wrjpgcom.c

game engine, which is useful for everyone who is interested in it. I hope you can enjoy it.

  /* Expect SOI at start of file */
  if (first_marker() != M_SOI)
    ERREXIT("Expected SOI marker first");
  write_marker(M_SOI);

  /* Scan miscellaneous markers until we reach SOFn. */
  for (;;) {
    marker = next_marker();
    switch (marker) {
      /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be,
       * treated as SOFn.  C4 in particular is actually DHT.
       */
    case M_SOF0:		/* Baseline */
    case M_SOF1:		/* Extended sequential, Huffman */
    case M_SOF2:		/* Progressive, Huffman */
    case M_SOF3:		/* Lossless, Huffman */
    case M_SOF5:		/* Differential sequential, Huffman */
    case M_SOF6:		/* Differential progressive, Huffman */
    case M_SOF7:		/* Differential lossless, Huffman */
    case M_SOF9:		/* Extended sequential, arithmetic */
    case M_SOF10:		/* Progressive, arithmetic */
    case M_SOF11:		/* Lossless, arithmetic */
    case M_SOF13:		/* Differential sequential, arithmetic */
    case M_SOF14:		/* Differential progressive, arithmetic */
    case M_SOF15:		/* Differential lossless, arithmetic */
      return marker;

    case M_SOS:			/* should not see compressed data before SOF */
      ERREXIT("SOS without prior SOFn");
      break;

    case M_EOI:			/* in case it's a tables-only JPEG stream */
      return marker;

    case M_COM:			/* Existing COM: conditionally discard */
      if (keep_COM) {
	write_marker(marker);
	copy_variable();
      } else {
	skip_variable();
      }
      break;

    default:			/* Anything else just gets copied */
      write_marker(marker);
      copy_variable();		/* we assume it has a parameter count... */
      break;
    }
  } /* end loop */
}


/* Command line parsing code */

static const char * progname;	/* program name for error messages */


static void
usage (void)
/* complain about bad command line */
{
  fprintf(stderr, "wrjpgcom inserts a textual comment in a JPEG file.\n");
  fprintf(stderr, "You can add to or replace any existing comment(s).\n");

  fprintf(stderr, "Usage: %s [switches] ", progname);
#ifdef TWO_FILE_COMMANDLINE
  fprintf(stderr, "inputfile outputfile\n");
#else
  fprintf(stderr, "[inputfile]\n");
#endif

  fprintf(stderr, "Switches (names may be abbreviated):\n");
  fprintf(stderr, "  -replace         Delete any existing comments\n");
  fprintf(stderr, "  -comment \"text\"  Insert comment with given text\n");
  fprintf(stderr, "  -cfile name      Read comment from named file\n");
  fprintf(stderr, "Notice that you must put quotes around the comment text\n");
  fprintf(stderr, "when you use -comment.\n");
  fprintf(stderr, "If you do not give either -comment or -cfile on the command line,\n");
  fprintf(stderr, "then the comment text is read from standard input.\n");
  fprintf(stderr, "It can be multiple lines, up to %u characters total.\n",
	  (unsigned int) MAX_COM_LENGTH);
#ifndef TWO_FILE_COMMANDLINE
  fprintf(stderr, "You must specify an input JPEG file name when supplying\n");
  fprintf(stderr, "comment text from standard input.\n");
#endif

  exit(EXIT_FAILURE);
}


static int
keymatch (char * arg, const char * keyword, int minchars)
/* Case-insensitive matching of (possibly abbreviated) keyword switches. */
/* keyword is the constant keyword (must be lower case already), */
/* minchars is length of minimum legal abbreviation. */
{
  register int ca, ck;
  register int nmatched = 0;

  while ((ca = *arg++) != '\0') {
    if ((ck = *keyword++) == '\0')
      return 0;			/* arg longer than keyword, no good */
    if (isupper(ca))		/* force arg to lcase (assume ck is already) */
      ca = tolower(ca);
    if (ca != ck)
      return 0;			/* no good */
    nmatched++;			/* count matched characters */
  }
  /* reached end of argument; fail if it's too short for unique abbrev */
  if (nmatched < minchars)
    return 0;
  return 1;			/* A-OK */
}


/*
 * The main program.
 */

int
main (int argc, char **argv)
{
  int argn;
  char * arg;
  int keep_COM = 1;
  char * comment_arg = NULL;
  FILE * comment_file = NULL;
  unsigned int comment_length = 0;
  int marker;

  /* On Mac, fetch a command line. */
#ifdef USE_CCOMMAND
  argc = ccommand(&argv);
#endif

  progname = argv[0];
  if (progname == NULL || progname[0] == 0)
    progname = "wrjpgcom";	/* in case C library doesn't provide it */

  /* Parse switches, if any */
  for (argn = 1; argn < argc; argn++) {
    arg = argv[argn];
    if (arg[0] != '-')
      break;			/* not switch, must be file name */
    arg++;			/* advance over '-' */
    if (keymatch(arg, "replace", 1)) {
      keep_COM = 0;
    } else if (keymatch(arg, "cfile", 2)) {
      if (++argn >= argc) usage();
      if ((comment_file = fopen(argv[argn], "r")) == NULL) {
	fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
	exit(EXIT_FAILURE);
      }
    } else if (keymatch(arg, "comment", 1)) {
      if (++argn >= argc) usage();
      comment_arg = argv[argn];
      /* If the comment text starts with '"', then we are probably running
       * under MS-DOG and must parse out the quoted string ourselves.  Sigh.
       */
      if (comment_arg[0] == '"') {
	comment_arg = (char *) malloc((size_t) MAX_COM_LENGTH);
	if (comment_arg == NULL)
	  ERREXIT("Insufficient memory");
	strcpy(comment_arg, argv[argn]+1);
	for (;;) {
	  comment_length = (unsigned int) strlen(comment_arg);
	  if (comment_length > 0 && comment_arg[comment_length-1] == '"') {
	    comment_arg[comment_length-1] = '\0'; /* zap terminating quote */
	    break;
	  }
	  if (++argn >= argc)
	    ERREXIT("Missing ending quote mark");
	  strcat(comment_arg, " ");
	  strcat(comment_arg, argv[argn]);
	}
      }
      comment_length = (unsigned int) strlen(comment_arg);
    } else
      usage();
  }

  /* Cannot use both -comment and -cfile. */
  if (comment_arg != NULL && comment_file != NULL)
    usage();
  /* If there is neither -comment nor -cfile, we will read the comment text
   * from stdin; in this case there MUST be an input JPEG file name.
   */
  if (comment_arg == NULL && comment_file == NULL && argn >= argc)
    usage();

  /* Open the input file. */
  if (argn < argc) {
    if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) {
      fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
      exit(EXIT_FAILURE);
    }
  } else {
    /* default input file is stdin */
#ifdef USE_SETMODE		/* need to hack file mode? */
    setmode(fileno(stdin), O_BINARY);
#endif
#ifdef USE_FDOPEN		/* need to re-open in binary mode? */
    if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) {
      fprintf(stderr, "%s: can't open stdin\n", progname);
      exit(EXIT_FAILURE);
    }
#else
    infile = stdin;
#endif
  }

  /* Open the output file. */
#ifdef TWO_FILE_COMMANDLINE
  /* Must have explicit output file name */
  if (argn != argc-2) {
    fprintf(stderr, "%s: must name one input and one output file\n",
	    progname);
    usage();
  }
  if ((outfile = fopen(argv[argn+1], WRITE_BINARY)) == NULL) {
    fprintf(stderr, "%s: can't open %s\n", progname, argv[argn+1]);
    exit(EXIT_FAILURE);
  }
#else
  /* Unix style: expect zero or one file name */
  if (argn < argc-1) {
    fprintf(stderr, "%s: only one input file\n", progname);
    usage();
  }
  /* default output file is stdout */
#ifdef USE_SETMODE		/* need to hack file mode? */
  setmode(fileno(stdout), O_BINARY);
#endif
#ifdef USE_FDOPEN		/* need to re-open in binary mode? */
  if ((outfile = fdopen(fileno(stdout), WRITE_BINARY)) == NULL) {
    fprintf(stderr, "%s: can't open stdout\n", progname);
    exit(EXIT_FAILURE);
  }
#else
  outfile = stdout;
#endif
#endif /* TWO_FILE_COMMANDLINE */

  /* Collect comment text from comment_file or stdin, if necessary */
  if (comment_arg == NULL) {
    FILE * src_file;
    int c;

    comment_arg = (char *) malloc((size_t) MAX_COM_LENGTH);
    if (comment_arg == NULL)
      ERREXIT("Insufficient memory");
    comment_length = 0;
    src_file = (comment_file != NULL ? comment_file : stdin);
    while ((c = getc(src_file)) != EOF) {
      if (comment_length >= (unsigned int) MAX_COM_LENGTH) {
	fprintf(stderr, "Comment text may not exceed %u bytes\n",
		(unsigned int) MAX_COM_LENGTH);
	exit(EXIT_FAILURE);
      }
      comment_arg[comment_length++] = (char) c;
    }
    if (comment_file != NULL)
      fclose(comment_file);
  }

  /* Copy JPEG headers until SOFn marker;
   * we will insert the new comment marker just before SOFn.
   * This (a) causes the new comment to appear after, rather than before,
   * existing comments; and (b) ensures that comments come after any JFIF
   * or JFXX markers, as required by the JFIF specification.
   */
  marker = scan_JPEG_header(keep_COM);
  /* Insert the new COM marker, but only if nonempty text has been supplied */
  if (comment_length > 0) {
    write_marker(M_COM);
    write_2_bytes(comment_length + 2);
    while (comment_length > 0) {
      write_1_byte(*comment_arg++);
      comment_length--;
    }
  }
  /* Duplicate the remainder of the source file.
   * Note that any COM markers occuring after SOF will not be touched.
   */
  write_marker(marker);
  copy_rest_of_file();

  /* All done. */
  exit(EXIT_SUCCESS);
  return 0;			/* suppress no-return-value warnings */
}