apple2a/main.c

826 lines
21 KiB
C
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#include <string.h>
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#include "exporter.h"
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#include "platform.h"
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#include "runtime.h"
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uint8_t *title = "Apple IIa";
uint8_t title_length = 9;
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// 6502 instructions.
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#define I_CLC 0x18
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#define I_JSR 0x20
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#define I_SEC 0x38
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#define I_JMP_ABS 0x4C
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#define I_RTS 0x60
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#define I_STA_ZPG 0x85
#define I_STX_ZPG 0x86
#define I_STA_IND_Y 0x91
#define I_LDY_IMM 0xA0
#define I_LDX_IMM 0xA2
#define I_LDA_ZPG 0xA5
#define I_LDX_ZPG 0xA6
#define I_LDA_IMM 0xA9
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// Tokens.
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#define T_HOME 0x80
#define T_PRINT 0x81
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#define T_LIST 0x82
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#define T_POKE 0x83
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#define T_RUN 0x84
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#define T_NEW 0x85
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#define T_PLUS 0x86
#define T_MINUS 0x87
#define T_TIMES 0x88
#define T_DIVIDE 0x89
#define T_CARET 0x8A
#define T_AND 0x8B
#define T_OR 0x8C
#define T_GREATER_THAN 0x8D
#define T_EQUALS 0x8E
#define T_LESS_THAN 0x8F
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#define T_GOTO 0x90
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// Line number used for "no line number".
#define INVALID_LINE_NUMBER 0xFFFF
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// Variable for "No more space for variables".
#define OUT_OF_VARIABLE_SPACE 0xFF
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// Maximum number of lines in stored program.
#define MAX_LINES 128
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// Test for whether a character is a digit.
#define IS_DIGIT(ch) ((ch) >= '0' && (ch) <= '9')
// Test for first and subsequent variable name letters.
#define IS_FIRST_VARIABLE_LETTER(ch) ((ch) >= 'A' && (ch) <= 'Z')
#define IS_SUBSEQUENT_VARIABLE_LETTER(ch) (IS_FIRST_VARIABLE_LETTER(ch) || IS_DIGIT(ch))
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// List of tokens. The token value is the index plus 0x80.
static uint8_t *TOKEN[] = {
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"HOME",
"PRINT",
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"LIST",
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"POKE",
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"RUN",
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"NEW",
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"+",
"-",
"*",
"/",
"^",
"AND",
"OR",
">",
"=",
"<",
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"GOTO",
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};
static int16_t TOKEN_COUNT = sizeof(TOKEN)/sizeof(TOKEN[0]);
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uint8_t g_input_buffer[40];
int16_t g_input_buffer_length = 0;
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// Compiled binary.
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uint8_t g_compiled[1024];
int16_t g_compiled_length = 0;
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void (*g_compiled_function)() = (void (*)()) g_compiled;
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// 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];
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// Address of each line of code when compiled (for GOTO statements).
// Each line takes two words: one for the line number and
// one for the address in memory of the compiled code.
uint16_t g_line_address[MAX_LINES*2];
uint16_t g_line_address_count;
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/**
* Print the tokenized string, with tokens displayed as their full text.
* Prints a newline at the end.
*/
static void print_detokenized(uint8_t *s) {
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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);
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}
/**
* Get the line number of a stored program line.
*/
static uint16_t get_line_number(uint8_t *line) {
return *((uint16_t *) (line + 2));
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}
/**
* 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
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* 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;
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if (line == 0) {
// Start at the beginning if not specified.
line = g_program;
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}
while ((next_line = get_next_line(line)) != 0) {
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line = next_line;
}
// Skip the null "next" pointer.
return line + 2;
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}
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/**
* Clear the stored program.
*/
static void new_statement() {
g_program[0] = '\0';
g_program[1] = '\0';
}
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/**
* List the stored program.
*/
static void list_statement() {
uint8_t *line = g_program;
uint8_t *next_line;
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print_newline();
while ((next_line = get_next_line(line)) != 0) {
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print_int(get_line_number(line));
print_char(' ');
print_detokenized(line + 4);
line = next_line;
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}
}
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/**
* If a starts with string b, returns the position in a after b. Else returns null.
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*/
static uint8_t *skip_over(uint8_t *a, uint8_t *b) {
while (*a != '\0' && *b != '\0') {
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if (*a != *b) {
// Doesn't start with b.
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return 0;
}
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a += 1;
b += 1;
}
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// See if we're at the end of b.
return *b == '\0' ? a : 0;
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}
/**
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* Add a function call to the compiled buffer.
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*/
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static void add_call(void *function) {
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uint16_t addr = (uint16_t) function;
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g_compiled[g_compiled_length++] = I_JSR;
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g_compiled[g_compiled_length++] = addr & 0xFF;
g_compiled[g_compiled_length++] = addr >> 8;
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}
/**
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* Add a function return to the compiled buffer.
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*/
static void add_return() {
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g_compiled[g_compiled_length++] = I_RTS;
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}
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/**
* 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;
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while (IS_DIGIT(*s)) {
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value = value*10 + (*s - '0');
s += 1;
}
*s_ptr = s;
return value;
}
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/**
* Generate code to put the value into AX.
*/
static void compile_load_ax(uint16_t value) {
g_compiled[g_compiled_length++] = I_LDX_IMM;
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g_compiled[g_compiled_length++] = value >> 8;
g_compiled[g_compiled_length++] = I_LDA_IMM;
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g_compiled[g_compiled_length++] = value & 0xFF;
}
/**
* Find a variable by name. Only the first two letters are considered.
* Advances the pointer past the variable name (including letters after
* the first two). Returns the memory address of the variable. If we
* ran out of space for variables, returns OUT_OF_VARIABLE_SPACE
* and does not modify the buffer pointer.
*/
static uint8_t find_variable(uint8_t **buffer) {
uint8_t *s = *buffer;
uint8_t *existing_name = g_variable_names;
uint8_t name[2];
int16_t var;
// Pull out the variable name.
name[0] = *s++;
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if (IS_SUBSEQUENT_VARIABLE_LETTER(*s)) {
name[1] = *s++;
} else {
name[1] = 0;
}
// Skip rest of name.
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while (IS_SUBSEQUENT_VARIABLE_LETTER(*s)) {
s++;
}
for (var = 0; var < MAX_VARIABLES; var++) {
if (existing_name[0] == 0 && existing_name[1] == 0) {
// First free entry. Allocate it.
existing_name[0] = name[0];
existing_name[1] = name[1];
break;
} else if (existing_name[0] == name[0] && existing_name[1] == name[1]) {
// Found it.
break;
}
existing_name += 2;
}
if (var == MAX_VARIABLES) {
var = OUT_OF_VARIABLE_SPACE;
} else {
// Convert index to address.
var = FIRST_VARIABLE + 2*var;
// Advance pointer.
*buffer = s;
}
return (uint8_t) var;
}
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/**
* Find the address of a line in the compiled buffer, or 0xFFFF if not found.
*/
static uint16_t find_line_address(uint16_t line_number) {
int i;
for (i = 0; i < g_line_address_count; i++) {
if (g_line_address[i*2] == line_number) {
return g_line_address[i*2 + 1];
}
}
return 0xFFFF;
}
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/**
* 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;
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while (1) {
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if (IS_DIGIT(*s)) {
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// Parse number.
uint16_t value;
if (have_value_in_ax) {
// Push on the number stack.
add_call(pushax);
}
value = parse_uint16(&s);
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compile_load_ax(value);
have_value_in_ax = 1;
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} else if (IS_FIRST_VARIABLE_LETTER(*s)) {
// Variable reference.
uint8_t var = find_variable(&s);
if (have_value_in_ax) {
// Push on the number stack.
add_call(pushax);
}
if (var == OUT_OF_VARIABLE_SPACE) {
// TODO: Not sure how to deal with this. For now just
// fill in with zero, since assigning to this elsewhere
// will cause an error.
compile_load_ax(0);
} else {
// Load from var.
g_compiled[g_compiled_length++] = I_LDA_ZPG;
g_compiled[g_compiled_length++] = var;
g_compiled[g_compiled_length++] = I_LDX_ZPG;
g_compiled[g_compiled_length++] = var + 1;
}
have_value_in_ax = 1;
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} else if (*s == T_PLUS) {
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plus_count += 1;
s += 1;
} else {
break;
}
}
while (plus_count > 0) {
add_call(tosaddax);
plus_count -= 1;
}
return s;
}
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/**
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* Tokenize a string in place. Returns (and removes) any line number, or
* INVALID_LINE_NUMBER if there's none.
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*/
static uint16_t tokenize(uint8_t *s) {
uint8_t *t = s; // Tokenized version.
int16_t line_number;
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// Parse optional line number.
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if (IS_DIGIT(*s)) {
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line_number = parse_uint16(&s);
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} else {
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line_number = INVALID_LINE_NUMBER;
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}
// Convert tokens.
while (*s != '\0') {
if (*s == ' ') {
// Skip spaces.
s++;
} else {
int16_t i;
uint8_t *skipped = 0;
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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.
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*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.
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*/
static uint8_t *find_line(uint16_t line_number) {
uint8_t *line = g_program;
uint8_t *next_line;
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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;
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}
line = next_line;
}
return line;
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}
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/**
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* Call to configure the compilation step.
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*/
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static void set_up_compile(void) {
g_compiled_length = 0;
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g_line_address_count = 0;
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}
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/**
* Compile the tokenized line of BASIC, adding it to the g_compiled binary.
*/
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static void compile_buffer(uint8_t *buffer, uint16_t line_number) {
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uint8_t *s = buffer;
uint8_t done;
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do {
int8_t error = 0;
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// Default to being done after one statement.
done = 1;
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if (*s == '\0' || *s == ':') {
// Empty statement. We skip the colon below.
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} else if (IS_FIRST_VARIABLE_LETTER(*s)) {
// Must be variable assignment.
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uint8_t var = find_variable(&s);
if (var == OUT_OF_VARIABLE_SPACE) {
// TODO: Nicer error specifically for out of variable space.
error = 1;
} else {
if (*s != T_EQUALS) {
error = 1;
} else {
s += 1;
// Parse address.
s = compile_expression(s);
// Copy to var.
g_compiled[g_compiled_length++] = I_STA_ZPG;
g_compiled[g_compiled_length++] = var;
g_compiled[g_compiled_length++] = I_STX_ZPG;
g_compiled[g_compiled_length++] = var + 1;
}
}
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} else if (*s == T_HOME) {
s += 1;
add_call(home);
} else if (*s == T_PRINT) {
s += 1;
if (*s != '\0' && *s != ':') {
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// Parse expression.
s = compile_expression(s);
add_call(print_int);
}
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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;
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if (*s != ',') {
error = 1;
} else {
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s++;
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// 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;
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}
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} else if (*s == T_GOTO) {
s += 1;
if (!IS_DIGIT(*s)) {
error = 1;
} else {
uint16_t target_line_number = parse_uint16(&s);
uint16_t addr = find_line_address(target_line_number);
if (addr == 0xFFFF) {
// Line not found.
// TODO better error message.
error = 1;
} else {
g_compiled[g_compiled_length++] = I_JMP_ABS;
g_compiled[g_compiled_length++] = addr & 0xFF;
g_compiled[g_compiled_length++] = addr >> 8;
}
}
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} else {
error = 1;
}
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// Now we're at the end of our statement.
if (!error) {
if (*s == ':') {
// Skip colon.
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s += 1;
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// Next statement.
done = 0;
} else if (*s != '\0') {
// Junk at the end of the statement.
error = 1;
}
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}
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if (error) {
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if (line_number != INVALID_LINE_NUMBER) {
compile_load_ax(line_number);
add_call(syntax_error_in_line);
} else {
add_call(syntax_error);
}
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}
} while (!done);
}
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/**
* 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;
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// Size of program (including initial address).
debug_port[0] = 2 + g_compiled_length;
// Address of program start, little endian.
debug_port[1] = ((uint16_t) &g_compiled[0]) & 0xFF;
debug_port[1] = ((uint16_t) &g_compiled[0]) >> 8;
// Program bytes.
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for (i = 0; i < g_compiled_length; i++) {
debug_port[1] = g_compiled[i];
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}
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}
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();
}
}
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/**
* Clear out all variables. This does not clear their value, only our
* knowledge of them.
*/
void clear_variables(void) {
memset(g_variable_names, 0, sizeof(g_variable_names));
}
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/**
* Compile the stored program and execute it.
*/
static void compile_stored_program(void) {
uint8_t *line = g_program;
uint8_t *next_line;
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// Clear out all variables.
clear_variables();
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set_up_compile();
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// Generate code to zero out all variable values. Do this in the program
// itself because each RUN should clear them out.
add_call(clear_variable_values);
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while ((next_line = get_next_line(line)) != 0) {
uint16_t line_number = get_line_number(line);
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// Store address of line in compiled buffer.
if (g_line_address_count == MAX_LINES) {
// TODO not sure what to do here.
print("Program too large");
break;
} else {
g_line_address[g_line_address_count++] = line_number;
g_line_address[g_line_address_count++] = (uint16_t) (g_compiled + g_compiled_length);
}
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compile_buffer(line + 4, line_number);
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line = next_line;
}
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complete_compile_and_execute();
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}
/**
* 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.
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if (g_input_buffer[0] == T_RUN) {
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// We don't compile "RUN".
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compile_stored_program();
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} else if (g_input_buffer[0] == T_NEW) {
// We don't compile "NEW".
new_statement();
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} else {
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// Compile the immediate mode line.
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set_up_compile();
compile_buffer(g_input_buffer, INVALID_LINE_NUMBER);
complete_compile_and_execute();
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}
} 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;
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if (next_line == 0 || get_line_number(line) != line_number) {
// Didn't find line. Insert it here.
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// 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;
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// Line number.
*((uint16_t *) (line + 2)) = line_number;
// Buffer and nul.
memmove(line + 4, g_input_buffer, buffer_length + 1);
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} 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);
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} 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;
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}
}
}
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}
int16_t main(void)
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{
int16_t blink;
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// Clear stored program.
new_statement();
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// Clear out all variables.
clear_variables();
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// Initialize UI.
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home();
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// Display the character set.
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/*
if (1) {
int16_t i;
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for (i = 0; i < 256; i++) {
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uint8_t *loc;
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// 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);
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}
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*/
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// Print title.
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move_cursor((40 - title_length) / 2, 0);
print(title);
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// Prompt.
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print("\n\n]");
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// Keyboard input.
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blink = 0;
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g_input_buffer_length = 0;
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show_cursor();
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while(1) {
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// Blink cursor.
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blink += 1;
if (blink == 3000) {
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if (g_showing_cursor) {
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hide_cursor();
} else {
show_cursor();
}
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blink = 0;
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}
if(keyboard_test()) {
hide_cursor();
while(keyboard_test()) {
uint8_t key;
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key = keyboard_get();
if (key == 8) {
// Backspace.
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if (g_input_buffer_length > 0) {
move_cursor(g_cursor_x - 1, g_cursor_y);
g_input_buffer_length -= 1;
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}
} else if (key == 13) {
// Return.
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clear_to_eol();
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print_char('\n');
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process_input_buffer();
print("\n]");
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g_input_buffer_length = 0;
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} else {
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if (g_input_buffer_length < sizeof(g_input_buffer) - 1) {
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uint8_t *loc = cursor_pos();
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*loc = key | 0x80;
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move_cursor(g_cursor_x + 1, g_cursor_y);
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g_input_buffer[g_input_buffer_length++] = key;
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}
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}
}
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show_cursor();
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}
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}
return 0;
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}