From da574b6a107b63fb0de41a642243c2037c6b980e Mon Sep 17 00:00:00 2001
From: Forest Belton <forest@homolo.gy>
Date: Wed, 29 Sep 2021 03:48:51 -0400
Subject: [PATCH] Add VRAM engine for copying tile data

---
 src/main.c  |  2 ++
 src/title.c |  3 +++
 src/vram.c  | 19 +++++++++++++++++++
 src/vram.h  | 35 +++++++++++++++++++++++++++++++++++
 4 files changed, 59 insertions(+)
 create mode 100644 src/vram.c
 create mode 100644 src/vram.h

diff --git a/src/main.c b/src/main.c
index c8dc35e..335524e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -4,6 +4,7 @@
 #include "game.h"
 #include "sdk/hardware.h"
 #include "sdk/oam.h"
+#include "vram.h"
 
 game_state_t game_state;
 
@@ -12,6 +13,7 @@ void main() {
 
     // Setup the OAM for sprite drawing
     oam_init();
+    vram_init();
 
     // Set up background & sprites
     rBGP = 0b11100100;
diff --git a/src/title.c b/src/title.c
index 1b7778f..be6e638 100644
--- a/src/title.c
+++ b/src/title.c
@@ -6,6 +6,7 @@
 #include "sdk/joypad.h"
 #include "sdk/oam.h"
 #include "sdk/video.h"
+#include "vram.h"
 
 ASSET(bg_tiles, "bg/title.2bpp");
 ASSET(bg_map, "bg/title.map");
@@ -39,5 +40,7 @@ void title(void) {
         // Wait for VBLANK. Clear IF since global interrupts are disabled.
         HALT();
         rIF = 0;
+
+        vram_update();
     }
 }
diff --git a/src/vram.c b/src/vram.c
new file mode 100644
index 0000000..5e93fb0
--- /dev/null
+++ b/src/vram.c
@@ -0,0 +1,19 @@
+#include "vram.h"
+
+#include <string.h>
+
+#include "sdk/video.h"
+
+mem_xfer_t mem_xfer_queue[MAX_XFERS];
+uint8_t mem_xfer_queue_size;
+
+void vram_init(void) { mem_xfer_queue_size = 0; }
+
+void vram_update(void) {
+    mem_xfer_t *xfer = &mem_xfer_queue[0];
+    for (uint8_t i = 0; i < mem_xfer_queue_size; i++) {
+        vram_memcpy((uint16_t)xfer->dest, (void *)xfer->source, xfer->size);
+        xfer++;
+    }
+    mem_xfer_queue_size = 0;
+}
diff --git a/src/vram.h b/src/vram.h
new file mode 100644
index 0000000..59fa840
--- /dev/null
+++ b/src/vram.h
@@ -0,0 +1,35 @@
+#ifndef IS_VRAM_H_
+#define IS_VRAM_H_
+
+#include <stdint.h>
+
+#define MAX_XFERS 5
+
+typedef struct {
+    uint8_t *dest;
+    const uint8_t *source;
+    uint8_t size;
+} mem_xfer_t;
+
+extern mem_xfer_t mem_xfer_queue[MAX_XFERS];
+extern uint8_t mem_xfer_queue_size;
+
+/**
+ * @brief Initialize VRAM engine
+ */
+void vram_init(void);
+
+/**
+ * @brief Process VRAM memory transfers
+ */
+void vram_update(void);
+
+#define vram_enqueue_mem_xfer(_dest, _source, _size)               \
+    do {                                                           \
+        mem_xfer_t *node = &mem_xfer_queue[mem_xfer_queue_size++]; \
+        node->dest = (_dest);                                      \
+        node->source = (_source);                                  \
+        node->size = (_size);                                      \
+    } while (0)
+
+#endif