text: /*
   * 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 */
  }
  