#include "signature.h"

#include "fake_devices.h"

#include "memory.h"

#include "cpu/registers.h"

#include <stdint.h>

extern struct regs regs;

extern uint32_t clockticks6502;

extern uint8_t *RAM;

// FNV-1a. Chosen because it is short enough to read and verify at a glance,

// which matters more here than distribution: this is change detection, not

// cryptography.

static void

mix(uint64_t *h, const void *data, size_t len)

{

	const uint8_t *p = (const uint8_t *)data;

	for (size_t i = 0; i < len; i++) {

		*h ^= p[i];

		*h *= 0x100000001b3ULL;

	}

}

machine_sig_t

machine_signature(void)

{

	uint64_t h = 0xcbf29ce484222325ULL;

	// CPU: registers and what they have cost so far.

	mix(&h, &regs, sizeof regs);

	mix(&h, &clockticks6502, sizeof clockticks6502);

	// Memory: the low 64K, which is everything these fixtures touch.

	if (RAM != NULL) {

		mix(&h, RAM, 0x10000);

	}

	// Which banks are mapped, since a read through a window depends on it.

	uint8_t ram_bank = memory_get_ram_bank();

	uint8_t rom_bank = memory_get_rom_bank();

	mix(&h, &ram_bank, sizeof ram_bank);

	mix(&h, &rom_bank, sizeof rom_bank);

	// Devices: how often each was touched, and whether it moved.

	mix(&h, fake_dev, sizeof(fake_dev_log_t) * FAKE_DEV_COUNT);

	machine_sig_t sig = { h };

	return sig;

}

int

machine_sig_equal(machine_sig_t a, machine_sig_t b)

{

	return a.value == b.value;

}