vector: add vlc_vector_push_hole()

include/vlc_vector.h

@@ -319,6 +319,26 @@ vlc_vector_growsize_(size_t value)
     ) \
 )
 
+/**
+ * Push a hole at the end of the vector.
+ *
+ * The amortized complexity is O(1). The items in the hole are left
+ * uninitialized and can be accessed in the range [size-count; size-1].
+ *
+ * \param pv a pointer to the vector
+ * \param count the number of items in the hole
+ * \retval true if no allocation failed
+ * \retval false on allocation failure (the vector is left untouched)
+ */
+#define vlc_vector_push_hole(pv, count) \
+( \
+    vlc_vector_reserve(pv, (pv)->size + vlc_vector_enforce_size_t_(count)) && \
+    ( \
+        (pv)->size += vlc_vector_enforce_size_t_(count), \
+        true \
+    ) \
+)
+
 /**
  * Append `count` items at the end of the vector.
  *

src/test/vector.c

@@ -87,9 +87,15 @@ static void test_vector_push_array(void)
 
     int items[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
     ok = vlc_vector_push_all(&vec, items, 8);
+    assert(ok);
 
+    int items_hole[] = { 7, 6, 5, 4, 3, 2, 1, 0 };
+    ok = vlc_vector_push_hole(&vec, 8);
     assert(ok);
-    assert(vec.size == 13);
+    for (size_t i = 0; i < 8; ++i)
+        vec.data[vec.size-8+i] = items_hole[i];
+
+    assert(vec.size == 21);
     assert(vec.data[0] == 3);
     assert(vec.data[1] == 14);
     assert(vec.data[2] == 15);
@@ -103,6 +109,14 @@ static void test_vector_push_array(void)
     assert(vec.data[10] == 6);
     assert(vec.data[11] == 7);
     assert(vec.data[12] == 8);
+    assert(vec.data[13] == 7);
+    assert(vec.data[14] == 6);
+    assert(vec.data[15] == 5);
+    assert(vec.data[16] == 4);
+    assert(vec.data[17] == 3);
+    assert(vec.data[18] == 2);
+    assert(vec.data[19] == 1);
+    assert(vec.data[20] == 0);
 
     vlc_vector_destroy(&vec);
 }