很普遍。
引用者不能直接访问结构体的数据成员。

群雄逐鹿

这个办法很好。不然牵一发动全身真的很麻烦

epegasus

>>引用者不能直接访问结构体的数据成员
那引用者还拿这个结构体有什么用?请举个例子

群雄逐鹿

就是handle, 类似于文件fd

zhoubug

原帖由 epegasus 于 2009-8-27 14:31 发表
>>引用者不能直接访问结构体的数据成员
那引用者还拿这个结构体有什么用?请举个例子

一个是通过提供的接口函数访问
第二个理由是有些里面的数据是使用者不需要知道的，接口函数内部使用的。
e.g.apache 对于共享内存的一个封装的例子：

#ifndef APR_SHM_H #define APR_SHM_H /**  * @file apr_shm.h  * @brief APR Shared Memory Routines  */ #include "apr.h" #include "apr_pools.h" #include "apr_errno.h" #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ /**  * @defgroup apr_shm Shared Memory Routines  * @ingroup APR  * @{  */ /**  * Private, platform-specific data struture representing a shared memory  * segment.  */ typedef struct apr_shm_t apr_shm_t; /**  * Create and make accessable a shared memory segment.  * @param m The shared memory structure to create.  * @param reqsize The desired size of the segment.  * @param filename The file to use for shared memory on platforms that  *        require it.  * @param pool the pool from which to allocate the shared memory  *        structure.  * @remark A note about Anonymous vs. Named shared memory segments:  *         Not all plaforms support anonymous shared memory segments, but in  *         some cases it is prefered over other types of shared memory  *         implementations. Passing a NULL 'file' parameter to this function  *         will cause the subsystem to use anonymous shared memory segments.  *         If such a system is not available, APR_ENOTIMPL is returned.  * @remark A note about allocation sizes:  *         On some platforms it is necessary to store some metainformation  *         about the segment within the actual segment. In order to supply  *         the caller with the requested size it may be necessary for the  *         implementation to request a slightly greater segment length  *         from the subsystem. In all cases, the apr_shm_baseaddr_get()  *         function will return the first usable byte of memory.  *  */ APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m,                                          apr_size_t reqsize,                                          const char *filename,                                          apr_pool_t *pool); /**  * Remove named resource associated with a shared memory segment,  * preventing attachments to the resource, but not destroying it.  * @param filename The filename associated with shared-memory segment which  *        needs to be removed  * @param pool The pool used for file operations  * @remark This function is only supported on platforms which support  * name-based shared memory segments, and will return APR_ENOTIMPL on  * platforms without such support.  Removing the file while the shm  * is in use is not entirely portable, caller may use this to enhance  * obscurity of the resource, but be prepared for the the call to fail,  * and for concurrent attempts to create a resource of the same name  * to also fail.  The pool cleanup of apr_shm_create (apr_shm_destroy)  * also removes the named resource.  */ APR_DECLARE(apr_status_t) apr_shm_remove(const char *filename,                                          apr_pool_t *pool); /**  * Destroy a shared memory segment and associated memory.  * @param m The shared memory segment structure to destroy.  */ APR_DECLARE(apr_status_t) apr_shm_destroy(apr_shm_t *m); /**  * Attach to a shared memory segment that was created  * by another process.  * @param m The shared memory structure to create.  * @param filename The file used to create the original segment.  *        (This MUST match the original filename.)  * @param pool the pool from which to allocate the shared memory  *        structure for this process.  */ APR_DECLARE(apr_status_t) apr_shm_attach(apr_shm_t **m,                                          const char *filename,                                          apr_pool_t *pool); /**  * Detach from a shared memory segment without destroying it.  * @param m The shared memory structure representing the segment  *        to detach from.  */ APR_DECLARE(apr_status_t) apr_shm_detach(apr_shm_t *m); /**  * Retrieve the base address of the shared memory segment.  * NOTE: This address is only usable within the callers address  * space, since this API does not guarantee that other attaching  * processes will maintain the same address mapping.  * @param m The shared memory segment from which to retrieve  *        the base address.  * @return address, aligned by APR_ALIGN_DEFAULT.  */ APR_DECLARE(void *) apr_shm_baseaddr_get(const apr_shm_t *m); /**  * Retrieve the length of a shared memory segment in bytes.  * @param m The shared memory segment from which to retrieve  *        the segment length.  */ APR_DECLARE(apr_size_t) apr_shm_size_get(const apr_shm_t *m); /**  * Get the pool used by this shared memory segment.  */ APR_POOL_DECLARE_ACCESSOR(shm); /** @} */ #ifdef __cplusplus } #endif #endif  /* APR_SHM_T */

我个人很欣赏apr的代码组织，另外要说下这个结构体的实际定义是分布到各个针对不同平台的文件里定义，因为apr是跨平台的，这样还避免了为了跨平台代码里大量预处理的定义，代码读起来更方便。c项目有时候给人感觉代码没有cpp好组织，比较凌乱，我觉得这个讨论代码组织的话题不错，看看这些经典项目或许能有新的认识。

./include/apr_shm.h                                                          43,1           36% __Tag_List__   15,5        All &nbsp;&nbsp;# pri kind tag               file > 1 F C t    apr_shm_t         include/apr_shm.h &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;language:C++ typeref:struct:apr_shm_t &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;typedef struct apr_shm_t apr_shm_t; &nbsp;&nbsp;2 F   s    apr_shm_t         include/arch/unix/apr_arch_shm.h &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;language:C++ &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;struct apr_shm_t { &nbsp;&nbsp;3 FS  s    apr_shm_t         shmem/beos/shm.c &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;language:C &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;struct apr_shm_t { &nbsp;&nbsp;4 FS  s    apr_shm_t         shmem/os2/shm.c &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;language:C &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;struct apr_shm_t { &nbsp;&nbsp;5 FS  s    apr_shm_t         shmem/win32/shm.c &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;language:C &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;struct apr_shm_t { Type number and <Enter> (empty cancels):

[ 本帖最后由 zhoubug 于 2009-8-27 17:14 编辑 ]

eelb123

引用着可以把他当做参数来用啊

很多情况，一个类没有公开，那么他的初始化，处理到最后的撤销都是应该有对应的函数的。
引用着只要定义一个指针即可。