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ChibiOS
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Added module description. 

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@12952 27425a3e-05d8-49a3-a47f-9c15f0e5edd8
This commit is contained in:
Giovanni Di Sirio 2019-08-23 08:04:00 +00:00
parent db364ffee4
commit 80b3141de4
2 changed files with 26 additions and 11 deletions
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5
os/oslib/include/chobjcaches.h
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@ -39,8 +39,9 @@
* @{
*/
#define OC_FLAG_INVALID 0x00000001U
#define OC_FLAG_CACHEHIT 0x00000002U
#define OC_FLAG_ERROR 0x00000004U
#define OC_FLAG_INLRU 0x00000002U
#define OC_FLAG_CACHEHIT 0x00000004U
#define OC_FLAG_ERROR 0x00000008U
/** @} */
/**

32
os/oslib/src/chobjcaches.c
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@ -20,16 +20,30 @@
/**
* @file chobjcaches.c
* @brief Objects Caches code.
* @details Byte pipes.
* @details Objects caches.
* <h2>Operation mode</h2>
* A pipe is an asynchronous communication mechanism.<br>
* Operations defined for mailboxes:
* - <b>Write</b>: Writes a buffer of data in the pipe in FIFO order.
* - <b>Read</b>: A buffer of data is read from the read and removed.
* - <b>Reset</b>: The pipe is emptied and all the stored data
* is lost.
* An object cache allows to retrieve and release objects from a
* slow media, for example a disk or flash.<br>
* The most recently used objects are kept in a series of RAM
* buffers making access faster. Objects are identified by a
* pair <group, key> which could be mapped, for example, to a
* disk drive identifier and sector identifier.<br>
* Read and write operations are performed using externally-supplied
* functions, the cache is device-agnostic.<br>
* The cache uses internally an hash table, the size of the table
* should be dimensioned to minimize the risk of hash collisions,
* a factor of two is usually acceptable, it depends on the specific
* application requirements.<br>
* Operations defined for caches:
* - <b>Get Object</b>: Retrieves an object from cache, if not
* present then an empty buffer is returned.
* - <b>Read Object</b>: Retrieves an object from cache, if not
* present a buffer is allocated and the object is read from the
* media.
* - <b>Release Object</b>: Releases an object to the cache handling
* the media update, if required.
* .
* @pre In order to use the pipes APIs the @p CH_CFG_USE_PIPES
* @pre In order to use the pipes APIs the @p CH_CFG_USE_OBJ_CACHES
* option must be enabled in @p chconf.h.
* @note Compatible with RT and NIL.
*
@ -151,7 +165,7 @@ void chCacheObjectInit(objects_cache_t *ocp,
LRU_INSERT_HEAD(ocp, objp);
objp->obj_group = OC_NO_GROUP;
objp->obj_key = 0U;
objp->obj_flags = OC_FLAG_INVALID;
objp->obj_flags = OC_FLAG_INLRU | OC_FLAG_INVALID;
objp->data = NULL;
}
}