alloc: New varena_grow() function

2 files changed, 29 insertions, 0 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 8a4dc3a..0b978ba 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -283,6 +283,21 @@ void *varena_realloc(struct varena *varena, void *ptr, size_t old_count, size_t
 	return ret;
 }
 
+void *varena_grow(struct varena *varena, void *ptr, size_t *count) {
+	size_t old_count = *count;
+
+	// Round up to the limit of the current size class.  If we're already at
+	// the limit, go to the next size class.
+	size_t new_shift = varena_size_class(varena, old_count + 1) + varena->shift;
+	size_t new_count = (size_t)1 << new_shift;
+
+	ptr = varena_realloc(varena, ptr, old_count, new_count);
+	if (ptr) {
+		*count = new_count;
+	}
+	return ptr;
+}
+
 void varena_free(struct varena *varena, void *ptr, size_t count) {
 	struct arena *arena = varena_get(varena, count);
 	arena_free(arena, ptr);
diff --git a/src/alloc.h b/src/alloc.h
index b5dfa68..5f0c423 100644
--- a/src/alloc.h
+++ b/src/alloc.h
@@ -271,6 +271,20 @@ void *varena_alloc(struct varena *varena, size_t count);
 void *varena_realloc(struct varena *varena, void *ptr, size_t old_count, size_t new_count);
 
 /**
+ * Grow a flexible struct by an arbitrary amount.
+ *
+ * @param varena
+ *         The varena to allocate from.
+ * @param ptr
+ *         The object to resize.
+ * @param count
+ *         Pointer to the flexible array length.
+ * @return
+ *         The resized struct, or NULL on failure.
+ */
+void *varena_grow(struct varena *varena, void *ptr, size_t *count);
+
+/**
  * Free an arena-allocated flexible struct.
  *
  * @param varena