Add cheats API, with GameShark and GameGenie import

Core/cheats.c

@@ -0,0 +1,173 @@
+#include "gb.h"
+#include "cheats.h"
+#include <stdio.h>
+
+static inline uint8_t hash_addr(uint16_t addr)
+{
+    return addr;
+}
+
+static uint16_t bank_for_addr(GB_gameboy_t *gb, uint16_t addr)
+{
+    if (addr < 0x4000) {
+        return gb->mbc_rom0_bank;
+    }
+    
+    if (addr < 0x8000) {
+        return gb->mbc_rom_bank;
+    }
+    
+    if (addr < 0xD000) {
+        return 0;
+    }
+    
+    if (addr < 0xE000) {
+        return gb->cgb_ram_bank;
+    }
+    
+    return 0;
+}
+
+void GB_apply_cheat(GB_gameboy_t *gb, uint16_t address, uint8_t *value)
+{
+    const GB_cheat_hash_t *hash = gb->cheat_hash[hash_addr(address)];
+    if (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)) {
+                if (cheat->bank == GB_CHEAT_ANY_BANK || cheat->bank == bank_for_addr(gb, address)) {
+                    *value = cheat->value;
+                    break;
+                }
+            }
+        }
+    }
+}
+
+void GB_add_cheat(GB_gameboy_t *gb, const char *description, uint16_t address, uint16_t bank, uint8_t value, uint8_t old_value, bool use_old_value, bool enabled)
+{
+    GB_cheat_t *cheat = malloc(sizeof(*cheat));
+    cheat->address = address;
+    cheat->bank = bank;
+    cheat->value = value;
+    cheat->old_value = old_value;
+    cheat->use_old_value = use_old_value;
+    cheat->enabled = enabled;
+    strncpy(cheat->description, description, sizeof(cheat->description));
+    cheat->description[sizeof(cheat->description) - 1] = 0;
+    gb->cheats = realloc(gb->cheats, (++gb->cheat_count) * sizeof(*cheat));
+    gb->cheats[gb->cheat_count - 1] = cheat;
+    
+    GB_cheat_hash_t **hash = &gb->cheat_hash[hash_addr(address)];
+    if (!*hash) {
+        *hash = malloc(sizeof(GB_cheat_hash_t) + sizeof(cheat));
+        (*hash)->size = 1;
+        (*hash)->cheats[0] = cheat;
+    }
+    else {
+        (*hash)->size++;
+        *hash = malloc(sizeof(GB_cheat_hash_t) + sizeof(cheat) * (*hash)->size);
+        (*hash)->cheats[(*hash)->size - 1] = cheat;
+    }
+}
+
+const GB_cheat_t *const *GB_get_cheats(GB_gameboy_t *gb, size_t *size)
+{
+    *size = gb->cheat_count;
+    return (void *)gb->cheats;
+}
+void GB_remove_cheat(GB_gameboy_t *gb, const GB_cheat_t *cheat)
+{
+    for (unsigned i = 0; i < gb->cheat_count; i++) {
+        if (gb->cheats[i] == cheat) {
+            gb->cheats[i] = gb->cheats[--gb->cheat_count];
+            if (gb->cheat_count == 0) {
+                free(gb->cheats);
+                gb->cheats = NULL;
+            }
+            else {
+                gb->cheats = realloc(gb->cheats, gb->cheat_count * sizeof(*cheat));
+            }
+            break;
+        }
+    }
+    
+    GB_cheat_hash_t **hash = &gb->cheat_hash[hash_addr(cheat->address)];
+    for (unsigned i = 0; i < (*hash)->size; i++) {
+        if ((*hash)->cheats[i] == cheat) {
+            (*hash)->cheats[i] = (*hash)->cheats[(*hash)->size--];
+            if ((*hash)->size == 0) {
+                free(*hash);
+                *hash = NULL;
+            }
+            else {
+                *hash = malloc(sizeof(GB_cheat_hash_t) + sizeof(cheat) * (*hash)->size);
+            }
+            break;
+        }
+    }
+    
+    free((void *)cheat);
+}
+
+bool GB_import_cheat(GB_gameboy_t *gb, const char *cheat, const char *description, bool enabled)
+{
+    uint8_t dummy;
+    /* GameShark */
+    {
+        uint8_t bank;
+        uint8_t value;
+        uint16_t address;
+        if (sscanf(cheat, "%02hhx%02hhx%04hx%c", &bank, &value, &address, &dummy) == 3) {
+            if (address > 0x7FFF) {
+                return false;
+            }
+            if (bank >= 0x80) {
+                bank &= 0xF;
+            }
+            GB_add_cheat(gb, description, address, bank, value, 0, false, enabled);
+            return true;
+        }
+    }
+    
+    /* GameGnie */
+    {
+        char stripped_cheat[10] = {0,};
+        for (unsigned i = 0; i < 9 && *cheat; i++) {
+            stripped_cheat[i] = *(cheat++);
+            while (*cheat == '-') {
+                cheat++;
+            }
+        }
+        
+        // Delete the 7th character;
+        stripped_cheat[7] = stripped_cheat[8];
+        stripped_cheat[8] = 0;
+        
+        uint8_t old_value;
+        uint8_t value;
+        uint16_t address;
+        if (sscanf(stripped_cheat, "%02hhx%04hx%02hhx%c", &value, &address, &old_value, &dummy) == 3) {
+            address = (uint16_t)(address >> 4) | (uint16_t)(address << 12);
+            address ^= 0xF000;
+            if (address > 0x7FFF) {
+                return false;
+            }
+            old_value = (uint8_t)(old_value >> 2) | (uint8_t)(old_value << 6);
+            old_value ^= 0xBA;
+            GB_add_cheat(gb, description, address, GB_CHEAT_ANY_BANK, value, old_value, true, enabled);
+            return true;
+        }
+        
+        if (sscanf(stripped_cheat, "%02hhx%04hx%c", &value, &address, &dummy) == 2) {
+            address = (uint16_t)(address >> 4) | (uint16_t)(address << 12);
+            address ^= 0xF000;
+            if (address > 0x7FFF) {
+                return false;
+            }
+            GB_add_cheat(gb, description, address, GB_CHEAT_ANY_BANK, value, false, true, enabled);
+            return true;
+        }
+    }
+    return false;
+}

Core/cheats.h

@@ -0,0 +1,33 @@
+#ifndef cheats_h
+#define cheats_h
+#include "gb_struct_def.h"
+
+#define GB_CHEAT_ANY_BANK 0xFFFF
+
+typedef struct GB_cheat_s GB_cheat_t;
+
+void GB_add_cheat(GB_gameboy_t *gb, const char *description, uint16_t address, uint16_t bank, uint8_t value, uint8_t old_value, bool use_old_value, bool enabled);
+bool GB_import_cheat(GB_gameboy_t *gb, const char *cheat, const char *description, bool enabled);
+const GB_cheat_t *const *GB_get_cheats(GB_gameboy_t *gb, size_t *size);
+void GB_remove_cheat(GB_gameboy_t *gb, const GB_cheat_t *cheat);
+
+#ifdef GB_INTERNAL
+void GB_apply_cheat(GB_gameboy_t *gb, uint16_t address, uint8_t *value);
+#endif
+
+typedef struct {
+    size_t size;
+    GB_cheat_t *cheats[];
+} GB_cheat_hash_t;
+
+struct GB_cheat_s {
+    uint16_t address;
+    uint16_t bank;
+    uint8_t value;
+    uint8_t old_value;
+    bool use_old_value;
+    bool enabled;
+    char description[128];
+};
+
+#endif

Core/gb.c

@@ -197,6 +197,9 @@ void GB_free(GB_gameboy_t *gb)
     GB_debugger_clear_symbols(gb);
 #endif
     GB_rewind_free(gb);
+    while (gb->cheats) {
+        GB_remove_cheat(gb, gb->cheats[0]);
+    }
     memset(gb, 0, sizeof(*gb));
 }
 

Core/gb.h

@@ -21,6 +21,7 @@
 #include "sm83_cpu.h"
 #include "symbol_hash.h"
 #include "sgb.h"
+#include "cheats.h"
 
 #define GB_STRUCT_VERSION 13
 
@@ -645,6 +646,11 @@ struct GB_gameboy_internal_s {
         double sgb_intro_sweep_phase;
         double sgb_intro_sweep_previous_sample;
                
+        /* Cheats */
+        size_t cheat_count;
+        GB_cheat_t **cheats;
+        GB_cheat_hash_t *cheat_hash[256];
+
         /* Misc */
         bool turbo;
         bool turbo_dont_skip;

Core/memory.c

@@ -435,12 +435,12 @@ uint8_t GB_read_memory(GB_gameboy_t *gb, uint16_t addr)
     if (is_addr_in_dma_use(gb, addr)) {
         addr = gb->dma_current_src;
     }
-    if (gb->read_memory_callback) {
     uint8_t data = read_map[addr >> 12](gb, addr);
+    GB_apply_cheat(gb, addr, &data);
+    if (gb->read_memory_callback) {
         data = gb->read_memory_callback(gb, addr, data);
-        return data;
     }
-    return read_map[addr >> 12](gb, addr);
+    return data;
 }
 
 static void write_mbc(GB_gameboy_t *gb, uint16_t addr, uint8_t value)