flex_array: add helpers to get and put to make pointers easy to use

Getting and putting arrays of pointers with flex arrays is a PITA. You have to remember to pass &ptr to the _put and you have to do weird and wacky casting to get the ptr back from the _get. Add two functions flex_array_get_ptr() and flex_array_put_ptr() to handle all of the magic. [akpm@linux-foundation.org: simplification suggested by Joe] Signed-off-by: Eric Paris <eparis@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Dave Hansen <dave@linux.vnet.ibm.com> Cc: Joe Perches <joe@perches.com> Cc: James Morris <jmorris@namei.org> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

flex_array: add helpers to get and put to make pointers easy to use
Getting and putting arrays of pointers with flex arrays is a PITA. You have to remember to pass &ptr to the _put and you have to do weird and wacky casting to get the ptr back from the _get. Add two functions flex_array_get_ptr() and flex_array_put_ptr() to handle all of the magic. [akpm@linux-foundation.org: simplification suggested by Joe] Signed-off-by: Eric Paris <eparis@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Dave Hansen <dave@linux.vnet.ibm.com> Cc: Joe Perches <joe@perches.com> Cc: James Morris <jmorris@namei.org> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Eric Paris · Linus Torvalds
1 parent 559b140a36
Showing 2 changed files with 29 additions and 1 deletions Side-by-side Diff
include/linux/flex_array.h
lib/flex_array.c
@@ -70,5 +70,10 @@
 void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
 int flex_array_shrink(struct flex_array *fa);
  
+#define flex_array_put_ptr(fa, nr, src, gfp) \
+	flex_array_put(fa, nr, &(void *)(src), gfp)
+
+void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr);
+
 #endif /* _FLEX_ARRAY_H */
@@ -171,6 +171,8 @@
  * Note that this *copies* the contents of @src into
  * the array.  If you are trying to store an array of
  * pointers, make sure to pass in &ptr instead of ptr.
+ * You may instead wish to use the flex_array_put_ptr()
+ * helper function.
  *
  * Locking must be provided by the caller.
  */
@@ -265,7 +267,8 @@
  *
  * Returns a pointer to the data at index @element_nr.  Note
  * that this is a copy of the data that was passed in.  If you
- * are using this to store pointers, you'll get back &ptr.
+ * are using this to store pointers, you'll get back &ptr.  You
+ * may instead wish to use the flex_array_get_ptr helper.
  *
  * Locking must be provided by the caller.
  */
@@ -284,6 +287,26 @@
 			return NULL;
 	}
 	return &part->elements[index_inside_part(fa, element_nr)];
+}
+
+/**
+ * flex_array_get_ptr - pull a ptr back out of the array
+ * @fa:		the flex array from which to extract data
+ * @element_nr:	index of the element to fetch from the array
+ *
+ * Returns the pointer placed in the flex array at element_nr using
+ * flex_array_put_ptr().  This function should not be called if the
+ * element in question was not set using the _put_ptr() helper.
+ */
+void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr)
+{
+	void **tmp;
+
+	tmp = flex_array_get(fa, element_nr);
+	if (!tmp)
+		return NULL;
+
+	return *tmp;
 }
  
 static int part_is_free(struct flex_array_part *part)
...	...	@@ -70,5 +70,10 @@
70	70	void flex_array_get(struct flex_array fa, unsigned int element_nr);
71	71	int flex_array_shrink(struct flex_array *fa);
72	72
	73	+#define flex_array_put_ptr(fa, nr, src, gfp) \
	74	+ flex_array_put(fa, nr, &(void *)(src), gfp)
	75	+
	76	+void flex_array_get_ptr(struct flex_array fa, unsigned int element_nr);
	77	+
73	78	#endif /* _FLEX_ARRAY_H */
...	...	@@ -171,6 +171,8 @@
171	171	* Note that this copies the contents of @src into
172	172	* the array. If you are trying to store an array of
173	173	* pointers, make sure to pass in &ptr instead of ptr.
	174	+ * You may instead wish to use the flex_array_put_ptr()
	175	+ * helper function.
174	176	*
175	177	* Locking must be provided by the caller.
176	178	*/
...	...	@@ -265,7 +267,8 @@
265	267	*
266	268	* Returns a pointer to the data at index @element_nr. Note
267	269	* that this is a copy of the data that was passed in. If you
268		- * are using this to store pointers, you'll get back &ptr.
	270	+ * are using this to store pointers, you'll get back &ptr. You
	271	+ * may instead wish to use the flex_array_get_ptr helper.
269	272	*
270	273	* Locking must be provided by the caller.
271	274	*/
...	...	@@ -284,6 +287,26 @@
284	287	return NULL;
285	288	}
286	289	return &part->elements[index_inside_part(fa, element_nr)];
	290	+}
	291	+
	292	+/**
	293	+ * flex_array_get_ptr - pull a ptr back out of the array
	294	+ * @fa: the flex array from which to extract data
	295	+ * @element_nr: index of the element to fetch from the array
	296	+ *
	297	+ * Returns the pointer placed in the flex array at element_nr using
	298	+ * flex_array_put_ptr(). This function should not be called if the
	299	+ * element in question was not set using the _put_ptr() helper.
	300	+ */
	301	+void flex_array_get_ptr(struct flex_array fa, unsigned int element_nr)
	302	+{
	303	+ void **tmp;
	304	+
	305	+ tmp = flex_array_get(fa, element_nr);
	306	+ if (!tmp)
	307	+ return NULL;
	308	+
	309	+ return *tmp;
287	310	}
288	311
289	312	static int part_is_free(struct flex_array_part *part)