Fixed bugs in `rshift` subroutine.

[vvhitespace] / vv_compiler.c

/*
* (c) 2019 Aaron Taylor <ataylor at subgeniuskitty dot com>
* All rights reserved.
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <getopt.h>
#include <stdint.h>

#define VERSION 1

void
print_usage(char ** argv)
{
   printf( "VVhitespace Interpreter v%d (www.subgeniuskitty.com)\n"
           "Usage: %s -i <file> -o <file>\n"
           "  -h         Help (prints this message)\n"
           "  -i <file>  Specify a pseudo-VVhitespace source file as input.\n"
           "  -o <file>  Specify location for VVhitespace output.\n"
           , VERSION, argv[0]
   );
}

/* Builds an ASCII string on the stack using VVS PUSH_IMMEDIATE commands.    */
/* The syntax: A"test" results in six PUSH_IMMEDIATE commands for the four   */
/*   letters, newline, and null-terminator.                                  */
/* Expects 'input' to present a double-quoted ('"') ASCII string.            */
/* The 'A' has already been chomped.                                         */
void
parse_ascii_string(FILE * input, FILE * output)
{
   uint8_t temp_byte;
   fread(&temp_byte, 1, 1, input);
   if (temp_byte != '"') {
       /* Die here since we walk the string backward and look for '"' as a terminator. */
       fprintf(stderr, "ERROR: Expected double-quote to begin string.\n");
       exit(EXIT_FAILURE);
   }

   /* Put the letters on the stack in reverse. Don't forget to put a null-terminator first. */
   for (fread(&temp_byte,1,1,input); temp_byte != '"'; fread(&temp_byte,1,1,input)) continue;
   temp_byte = '\0';

   while (temp_byte != '"') {
       /* First, push three spaces to start a PUSH_IMMEDIATE command for a positive number. */
       uint8_t temp_output = ' ';
       for(int i=0;i<3;i++) fwrite(&temp_output, 1, 1, output);
       /* Second, push the ASCII character, 7 bits total, most significant bit first. */
       /* Remember, [Tab]=1 and [Space]=0. */
       uint8_t index = 7; /* 7 bits needed per ASCII character. */
       while (index) {
           ((temp_byte >> (index-1)) & 1) ? (temp_output = '\t') : (temp_output = ' ');
           fwrite(&temp_output, 1, 1, output);
           index--;
       }
       /* Third, close the number with a newline. */
       temp_output = '\n';
       fwrite(&temp_output, 1, 1, output);

       /* Read the next byte to prepare for the loop test. */
       fseek(input, -2, SEEK_CUR);
       fread(&temp_byte, 1, 1, input);
   }
}

int
main(int argc, char ** argv)
{
   /*
    * Process command line arguments
    */
   int c;
   FILE * input = NULL, * output = NULL;
   while ((c = getopt(argc,argv,"i:o:h")) != -1) {
       switch (c) {
           case 'i':
               if ((input = fopen(optarg, "r")) == NULL) {
                   fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
               }
               break;
           case 'o':
               if ((output = fopen(optarg, "w+")) == NULL) {
                   fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
               }
               break;
           case 'h':
               print_usage(argv);
               exit(EXIT_SUCCESS);
               break;
           default:
               break;
       }
   }
   if (input == NULL) {
       fprintf(stderr, "ERROR: Must specify a pseudo-VVhitespace source file with -i flag.\n");
       print_usage(argv);
       exit(EXIT_FAILURE);
   }
   if (output == NULL) {
       fprintf(stderr, "ERROR: Must specify destination for VVhitespace source file with -o flag.\n");
       print_usage(argv);
       exit(EXIT_FAILURE);
   }

   /*
    * Main Loop
    */
   uint8_t temp_byte;
   while (fread(&temp_byte, 1, 1, input)) {
       switch (temp_byte) {
           case 't':
           case 'T':
               temp_byte = '\t';
               fwrite(&temp_byte, 1, 1, output);
               break;
           case 's':
           case 'S':
               temp_byte = ' ';
               fwrite(&temp_byte, 1, 1, output);
               break;
           case 'n':
           case 'N':
               temp_byte = '\n';
               fwrite(&temp_byte, 1, 1, output);
               break;
           case 'v':
           case 'V':
               temp_byte = '\v';
               fwrite(&temp_byte, 1, 1, output);
               break;
           case 'a':
           case 'A':
               parse_ascii_string(input, output);
               break;
           case '\n':
               /* Intentionally empty */
               break;
           default:
               /* The first non-[tTsSnNvVaA] character begins a comment lasting until end of line. */
               while (fread(&temp_byte, 1, 1, input)) {
                   if (temp_byte == '\n') break;
               }
               break;
       }
   }

   /*
    * Cleanup and exit
    */
   fclose(input);
   fclose(output);

   exit(EXIT_SUCCESS);
}