Add reserve function to vectors

3 files changed, 34 insertions, 1 deletions

diff --git a/collections/vector/vector.adoc b/collections/vector/vector.adoc
index ce91c71..7c4bc7f 100644
--- a/collections/vector/vector.adoc
+++ b/collections/vector/vector.adoc
@@ -1,7 +1,7 @@
 Vector
 ======
 Tucker Evans
-v0.16, 2020-07-04
+v0.17, 2020-07-04
 
 A basic vector, that hold pointers to your data structures.
 
@@ -400,6 +400,24 @@ vec_truncate(vector, 1);
 assert(vec_size == 1);
 ----
 
+[[vec_reserve]]
++void vec_reserve(vec *self, int additional)+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Reserves space for +additional+ items. May reserve more memory to avoid too
+many reallocations.
+
+Examples
+^^^^^^^^
+[source,c]
+----
+#include "vector.h"
+
+vec *vector = vec_with_capacity(16);
+
+vec_reserve(vector, 20);
+assert(vec_capacity(vector) >= 20);
+----
+
 [[vec_clear]]
 +void vec_clear(vec *self)+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/collections/vector/vector.c b/collections/vector/vector.c
index 391b5a6..f14c302 100644
--- a/collections/vector/vector.c
+++ b/collections/vector/vector.c
@@ -250,6 +250,20 @@ int size;
 	root->end = size;
 }
 
+void vec_reserve(root, n)
+vec *root;
+int n;
+{
+	int i;
+
+	if (!root || n + root->end <= root->limit)
+		return;
+
+	for (i = root->limit; i < root->end + n; i*=2);
+
+	root->base = reallocarray(root->base, i, sizeof(void*));
+}
+
 void vec_clear(root)
 vec *root;
 {
diff --git a/collections/vector/vector.h b/collections/vector/vector.h
index b997b46..4d6d04c 100644
--- a/collections/vector/vector.h
+++ b/collections/vector/vector.h
@@ -30,6 +30,7 @@ void* vec_swap_pop(vec*, int);
 
 /*memory*/
 void vec_truncate(vec*, int);
+void vec_reserve(vec*, int);
 
 void vec_clear(vec*);
 void vec_free(vec*);