Add functions to manipulate fill-pointer of arrays

core/utils.lisp

@@ -12,6 +12,7 @@
            #:add-hook #:remove-hook #:run-hook
            #:node #:parent #:children #:attach-node #:detach-node
            #:shared-object #:refcount #:inc-ref #:dec-ref
+           #:extend-array #:shrink-array
            #:error-implementation-unsupported
            #:get-command-line-option
            #:get-command-line-option-number
@@ -122,6 +123,19 @@
     (when (> refcount 0)
       (decf refcount))))
 
+(let ((extend-ratio 1.5))
+  (defun extend-array (array)
+    "Extend an array to extend-ratio coefficient."
+    (when (= (fill-pointer array) (array-total-size array))
+      (adjust-array array (floor (* (array-total-size array) extend-ratio))))
+    (prog1
+        (fill-pointer array)
+      (incf (fill-pointer array))))
+
+  (defun shrink-array (array new-fill-pointer)
+    "Shrink an array to its fill-pointer."
+    (setf (fill-pointer array) new-fill-pointer)))
+
 (defun error-implementation-unsupported ()
   "Return an error specifying the current lisp implementation is not supported."
   (error "For now, only sbcl is supported."))