apple2a/main.c
2018-08-03 12:02:14 -07:00

620 lines
15 KiB
C

#include <string.h>
#include "exporter.h"
#include "platform.h"
#include "runtime.h"
uint8_t *title = "Apple IIa";
uint8_t title_length = 9;
// 6502 instructions.
#define I_CLC 0x18
#define I_JSR 0x20
#define I_SEC 0x38
#define I_RTS 0x60
#define I_STA_ZPG 0x85
#define I_STX_ZPG 0x86
#define I_STA_IND_Y 0x91
#define I_LDY_IMM 0xA0
#define I_LDX 0xA2
#define I_LDA 0xA9
// Tokens.
#define T_HOME 0x80
#define T_PRINT 0x81
#define T_LIST 0x82
#define T_POKE 0x83
#define T_RUN 0x84
#define T_NEW 0x85
// Line number used for "no line number".
#define INVALID_LINE_NUMBER 0xFFFF
// List of tokens. The token value is the index plus 0x80.
static uint8_t *TOKEN[] = {
"HOME",
"PRINT",
"LIST",
"POKE",
"RUN",
"NEW",
};
static int16_t TOKEN_COUNT = sizeof(TOKEN)/sizeof(TOKEN[0]);
uint8_t g_input_buffer[40];
int16_t g_input_buffer_length = 0;
// Compiled binary.
uint8_t g_compiled[1024];
int16_t g_compiled_length = 0;
void (*g_compiled_function)() = (void (*)()) g_compiled;
// Stored program. Each line is:
// - Two bytes for pointer to next line (or zero if none).
// - Two bytes for line number.
// - Program line.
// - Nul.
uint8_t g_program[1024];
/**
* Print the tokenized string, with tokens displayed as their full text.
* Prints a newline at the end.
*/
static void print_detokenized(uint8_t *s) {
while (*s != '\0') {
if (*s >= 0x80) {
print_char(' ');
print(TOKEN[*s - 0x80]);
print_char(' ');
} else {
print_char(*s);
}
s += 1;
}
print_char('\n');
}
/**
* Get the pointer to the next line in the stored program. Returns 0
* if we're at the end.
*/
static uint8_t *get_next_line(uint8_t *line) {
return *((uint8_t **) line);
}
/**
* Get the line number of a stored program line.
*/
static uint16_t get_line_number(uint8_t *line) {
return *((uint16_t *) (line + 2));
}
/**
* Return a pointer to the end of the program. This is one byte PAST the
* last bytes in the program, which are two nuls. The "line" parameter is
* an optional starting point, to use as an optimization instead of starting
* from the beginning.
*/
static uint8_t *get_end_of_program(uint8_t *line) {
uint8_t *next_line;
if (line == 0) {
// Start at the beginning if not specified.
line = g_program;
}
while ((next_line = get_next_line(line)) != 0) {
line = next_line;
}
// Skip the null "next" pointer.
return line + 2;
}
/**
* Clear the stored program.
*/
static void new_statement() {
g_program[0] = '\0';
g_program[1] = '\0';
}
/**
* List the stored program.
*/
static void list_statement() {
uint8_t *line = g_program;
uint8_t *next_line;
print_newline();
while ((next_line = get_next_line(line)) != 0) {
print_int(get_line_number(line));
print_char(' ');
print_detokenized(line + 4);
line = next_line;
}
}
/**
* If a starts with string b, returns the position in a after b. Else returns null.
*/
static uint8_t *skip_over(uint8_t *a, uint8_t *b) {
while (*a != '\0' && *b != '\0') {
if (*a != *b) {
// Doesn't start with b.
return 0;
}
a += 1;
b += 1;
}
// See if we're at the end of b.
return *b == '\0' ? a : 0;
}
/**
* Add a function call to the compiled buffer.
*/
static void add_call(void *function) {
uint16_t addr = (int16_t) function;
g_compiled[g_compiled_length++] = I_JSR;
g_compiled[g_compiled_length++] = addr & 0xFF;
g_compiled[g_compiled_length++] = addr >> 8;
}
/**
* Add a function return to the compiled buffer.
*/
static void add_return() {
g_compiled[g_compiled_length++] = I_RTS;
}
/**
* Parse an unsigned integer, returning the value and moving the pointer
* past the end of the number. The pointer must already be at the beginning
* of the number.
*/
static uint16_t parse_uint16(uint8_t **s_ptr) {
uint16_t value = 0;
uint8_t *s = *s_ptr;
while (*s >= '0' && *s <= '9') {
value = value*10 + (*s - '0');
s += 1;
}
*s_ptr = s;
return value;
}
/**
* Generate code to put the value into AX.
*/
static void compile_load_ax(uint16_t value) {
g_compiled[g_compiled_length++] = I_LDX;
g_compiled[g_compiled_length++] = value >> 8;
g_compiled[g_compiled_length++] = I_LDA;
g_compiled[g_compiled_length++] = value & 0xFF;
}
/**
* Parse an expression, generating code to compute it, leaving the
* result in AX.
*/
static uint8_t *compile_expression(uint8_t *s) {
int plus_count = 0;
char have_value_in_ax = 0;
while (1) {
if (*s >= '0' && *s <= '9') {
// Parse number.
uint16_t value;
if (have_value_in_ax) {
// Push on the number stack.
add_call(pushax);
}
value = parse_uint16(&s);
compile_load_ax(value);
have_value_in_ax = 1;
} else if (*s == '+') {
plus_count += 1;
s += 1;
} else {
break;
}
}
while (plus_count > 0) {
add_call(tosaddax);
plus_count -= 1;
}
return s;
}
/**
* Tokenize a string in place. Returns (and removes) any line number, or
* INVALID_LINE_NUMBER if there's none.
*/
static uint16_t tokenize(uint8_t *s) {
uint8_t *t = s; // Tokenized version.
int16_t line_number;
// Parse optional line number.
if (*s >= '0' && *s <= '9') {
line_number = parse_uint16(&s);
} else {
line_number = INVALID_LINE_NUMBER;
}
// Convert tokens.
while (*s != '\0') {
if (*s == ' ') {
// Skip spaces.
s++;
} else {
int16_t i;
uint8_t *skipped = 0;
for (i = 0; i < TOKEN_COUNT; i++) {
skipped = skip_over(s, TOKEN[i]);
if (skipped != 0) {
// Record token.
*t++ = 0x80 + i;
s = skipped;
break;
}
}
if (skipped == 0) {
// Didn't find a token, just copy text.
*t++ = *s++;
}
}
}
// Terminate string.
*t++ = '\0';
return line_number;
}
/**
* Find the stored program line with the given line number. If the line does
* not exist, returns a pointer to the location where it should be inserted.
*/
static uint8_t *find_line(uint16_t line_number) {
uint8_t *line = g_program;
uint8_t *next_line;
while ((next_line = get_next_line(line)) != 0) {
// See if we hit it or just blew past it.
if (get_line_number(line) >= line_number) {
break;
}
line = next_line;
}
return line;
}
/**
* Call to configure the compilation step.
*/
static void set_up_compile(void) {
g_compiled_length = 0;
}
/**
* Compile the tokenized line of BASIC, adding it to the g_compiled binary.
*/
static void compile_buffer(uint8_t *buffer, uint16_t line_number) {
uint8_t *s = buffer;
uint8_t done;
do {
int8_t error = 0;
// Default to being done after one statement.
done = 1;
if (*s == '\0' || *s == ':') {
// Empty statement. We skip the colon below.
} else if (*s == T_HOME) {
s += 1;
add_call(home);
} else if (*s == T_PRINT) {
s += 1;
if (*s >= '0' && *s <= '9') { // TODO: Add negative sign and open parenthesis.
// Parse expression.
s = compile_expression(s);
add_call(print_int);
}
add_call(print_newline);
} else if (*s == T_LIST) {
s += 1;
add_call(list_statement);
} else if (*s == T_POKE) {
s += 1;
// Parse address.
s = compile_expression(s);
// Copy from AX to ptr1.
g_compiled[g_compiled_length++] = I_STA_ZPG;
g_compiled[g_compiled_length++] = (uint8_t) &ptr1;
g_compiled[g_compiled_length++] = I_STX_ZPG;
g_compiled[g_compiled_length++] = (uint8_t) &ptr1 + 1;
if (*s == ',') {
s++;
}
// Parse value. LSB is in A.
s = compile_expression(s);
g_compiled[g_compiled_length++] = I_LDY_IMM;
g_compiled[g_compiled_length++] = 0;
g_compiled[g_compiled_length++] = I_STA_IND_Y;
g_compiled[g_compiled_length++] = (uint8_t) &ptr1;
} else {
error = 1;
}
// Now we're at the end of our statement.
if (!error) {
if (*s == ':') {
// Skip colon.
s += 1;
// Next statement.
done = 0;
} else if (*s != '\0') {
// Junk at the end of the statement.
error = 1;
}
}
if (error) {
if (line_number != INVALID_LINE_NUMBER) {
compile_load_ax(line_number);
add_call(syntax_error_in_line);
} else {
add_call(syntax_error);
}
}
} while (!done);
}
/**
* Complete the compilation buffer and run it.
*/
static void complete_compile_and_execute(void) {
// Return from function.
add_return();
// Dump compiled buffer to the terminal.
{
int i;
uint8_t *debug_port = (uint8_t *) 0xBFFE;
debug_port[0] = g_compiled_length;
for (i = 0; i < g_compiled_length; i++) {
debug_port[1] = g_compiled[i];
}
}
if (g_compiled_length > sizeof(g_compiled)) {
// TODO: Check while adding bytes, not at the end.
print("\n?Binary length exceeded");
} else {
// Call it.
g_compiled_function();
}
}
/**
* Compile the stored program and execute it.
*/
static void compile_stored_program(void) {
uint8_t *line = g_program;
uint8_t *next_line;
set_up_compile();
while ((next_line = get_next_line(line)) != 0) {
uint16_t line_number = get_line_number(line);
compile_buffer(line + 4, line_number);
line = next_line;
}
complete_compile_and_execute();
}
/**
* Process the user's line of input, possibly compiling the code.
* and executing it.
*/
static void process_input_buffer() {
uint16_t line_number;
g_input_buffer[g_input_buffer_length] = '\0';
// Tokenize in-place.
line_number = tokenize(g_input_buffer);
if (line_number == INVALID_LINE_NUMBER) {
// Immediate mode.
if (g_input_buffer[0] == T_RUN) {
// We don't compile "RUN".
compile_stored_program();
} else if (g_input_buffer[0] == T_NEW) {
// We don't compile "NEW".
new_statement();
} else {
// Compile the immediate mode line.
set_up_compile();
compile_buffer(g_input_buffer, INVALID_LINE_NUMBER);
complete_compile_and_execute();
}
} else {
// Stored mode. Add line to program.
// Return line to replace or delete, or location to insert new line.
uint8_t *line = find_line(line_number);
uint8_t *next_line = get_next_line(line);
uint8_t *end_of_program = get_end_of_program(line);
int16_t adjustment = 0;
if (next_line == 0 || get_line_number(line) != line_number) {
// Didn't find line. Insert it here.
// Next pointer, line number, line, and nul.
uint8_t buffer_length = strlen(g_input_buffer);
adjustment = 4 + buffer_length + 1;
// Shift rest of program over.
memmove(line + adjustment, line, end_of_program - line);
// Next line. Point to yourself initially, we'll adjust below.
*((uint8_t **) line) = line;
// Line number.
*((uint16_t *) (line + 2)) = line_number;
// Buffer and nul.
memmove(line + 4, g_input_buffer, buffer_length + 1);
} else {
// Found line.
if (g_input_buffer[0] == '\0') {
// Empty line, delete old one.
// Adjustment is negative.
adjustment = line - next_line;
memmove(line, next_line, end_of_program - next_line);
} else {
// Replace line.
// Compute adjustment.
uint8_t buffer_length = strlen(g_input_buffer);
adjustment = line - next_line + 4 + buffer_length + 1;
memmove(next_line + adjustment, next_line, end_of_program - next_line);
// Buffer and nul.
memmove(line + 4, g_input_buffer, buffer_length + 1);
}
}
if (adjustment != 0) {
// Adjust all the next pointers.
while ((next_line = get_next_line(line)) != 0) {
// Adjust by the amount we inserted or deleted.
next_line += adjustment;
*((uint8_t **) line) = next_line;
line = next_line;
}
}
}
}
int16_t main(void)
{
int16_t blink;
// Clear stored program.
new_statement();
// Initialize UI.
home();
// Display the character set.
/*
if (1) {
int16_t i;
for (i = 0; i < 256; i++) {
uint8_t *loc;
// Fails with: unhandled instruction B2
move_cursor(i % 16, i >> 4);
// Works.
// move_cursor(i & 0x0F, i >> 4);
loc = cursor_pos();
*loc = i;
}
while(1);
}
*/
// Print title.
move_cursor((40 - title_length) / 2, 0);
print(title);
// Prompt.
print("\n\n]");
// TODO crashes 6502. Delete:
// asm("ldy #1");
// asm("sta $FFFF,y");
// Keyboard input.
blink = 0;
g_input_buffer_length = 0;
show_cursor();
while(1) {
// Blink cursor.
blink += 1;
if (blink == 3000) {
if (g_showing_cursor) {
hide_cursor();
} else {
show_cursor();
}
blink = 0;
}
if(keyboard_test()) {
hide_cursor();
while(keyboard_test()) {
uint8_t key;
key = keyboard_get();
if (key == 8) {
// Backspace.
if (g_input_buffer_length > 0) {
move_cursor(g_cursor_x - 1, g_cursor_y);
g_input_buffer_length -= 1;
}
} else if (key == 13) {
// Return.
clear_to_eol();
print_char('\n');
process_input_buffer();
print("\n]");
g_input_buffer_length = 0;
} else {
if (g_input_buffer_length < sizeof(g_input_buffer) - 1) {
uint8_t *loc = cursor_pos();
*loc = key | 0x80;
move_cursor(g_cursor_x + 1, g_cursor_y);
g_input_buffer[g_input_buffer_length++] = key;
}
}
}
show_cursor();
}
}
return 0;
}