/*
 * wrjpgcom.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1997, Thomas G. Lane.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2014, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * 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
#define READ_BINARY     "rb"
#define WRITE_BINARY    "wb"
#endif

#ifndef EXIT_FAILURE            /* define exit() codes if not provided */
#define EXIT_FAILURE  1
#endif
#ifndef EXIT_SUCCESS
#define EXIT_SUCCESS  0
#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;
	/* Skip over 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]) + 2 >= (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) + strlen(argv[argn]) + 2 >=
					    (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(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);
			}
			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 */
}
