117 lines
2.8 KiB
C
117 lines
2.8 KiB
C
/* RETRO ------------------------------------------------------
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A personal, minimalistic forth
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Copyright (c) 2016 - 2020 Charles Childers
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This is a minimalist implementation of an interactive
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RETRO system with an embedded image and the listerner loop
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being written in RETRO.
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Building:
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cp ngaImage barebones.image
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retro-extend barebones.image interface/barebones.retro
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retro-embedimage barebones.image >vm/nga-c/barebones_image.c
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cd vm/nga-c
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make barebones
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---------------------------------------------------------- */
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <limits.h>
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#define CELL int32_t
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#define CELL_MIN INT_MIN + 1
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#define CELL_MAX INT_MAX - 1
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#define IMAGE_SIZE 242000 /* Amount of RAM. 968kB by default. */
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#define ADDRESSES 256 /* Depth of address stack */
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#define STACK_DEPTH 128 /* Depth of data stack */
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CELL sp, rp, ip; /* Data, address, instruction pointers */
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CELL data[STACK_DEPTH]; /* The data stack */
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CELL address[ADDRESSES]; /* The address stack */
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CELL memory[IMAGE_SIZE + 1]; /* The memory for the image */
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#define TOS data[sp] /* Shortcut for top item on stack */
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#define NOS data[sp-1] /* Shortcut for second item on stack */
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#define TORS address[rp] /* Shortcut for top item on address stack */
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#define NUM_DEVICES 2
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typedef void (*Handler)(void);
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Handler IO_deviceHandlers[NUM_DEVICES + 1];
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Handler IO_queryHandlers[NUM_DEVICES + 1];
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#include "barebones_image.c"
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CELL stack_pop();
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void stack_push(CELL value);
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void execute(CELL cell);
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CELL load_image();
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void prepare_vm();
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void process_opcode(CELL opcode);
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void process_opcode_bundle(CELL opcode);
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int validate_opcode_bundle(CELL opcode);
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CELL stack_pop() {
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sp--;
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return data[sp + 1];
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}
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void stack_push(CELL value) {
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sp++;
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data[sp] = value;
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}
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void generic_output() {
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putc(stack_pop(), stdout);
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fflush(stdout);
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}
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void generic_output_query() {
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stack_push(0);
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stack_push(0);
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}
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void generic_input() {
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stack_push(getc(stdin));
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if (TOS == 127) TOS = 8;
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}
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void generic_input_query() {
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stack_push(0);
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stack_push(1);
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}
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void execute(CELL cell) {
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CELL opcode;
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rp = 1;
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ip = cell;
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while (ip < IMAGE_SIZE) {
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opcode = memory[ip];
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if (validate_opcode_bundle(opcode) != 0) {
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process_opcode_bundle(opcode);
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} else {
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printf("Invalid instruction!\n");
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exit(1);
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}
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ip++;
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if (rp == 0)
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ip = IMAGE_SIZE;
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}
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}
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int main(int argc, char **argv) {
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IO_deviceHandlers[0] = generic_output;
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IO_deviceHandlers[1] = generic_input;
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IO_queryHandlers[0] = generic_output_query;
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IO_queryHandlers[1] = generic_input_query;
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prepare_vm();
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load_image();
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execute(0);
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exit(0);
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}
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#include "nga.c"
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