[mpp_list]: Add list_sort func

Porting from kernel lib/list_sort.c

Signed-off-by: Yandong Lin <yandong.lin@rock-chips.com>
Change-Id: If6b0e07a863a8e95b47f2b89a2941d21674c9108

osal/mpp_list.cpp

@@ -23,6 +23,7 @@
 
 #include "mpp_log.h"
 #include "mpp_list.h"
+#include "mpp_common.h"
 
 
 #define LIST_DEBUG(fmt, ...) mpp_log(fmt, ## __VA_ARGS__)
@@ -325,6 +326,166 @@ mpp_list::~mpp_list()
     destroy = NULL;
 }
 
+/* list sort porting from kernel list_sort.c */
+
+/*
+ * Returns a list organized in an intermediate format suited
+ * to chaining of merge() calls: null-terminated, no reserved or
+ * sentinel head node, "prev" links not maintained.
+ */
+static struct list_head *merge(void *priv, list_cmp_func_t cmp,
+                               struct list_head *a, struct list_head *b)
+{
+    struct list_head *head, **tail = &head;
+
+    for (;;) {
+        /* if equal, take 'a' -- important for sort stability */
+        if (cmp(priv, a, b) <= 0) {
+            *tail = a;
+            tail = &a->next;
+            a = a->next;
+            if (!a) {
+                *tail = b;
+                break;
+            }
+        } else {
+            *tail = b;
+            tail = &b->next;
+            b = b->next;
+            if (!b) {
+                *tail = a;
+                break;
+            }
+        }
+    }
+    return head;
+}
+
+/*
+ * Combine final list merge with restoration of standard doubly-linked
+ * list structure.  This approach duplicates code from merge(), but
+ * runs faster than the tidier alternatives of either a separate final
+ * prev-link restoration pass, or maintaining the prev links
+ * throughout.
+ */
+static void merge_final(void *priv, list_cmp_func_t cmp, struct list_head *head,
+                        struct list_head *a, struct list_head *b)
+{
+    struct list_head *tail = head;
+    RK_U8 count = 0;
+
+    for (;;) {
+        /* if equal, take 'a' -- important for sort stability */
+        if (cmp(priv, a, b) <= 0) {
+            tail->next = a;
+            a->prev = tail;
+            tail = a;
+            a = a->next;
+            if (!a)
+                break;
+        } else {
+            tail->next = b;
+            b->prev = tail;
+            tail = b;
+            b = b->next;
+            if (!b) {
+                b = a;
+                break;
+            }
+        }
+    }
+
+    /* Finish linking remainder of list b on to tail */
+    tail->next = b;
+    do {
+        /*
+         * If the merge is highly unbalanced (e.g. the input is
+         * already sorted), this loop may run many iterations.
+         * Continue callbacks to the client even though no
+         * element comparison is needed, so the client's cmp()
+         * routine can invoke cond_resched() periodically.
+         */
+        if (!++count)
+            cmp(priv, b, b);
+        b->prev = tail;
+        tail = b;
+        b = b->next;
+    } while (b);
+
+    /* And the final links to make a circular doubly-linked list */
+    tail->next = head;
+    head->prev = tail;
+}
+
+void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp)
+{
+    struct list_head *list = head->next, *pending = NULL;
+    size_t count = 0;   /* Count of pending */
+
+    if (list == head->prev) /* Zero or one elements */
+        return;
+
+    /* Convert to a null-terminated singly-linked list. */
+    head->prev->next = NULL;
+
+    /*
+     * Data structure invariants:
+     * - All lists are singly linked and null-terminated; prev
+     *   pointers are not maintained.
+     * - pending is a prev-linked "list of lists" of sorted
+     *   sublists awaiting further merging.
+     * - Each of the sorted sublists is power-of-two in size.
+     * - Sublists are sorted by size and age, smallest & newest at front.
+     * - There are zero to two sublists of each size.
+     * - A pair of pending sublists are merged as soon as the number
+     *   of following pending elements equals their size (i.e.
+     *   each time count reaches an odd multiple of that size).
+     *   That ensures each later final merge will be at worst 2:1.
+     * - Each round consists of:
+     *   - Merging the two sublists selected by the highest bit
+     *     which flips when count is incremented, and
+     *   - Adding an element from the input as a size-1 sublist.
+     */
+    do {
+        size_t bits;
+        struct list_head **tail = &pending;
+
+        /* Find the least-significant clear bit in count */
+        for (bits = count; bits & 1; bits >>= 1)
+            tail = &(*tail)->prev;
+        /* Do the indicated merge */
+        if (bits) {
+            struct list_head *a = *tail, *b = a->prev;
+
+            a = merge(priv, cmp, b, a);
+            /* Install the merged result in place of the inputs */
+            a->prev = b->prev;
+            *tail = a;
+        }
+
+        /* Move one element from input list to pending */
+        list->prev = pending;
+        pending = list;
+        list = list->next;
+        pending->next = NULL;
+        count++;
+    } while (list);
+
+    /* End of input; merge together all the pending lists. */
+    list = pending;
+    pending = pending->prev;
+    for (;;) {
+        struct list_head *next = pending->prev;
+
+        if (!next)
+            break;
+        list = merge(priv, cmp, pending, list);
+        pending = next;
+    }
+    /* The final merge, rebuilding prev links */
+    merge_final(priv, cmp, head, pending, list);
+}
+
 #if BUILD_RK_LIST_TEST
 #include "vpu_mem.h"
 #include <stdio.h>