add vec_grow_to

include/lfvector.h

@@ -18,6 +18,8 @@ void vec_clear(Vector *vec);
 
 void vec_destroy(Vector *vec);
 
+int vec_grow_to(Vector *vec, const size_t new_cap);
+
 int vec_insert(Vector *vec, void *data, size_t index);
 
 int vec_push(Vector *vec, void *data);

src/vector.c

@@ -33,14 +33,9 @@ int vec_init_with_capacity(Vector *vec, void (*destroy)(void *data), size_t capa
     return 0;
 }
 
-static int vec_grow(Vector *const vec) {
+static int vec_expand(Vector *vec, size_t new_cap) {
-    if (vec->capacity == 0) {
+    vec->capacity = new_cap;
-        vec->capacity = 1;
+    vec->elements = reallocarray(vec->elements, new_cap, sizeof(void *));
-    } else {
-        vec->capacity *= 2;
-    }
-
-    vec->elements = reallocarray(vec->elements, vec->capacity, sizeof(void *));
 
     if (vec->elements == NULL) {
         return -1;
@@ -48,6 +43,23 @@ static int vec_grow(Vector *const vec) {
     return 0;
 }
 
+static int vec_grow(Vector *const vec) {
+    size_t new_cap;
+    if (vec->capacity == 0) {
+        new_cap = VEC_INIT_CAP; ;
+    } else {
+        new_cap = vec->capacity * 2;
+    }
+    return vec_expand(vec, new_cap);
+}
+
+int vec_grow_to(Vector *vec, const size_t new_cap) {
+    if (vec->capacity > new_cap) {
+        return -1;
+    }
+    return vec_expand(vec, new_cap);
+}
+
 void vec_clear(Vector *vec) {
     vec_destroy(vec);
     vec_init(vec, vec->destroy);

tests/tests.c

@@ -271,6 +271,10 @@ void test_vector() {
     printf("\ncap after clear: %zu\n", vec_cap(v));
     printf("len after clear: %zu\n", vec_len(v));
 
+    vec_grow_to(v, 10);
+    assert(vec_cap(v) == 10);
+    assert(vec_len(v) == 0);
+
     vec_destroy(v);
     free(v);
 }