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Handle forward GOTOs.

This commit is contained in:
Lawrence Kesteloot 2018-08-04 17:32:36 -07:00
parent d5ce35342e
commit 013056e778
3 changed files with 161 additions and 32 deletions
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184
main.c
View File

@ -89,6 +89,9 @@ uint8_t title_length = 9;
// Maximum number of operators in the operator stack.
#define MAX_OP_STACK 16
// Maximum number of forward GOTOs.
#define MAX_FORWARD_GOTO 16
// Test for whether a character is a digit.
#define IS_DIGIT(ch) ((ch) >= '0' && (ch) <= '9')
@ -96,6 +99,28 @@ uint8_t title_length = 9;
#define IS_FIRST_VARIABLE_LETTER(ch) ((ch) >= 'A' && (ch) <= 'Z')
#define IS_SUBSEQUENT_VARIABLE_LETTER(ch) (IS_FIRST_VARIABLE_LETTER(ch) || IS_DIGIT(ch))
// Info for each "forward GOTO", which is a GOTO to a line that we've
// not compiled yet.
typedef struct {
// The line number the GOTO is on. This is for error messages.
uint16_t source_line_number;
// The line number it's trying to jump to.
uint16_t target_line_number;
// The address of the JMP instructions. This is 0 if this entry is unused.
uint8_t *jmp_address;
} ForwardGoto;
// Info for each compiled line.
typedef struct {
// The line's number.
uint16_t line_number;
// The address in memory where its code was compiled.
uint8_t *code;
} LineInfo;
// List of tokens. The token value is the index plus 0x80.
static uint8_t *TOKEN[] = {
"HOME",
@ -139,17 +164,20 @@ void (*g_compiled_function)() = (void (*)()) g_compiled;
// - Nul.
uint8_t g_program[1024];
// 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;
// Info about each compiled line.
LineInfo g_line_info[MAX_LINES];
uint8_t g_line_info_count;
// Operator stack, of the expression-evaluation routines. These are from the
// OP_ constants.
uint8_t g_op_stack[MAX_OP_STACK];
uint8_t g_op_stack_size = 0;
// List of all forward GOTOs. These are packed at the beginning, so the
// first invalid (jmp_address == 0) entry marks the end.
ForwardGoto g_forward_goto[MAX_FORWARD_GOTO];
uint8_t g_forward_goto_count = 0;
/**
* Print the tokenized string, with tokens displayed as their full text.
* Prints a newline at the end.
@ -350,18 +378,20 @@ static uint8_t find_variable(uint8_t **buffer) {
}
/**
* Find the address of a line in the compiled buffer, or 0xFFFF if not found.
* Find the address of a line in the compiled buffer, or 0 if not found.
*/
static uint16_t find_line_address(uint16_t line_number) {
static uint8_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];
for (i = 0; i < g_line_info_count; i++) {
LineInfo *l = &g_line_info[i];
if (l->line_number == line_number) {
return l->code;
}
}
return 0xFFFF;
return 0;
}
/**
@ -593,6 +623,7 @@ static uint16_t tokenize(uint8_t *s) {
int16_t i;
uint8_t *skipped = 0;
// Try every token.
for (i = 0; i < TOKEN_COUNT; i++) {
skipped = skip_over(s, TOKEN[i]);
if (skipped != 0) {
@ -636,12 +667,84 @@ static uint8_t *find_line(uint16_t line_number) {
return line;
}
/**
* Adds a new entry to the list for forward GOTOs. Returns whether successful.
*/
static uint8_t add_forward_goto(uint16_t source_line_number, uint16_t target_line_number,
uint8_t *jmp_address) {
ForwardGoto *f;
if (g_forward_goto_count == MAX_FORWARD_GOTO) {
return 0;
}
f = &g_forward_goto[g_forward_goto_count++];
f->source_line_number = source_line_number;
f->target_line_number = target_line_number;
f->jmp_address = jmp_address;
return 1;
}
/**
* Go through the list of forward GOTOs and set their jumps to this code.
*/
static void fix_up_forward_gotos(uint16_t line_number, uint8_t *code) {
int i;
ForwardGoto *f;
uint16_t addr = (uint16_t) code;
for (i = 0; i < g_forward_goto_count; i++) {
f = &g_forward_goto[i];
if (f->target_line_number == line_number) {
// Fill in jump address.
f->jmp_address[1] = addr & 0xFF;
f->jmp_address[2] = addr >> 8;
// Swap last entry with this one. It's okay if these
// are the same entry.
*f = g_forward_goto[g_forward_goto_count - 1];
// Reduce size of array.
g_forward_goto_count -= 1;
// Re-process this entry, since we've swapped it.
i -= 1;
}
}
}
/**
* Adds an entry to the list of line infos. Returns whether successful.
*/
static uint8_t add_line_info(uint16_t line_number, uint8_t *code) {
LineInfo *l;
if (g_line_info_count == MAX_LINES) {
// TODO not sure what to do here.
print("Program too large");
return 0;
}
l = &g_line_info[g_line_info_count++];
l->line_number = line_number;
l->code = code;
// Fix up any forward GOTOs to this line.
fix_up_forward_gotos(line_number, code);
return 1;
}
/**
* Call to configure the compilation step.
*/
static void set_up_compile(void) {
g_compiled_length = 0;
g_line_address_count = 0;
g_line_info_count = 0;
g_forward_goto_count = 0;
}
/**
@ -726,17 +829,21 @@ static void compile_buffer(uint8_t *buffer, uint16_t line_number) {
error = 1;
} else {
uint16_t target_line_number = parse_uint16(&s);
uint16_t addr = find_line_address(target_line_number);
uint16_t addr = (uint16_t) 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;
if (addr == 0) {
// Line not found. Must be a forward GOTO. Record it
// and keep going.
uint8_t success = add_forward_goto(line_number, target_line_number,
&g_compiled[g_compiled_length]);
if (!success) {
// TODO handle error.
}
}
g_compiled[g_compiled_length++] = I_JMP_ABS;
g_compiled[g_compiled_length++] = addr & 0xFF;
g_compiled[g_compiled_length++] = addr >> 8;
}
} else if (*s == T_IF) {
uint16_t saved_compiled_length = g_compiled_length;
@ -824,6 +931,7 @@ static void compile_buffer(uint8_t *buffer, uint16_t line_number) {
} else {
add_call(syntax_error);
}
// Terminate program.
// TODO This won't work after a GOSUB. Maybe we should have our
// own stack for that.
add_return();
@ -840,11 +948,30 @@ static void compile_buffer(uint8_t *buffer, uint16_t line_number) {
* Complete the compilation buffer and run it.
*/
static void complete_compile_and_execute(void) {
int i;
// Return from function.
add_return();
// Forward GOTOs that couldn't be resolved are changed to
// jumps to error messages.
for (i = 0; i < g_forward_goto_count; i++) {
ForwardGoto *f = &g_forward_goto[i];
uint16_t addr = (uint16_t) &g_compiled[g_compiled_length];
// Jump to end of buffer.
f->jmp_address[1] = addr & 0xFF;
f->jmp_address[2] = addr >> 8;
// Add code at end of buffer to show error.
compile_load_ax(f->source_line_number);
add_call(undefined_statement_error);
// Terminate program.
add_return();
}
// Dump compiled buffer to the terminal.
{
if (1) {
int i;
uint8_t *debug_port = (uint8_t *) 0xBFFE;
@ -894,21 +1021,14 @@ static void compile_stored_program(void) {
while ((next_line = get_next_line(line)) != 0) {
uint16_t line_number = get_line_number(line);
uint8_t success = add_line_info(line_number, g_compiled + g_compiled_length);
// 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);
}
// Compile just this line.
compile_buffer(line + 4, line_number);
line = next_line;
}
complete_compile_and_execute();
}

8
runtime.c
View File

@ -239,6 +239,14 @@ void syntax_error_in_line(uint16_t line_number) {
// No linefeed, assume prompt will do it.
}
/**
* Display an error for a GOTO that went to a line that doesn't exist.
*/
void undefined_statement_error(uint16_t line_number) {
print("\n?UNDEF'D STATEMENT ERROR IN ");
print_int(line_number);
}
/**
* Switch to graphics mode.
*/

1
runtime.h
View File

@ -35,6 +35,7 @@ void print_newline(void);
void syntax_error(void);
void syntax_error_in_line(uint16_t line_number);
void undefined_statement_error(uint16_t line_number);
void gr_statement(void);
void text_statement(void);