Added documentation on the cache interface

cache.h

@@ -18,27 +18,99 @@
 extern int cache_error;
 #endif
 
-typedef int cache_constructor_t(void *, void *, int);
-typedef void cache_destructor_t(void *, void *);
+/**
+ * Constructor used to initialize allocated objects
+ *
+ * @param obj pointer to the object to initialized.
+ * @param notused1 This parameter is currently not used.
+ * @param notused2 This parameter is currently not used.
+ * @return you should return 0, but currently this is not checked
+ */
+typedef int cache_constructor_t(void* obj, void* notused1, int notused2);
+/**
+ * Destructor used to clean up allocated objects before they are
+ * returned to the operating system.
+ *
+ * @param obj pointer to the object to initialized.
+ * @param notused1 This parameter is currently not used.
+ * @param notused2 This parameter is currently not used.
+ * @return you should return 0, but currently this is not checked
+ */
+typedef void cache_destructor_t(void* obj, void* notused);
 
+/**
+ * Definition of the structure to keep track of the internal details of
+ * the cache allocator. Touching any of these variables results in
+ * undefined behavior.
+ */
 typedef struct {
+    /** Mutex to protect access to the structure */
     pthread_mutex_t mutex;
+    /** Name of the cache objects in this cache (provided by the caller) */
     char *name;
+    /** List of pointers to available buffers in this cache */
     void **ptr;
+    /** The size of each element in this cache */
     size_t bufsize;
+    /** The capacity of the list of elements */
     int freetotal;
+    /** The current number of free elements */
     int freecurr;
+    /** The constructor to be called each time we allocate more memory */
     cache_constructor_t* constructor;
+    /** The destructor to be called each time before we release memory */
     cache_destructor_t* destructor;
 } cache_t;
 
-
-cache_t* cache_create(const char *name, size_t bufsize, size_t align,
+/**
+ * Create an object cache.
+ *
+ * The object cache will let you allocate objects of the same size. It is fully
+ * MT safe, so you may allocate objects from multiple threads without having to
+ * do any syncrhonization in the application code.
+ *
+ * @param name the name of the object cache. This name may be used for debug purposes
+ *             and may help you track down what kind of object you have problems with
+ *             (buffer overruns, leakage etc)
+ * @param bufsize the size of each object in the cache
+ * @param align the alignment requirements of the objects in the cache.
+ * @param constructor the function to be called to initialize memory when we need
+ *                    to allocate more memory from the os.
+ * @param destructor the function to be called before we release the memory back
+ *                   to the os.
+ * @return a handle to an object cache if successful, NULL otherwise.
+ */
+cache_t* cache_create(const char* name, size_t bufsize, size_t align,
                       cache_constructor_t* constructor,
                       cache_destructor_t* destructor);
-void cache_destroy(cache_t*);
-void* cache_alloc(cache_t*);
-void cache_free(cache_t*, void*);
+/**
+ * Destroy an object cache.
+ *
+ * Destroy and invalidate an object cache. You should return all buffers allocated
+ * with cache_alloc by using cache_free before calling this function. Not doing
+ * so results in undefined behavior (the buffers may or may not be invalidated)
+ *
+ * @param handle the handle to the object cache to destroy.
+ */
+void cache_destroy(cache_t* handle);
+/**
+ * Allocate an object from the cache.
+ *
+ * @param handle the handle to the object cache to allocate from
+ * @return a pointer to an initialized object from the cache, or NULL if
+ *         the allocation cannot be satisfied.
+ */
+void* cache_alloc(cache_t* handle);
+/**
+ * Return an object back to the cache.
+ *
+ * The caller should return the object in an initialized state so that
+ * the object may be returned in an expected state from cache_alloc.
+ *
+ * @param handle handle to the object cache to return the object to
+ * @param ptr pointer to the object to return.
+ */
+void cache_free(cache_t* handle, void* ptr);
 #endif
 
 #endif