Linux 如何使用 sys/queue.h 中的列表？
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How to use list from sys/queue.h?
提问by rps
Currently, I have implemented a singly linked list, like so:
目前，我已经实现了一个单链表，如下所示：
struct PeerNode {
struct Peer* cargo;
struct PeerNode* next;
};
...and I have a struct that contains a couple of these linked lists, like so:
...我有一个包含几个这样的链表的结构，如下所示：
struct Torrent {
...
struct PeerNode* peer_list;
struct PeerNode* unchoked_peers;
...
}
I would like to replace this by using the macros provided by sys/queue.h. I gather that I could replace my code with something like this:
我想通过使用提供的宏来替换它sys/queue.h。我认为我可以用这样的东西替换我的代码：
struct Torrent {
...
LIST_ENTRY(PeerNode, Peer) peer_list;
struct PeerNode* unchoked_peers;
...
}
Then, from looking at man queue, I believe I would initialize the lists by doing something like this:
然后，从查看man queue，我相信我会通过执行以下操作来初始化列表：
LIST_INIT(&peer_list);
LIST_INIT(unchoked_peers);
However, I don't understand how LIST_ENTRYfactors into usage of the list. From the manpage, it says: "The macro LIST_ENTRYdeclares a structure that connects the elements in the list," but I don't really understand what this means.
但是，我不明白如何LIST_ENTRY影响列表的使用。从man页面上看，它说：“宏LIST_ENTRY声明了一个连接列表中元素的结构”，但我真的不明白这是什么意思。
Why would I want to declare a structure to connect the elements in the list? Shouldn't each node be connected to the next node via a pointer, like my initial linked list implementation? How would I replace my linked lists with the implementation provided by sys/queue.h? How would I insert an element into the list?
为什么我要声明一个结构来连接列表中的元素？每个节点不应该通过指针连接到下一个节点，就像我最初的链表实现一样吗？我将如何用提供的实现替换我的链表sys/queue.h？如何在列表中插入元素？
采纳答案by tinman
LIST_ENTRY creates fields to put into your structure that are suitable for linking the elements, so you do not have to concern yourself with the specifics of those pointers.
LIST_ENTRY 创建要放入适合链接元素的结构的字段，因此您不必关心这些指针的细节。
struct foo {
int a, b, c;
/* This is instead of "struct foo *next" */
LIST_ENTRY(foo) pointers;
};
To then create a list you'd use LIST_HEAD():
然后创建一个列表，您将使用 LIST_HEAD()：
struct Torrent {
LIST_HEAD(foo_list, foo) bar;
};
You can initialise the list header using LIST_INIT():
您可以使用 LIST_INIT() 初始化列表头：
struct Torrent t;
LIST_INIT(&t.bar);
You can insert elements using the LIST_INSERT_*() macros:
您可以使用 LIST_INSERT_*() 宏插入元素：
struct foo *item = malloc(sizeof(struct foo));
LIST_INSERT_HEAD(&t.bar, item, pointers);
This was all taken from the list example in the man pages at http://www.manpagez.com/man/3/queue/
这全部取自http://www.manpagez.com/man/3/queue/手册页中的列表示例
