    /*
     * wrjpgcom.c
     *
     * Copyright (C) 1994-1997, Thomas G. Lane.
     * Modified 2015-2017 by Guido Vollbeding.
     * This file is part of the Independent JPEG Group's software.
     * For conditions of distribution and use, see the accompanying README file.
     *
     * This file contains a very simple stand-alone application that inserts
     * user-supplied text as a COM (comment) marker in a JFIF file.
     * This may be useful as an example of the minimum logic needed to parse
     * JPEG markers.
     */

    #define JPEG_CJPEG_DJPEG	/* to get the command-line config symbols */
    #include "jinclude.h"		/* get auto-config symbols, <stdio.h> */

    #ifndef HAVE_STDLIB_H		/* <stdlib.h> should declare malloc() */
    extern void * malloc ();
    #endif
    #include <ctype.h>		/* to declare isupper(), tolower() */
    #ifdef USE_SETMODE
    #include <fcntl.h>		/* to declare setmode()'s parameter macros */
    /* If you have setmode() but not <io.h>, just delete this line: */
    #include <io.h>			/* to declare setmode() */
    #endif

    #ifdef USE_CCOMMAND		/* command-line reader for Macintosh */
    #ifdef __MWERKS__
    #include <SIOUX.h>              /* Metrowerks needs this */
    #include <console.h>		/* ... and this */
    #endif
    #ifdef THINK_C
    #include <console.h>		/* Think declares it here */
    #endif
    #endif

    #ifdef DONT_USE_B_MODE		/* define mode parameters for fopen() */
    #define READ_BINARY	"r"
    #define WRITE_BINARY	"w"
    #else
    #ifdef VMS			/* VMS is very nonstandard */
    #define READ_BINARY	"rb", "ctx=stm"
    #define WRITE_BINARY	"wb", "ctx=stm"
    #else				/* standard ANSI-compliant case */
    #define READ_BINARY	"rb"
    #define WRITE_BINARY	"wb"
    #endif
    #endif

    #ifndef EXIT_FAILURE		/* define exit() codes if not provided */
    #define EXIT_FAILURE  1
    #endif
    #ifndef EXIT_SUCCESS
    #ifdef VMS
    #define EXIT_SUCCESS  1		/* VMS is very nonstandard */
    #else
    #define EXIT_SUCCESS  0
    #endif
    #endif

    /* Reduce this value if your malloc() can't allocate blocks up to 64K.
     * On DOS, compiling in large model is usually a better solution.
     */

    #ifndef MAX_COM_LENGTH
    #define MAX_COM_LENGTH 65000L	/* must be <= 65533 in any case */
    #endif

    /*
     * These macros are used to read the input file and write the output file.
     * To reuse this code in another application, you might need to change these.
     */

    static FILE * infile;		/* input JPEG file */

    /* Return next input byte, or EOF if no more */
    #define NEXTBYTE()  getc(infile)

    static FILE * outfile;		/* output JPEG file */

    /* Emit an output byte */
    #define PUTBYTE(x)  putc((x), outfile)

    /* Error exit handler */
    #define ERREXIT(msg)  (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE))

    /* Read one byte, testing for EOF */
    static int
    read_1_byte (void)
    {
      int c;

      c = NEXTBYTE();
      if (c == EOF)
        ERREXIT("Premature EOF in JPEG file");
      return c;
    }

    /* Read 2 bytes, convert to unsigned int */
    /* All 2-byte quantities in JPEG markers are MSB first */
    static unsigned int
    read_2_bytes (void)
    {
      int c1, c2;

      c1 = NEXTBYTE();
      if (c1 == EOF)
        ERREXIT("Premature EOF in JPEG file");
      c2 = NEXTBYTE();
      if (c2 == EOF)
        ERREXIT("Premature EOF in JPEG file");
      return (((unsigned int) c1) << 8) + ((unsigned int) c2);
    }

    /* Routines to write data to output file */

    static void
    write_1_byte (int c)
    {
      PUTBYTE(c);
    }

    static void
    write_2_bytes (unsigned int val)
    {
      PUTBYTE((val >> 8) & 0xFF);
      PUTBYTE(val & 0xFF);
    }

    static void
    write_marker (int marker)
    {
      PUTBYTE(0xFF);
      PUTBYTE(marker);
    }

    static void
    copy_rest_of_file (void)
    {
      int c;

      while ((c = NEXTBYTE()) != EOF)
        PUTBYTE(c);
    }

    /*
     * JPEG markers consist of one or more 0xFF bytes, followed by a marker
     * code byte (which is not an FF).  Here are the marker codes of interest
     * in this program.  (See jdmarker.c for a more complete list.)
     */

    #define M_SOF0  0xC0		/* Start Of Frame N */
    #define M_SOF1  0xC1		/* N indicates which compression process */
    #define M_SOF2  0xC2		/* Only SOF0-SOF2 are now in common use */
    #define M_SOF3  0xC3
    #define M_SOF5  0xC5		/* NB: codes C4 and CC are NOT SOF markers */
    #define M_SOF6  0xC6
    #define M_SOF7  0xC7
    #define M_SOF9  0xC9
    #define M_SOF10 0xCA
    #define M_SOF11 0xCB
    #define M_SOF13 0xCD
    #define M_SOF14 0xCE
    #define M_SOF15 0xCF
    #define M_SOI   0xD8		/* Start Of Image (beginning of datastream) */
    #define M_EOI   0xD9		/* End Of Image (end of datastream) */
    #define M_SOS   0xDA		/* Start Of Scan (begins compressed data) */
    #define M_COM   0xFE		/* COMment */

    /*
     * Find the next JPEG marker and return its marker code.
     * We expect at least one FF byte, possibly more if the compressor used FFs
     * to pad the file.  (Padding FFs will NOT be replicated in the output file.)
     * There could also be non-FF garbage between markers.  The treatment of such
     * garbage is unspecified; we choose to skip over it but emit a warning msg.
     * NB: this routine must not be used after seeing SOS marker, since it will
     * not deal correctly with FF/00 sequences in the compressed image data...
     */

    static int
    next_marker (void)
    {
      int c;
      int discarded_bytes = 0;

      /* Find 0xFF byte; count and skip any non-FFs. */
      c = read_1_byte();
      while (c != 0xFF) {
        discarded_bytes++;
        c = read_1_byte();
      }
      /* Get marker code byte, swallowing any duplicate FF bytes.  Extra FFs
       * are legal as pad bytes, so don't count them in discarded_bytes.
       */
      do {
        c = read_1_byte();
      } while (c == 0xFF);

      if (discarded_bytes != 0) {
        fprintf(stderr, "Warning: garbage data found in JPEG file\n");
      }

      return c;
    }

    /*
     * Read the initial marker, which should be SOI.
     * For a JFIF file, the first two bytes of the file should be literally
     * 0xFF M_SOI.  To be more general, we could use next_marker, but if the
     * input file weren't actually JPEG at all, next_marker might read the whole
     * file and then return a misleading error message...
     */

    static int
    first_marker (void)
    {
      int c1, c2;

      c1 = NEXTBYTE();
      c2 = NEXTBYTE();
      if (c1 != 0xFF || c2 != M_SOI)
        ERREXIT("Not a JPEG file");
      return c2;
    }

    /*
     * Most types of marker are followed by a variable-length parameter segment.
     * This routine skips over the parameters for any marker we don't otherwise
     * want to process.
     * Note that we MUST skip the parameter segment explicitly in order not to
     * be fooled by 0xFF bytes that might appear within the parameter segment;
     * such bytes do NOT introduce new markers.
     */

    static void
    copy_variable (void)
    /* Copy an unknown or uninteresting variable-length marker */
    {
      unsigned int length;

      /* Get the marker parameter length count */
      length = read_2_bytes();
      write_2_bytes(length);
      /* Length includes itself, so must be at least 2 */
      if (length < 2)
        ERREXIT("Erroneous JPEG marker length");
      length -= 2;
      /* Copy the remaining bytes */
      while (length > 0) {
        write_1_byte(read_1_byte());
        length--;
      }
    }

    static void
    skip_variable (void)
    /* Skip over an unknown or uninteresting variable-length marker */
    {
      unsigned int length;

      /* Get the marker parameter length count */
      length = read_2_bytes();
      /* Length includes itself, so must be at least 2 */
      if (length < 2)
        ERREXIT("Erroneous JPEG marker length");
      length -= 2;
      /* Skip over the remaining bytes */
      while (length > 0) {
        (void) read_1_byte();
        length--;
      }
    }

    /*
     * Parse the marker stream until SOFn or EOI is seen;
     * copy data to output, but discard COM markers unless keep_COM is true.
     */

    static int
    scan_JPEG_header (int keep_COM)
    {
      int marker;

      /* 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");
    	if (strlen(argv[argn]+1) >= (size_t) MAX_COM_LENGTH) {
    	  fprintf(stderr, "Comment text may not exceed %u bytes\n",
    		  (unsigned int) MAX_COM_LENGTH);
    	  exit(EXIT_FAILURE);
    	}
    	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");
    	  if (strlen(comment_arg) + 1 + strlen(argv[argn]) >=
    	      (size_t) MAX_COM_LENGTH) {
    	    fprintf(stderr, "Comment text may not exceed %u bytes\n",
    		    (unsigned int) MAX_COM_LENGTH);
    	    exit(EXIT_FAILURE);
    	  }
    	  strcat(comment_arg, " ");
    	  strcat(comment_arg, argv[argn]);
    	}
          } else if (strlen(comment_arg) >= (size_t) MAX_COM_LENGTH) {
    	fprintf(stderr, "Comment text may not exceed %u bytes\n",
    		(unsigned int) MAX_COM_LENGTH);
    	exit(EXIT_FAILURE);
          }
          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 */
    }