From 06b744259be749cb7a5d6611d76b04581541ea99 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Fri, 26 Nov 2021 14:09:41 +0200
Subject: [PATCH] Add memory write callback, optimize memory access with
 likely/unlikely

---
 Core/cheats.c |  7 ++++---
 Core/defs.h   |  4 ++--
 Core/gb.h     |  1 +
 Core/memory.c | 22 ++++++++++++++++------
 Core/memory.h |  2 ++
 5 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/Core/cheats.c b/Core/cheats.c
index 1263183..8b5a7a0 100644
--- a/Core/cheats.c
+++ b/Core/cheats.c
@@ -32,10 +32,11 @@ static uint16_t bank_for_addr(GB_gameboy_t *gb, uint16_t addr)
 
 void GB_apply_cheat(GB_gameboy_t *gb, uint16_t address, uint8_t *value)
 {
-    if (!gb->cheat_enabled) return;
-    if (!gb->boot_rom_finished) return;
+    if (likely(!gb->cheat_enabled)) return;
+    if (likely(gb->cheat_count == 0)) return; // Optimization
+    if (unlikely(!gb->boot_rom_finished)) return;
     const GB_cheat_hash_t *hash = gb->cheat_hash[hash_addr(address)];
-    if (hash) {
+    if (unlikely(hash)) {
         for (unsigned i = 0; i < hash->size; i++) {
             GB_cheat_t *cheat = hash->cheats[i];
             if (cheat->address == address && cheat->enabled && (!cheat->use_old_value || cheat->old_value == *value)) {
diff --git a/Core/defs.h b/Core/defs.h
index b4f13f5..0517b22 100644
--- a/Core/defs.h
+++ b/Core/defs.h
@@ -4,8 +4,8 @@
 #ifdef GB_INTERNAL
 
 // "Keyword" definitions
-#define likely(x)   __builtin_expect((x), 1)
-#define unlikely(x) __builtin_expect((x), 0)
+#define likely(x)   __builtin_expect((bool)(x), 1)
+#define unlikely(x) __builtin_expect((bool)(x), 0)
 
 #define internal __attribute__((visibility("internal")))
 
diff --git a/Core/gb.h b/Core/gb.h
index d7d988d..cc235e8 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -658,6 +658,7 @@ struct GB_gameboy_internal_s {
         GB_icd_vreset_callback_t icd_hreset_callback;
         GB_icd_vreset_callback_t icd_vreset_callback;
         GB_read_memory_callback_t read_memory_callback;
+        GB_write_memory_callback_t write_memory_callback;
         GB_boot_rom_load_callback_t boot_rom_load_callback;
         GB_print_image_callback_t printer_callback;
         GB_workboy_set_time_callback workboy_set_time_callback;
diff --git a/Core/memory.c b/Core/memory.c
index f428f05..bedf339 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -688,15 +688,15 @@ void GB_set_read_memory_callback(GB_gameboy_t *gb, GB_read_memory_callback_t cal
 
 uint8_t GB_read_memory(GB_gameboy_t *gb, uint16_t addr)
 {
-    if (gb->n_watchpoints) {
+    if (unlikely(gb->n_watchpoints)) {
         GB_debugger_test_read_watchpoint(gb, addr);
     }
-    if (is_addr_in_dma_use(gb, addr)) {
+    if (unlikely(is_addr_in_dma_use(gb, addr))) {
         addr = gb->dma_current_src;
     }
     uint8_t data = read_map[addr >> 12](gb, addr);
     GB_apply_cheat(gb, addr, &data);
-    if (gb->read_memory_callback) {
+    if (unlikely(gb->read_memory_callback)) {
         data = gb->read_memory_callback(gb, addr, data);
     }
     return data;
@@ -708,7 +708,7 @@ uint8_t GB_safe_read_memory(GB_gameboy_t *gb, uint16_t addr)
     uint8_t data = read_map[addr >> 12](gb, addr);
     gb->disable_oam_corruption = false;
     GB_apply_cheat(gb, addr, &data);
-    if (gb->read_memory_callback) {
+    if (unlikely(gb->read_memory_callback)) {
         data = gb->read_memory_callback(gb, addr, data);
     }
     return data;
@@ -1563,12 +1563,22 @@ static write_function_t *const write_map[] =
     write_ram,         write_high_memory,                      /* EXXX FXXX */
 };
 
+void GB_set_write_memory_callback(GB_gameboy_t *gb, GB_write_memory_callback_t callback)
+{
+    gb->write_memory_callback = callback;
+}
+
 void GB_write_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
 {
-    if (gb->n_watchpoints) {
+    if (unlikely(gb->n_watchpoints)) {
         GB_debugger_test_write_watchpoint(gb, addr, value);
     }
-    if (is_addr_in_dma_use(gb, addr)) {
+    
+    if (unlikely(gb->write_memory_callback)) {
+        if (!gb->write_memory_callback(gb, addr, value)) return;
+    }
+    
+    if (unlikely(is_addr_in_dma_use(gb, addr))) {
         /* Todo: What should happen? Will this affect DMA? Will data be written? What and where? */
         return;
     }
diff --git a/Core/memory.h b/Core/memory.h
index f351339..adfdcaa 100644
--- a/Core/memory.h
+++ b/Core/memory.h
@@ -4,7 +4,9 @@
 #include <stdint.h>
 
 typedef uint8_t (*GB_read_memory_callback_t)(GB_gameboy_t *gb, uint16_t addr, uint8_t data);
+typedef bool (*GB_write_memory_callback_t)(GB_gameboy_t *gb, uint16_t addr, uint8_t data); // Return false to prevent the write
 void GB_set_read_memory_callback(GB_gameboy_t *gb, GB_read_memory_callback_t callback);
+void GB_set_write_memory_callback(GB_gameboy_t *gb, GB_write_memory_callback_t callback);
 
 uint8_t GB_read_memory(GB_gameboy_t *gb, uint16_t addr);
 uint8_t GB_safe_read_memory(GB_gameboy_t *gb, uint16_t addr); // Without side effects