arno/linux-insides
1
0
Fork 0
mirror of https://github.com/0xAX/linux-insides.git synced 2024-12-22 06:38:07 +00:00
Code Issues Releases Wiki Activity

DataStructures: Fixing some typos and grammar issues

Browse Source 
Signed-off-by: Simarpreet Singh <simar@linux.com>
This commit is contained in:
Simarpreet Singh 2015-04-22 10:58:25 -04:00
parent fa88fef61d
commit 780ad24b3d
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
DataStructures/dlist.md
View File

@ -205,7 +205,7 @@ int main() {
will print `2`. will print `2`.
The next point is `typeof`, it's simple. As you can understand from its name, it just returns the type of the given varible. When I first time saw implementation of the `container_of` macro, the stranges thing for me was the zero in the `((type *)0)` expression. Actually this pointers magic calculates the offset of the given field from the address of the structure, but as we have `0` here, it will be just adds offset of the given field to zero. Let's look on the one simple example: The next point is `typeof`, it's simple. As you can understand from its name, it just returns the type of the given variable. When I first saw the implementation of the `container_of` macro, the strangest thing for me was the zero in the `((type *)0)` expression. Actually this pointer magic calculates the offset of the given field from the address of the structure, but as we have `0` here, it will be just a zero offset alongwith the field width. Let's look at a simple example:
```C ```C
#include <stdio.h> #include <stdio.h>
@ -230,7 +230,7 @@ The next offsetof macro calculates offset from the beginning of the structure to
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
``` ```
Let's summarize all about `container_of` macro. `container_of` macro returns address of the structure by the given address of the structure's field with `list_head` type, the name of the structure field with `list_head` type and type of the container structure. At the first line this macro declares the `__mptr` pointer which points to the field of the structure that `ptr` points to and assigns it to the `ptr`. Now `ptr` and `__mptr` points have the same address. Techincally we no need in this line, it needs for the type checking. First line ensures that that given structure (`type` parameter) has a member which called `member`. In the second line it calculates offset of the field from the structure with the `offsetof` macro and subtracts it from the structure address. That's all. Let's summarize all about `container_of` macro. `container_of` macro returns address of the structure by the given address of the structure's field with `list_head` type, the name of the structure field with `list_head` type and type of the container structure. At the first line this macro declares the `__mptr` pointer which points to the field of the structure that `ptr` points to and assigns it to the `ptr`. Now `ptr` and `__mptr` point to the same address. Technically we don't need this line but its useful for type checking. First line ensures that that given structure (`type` parameter) has a member called `member`. In the second line it calculates offset of the field from the structure with the `offsetof` macro and subtracts it from the structure address. That's all.
Of course `list_add` and `list_entry` is not only functions which provides `<linux/list.h>`. Implementation of the doubly linked list provides the following API: Of course `list_add` and `list_entry` is not only functions which provides `<linux/list.h>`. Implementation of the doubly linked list provides the following API: