[PATCH 04/16] Add embedded list interface (header only) - Mailing list pgsql-hackers

From: Andres Freund <andres@anarazel.de>

Adds a single and a double linked list which can easily embedded into other
datastructures and can be used without any additional allocations.

Problematic: It requires USE_INLINE to be used. It could be remade to fallback
to to externally defined functions if that is not available but that hardly
seems sensibly at this day and age. Besides, the speed hit would be noticeable
and its only used in new code which could be disabled on machines - given they
still exists - without proper support for inline functions
---src/include/utils/ilist.h |  253 +++++++++++++++++++++++++++++++++++++++++++++1 file changed, 253
insertions(+)createmode 100644 src/include/utils/ilist.h
 

diff --git a/src/include/utils/ilist.h b/src/include/utils/ilist.h
new file mode 100644
index 0000000..81d540e
--- /dev/null
+++ b/src/include/utils/ilist.h
@@ -0,0 +1,253 @@
+#ifndef ILIST_H
+#define ILIST_H
+
+#ifdef __GNUC__
+#define unused_attr __attribute__((unused))
+#else
+#define unused_attr
+#endif
+
+#ifndef USE_INLINE
+#error "a compiler supporting static inlines is required"
+#endif
+
+#include <assert.h>
+
+typedef struct ilist_d_node ilist_d_node;
+
+struct ilist_d_node
+{
+    ilist_d_node* prev;
+    ilist_d_node* next;
+};
+
+typedef struct
+{
+    ilist_d_node head;
+} ilist_d_head;
+
+typedef struct ilist_s_node ilist_s_node;
+
+struct ilist_s_node
+{
+    ilist_s_node* next;
+};
+
+typedef struct
+{
+    ilist_s_node head;
+} ilist_s_head;
+
+#ifdef ILIST_DEBUG
+void ilist_d_check(ilist_d_head* head);
+#else
+static inline void ilist_d_check(ilist_d_head* head)
+{
+}
+#endif
+
+static inline void ilist_d_init(ilist_d_head *head)
+{
+    head->head.next = head->head.prev = &head->head;
+    ilist_d_check(head);
+}
+
+/*
+ * adds a node at the beginning of the list
+ */
+static inline void ilist_d_push_front(ilist_d_head *head, ilist_d_node *node)
+{
+    node->next = head->head.next;
+    node->prev = &head->head;
+    node->next->prev = node;
+    head->head.next = node;
+    ilist_d_check(head);
+}
+
+
+/*
+ * adds a node at the end of the list
+ */
+static inline void ilist_d_push_back(ilist_d_head *head, ilist_d_node *node)
+{
+    node->next = &head->head;
+    node->prev = head->head.prev;
+    node->prev->next = node;
+    head->head.prev = node;
+    ilist_d_check(head);
+}
+
+
+/*
+ * adds a node after another *in the same list*
+ */
+static inline void ilist_d_add_after(unused_attr ilist_d_head *head, ilist_d_node *after, ilist_d_node *node)
+{
+    node->prev = after;
+    node->next = after->next;
+    after->next = node;
+    node->next->prev = node;
+    ilist_d_check(head);
+}
+
+/*
+ * adds a node after another *in the same list*
+ */
+static inline void ilist_d_add_before(unused_attr ilist_d_head *head, ilist_d_node *before, ilist_d_node *node)
+{
+    node->prev = before->prev;
+    node->next = before;
+    before->prev = node;
+    node->prev->next = node;
+    ilist_d_check(head);
+}
+
+
+/*
+ * removes a node from a list
+ */
+static inline void ilist_d_remove(unused_attr ilist_d_head *head, ilist_d_node *node)
+{
+    ilist_d_check(head);
+    node->prev->next = node->next;
+    node->next->prev = node->prev;
+    ilist_d_check(head);
+}
+
+/*
+ * removes the first node from a list or returns NULL
+ */
+static inline ilist_d_node* ilist_d_pop_front(ilist_d_head *head)
+{
+    ilist_d_node* ret;
+
+    if (&head->head == head->head.next)
+        return NULL;
+
+    ret = head->head.next;
+    ilist_d_remove(head, head->head.next);
+    return ret;
+}
+
+
+static inline bool ilist_d_has_next(ilist_d_head *head, ilist_d_node *node)
+{
+    return node->next != &head->head;
+}
+
+static inline bool ilist_d_has_prev(ilist_d_head *head, ilist_d_node *node)
+{
+    return node->prev != &head->head;
+}
+
+static inline bool ilist_d_is_empty(ilist_d_head *head)
+{
+    return head->head.next == head->head.prev;
+}
+
+#define ilist_d_front(type, membername, ptr) (&((ptr)->head) == (ptr)->head.next) ? \
+    NULL : ilist_container(type, membername, (ptr)->head.next)
+
+#define ilist_d_front_unchecked(type, membername, ptr) ilist_container(type, membername, (ptr)->head.next)
+
+#define ilist_d_back(type, membername, ptr)  (&((ptr)->head) == (ptr)->head.prev) ? \
+    NULL : ilist_container(type, membername, (ptr)->head.prev)
+
+#define ilist_container(type, membername, ptr) ((type*)((char*)(ptr) - offsetof(type, membername)))
+
+#define ilist_d_foreach(name, ptr) for(name = (ptr)->head.next;    \
+                                     name != &(ptr)->head;    \
+                                     name = name->next)
+
+#define ilist_d_foreach_modify(name, nxt, ptr) for(name = (ptr)->head.next,    \
+                                                       nxt = name->next;       \
+                                                   name != &(ptr)->head        \
+                                                       ;                       \
+                                                   name = nxt, nxt = name->next)
+
+static inline void ilist_s_init(ilist_s_head *head)
+{
+    head->head.next = NULL;
+}
+
+static inline void ilist_s_push_front(ilist_s_head *head, ilist_s_node *node)
+{
+    node->next = head->head.next;
+    head->head.next = node;
+}
+
+/*
+ * fails if the list is empty
+ */
+static inline ilist_s_node* ilist_s_pop_front(ilist_s_head *head)
+{
+    ilist_s_node* front = head->head.next;
+    head->head.next = head->head.next->next;
+    return front;
+}
+
+/*
+ * removes a node from a list
+ * Attention: O(n)
+ */
+static inline void ilist_s_remove(ilist_s_head *head,
+                                  ilist_s_node *node)
+{
+    ilist_s_node *last = &head->head;
+    ilist_s_node *cur;
+#ifndef NDEBUG
+    bool found = false;
+#endif
+    while ((cur = last->next))
+    {
+        if (cur == node)
+        {
+            last->next = cur->next;
+#ifndef NDEBUG
+            found = true;
+#endif
+            break;
+        }
+        last = cur;
+    }
+    assert(found);
+}
+
+
+static inline void ilist_s_add_after(unused_attr ilist_s_head *head,
+                                     ilist_s_node *after, ilist_s_node *node)
+{
+    node->next = after->next;
+    after->next = node;
+}
+
+
+static inline bool ilist_s_is_empty(ilist_s_head *head)
+{
+    return head->head.next == NULL;
+}
+
+static inline bool ilist_s_has_next(unused_attr ilist_s_head* head,
+                                    ilist_s_node *node)
+{
+    return node->next != NULL;
+}
+
+
+#define ilist_s_front(type, membername, ptr) (ilist_s_is_empty(ptr) ? \
+    ilist_container(type, membername, (ptr).next) : NULL
+
+#define ilist_s_front_unchecked(type, membername, ptr) \
+    ilist_container(type, membername, (ptr)->head.next)
+
+#define ilist_s_foreach(name, ptr) for(name = (ptr)->head.next;         \
+                                       name != NULL;                    \
+                                       name = name->next)
+
+#define ilist_s_foreach_modify(name, nxt, ptr) for(name = (ptr)->head.next, \
+                                                       nxt = name ? name->next : NULL; \
+                                                   name != NULL;            \
+                                                   name = nxt, nxt = name ? name->next : NULL)
+
+
+#endif
-- 
1.7.10.rc3.3.g19a6c.dirty