Implement disk controller

Makefile

@@ -5,6 +5,7 @@ TARGET=fox32
 CFILES = src/main.c \
 		src/bus.c \
 		src/cpu.c \
+		src/disk.c \
 		src/framebuffer.c \
 		src/mouse.c \
 		src/screen.c

src/bus.c

@@ -10,10 +10,12 @@
 
 #include "bus.h"
 #include "cpu.h"
+#include "disk.h"
 #include "framebuffer.h"
 #include "mouse.h"
 
 extern fox32_vm_t vm;
+extern disk_controller_t disk_controller;
 extern mouse_t mouse;
 
 int bus_io_read(void *user, uint32_t *value, uint32_t port) {
@@ -71,6 +73,26 @@ int bus_io_read(void *user, uint32_t *value, uint32_t port) {
 
             break;
         };
+
+        case 0x80001000 ... 0x80002003: { // disk controller port
+            size_t id = port & 0xFF;
+            uint8_t operation = (port & 0x0000F000) >> 8;
+            switch (operation) {
+                case 0x10: {
+                    // current insert state of specified disk id
+                    // size will be zero if disk isn't inserted
+                    *value = get_disk_size(id);
+                    break;
+                };
+                case 0x20: {
+                    // current buffer pointer
+                    *value = disk_controller.buffer_pointer;
+                    break;
+                };
+            }
+
+            break;
+        };
     }
 
     return 0;
@@ -140,6 +162,39 @@ int bus_io_write(void *user, uint32_t value, uint32_t port) {
 
             break;
         };
+
+        case 0x80001000 ... 0x80005003: { // disk controller port
+            size_t id = port & 0xFF;
+            uint8_t operation = (port & 0x0000F000) >> 8;
+            switch (operation) {
+                case 0x10: {
+                    // TODO: ask the user to insert a disk
+                    break;
+                };
+                case 0x20: {
+                    // set the buffer pointer
+                    disk_controller.buffer_pointer = value;
+                    break;
+                };
+                case 0x30: {
+                    // read specified disk sector into memory
+                    set_disk_sector(id, value);
+                    read_disk_into_memory(id);
+                    break;
+                };
+                case 0x40: {
+                    // TODO: write specified disk sector from memory
+                    break;
+                };
+                case 0x50: {
+                    // remove specified disk
+                    remove_disk(id);
+                    break;
+                };
+            }
+
+            break;
+        };
     }
 
     return 0;

src/disk.c

@@ -0,0 +1,54 @@
+#include <SDL2/SDL.h>
+#include <getopt.h>
+#include <math.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "cpu.h"
+#include "disk.h"
+
+disk_controller_t disk_controller;
+
+extern fox32_vm_t vm;
+
+void new_disk(const char *filename, size_t id) {
+    if (id > 3) { puts("attempting to access disk with ID > 3\n"); return; }
+    printf("mounting %s as disk ID %d\n", filename, (int) id);
+    disk_controller.disks[id].file = fopen(filename, "r+b");
+    fseek(disk_controller.disks[id].file, 0, SEEK_END);
+    disk_controller.disks[id].size = ftell(disk_controller.disks[id].file);
+    rewind(disk_controller.disks[id].file);
+}
+
+void insert_disk(disk_t disk, size_t id) {
+    if (id > 3) { puts("attempting to access disk with ID > 3\n"); return; }
+    if (disk_controller.disks[id].size > 0) remove_disk(id);
+    printf("mounting disk ID %d\n", (int) id);
+    disk_controller.disks[id] = disk;
+}
+
+void remove_disk(size_t id) {
+    if (id > 3) { puts("attempting to access disk with ID > 3\n"); return; }
+    printf("unmounting disk ID %d\n", (int) id);
+    fclose(disk_controller.disks[id].file);
+    disk_controller.disks[id].size = 0;
+}
+
+uint64_t get_disk_size(size_t id) {
+    if (id > 3) { puts("attempting to access disk with ID > 3\n"); return 0; }
+    return disk_controller.disks[id].size;
+}
+
+void set_disk_sector(size_t id, uint64_t sector) {
+    if (id > 3) { puts("attempting to access disk with ID > 3\n"); return; }
+    fseek(disk_controller.disks[id].file, sector * 512, 0);
+}
+
+size_t read_disk_into_memory(size_t id) {
+    if (id > 3) { puts("attempting to access disk with ID > 3\n"); return 0; }
+    return fread(&vm.memory_ram[disk_controller.buffer_pointer], 1, 512, disk_controller.disks[id].file);
+}

src/disk.h

@@ -0,0 +1,18 @@
+#pragma once
+
+typedef struct {
+    FILE *file;
+    uint64_t size;
+} disk_t;
+
+typedef struct {
+    disk_t disks[4];
+    size_t buffer_pointer;
+} disk_controller_t;
+
+void new_disk(const char *filename, size_t id);
+void insert_disk(disk_t disk, size_t id);
+void remove_disk(size_t id);
+uint64_t get_disk_size(size_t id);
+void set_disk_sector(size_t id, uint64_t sector);
+size_t read_disk_into_memory(size_t id);

src/main.c

@@ -9,6 +9,7 @@
 
 #include "bus.h"
 #include "cpu.h"
+#include "disk.h"
 #include "framebuffer.h"
 #include "mouse.h"
 #include "screen.h"
@@ -21,12 +22,14 @@
 
 fox32_vm_t vm;
 
+extern disk_controller_t disk_controller;
+
 uint32_t tick_start;
 uint32_t tick_end;
 int ticks = 0;
 bool done = false;
 
-void MainLoop(void);
+void main_loop(void);
 
 int main(int argc, char *argv[]) {
     if (SDL_Init(SDL_INIT_VIDEO) != 0) {
@@ -42,6 +45,12 @@ int main(int argc, char *argv[]) {
 
     memcpy(vm.memory_rom, fox32rom, sizeof(fox32rom));
 
+    if (argc > 1) {
+        for (int i = 0; i + 1 < argc; i++) {
+            new_disk(argv[i + 1], i);
+        }
+    }
+
     ScreenCreate(
         FRAMEBUFFER_WIDTH, FRAMEBUFFER_HEIGHT,
         draw_framebuffer,
@@ -59,7 +68,7 @@ int main(int argc, char *argv[]) {
     tick_end = SDL_GetTicks();
 
     while (!done) {
-        MainLoop();
+        main_loop();
 
         tick_end = SDL_GetTicks();
         int delay = 1000/TPS - (tick_end - tick_start);
@@ -73,7 +82,7 @@ int main(int argc, char *argv[]) {
     return 0;
 }
 
-void MainLoop(void) {
+void main_loop(void) {
     int dt = SDL_GetTicks() - tick_start;
     tick_start = SDL_GetTicks();
     if (!dt)