Implement hardware blitter

1 files changed, 56 insertions, 2 deletions

diff --git a/tr8vm.c b/tr8vm.c
index d4adb67..59d08b7 100644
--- a/tr8vm.c
+++ b/tr8vm.c
@@ -102,7 +102,7 @@ static void update_fb()
 
 void write_m(uint16_t addr, uint8_t b)
 {
-    if (addr >= VIDEO_RAM && addr < (VIDEO_RAM + 16384))
+    if (addr >= VIDEO_RAM && addr < VIDEO_RAM + 16384)
         fb_data[addr - VIDEO_RAM] = palette[b & 15];
 
     ram[addr] = b;
@@ -113,6 +113,60 @@ uint8_t read_m(uint16_t addr)
     return ram[addr];
 }
 
+uint8_t blt_set = 0;
+uint8_t blt_paramc = 0;
+uint8_t blt_param[6] = { 0 };
+
+uint8_t port(uint8_t p, uint8_t v)
+{
+    switch (p)
+    {
+        case 0xb0:
+            if (v & 128)
+            {
+                blt_set = 1;
+                blt_paramc = 0;
+                return p;
+            }
+            if (v & 1)
+            {
+                blt_set = 0;
+
+                if (blt_paramc != 6)
+                    return 0xff;
+
+                /* draw */
+                uint16_t src = blt_param[0] | (blt_param[1] << 8);
+                uint16_t dst = VIDEO_RAM + blt_param[2] + blt_param[3] * 128;
+
+                for (uint8_t y = 0; y < blt_param[5]; y++)
+                    for (uint8_t x = 0; x < blt_param[4]; x++)
+                    {
+                        uint8_t b = read_m(src++);
+
+                        /* skip transparent if transparent flag is set */
+                        if ((v & 2) && (b & 128))
+                            continue;
+
+                        write_m(dst + x + y * 128, b);
+                    }
+
+                return p;
+            }
+            return 0xff;
+
+        case 0xb1:
+            if (!blt_set || blt_paramc > 5)
+                return 0xff;
+
+            blt_param[blt_paramc++] = v;
+            return p;
+
+        default:
+            return 0xff;
+    }
+}
+
 int main(int argc, char *argv[])
 {
     FILE *fd;
@@ -188,7 +242,7 @@ int main(int argc, char *argv[])
     SDL_RenderPresent(renderer);
 
     Tr8 vm;
-    tr8_init(&vm, write_m, read_m);
+    tr8_init(&vm, write_m, read_m, port);
     int pitch = 0;
     uint8_t rc;