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369 lines
9.5 KiB
C
369 lines
9.5 KiB
C
/*
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* apple2.c
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*
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* Here we have support for the apple2 machine. I suspect that we will
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* need to break this file up into components in the future...
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*/
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#include "apple2.h"
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#include "apple2.draw.h"
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#include "apple2.mem.h"
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#include "mos6502.enums.h"
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#include "mos6502.dis.h"
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#include "objstore.h"
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#include "option.h"
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#include "vm_segment.h"
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/*
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* This is the memory address where an apple program can find the value
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* of the key that was last pressed.
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*/
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#define LAST_KEY 0xC000
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/*
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* This is the address in memory where you can find whether a key is
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* currently pressed or not.
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*/
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#define ANY_KEY_DOWN 0xC010
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/*
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* Create the basic apple2 structure.
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*/
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apple2 *
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apple2_create(int width, int height)
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{
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apple2 *mach;
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int err;
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objstore_init();
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mach = malloc(sizeof(apple2));
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if (mach == NULL) {
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return NULL;
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}
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// Forward set these to NULL in case we fail to build the machine
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// properly; that way, we won't try to free garbage data
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mach->rom = NULL;
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mach->ram2 = NULL;
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mach->sysfont = NULL;
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mach->screen = NULL;
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mach->drive1 = NULL;
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mach->drive2 = NULL;
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mach->cpu = mos6502_create();
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if (mach->cpu == NULL) {
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log_critical("Could not create CPU!");
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apple2_free(mach);
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return NULL;
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}
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// Our memory is that which is owned by the CPU.
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mach->memory = mach->cpu->memory;
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// Set the read/write mappers for everything
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apple2_mem_map(mach);
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// Initliaze our system ROM and separate bank-switched block of RAM
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mach->rom = vm_segment_create(APPLE2_ROM_SIZE);
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mach->ram2 = vm_segment_create(APPLE2_RAM2_SIZE);
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if (mach->rom == NULL || mach->ram2 == NULL) {
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log_critical("Could not initialize ROM / RAM2!");
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apple2_free(mach);
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return NULL;
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}
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if (apple2_mem_init_peripheral_rom(mach) != OK) {
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log_critical("Could not initialize disk2 ROM");
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apple2_free(mach);
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return NULL;
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}
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if (apple2_mem_init_sys_rom(mach) != OK) {
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log_critical("Could not initialize apple2 ROM");
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apple2_free(mach);
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return NULL;
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}
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// Our two drives -- we create both of them, even if we intend to
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// use only one.
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mach->drive1 = apple2_dd_create();
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mach->drive2 = apple2_dd_create();
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if (mach->drive1 == NULL || mach->drive2 == NULL) {
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log_critical("Could not create disk drives!");
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apple2_free(mach);
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return NULL;
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}
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// Let's build our screen abstraction!
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mach->screen = vm_screen_create();
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if (mach->screen == NULL) {
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log_critical("Screen creation failed!");
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apple2_free(mach);
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return NULL;
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}
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// We still need to add a window, since we want to render some
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// graphics.
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err = vm_screen_add_window(mach->screen, width, height);
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if (err != OK) {
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log_critical("Window creation failed!");
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apple2_free(mach);
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return NULL;
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}
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// Default to full color
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apple2_set_color(mach, COLOR_FULL);
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// We default to lo-res mode.
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apple2_set_video(mach, VIDEO_LORES);
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// By default we should have ROM be the addressable last 12k of
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// memory.
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apple2_set_memory(mach, MEMORY_BANK_ROM);
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// Let's install our bitmap font.
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mach->sysfont = vm_bitfont_create(mach->screen,
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objstore_apple2_sysfont(),
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APPLE2_SYSFONT_SIZE,
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7, 8, // 7 pixels wide, 8 pixels tall
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0x7f); // 7-bit values only
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if (mach->sysfont == NULL) {
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apple2_free(mach);
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log_critical("Could not initialize apple2: bad font");
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return NULL;
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}
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return mach;
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}
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/*
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* Change the memory mode of the apple2 to a given mode.
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*/
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void
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apple2_set_memory(apple2 *mach, int mode)
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{
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mach->memory_mode = mode;
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}
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/*
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* Return true if we are in a state that the apple2 would consider
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* double resolution. (In practice, this refers to horizontal screen
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* density; vertical screen density per-pixel is unchanged.)
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*/
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bool
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apple2_is_double_video(apple2 *mach)
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{
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return
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mach->video_mode == VIDEO_DOUBLE_HIRES ||
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mach->video_mode == VIDEO_DOUBLE_LORES ||
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mach->video_mode == VIDEO_80COL_TEXT;
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}
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/*
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* Try to "boot" the apple2 machine. Look for input sources indicated in
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* the option system and load those into our disk drives.
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*/
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int
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apple2_boot(apple2 *mach)
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{
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FILE *stream;
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int err;
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// Do we have any disks?
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stream = option_get_input(1);
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if (stream) {
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err = apple2_dd_insert(mach->drive1, stream);
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if (err != OK) {
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log_critical("Unable to insert disk1 into drive");
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return err;
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}
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}
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stream = option_get_input(2);
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if (stream) {
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err = apple2_dd_insert(mach->drive2, stream);
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if (err != OK) {
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log_critical("Unable to insert disk2 into drive");
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return err;
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}
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}
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if (option_flag(OPTION_FLASH)) {
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mos6502_flash_memory(mach->cpu, mach->drive1->data);
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}
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if (option_flag(OPTION_DISASSEMBLE)) {
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mos6502_dis_scan(mach->cpu, stdout, 0, mach->cpu->memory->size);
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}
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// Run the reset routine to get the machine ready to go.
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apple2_reset(mach);
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return OK;
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}
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/*
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* This function marks out the procedures that happen when the machine
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* is reset. A reset can happen at a cold boot, but it can also happen
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* after the computer is already operational.
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*/
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void
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apple2_reset(apple2 *mach)
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{
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mach->cpu->P = MOS_INTERRUPT;
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mach->cpu->PC = vm_segment_get16(mach->memory, 0xFFFC);
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mach->cpu->S = 0;
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}
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/*
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* This function will clear the 8th bit, which is the "strobe" bit, from
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* the position in memory where the value of the last key that was
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* pressed is held.
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*/
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void
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apple2_clear_strobe(apple2 *mach)
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{
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vm_8bit ch;
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ch = vm_segment_get(mach->memory, LAST_KEY);
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vm_segment_set(mach->memory, LAST_KEY, ch & 0x7F);
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}
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/*
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* Free the memory reserved for an apple2 struct.
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*/
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void
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apple2_free(apple2 *mach)
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{
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if (mach->cpu) {
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mos6502_free(mach->cpu);
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}
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if (mach->rom) {
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vm_segment_free(mach->rom);
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}
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if (mach->ram2) {
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vm_segment_free(mach->ram2);
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}
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if (mach->sysfont) {
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vm_bitfont_free(mach->sysfont);
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}
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if (mach->drive1) {
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apple2_dd_free(mach->drive1);
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}
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if (mach->drive2) {
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apple2_dd_free(mach->drive2);
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}
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if (mach->screen) {
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vm_screen_free(mach->screen);
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}
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// NOTE: we do _NOT_ want to clear the memory field of mach, as it's
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// co-owned with the cpu struct that we just freed above.
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free(mach);
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}
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/*
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* Emulate the notion of a pressed key in the apple2 with a given
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* character.
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*/
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void
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apple2_press_key(apple2 *mach, vm_8bit ch)
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{
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// The apple2 can only handle ASCII values of 0 through 127.
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// However, the eigth bit is called the "strobe" bit, and is treated
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// specially. In particular, the strobe bit is 1 if a key was
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// pressed down, and remains 1 until you reset it by reading from
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// the clear-strobe location.
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ch = ch | 0x80;
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// This is the location in memory where a program will expect to
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// find the value of the last key that was pressed.
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vm_segment_set(mach->memory, LAST_KEY, ch);
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// This area is a combination of flags; the eighth bit here is the
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// "any-key-down" flag, which is a bit of a mouthful. It's 1 if a
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// key is pressed, and 0 if not. The effect of reading this bit will
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// also _clear_ the strobe bit in the $C000 address (above).
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vm_segment_set(mach->memory, ANY_KEY_DOWN, 0x80);
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}
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/*
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* This function will clear the value of the any-key-down switch/flag.
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*/
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void
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apple2_release_key(apple2 *mach)
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{
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vm_segment_set(mach->memory, ANY_KEY_DOWN, 0);
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}
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/*
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* The run loop is the function that essentially waits for user input
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* and continues to present the apple2 abstraction for you to use. At
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* some point the user will indicate they are done, whereby
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* vm_screen_active() will no longer be true and we exit.
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*/
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void
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apple2_run_loop(apple2 *mach)
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{
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if (option_flag(OPTION_DISASSEMBLE)) {
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return;
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}
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while (vm_screen_active(mach->screen)) {
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mos6502_dis_opcode(mach->cpu, stdout, mach->cpu->PC);
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mos6502_execute(mach->cpu, mos6502_next_byte(mach->cpu));
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vm_screen_refresh(mach->screen);
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}
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}
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/*
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* Set the color mode of the apple2, which is to say if we are emulating
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* a monochromatic display, or full color, or just black-and-white.
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*/
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void
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apple2_set_color(apple2 *mach, int mode)
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{
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mach->color_mode = mode;
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// FIXME: doing this should force us to redraw everything in the
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// correct color interpretation
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}
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/*
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* Set the video mode of the display. This would be the type of
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* resolution (text by which number of columns, lo-res, hi-res, etc.)
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*/
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void
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apple2_set_video(apple2 *mach, int mode)
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{
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int width, height;
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mach->video_mode = mode;
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// In the traditional video modes that Apple II first came in, you
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// would have a maximum width of 280 pixels. (In lo-res, you have
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// fewer pixels, but that is something we have to handle in our
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// drawing functions rather than by changing the logical size.)
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width = 280;
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height = 192;
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// In double video modes, the width is effectively doubled, but the
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// height is untouched.
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if (mach->video_mode == VIDEO_DOUBLE_LORES ||
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mach->video_mode == VIDEO_DOUBLE_HIRES
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) {
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width = 560;
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}
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vm_screen_set_logical_coords(mach->screen, width, height);
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}
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