mx_util: Add mx_sort_linked_list

This is a general purpose routine to sort a single linked list of
objects. It requires callbacks for comparison and for locating
the next pointer in the object.

mx_util.c

@@ -1304,3 +1304,30 @@ int mx_daemon(int nochdir, int noclose)
 {
     return daemon(nochdir, noclose);
 }
+
+void _mx_sort_linked_list (void **list,  int (*cmp)(void *o1,void *o2), void ** getnextptr(void *o)) {
+
+    void *unsorted=*list;
+    void *sorted=NULL;
+
+    while (unsorted) {
+        void *o;
+        void **s_ptr;
+        void *s;
+
+        o=unsorted;
+        unsorted=*(getnextptr(o));
+
+        s_ptr=&sorted;
+        while(1) {
+            s=*s_ptr;
+            if (s==NULL || cmp(o,s)<0) {
+                break;
+            }
+            s_ptr=getnextptr(s);
+        }
+        *(getnextptr(o))=s;
+        *s_ptr=o;
+    }
+    *list=sorted;
+}

mx_util.h

@@ -166,4 +166,8 @@ int mx_mkdir_p(char *path, mode_t mode);
 
 int mx_daemon(int nochdir, int noclose);
 
+void _mx_sort_linked_list(void **list, int (*cmp)(void *o1,void *o2), void ** (*getnextptr)(void *o));
+#define mx_sort_linked_list(list,cmp,getnextptr) _mx_sort_linked_list((void **)(list),(int (*)(void *,void *))(cmp),(void ** (*)(void *))(getnextptr)) 
+
+
 #endif

test_mx_util.c

@@ -450,6 +450,86 @@ static void test_mx_cpuset(void)
     assert(mx_str_to_cpuset(&cpuset,"4-")<0);
 }
 
+struct obj {
+    int i;
+    struct obj *next;
+};
+
+int obj_compare(struct obj *o1,struct obj *o2)
+{
+    return
+        o1->i > o2->i ? 1
+          : o1->i < o2->i ? -1
+          : 0;
+}
+
+struct obj **obj_getnextptr(struct obj *o) {
+    return &o->next;
+}
+
+static void test_listsort(void)
+{
+    struct obj o[10];
+    struct obj *list;
+
+    for (int i=0;i<10;i++) {
+        o[i].i=i;
+        o[i].next= i==9 ? NULL : &o[i+1];
+    }
+
+    /* () -> () */
+    list=NULL;
+    mx_sort_linked_list(&list,obj_compare,obj_getnextptr);
+    assert(list==NULL);
+
+    /* (9) -> (9) */
+
+    list=&o[9];
+    mx_sort_linked_list(&list,obj_compare,obj_getnextptr);
+    assert(list==&o[9]);
+    assert(o[9].next==NULL);
+
+    /* (9 8 7 6 5 4 3 2 1 0) -> (0 1 2 3 4 5 6 7 8 9) */
+
+    list=&o[0];
+    for (int i=0;i<10;i++) {
+        o[i].i = 9-i;
+    }
+    mx_sort_linked_list(&list,obj_compare,obj_getnextptr);
+    assert(list==&o[9]);
+    for (int i=0;i<10;i++) {
+        assert(o[i].next == (i==0 ? NULL : &o[i-1]));
+    }
+
+    /* (100 0 1 2 50 50 2 1 0 100)  -> ( 0 0 1 1 2 2 50 50 100 100) stable */
+    for (int i=0;i<10;i++) {
+        o[i].next= i==9 ? NULL : &o[i+1];
+    }
+    list=&o[0];
+    o[0].i=100;
+    o[1].i=0;
+    o[2].i=1;
+    o[3].i=2;
+    o[4].i=50;
+    o[5].i=50;
+    o[6].i=2;
+    o[7].i=1;
+    o[8].i=0;
+    o[9].i=100;
+    mx_sort_linked_list(&list,obj_compare,obj_getnextptr);
+    assert(list==&o[1]);
+    assert(o[1].next==&o[8]);
+    assert(o[8].next==&o[2]);
+    assert(o[2].next==&o[7]);
+    assert(o[7].next==&o[3]);
+    assert(o[3].next==&o[6]);
+    assert(o[6].next==&o[4]);
+    assert(o[4].next==&o[5]);
+    assert(o[5].next==&o[0]);
+    assert(o[0].next==&o[9]);
+    assert(o[9].next==NULL);
+}
+
 int main(int argc, char *argv[])
 {
     test_mx_strskipwhitespaces();
@@ -469,5 +549,6 @@ int main(int argc, char *argv[])
     test_mx_strvec_cachebug();
     test_mx_strcat();
     test_mx_cpuset();
+    test_listsort();
     return 0;
 }