/*
 * rdjpgcom.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1997, Thomas G. Lane.
 * Modified 2009 by Bill Allombert, Guido Vollbeding.
 * It was modified by The libjpeg-turbo Project to include only code relevant
 * to libjpeg-turbo.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains a very simple stand-alone application that displays
 * the text in COM (comment) markers 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> */

#ifdef HAVE_LOCALE_H
#include <locale.h>             /* Bill Allombert: use locale for isprint */
#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"
#else
#define READ_BINARY     "rb"
#endif

#ifndef EXIT_FAILURE            /* define exit() codes if not provided */
#define EXIT_FAILURE  1
#endif
#ifndef EXIT_SUCCESS
#define EXIT_SUCCESS  0
#endif


/*
 * These macros are used to read the input 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)


/* 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);
}


/*
 * 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_APP0  0xE0            /* Application-specific marker, type N */
#define M_APP12 0xEC            /* (we don't bother to list all 16 APPn's) */
#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.
 * 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
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--;
	}
}


/*
 * Process a COM marker.
 * We want to print out the marker contents as legible text;
 * we must guard against non-text junk and varying newline representations.
 */

static void
process_COM(int raw) {
	unsigned int length;
	int ch;
	int lastch = 0;

	/* Bill Allombert: set locale properly for isprint */
#ifdef HAVE_LOCALE_H
	setlocale(LC_CTYPE, "");
#endif

	/* 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;

	while (length > 0) {
		ch = read_1_byte();
		if (raw) {
			putc(ch, stdout);
			/* Emit the character in a readable form.
			 * Nonprintables are converted to \nnn form,
			 * while \ is converted to \\.
			 * Newlines in CR, CR/LF, or LF form will be printed as one newline.
			 */
		} else if (ch == '\r') {
			printf("\n");
		} else if (ch == '\n') {
			if (lastch != '\r')
				printf("\n");
		} else if (ch == '\\') {
			printf("\\\\");
		} else if (isprint(ch)) {
			putc(ch, stdout);
		} else {
			printf("\\%03o", ch);
		}
		lastch = ch;
		length--;
	}
	printf("\n");

	/* Bill Allombert: revert to C locale */
#ifdef HAVE_LOCALE_H
	setlocale(LC_CTYPE, "C");
#endif
}


/*
 * Process a SOFn marker.
 * This code is only needed if you want to know the image dimensions...
 */

static void
process_SOFn(int marker) {
	unsigned int length;
	unsigned int image_height, image_width;
	int data_precision, num_components;
	const char *process;
	int ci;

	length = read_2_bytes();      /* usual parameter length count */

	data_precision = read_1_byte();
	image_height = read_2_bytes();
	image_width = read_2_bytes();
	num_components = read_1_byte();

	switch (marker) {
		case M_SOF0:
			process = "Baseline";
			break;
		case M_SOF1:
			process = "Extended sequential";
			break;
		case M_SOF2:
			process = "Progressive";
			break;
		case M_SOF3:
			process = "Lossless";
			break;
		case M_SOF5:
			process = "Differential sequential";
			break;
		case M_SOF6:
			process = "Differential progressive";
			break;
		case M_SOF7:
			process = "Differential lossless";
			break;
		case M_SOF9:
			process = "Extended sequential, arithmetic coding";
			break;
		case M_SOF10:
			process = "Progressive, arithmetic coding";
			break;
		case M_SOF11:
			process = "Lossless, arithmetic coding";
			break;
		case M_SOF13:
			process = "Differential sequential, arithmetic coding";
			break;
		case M_SOF14:
			process = "Differential progressive, arithmetic coding";
			break;
		case M_SOF15:
			process = "Differential lossless, arithmetic coding";
			break;
		default:
			process = "Unknown";
			break;
	}

	printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n",
	       image_width, image_height, num_components, data_precision);
	printf("JPEG process: %s\n", process);

	if (length != (unsigned int) (8 + num_components * 3))
		ERREXIT("Bogus SOF marker length");

	for (ci = 0; ci < num_components; ci++) {
		(void) read_1_byte();       /* Component ID code */
		(void) read_1_byte();       /* H, V sampling factors */
		(void) read_1_byte();       /* Quantization table number */
	}
}


/*
 * Parse the marker stream until SOS or EOI is seen;
 * display any COM markers.
 * While the companion program wrjpgcom will always insert COM markers before
 * SOFn, other implementations might not, so we scan to SOS before stopping.
 * If we were only interested in the image dimensions, we would stop at SOFn.
 * (Conversely, if we only cared about COM markers, there would be no need
 * for special code to handle SOFn; we could treat it like other markers.)
 */

static int
scan_JPEG_header(int verbose, int raw) {
	int marker;

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

	/* Scan miscellaneous markers until we reach SOS. */
	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 */
				if (verbose)
					process_SOFn(marker);
				else
					skip_variable();
				break;

			case M_SOS:                 /* stop before hitting compressed data */
				return marker;

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

			case M_COM:
				process_COM(raw);
				break;

			case M_APP12:
				/* Some digital camera makers put useful textual information into
				 * APP12 markers, so we print those out too when in -verbose mode.
				 */
				if (verbose) {
					printf("APP12 contains:\n");
					process_COM(raw);
				} else
					skip_variable();
				break;

			default:                    /* Anything else just gets skipped */
				skip_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, "rdjpgcom displays any textual comments in a JPEG file.\n");

	fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname);

	fprintf(stderr, "Switches (names may be abbreviated):\n");
	fprintf(stderr, "  -raw        Display non-printable characters in comments (unsafe)\n");
	fprintf(stderr, "  -verbose    Also display dimensions of JPEG image\n");

	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 verbose = 0, raw = 0;

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

	progname = argv[0];
	if (progname == NULL || progname[0] == 0)
		progname = "rdjpgcom";      /* 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, "verbose", 1)) {
			verbose++;
		} else if (keymatch(arg, "raw", 1)) {
			raw = 1;
		} else
			usage();
	}

	/* Open the input file. */
	/* Unix style: expect zero or one file name */
	if (argn < argc - 1) {
		fprintf(stderr, "%s: only one input file\n", progname);
		usage();
	}
	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
	}

	/* Scan the JPEG headers. */
	(void) scan_JPEG_header(verbose, raw);

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