From 9dd61937a48467e7949eb456380a00e69a8ed813 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Sat, 16 Jun 2018 20:50:18 -0400
Subject: add gb_handle_interrupts()

---
 ops.yaml | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 50 insertions(+), 9 deletions(-)

diff --git a/ops.yaml b/ops.yaml
index 08c8d8c..965b9d7 100644
--- a/ops.yaml
+++ b/ops.yaml
@@ -7582,6 +7582,9 @@ templates:
         uint8_t *rom;
         uint32_t rom_size;
 
+        // interrupt enable flags (0xFFFF)
+        uint8_t ei;
+
         // external ram (optional, 8k)
         uint8_t *eram;
       } mmu;
@@ -7600,8 +7603,6 @@ templates:
 
         // interrupt master enable
         bool ime;
-        uint32_t iev;
-        uint32_t ivs; // FIXME: uint8_t?
       } cpu;
     } gb_t;
 
@@ -7677,7 +7678,9 @@ templates:
 
           break;
         case 0x0F00:
-          if (addr < 0xFF80) {
+          if (addr == 0xFFFF) {
+            return ctx->mmu.ei;
+          } else if (addr < 0xFF80) {
             // TODO: io ports
             return 0;
           } else {
@@ -7690,6 +7693,7 @@ templates:
           // working ram (shadow)
           return ctx->mmu.ram[addr & 0x1FFF];
         }
+
         break;
       default:
         // never reached
@@ -7766,7 +7770,9 @@ templates:
 
           break;
         case 0x0F00:
-          if (addr < 0xFF80) {
+          if (addr == 0xFFFF) {
+            ctx->mmu.ei = val;
+          } else if (addr < 0xFF80) {
             // TODO: io ports
           } else {
             // zero page
@@ -8747,10 +8753,11 @@ templates:
             // process next scanline
             ctx->gpu.mode = GPU_MODE_OAM;
           } else {
-            // go to vblank
-            ctx->gpu.mode = GPU_MODE_VBLANK;
+            // trigger vblank interrupt
+            mmu_wb(ctx, 0xFF0F, mmu_rb(ctx, 0xFF0F) | 1);
 
-            // TODO: trigger vblank interrupt
+            // set gpu mode
+            ctx->gpu.mode = GPU_MODE_VBLANK;
           }
         }
 
@@ -8770,15 +8777,49 @@ templates:
       }
     }
 
+    static void
+    gb_handle_interrupts(
+      gb_t * const ctx
+    ) {
+      // handle interrupts
+      if (ctx->cpu.ime) {
+        // get interrupt vector (masked against enabled interrupts)
+        const uint8_t iv = mmu_rb(ctx, 0xFFFF) & mmu_rb(ctx, 0xFF0F);
+
+        for (uint8_t i = 0; i < 5; i++) {
+          const uint8_t m = (i ? (1 << i) : 1);
+
+          // has this interrupt been triggered?
+          if (iv & m) {
+            // disable ime
+            ctx->cpu.ime = false;
+
+            // clear interrupt flag
+            mmu_wb(ctx, 0xFF0F, mmu_rb(ctx, 0xFF0F) ^ m);
+
+
+            // trigger interrupt
+            rst(ctx, 0x0040 + (8 * i));
+
+            // break out of for loop
+            break;
+          }
+        }
+      }
+    }
+
     void
     gb_step(
       gb_t * const ctx
     ) {
+      // handle pending interrupts
+      gb_handle_interrupts(ctx);
+
+      // get pc, and current op
       const uint16_t old_pc = cpu_rw(ctx, RW_PC),
                      op = mmu_rb(ctx, old_pc);
 
-      // TODO: handle interrupts
-
+      // exec op
       switch (op) {
       <%= switches['main'] %>
       case 0xCB:
-- 
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