Implement state saving and loading for CPU and Bus, add tests for various functionalities

- Added `state.c` to handle saving and loading the state of the CPU and Bus.
- Implemented CRC32 checksum for data integrity verification during state operations.
- Enhanced `README.md` in tests/roms to document new test commands for decimal, interrupt, Apple I, and nestest.
- Created new test files: `run_apple1.c`, `run_decimal.c`, `run_interrupt.c`, `run_nestest.c`, and `run_vectors.c` to validate the new features.
- Updated `run_tests.c` to include tests for state saving/loading and other functionalities.
- Introduced `test_vectors.py` to facilitate downloading and running JSON test vectors for opcode verification.

include/apple1.h

@@ -0,0 +1,14 @@
+#ifndef APPLE1_H
+#define APPLE1_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include "bus.h"
+typedef struct {
+    uint8_t key;bool key_ready;bool stdout_enabled;
+    char output[8192];size_t output_length;
+} Apple1IO;
+void apple1_init(Apple1IO *io,Bus6502 *bus);
+void apple1_key(Apple1IO *io,uint8_t ascii);
+void apple1_enable_stdout(Apple1IO *io,bool enabled);
+#endif

include/bus.h

@@ -5,13 +5,20 @@
 #include <stdint.h>
 #include "memory.h"
 
-typedef struct Bus6502 {
+typedef struct Bus6502 Bus6502;
+typedef bool (*bus_read_hook_t)(void *userdata,uint16_t addr,uint8_t *value);
+typedef bool (*bus_write_hook_t)(void *userdata,uint16_t addr,uint8_t value);
+
+struct Bus6502 {
     Memory memory;
     uint8_t keyboard;
     uint32_t rng_state;
     bool easy6502_io;
     bool framebuffer_dirty;
-} Bus6502;
+    bus_read_hook_t read_hook;
+    bus_write_hook_t write_hook;
+    void *hook_userdata;
+};
 
 void bus_init(Bus6502 *bus);
 uint8_t bus_read(Bus6502 *bus, uint16_t addr);
@@ -20,5 +27,7 @@ uint16_t bus_read16(Bus6502 *bus, uint16_t addr);
 void bus_write16(Bus6502 *bus, uint16_t addr, uint16_t value);
 void bus_set_keyboard(Bus6502 *bus, uint8_t key);
 void bus_seed_rng(Bus6502 *bus, uint32_t seed);
+void bus_set_hooks(Bus6502 *bus,bus_read_hook_t read_hook,
+                   bus_write_hook_t write_hook,void *userdata);
 
 #endif

include/cpu.h

@@ -13,6 +13,7 @@ typedef struct CPU6502 {
     uint8_t P;
     bool nmi_pending;
     bool irq_asserted;
+    bool decimal_enabled;
 } CPU6502;
 
 enum {

include/nes.h

@@ -0,0 +1,28 @@
+#ifndef NES_H
+#define NES_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include "bus.h"
+#include "cpu.h"
+
+typedef struct {
+    uint8_t prg[512*1024],chr[256*1024],ram[2048],prg_ram[8192];
+    uint8_t nametable[4096],palette[32],oam[256];
+    size_t prg_size,chr_size;uint8_t mapper,prg_bank,chr_bank,mirroring;bool chr_ram;
+    uint8_t ppu_ctrl,ppu_mask,ppu_status,oam_addr,ppu_latch,read_buffer;
+    uint8_t scroll_x,scroll_y;
+    uint16_t ppu_addr;unsigned ppu_dot,ppu_scanline;bool frame_ready;
+    uint8_t controller,controller_shift;bool controller_strobe;
+    uint8_t apu_reg[0x18],apu_status;uint64_t apu_cycles;
+    double pulse_phase[2],triangle_phase,noise_phase;uint16_t noise_lfsr;
+    Bus6502 bus;CPU6502 cpu;
+} NES;
+
+int nes_load(NES *nes,const char *path);
+void nes_reset(NES *nes);
+cpu_step_result_t nes_step(NES *nes);
+void nes_set_controller(NES *nes,uint8_t buttons);
+void nes_render_frame(NES *nes,uint32_t pixels[256*240]);
+float nes_audio_sample(NES *nes,double sample_rate);
+#endif

include/state.h

@@ -0,0 +1,7 @@
+#ifndef STATE_H
+#define STATE_H
+#include "bus.h"
+#include "cpu.h"
+int state_save(const char *path,const CPU6502 *cpu,const Bus6502 *bus);
+int state_load(const char *path,CPU6502 *cpu,Bus6502 *bus);
+#endif