162 lines
4.1 KiB
C
162 lines
4.1 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#define EXIT_NO_INPUT 4
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#define TAPE_SIZE 30000
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#define MAX_LOOPS 1024
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static unsigned char tape[TAPE_SIZE]; /* BF memory cells. */
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static long loop_stack[MAX_LOOPS]; /* Loop stack. */
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static unsigned int tape_ptr = 0; /* Current tape position. */
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static unsigned int loop_ptr = 0; /* Loop stack top. */
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int main (int argc, char **argv) {
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FILE * f; /* The input file. */
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unsigned int i; /* The current file being processed. */
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unsigned int l; /* A counter for looping. */
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unsigned int done; /* Boolean for looping. */
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char c; /* Current BF instruction. */
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if (argc == 1) {
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/* There must be at leas one input file. */
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fprintf (stderr, "%s: fatal error: no input files\n", argv[0]);
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return EXIT_NO_INPUT;
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} else {
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/* Process all input files. */
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for (i = 1; i < argc; i++) {
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/* Reset everything. */
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memset (tape, 0, TAPE_SIZE * sizeof (unsigned char));
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memset (loop_stack, 0, MAX_LOOPS * sizeof (long));
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l = 0;
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c = 'a';
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/* Try to open the input file. */
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f = fopen (argv[i], "r");
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if (f == NULL) {
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fprintf (stderr, "Failed to open %s\n", argv[i]);
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continue;
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} else {
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/* If the file opened, then read characters from it one by one. */
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while ((c = fgetc (f)) != EOF) {
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/* Proccess the character. */
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switch (c) {
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case '.':
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/* BF output instruction. */
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putchar (tape[tape_ptr]);
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fflush (stdout);
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break;
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case ',':
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/* BF input instruction. */
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tape[tape_ptr] = (unsigned char) getchar ();
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break;
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case '+':
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/* BF tape increment instruction. */
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tape[tape_ptr]++;
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break;
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case '-':
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/* BF Tape decrement instruction. */
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tape[tape_ptr]--;
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break;
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case '>':
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/* BF move to next cell instruction. */
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tape_ptr = (tape_ptr + 1) % TAPE_SIZE;
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break;
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case '<':
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/* BF move to previous cell instruction. */
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tape_ptr = (tape_ptr == 0) ? TAPE_SIZE - 1 : tape_ptr - 1;
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break;
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case '[':
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/* BF open loop instruction. */
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/* Check if the program has reached the max supported number of open loops. */
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if (loop_ptr == MAX_LOOPS) {
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/* Fail if it has. */
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fprintf (stderr,
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"%s: Fatal error in %s: max number of nested loops reached\n",
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argv[0], argv[i]);
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goto skip;
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} else {
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/* Check if there is something on the tape. */
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if (tape[tape_ptr] != 0) {
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/* If there is, then store the instruction's position on the file
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so that the program car return to it at the loop's end. */
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loop_stack[loop_ptr] = ftell (f);
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loop_ptr++;
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} else {
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/* If there is nothing on the tape, then search for the corresponding loop
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end instruction. */
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done = 0;
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while (!done) {
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/* Read characters from the file until a [, ] or EOF, whichever happens
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first. */
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c = fgetc (f);
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switch(c) {
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case EOF:
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/* Skip the file on EOF. */
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fprintf (stderr, "%s: Fatal error in %s: premature EOF\n", argv[0], argv[i]);
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goto skip;
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break;
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case '[':
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/* If a loop opens, then increase the nested loops counter. */
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l++;
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break;
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case ']':
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/* If a ] instruction is found, */
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if (l > 0)
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l--;
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else
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done = 1;
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break;
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} /* switch(c) */
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} /* while(!done) */
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} /* else (tape[tape_ptr] == 0) */
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} /* else (loop_ptr < MAX_LOOPS) */
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break;
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case ']':
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/* BF close loop instruction. */
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/* Check if there is something on the tape. */
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if (tape[tape_ptr] != 0)
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/* If there is, then jump back to the corresponding ] instruction. */
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fseek (f, loop_stack[loop_ptr - 1], SEEK_SET);
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else
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/* If there is nothing, then remove the loop from the stack and continue. */
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loop_ptr--;
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break;
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default:
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continue;
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} /* switch(c) */
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} /* while(c = fgetc(f)) */
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skip:
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/* Done with this file. */
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fclose (f);
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} /* else (f != NULL) */
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} /* for(i = 1 to argc - 1) */
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} /* else (argc > 1) */
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return EXIT_SUCCESS;
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}
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