Fixed a bug with processing multiple input files. Added C implementation.

bf.c

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