1 files changed, 49 insertions, 13 deletions

diff --git a/cpu.c b/cpu.c
index 61b835c..968fcd8 100644
--- a/cpu.c
+++ b/cpu.c
@@ -1,8 +1,11 @@
+#include <libgen.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "rom.h"
+
 #define MAX(a, b)       ((a > b) ? a : b)
 
 #define STATUS_UPDATE_ZERO(r)           \
@@ -37,7 +40,9 @@ struct registers {
         struct cpu_flags status;
         uint16_t pc;
 };
-struct registers regs;
+struct registers regs = {0};
+
+struct Rom rom = {0};
 
 enum addressing_mode {
         AM_IMM,
@@ -56,9 +61,6 @@ enum addressing_mode {
 /* 64K address space, 16bit words */
 uint8_t memory[0x16000];
 
-/* example program taken from https://bugzmanov.github.io/nes_ebook/chapter_3_1.html */
-uint8_t program[] = { 0xa9, 0xc0, 0xaa, 0xe8, 0x00 };
-
 uint32_t cycles = 0;
 
 static uint8_t
@@ -66,7 +68,14 @@ peek(uint16_t addr)
 {
         MEMORY_MIRROR(addr);
 
-        return memory[addr];
+        if (addr > 0x7FFF) {
+                if (rom.prg_rom_size == 0x4000)
+                        return rom.prg_rom[(addr - 0x8000) % 0x4000];
+                else if (rom.prg_rom_size == 0x8000)
+                        return rom.prg_rom[addr - 0x8000];
+        } else {
+                return memory[addr];
+        }
 }
 
 static uint16_t
@@ -738,7 +747,7 @@ interpret(void)
         for (;;) {
                 opcode = peek(regs.pc++);
 
-                printf("opcode: $%02X\n", opcode);
+                printf("opcode: $%02X @ $%04X\n", opcode, regs.pc - 1);
 
                 switch (opcode) {
                 case 0x69:
@@ -1403,7 +1412,7 @@ interpret(void)
                     regs.status.decimal_mode, regs.status.brk,
                     regs.status.unused, regs.status.overflow,
                     regs.status.negative);
-                printf("A: $%02X, X: $%02X, Y: $%02X, SP: $%02X, PC: $%02X\n",
+                printf("A: $%02X, X: $%02X, Y: $%02X, SP: $%02X, PC: $%04X\n",
                     regs.a, regs.x, regs.y, regs.sp, regs.pc);
         }
 }
@@ -1416,26 +1425,51 @@ cpu_init(void)
         regs.pc = 0xFFFC;
         regs.sp = 0xFD;
 
-        memset(&regs.status, 0, sizeof(regs.status));
+        //memset(&regs.status, 0, sizeof(regs.status));
         regs.status.unused = 1;
 
         cycles += 7;
 }
 
 int
-main(void)
+main(int argc, char *argv[])
 {
+        FILE *fp;
+        uint8_t *buf;
+        size_t buflen;
+
+        if (argc != 2) {
+                fprintf(stderr, "Usage: %s rom.nes\n", basename(argv[0]));
+                return 1;
+        }
+
+        fp = fopen(argv[1], "r");
+        fseek(fp, 0, SEEK_END);
+        buflen = ftell(fp);
+        buf = calloc(1, buflen);
+        fseek(fp, 0, SEEK_SET);
+        if (fread(buf, 1, buflen, fp) != buflen && ferror(fp)) {
+                fprintf(stderr, "file %s was not read properly\n", argv[1]);
+                clearerr(fp);
+                fclose(fp);
+                return 1;
+        }
+        fclose(fp);
+
+        parse_rom(buf, buflen, &rom);
+        free(buf);
+
         cpu_init();
 
-        if (sizeof(program) > (0x10000 - 0x8000)) {
-                fprintf(stderr, "program is too big for memory\n");
+        /* TODO: move to separate file? */
+        if (rom.mapper != 0) {
+                fprintf(stderr, "Only iNES ROMs using Mapper 0 are supported for now.\n");
                 return 1;
         }
 
-        memcpy(memory + 0x8000, program, sizeof(program));
+        memwrite16(0xFFFC, 0x8000);
         regs.pc = 0x8000;
 
-        printf("Initial State:\n");
         printf("status: %i%i%i%i%i%i%i%i\n", regs.status.carry,
             regs.status.zero, regs.status.interrupt_disable,
             regs.status.decimal_mode, regs.status.brk,
@@ -1448,5 +1482,7 @@ main(void)
 
         interpret();
 
+        free_rom(&rom);
+
         return 0;
 }