From 22c14c51992e325604d67855c6517199f6573ae1 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Mon, 23 Oct 2023 22:17:11 -0400
Subject: Use tagged vector for bullet pool.

---
 game.scm | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/game.scm b/game.scm
index 925562e..74c4da8 100644
--- a/game.scm
+++ b/game.scm
@@ -368,38 +368,42 @@
     (abort-to-prompt %script-tag delay))
 
   ;; Bullets:
+  (define-type bullet-pool
+    %make-bullet-pool
+    bullet-pool?
+    (length bullet-pool-length set-bullet-pool-length!)
+    (capacity bullet-pool-capacity set-bullet-pool-capacity!)
+    (bullets bullet-pool-bullets set-bullet-pool-bullets!))
   ;; per bullet: type, x, y, dx, dy
   (define %bullet-size (+ 4 8 8 8 8))
   (define (make-bullet-pool capacity)
-    (let ((pool (make-bytevector (* capacity %bullet-size))))
-      (vector 0 capacity pool)))
+    (let ((bullets (make-bytevector (* capacity %bullet-size))))
+      (%make-bullet-pool 0 capacity bullets)))
   (define (bullet-pool-offset i)
     (* i %bullet-size))
   (define (bullet-pool-add! pool type x y dx dy)
     (match pool
-      (#(length capacity bullets)
+      (#('bullet-pool length capacity bullets)
        (let ((offset (bullet-pool-offset length)))
          (s32-set! bullets offset type)
          (f64-set! bullets (+ offset 4) x)
          (f64-set! bullets (+ offset 12) y)
          (f64-set! bullets (+ offset 20) dx)
          (f64-set! bullets (+ offset 28) dy)
-         (vector-set! pool 0 (+ length 1))))))
+         (set-bullet-pool-length! pool (+ length 1))))))
   (define (bullet-pool-remove! pool i)
     (match pool
-      (#(length capacity bullets)
+      (#('bullet-pool length capacity bullets)
        (when (and (>= i 0) (< i length))
          (let ((at (bullet-pool-offset i))
                (start (bullet-pool-offset (- length 1))))
            (bytevector-copy! bullets at bullets start (+ start %bullet-size))
-           (vector-set! pool 0 (- length 1)))))))
+           (set-bullet-pool-length! pool (- length 1)))))))
   (define (bullet-pool-reset! pool)
-    (match pool
-      (#(length capacity bullets)
-       (vector-set! pool 0 0))))
+    (set-bullet-pool-length! pool 0))
   (define (bullet-pool-update! pool collide)
     (match pool
-      (#(length capacity bullets)
+      (#('bullet-pool length capacity bullets)
        (let loop ((i 0) (k length))
          (when (< i k)
            (let* ((offset (bullet-pool-offset i))
@@ -420,7 +424,7 @@
                (loop (+ i 1) k)))))))))
   (define (draw-bullets pool image w h)
     (match pool
-      (#(length capacity bullets)
+      (#('bullet-pool length capacity bullets)
        (do ((i 0 (+ i 1)))
            ((= i length))
          (let* ((offset (bullet-pool-offset i))
-- 
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