Add example of multi B+Tree

example/ex-bptree02.c

@@ -0,0 +1,53 @@
+#include <stdlib.h>
+
+#include "m-bptree.h"
+
+BPTREE_MULTI_DEF2(multimap, 5, int, M_BASIC_OPLIST, int, M_BASIC_OPLIST)
+#define M_OPL_map_multimap_t() BPTREE_OPLIST2(multimap, M_BASIC_OPLIST, M_BASIC_OPLIST)
+
+// Fill in with multiple value
+static void
+fill_in(multimap_t map)
+{
+    for(int i = 1 ; i < 100; i++)
+        multimap_set_at(map, i, i);
+    for(int i = 1 ; i < 100; i+=2)
+        multimap_set_at(map, i, i*i);
+    for(int i = 1 ; i < 100; i+=3)
+        multimap_set_at(map, i, i*i*i);
+}
+
+static int
+count(multimap_t map, int key)
+{
+    int n = 0;
+    multimap_it_t it;
+    // it_from is O(n*ln n) complexity
+    // it_while_p and next are O(1) complexity
+    for(multimap_it_from(it, map, key); multimap_it_while_p(it, key); multimap_next(it))
+        n++;
+    return n;    
+}
+
+static void
+print(multimap_t map)
+{
+    for(int i = 0; i < 101;i++) {
+        printf("Key=%d Count=%d ", i, count(map, i));
+        multimap_it_t it;
+        for(multimap_it_from(it, map, i); multimap_it_while_p(it, i); multimap_next(it)) {
+            printf("Value=%d ", *multimap_ref(it)->value_ptr );
+        }
+        printf("\n");
+    }
+}
+
+int main(void)
+{
+    multimap_t map;
+    multimap_init(map);
+    fill_in(map);
+    print(map);
+    multimap_clear(map);
+    exit(0);
+}