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interpreter.c
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interpreter.c
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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "eli.h"
#include "parser.h"
#define MAXIMUM_STACK_SIZE 128 // Maximum depth of nested conditions.
#define MAXIMUM_ARRAY_SIZE 200 // Size of the main memory.
// Stack memory.
Instruction* stack[MAXIMUM_STACK_SIZE];
// Current size of the stack & first unused stack field.
int s_top = 0;
// Push instruction address onto the stack.
// Push, Pop and Top functions are used for conditional statements and loops.
void push(Instruction* addr) {
if ((s_top+1) >= MAXIMUM_STACK_SIZE)
error("Stack overflow.");
stack[s_top++] = addr;
}
// Remove one address from the stack.
void pop() {
if (s_top <= 0)
error("Stack underflow.");
s_top--;
}
// Get instruction address from the stack.
Instruction* top() {
return stack[s_top-1];
}
// Skip whole block of code after unsatisfied condition.
// Function can terminate program if unexpected EOF is inside the loop block.
Instruction* skip(Instruction* inst) {
int depth = 0;
while (*inst != EXIT) {
switch (*inst) {
case BRZ:
depth++;
break;
case BNZ:
depth--;
if (!depth)
return inst;
default:
break;
}
inst++;
}
error("Unexpected end of program.");
return NULL; // not reachable
}
// Dump content of the memory to stdout.
void dump_memory(int *array) {
int i, j;
printf("\n Mem |");
for (i = 0; i < 30; i++)
printf("%3d ", i);
printf("\n-------|");
for (i = 0; i < 30; i++)
printf("----");
printf("\n");
for (i = 0; i < MAXIMUM_ARRAY_SIZE; i+= 30) {
printf("%6d |", i);
for (j = 0; j < 30 && j+i < MAXIMUM_ARRAY_SIZE; j++)
printf("%3d ", array[i+j]);
printf("\n");
}
}
// Dump sequence of instructions to stdout.
void dump_instructions(Instruction* inst) {
int i;
printf("Instruction dump:\n");
for (i = 0; *inst != EXIT; i++, inst++) {
printf("%s ", InstructionTable[*inst]);
if (i == 30) {
i = 0;
printf("\n");
}
}
printf("\n\n");
}
// Run the virtual machine.
void run(Instruction* inst) {
int array[MAXIMUM_ARRAY_SIZE];
int ptr = 0;
memset(array, 0, MAXIMUM_ARRAY_SIZE * sizeof(int));
while (*inst != EXIT) {
switch (*inst) {
case INC:
array[ptr]++;
break;
case DEC:
array[ptr]--;
break;
case FWD:
ptr++;
break;
case BWD:
ptr--;
break;
case PRINTC:
putchar(array[ptr]);
break;
case SCANC:
array[ptr] = getchar();
break;
case BRZ:
if (array[ptr])
push(inst);
else
inst = skip(inst);
break;
case BNZ:
if (array[ptr])
inst = top();
else
pop();
break;
default:
error("Unknown instruction!");
break;
}
inst++;
}
if (r_memory_dump)
dump_memory((int*)&array);
}
// Print help block into stdout.
void help(char* name) {
printf("Esoteric language interpreter (ELI)\n");
printf("Usage:\n");
printf(" %s -ilm [FILE]\n\n", name);
printf(" i flag dumps used instructions.\n");
printf(" l flag shows used language.\n");
printf(" m flag dumps memory at the end of execution.\n");
exit(EXIT_SUCCESS);
}
int main(int argc, char *argv[]) {
char c;
if (argc < 2) help(argv[0]);
while ((c = getopt(argc, argv, "ilm")) != -1) {
switch (c) {
case 'i':
r_instr_dump = true;
break;
case 'l':
r_lang_dump = true;
break;
case 'm':
r_memory_dump = true;
break;
default:
printf("Unknown flag.\n");
help(argv[0]);
break;
}
}
Instruction* inst = parseFile(argv[optind]);
if (r_instr_dump)
dump_instructions(inst);
run(inst);
free(inst);
return EXIT_SUCCESS;
}