exif-entry.c

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/* exif-entry.c
 *
 * Copyright (c) 2001 Lutz Mueller <lutz@users.sourceforge.net>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301  USA.
 */

#include <config.h>

#include <libexif/exif-entry.h>
#include <libexif/exif-ifd.h>
#include <libexif/exif-utils.h>
#include <libexif/i18n.h>

#include <ctype.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <math.h>

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

struct _ExifEntryPrivate
{
        unsigned int ref_count;

        ExifMem *mem;
};

/* This function is hidden in exif-data.c */
ExifLog *exif_data_get_log (ExifData *);

#ifndef NO_VERBOSE_TAG_STRINGS
static void
exif_entry_log (ExifEntry *e, ExifLogCode code, const char *format, ...)
{
        va_list args;
        ExifLog *l = NULL;

        if (e && e->parent && e->parent->parent)
                l = exif_data_get_log (e->parent->parent);
        va_start (args, format);
        exif_logv (l, code, "ExifEntry", format, args);
        va_end (args);
}
#else
#if defined(__STDC_VERSION__) &&  __STDC_VERSION__ >= 199901L
#define exif_entry_log(...) do { } while (0)
#elif defined(__GNUC__)
#define exif_entry_log(x...) do { } while (0)
#else
#define exif_entry_log (void)
#endif
#endif

static void *
exif_entry_alloc (ExifEntry *e, unsigned int i)
{
        void *d;
        ExifLog *l = NULL;

        if (!e || !e->priv || !i) return NULL;

        d = exif_mem_alloc (e->priv->mem, i);
        if (d) return d;

        if (e->parent && e->parent->parent)
                l = exif_data_get_log (e->parent->parent);
        EXIF_LOG_NO_MEMORY (l, "ExifEntry", i);
        return NULL;
}

static void *
exif_entry_realloc (ExifEntry *e, void *d_orig, unsigned int i)
{
        void *d;
        ExifLog *l = NULL;

        if (!e || !e->priv) return NULL;

        if (!i) { exif_mem_free (e->priv->mem, d_orig); return NULL; }

        d = exif_mem_realloc (e->priv->mem, d_orig, i);
        if (d) return d;

        if (e->parent && e->parent->parent)
                l = exif_data_get_log (e->parent->parent);
        EXIF_LOG_NO_MEMORY (l, "ExifEntry", i);
        return NULL;
}

ExifEntry *
exif_entry_new (void)
{
        ExifMem *mem = exif_mem_new_default ();
        ExifEntry *e = exif_entry_new_mem (mem);

        exif_mem_unref (mem);

        return e;
}

ExifEntry *
exif_entry_new_mem (ExifMem *mem)
{
        ExifEntry *e = NULL;

        e = exif_mem_alloc (mem, sizeof (ExifEntry));
        if (!e) return NULL;
        e->priv = exif_mem_alloc (mem, sizeof (ExifEntryPrivate));
        if (!e->priv) { exif_mem_free (mem, e); return NULL; }
        e->priv->ref_count = 1;

        e->priv->mem = mem;
        exif_mem_ref (mem);

        return e;
}

void
exif_entry_ref (ExifEntry *e)
{
        if (!e) return;

        e->priv->ref_count++;
}

void
exif_entry_unref (ExifEntry *e)
{
        if (!e) return;

        e->priv->ref_count--;
        if (!e->priv->ref_count)
                exif_entry_free (e);
}

void
exif_entry_free (ExifEntry *e)
{
        if (!e) return;

        if (e->priv) {
                ExifMem *mem = e->priv->mem;
                if (e->data)
                        exif_mem_free (mem, e->data);
                exif_mem_free (mem, e->priv);
                exif_mem_free (mem, e);
                exif_mem_unref (mem);
        }
}

static inline ExifShort
exif_get_short_convert (const unsigned char *buf, ExifFormat format,
                        ExifByteOrder order)
{
        switch (format) {
        case EXIF_FORMAT_LONG:
                return (ExifShort) exif_get_long (buf, order);
        case EXIF_FORMAT_SLONG:
                return (ExifShort) exif_get_slong (buf, order);
        case EXIF_FORMAT_SHORT:
                return (ExifShort) exif_get_short (buf, order);
        case EXIF_FORMAT_SSHORT:
                return (ExifShort) exif_get_sshort (buf, order);
        case EXIF_FORMAT_BYTE:
        case EXIF_FORMAT_SBYTE:
                return (ExifShort) buf[0];
        default:
                /* Unsupported type */
                return (ExifShort) 0;
        }
}

void
exif_entry_fix (ExifEntry *e)
{
        unsigned int i, newsize;
        unsigned char *newdata;
        ExifByteOrder o;
        ExifRational r;
        ExifSRational sr;

        if (!e || !e->priv) return;

        switch (e->tag) {
        
        /* These tags all need to be of format SHORT. */
        case EXIF_TAG_YCBCR_SUB_SAMPLING:
        case EXIF_TAG_SUBJECT_AREA:
        case EXIF_TAG_COLOR_SPACE:
        case EXIF_TAG_PLANAR_CONFIGURATION:
        case EXIF_TAG_SENSING_METHOD:
        case EXIF_TAG_ORIENTATION:
        case EXIF_TAG_YCBCR_POSITIONING:
        case EXIF_TAG_PHOTOMETRIC_INTERPRETATION:
        case EXIF_TAG_CUSTOM_RENDERED:
        case EXIF_TAG_EXPOSURE_MODE:
        case EXIF_TAG_WHITE_BALANCE:
        case EXIF_TAG_SCENE_CAPTURE_TYPE:
        case EXIF_TAG_GAIN_CONTROL:
        case EXIF_TAG_SATURATION:
        case EXIF_TAG_CONTRAST:
        case EXIF_TAG_SHARPNESS:
        case EXIF_TAG_ISO_SPEED_RATINGS:
                switch (e->format) {
                case EXIF_FORMAT_LONG:
                case EXIF_FORMAT_SLONG:
                case EXIF_FORMAT_BYTE:
                case EXIF_FORMAT_SBYTE:
                case EXIF_FORMAT_SSHORT:
                        if (!e->parent || !e->parent->parent) break;
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag '%s' was of format '%s' (which is "
                                "against specification) and has been "
                                "changed to format '%s'."),
                                exif_tag_get_name_in_ifd(e->tag,
                                                        exif_entry_get_ifd(e)),
                                exif_format_get_name (e->format),
                                exif_format_get_name (EXIF_FORMAT_SHORT));

                        o = exif_data_get_byte_order (e->parent->parent);
                        newsize = e->components * exif_format_get_size (EXIF_FORMAT_SHORT);
                        newdata = exif_entry_alloc (e, newsize);
                        if (!newdata) {
                                exif_entry_log (e, EXIF_LOG_CODE_NO_MEMORY,
                                        "Could not allocate %lu byte(s).", (unsigned long)newsize);
                                break;
                        }

                        for (i = 0; i < e->components; i++)
                                exif_set_short (
                                        newdata + i *
                                        exif_format_get_size (
                                         EXIF_FORMAT_SHORT), o,
                                         exif_get_short_convert (
                                          e->data + i *
                                          exif_format_get_size (e->format),
                                          e->format, o));

                        exif_mem_free (e->priv->mem, e->data);
                        e->data = newdata;
                        e->size = newsize;
                        e->format = EXIF_FORMAT_SHORT;
                        break;
                case EXIF_FORMAT_SHORT:
                        /* No conversion necessary */
                        break;
                default:
                        exif_entry_log (e, EXIF_LOG_CODE_CORRUPT_DATA,
                                _("Tag '%s' is of format '%s' (which is "
                                "against specification) but cannot be changed "
                                "to format '%s'."),
                                exif_tag_get_name_in_ifd(e->tag,
                                                        exif_entry_get_ifd(e)),
                                exif_format_get_name (e->format),
                                exif_format_get_name (EXIF_FORMAT_SHORT));
                        break;
                }
                break;

        /* All these tags need to be of format 'Rational'. */
        case EXIF_TAG_FNUMBER:
        case EXIF_TAG_APERTURE_VALUE:
        case EXIF_TAG_EXPOSURE_TIME:
        case EXIF_TAG_FOCAL_LENGTH:
                switch (e->format) {
                case EXIF_FORMAT_SRATIONAL:
                        if (!e->parent || !e->parent->parent) break;
                        o = exif_data_get_byte_order (e->parent->parent);
                        for (i = 0; i < e->components; i++) {
                                sr = exif_get_srational (e->data + i * 
                                        exif_format_get_size (
                                                EXIF_FORMAT_SRATIONAL), o);
                                r.numerator = (ExifLong) sr.numerator;
                                r.denominator = (ExifLong) sr.denominator;
                                exif_set_rational (e->data + i *
                                        exif_format_get_size (
                                                EXIF_FORMAT_RATIONAL), o, r);
                        }
                        e->format = EXIF_FORMAT_RATIONAL;
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag '%s' was of format '%s' (which is "
                                "against specification) and has been "
                                "changed to format '%s'."),
                                exif_tag_get_name_in_ifd(e->tag,
                                                        exif_entry_get_ifd(e)),
                                exif_format_get_name (EXIF_FORMAT_SRATIONAL),
                                exif_format_get_name (EXIF_FORMAT_RATIONAL));
                        break;
                default:
                        break;
                }
                break;

        /* All these tags need to be of format 'SRational'. */
        case EXIF_TAG_EXPOSURE_BIAS_VALUE:
        case EXIF_TAG_BRIGHTNESS_VALUE:
        case EXIF_TAG_SHUTTER_SPEED_VALUE:
                switch (e->format) {
                case EXIF_FORMAT_RATIONAL:
                        if (!e->parent || !e->parent->parent) break;
                        o = exif_data_get_byte_order (e->parent->parent);
                        for (i = 0; i < e->components; i++) {
                                r = exif_get_rational (e->data + i * 
                                        exif_format_get_size (
                                                EXIF_FORMAT_RATIONAL), o);
                                sr.numerator = (ExifLong) r.numerator;
                                sr.denominator = (ExifLong) r.denominator;
                                exif_set_srational (e->data + i *
                                        exif_format_get_size (
                                                EXIF_FORMAT_SRATIONAL), o, sr);
                        }
                        e->format = EXIF_FORMAT_SRATIONAL;
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag '%s' was of format '%s' (which is "
                                "against specification) and has been "
                                "changed to format '%s'."),
                                exif_tag_get_name_in_ifd(e->tag,
                                                        exif_entry_get_ifd(e)),
                                exif_format_get_name (EXIF_FORMAT_RATIONAL),
                                exif_format_get_name (EXIF_FORMAT_SRATIONAL));
                        break;
                default:
                        break;
                }
                break;

        case EXIF_TAG_USER_COMMENT:

                /* Format needs to be UNDEFINED. */
                if (e->format != EXIF_FORMAT_UNDEFINED) {
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag 'UserComment' had invalid format '%s'. "
                                "Format has been set to 'undefined'."),
                                exif_format_get_name (e->format));
                        e->format = EXIF_FORMAT_UNDEFINED;
                }

                /* Some packages like Canon ZoomBrowser EX 4.5 store
                   only one zero byte followed by 7 bytes of rubbish */
                if ((e->size >= 8) && (e->data[0] == 0)) {
                        memcpy(e->data, "\0\0\0\0\0\0\0\0", 8);
                }

                /* There need to be at least 8 bytes. */
                if (e->size < 8) {
                        e->data = exif_entry_realloc (e, e->data, 8 + e->size);
                        if (!e->data) {
                                e->size = 0;
                                e->components = 0;
                                return;
                        }

                        /* Assume ASCII */
                        memmove (e->data + 8, e->data, e->size);
                        memcpy (e->data, "ASCII\0\0\0", 8);
                        e->size += 8;
                        e->components += 8;
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag 'UserComment' has been expanded to at "
                                "least 8 bytes in order to follow the "
                                "specification."));
                        break;
                }

                /*
                 * If the first 8 bytes are empty and real data starts
                 * afterwards, let's assume ASCII and claim the 8 first
                 * bytes for the format specifyer.
                 */
                for (i = 0; (i < e->size) && !e->data[i]; i++);
                if (!i) for ( ; (i < e->size) && (e->data[i] == ' '); i++);
                if ((i >= 8) && (i < e->size)) {
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag 'UserComment' is not empty but does not "
                                "start with a format identifier. "
                                "This has been fixed."));
                        memcpy (e->data, "ASCII\0\0\0", 8);
                        break;
                }

                /* 
                 * First 8 bytes need to follow the specification. If they don't, 
                 * assume ASCII.
                 */
                if (memcmp (e->data, "ASCII\0\0\0"     , 8) &&
                    memcmp (e->data, "UNICODE\0"       , 8) &&
                    memcmp (e->data, "JIS\0\0\0\0\0"   , 8) &&
                    memcmp (e->data, "\0\0\0\0\0\0\0\0", 8)) {
                        e->data = exif_entry_realloc (e, e->data, 8 + e->size);
                        if (!e->data) {
                                e->size = 0;
                                e->components = 0;
                                break;
                        }

                        /* Assume ASCII */
                        memmove (e->data + 8, e->data, e->size);
                        memcpy (e->data, "ASCII\0\0\0", 8);
                        e->size += 8;
                        e->components += 8;
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Tag 'UserComment' did not start with a "
                                "format identifier. This has been fixed."));
                        break;
                }

                break;
        default:
                break;
        }
}

static void
exif_entry_format_value(ExifEntry *e, char *val, size_t maxlen)
{
        ExifByte v_byte;
        ExifShort v_short;
        ExifSShort v_sshort;
        ExifLong v_long;
        ExifRational v_rat;
        ExifSRational v_srat;
        ExifSLong v_slong;
        unsigned int i;
        size_t len;
        const ExifByteOrder o = exif_data_get_byte_order (e->parent->parent);

        if (!e->size || !maxlen)
                return;
        ++maxlen; /* include the terminating NUL */
        switch (e->format) {
        case EXIF_FORMAT_UNDEFINED:
                snprintf (val, maxlen, _("%i bytes undefined data"), e->size);
                break;
        case EXIF_FORMAT_BYTE:
        case EXIF_FORMAT_SBYTE:
                v_byte = e->data[0];
                snprintf (val, maxlen, "0x%02x", v_byte);
                len = strlen (val);
                for (i = 1; i < e->components; i++) {
                        v_byte = e->data[i];
                        snprintf (val+len, maxlen-len, ", 0x%02x", v_byte);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_SHORT:
                v_short = exif_get_short (e->data, o);
                snprintf (val, maxlen, "%u", v_short);
                len = strlen (val);
                for (i = 1; i < e->components; i++) {
                        v_short = exif_get_short (e->data +
                                exif_format_get_size (e->format) * i, o);
                        snprintf (val+len, maxlen-len, ", %u", v_short);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_SSHORT:
                v_sshort = exif_get_sshort (e->data, o);
                snprintf (val, maxlen, "%i", v_sshort);
                len = strlen (val);
                for (i = 1; i < e->components; i++) {
                        v_sshort = exif_get_short (e->data +
                                exif_format_get_size (e->format) *
                                i, o);
                        snprintf (val+len, maxlen-len, ", %i", v_sshort);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_LONG:
                v_long = exif_get_long (e->data, o);
                snprintf (val, maxlen, "%lu", (unsigned long) v_long);
                len = strlen (val);
                for (i = 1; i < e->components; i++) {
                        v_long = exif_get_long (e->data +
                                exif_format_get_size (e->format) *
                                i, o);
                        snprintf (val+len, maxlen-len, ", %lu", (unsigned long) v_long);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_SLONG:
                v_slong = exif_get_slong (e->data, o);
                snprintf (val, maxlen, "%li", (long) v_slong);
                len = strlen (val);
                for (i = 1; i < e->components; i++) {
                        v_slong = exif_get_slong (e->data +
                                exif_format_get_size (e->format) * i, o);
                        snprintf (val+len, maxlen-len, ", %li", (long) v_slong);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_ASCII:
                strncpy (val, (char *) e->data, MIN (maxlen-1, e->size));
                val[MIN (maxlen-1, e->size)] = 0;
                break;
        case EXIF_FORMAT_RATIONAL:
                len = 0;
                for (i = 0; i < e->components; i++) {
                        if (i > 0) {
                                snprintf (val+len, maxlen-len, ", ");
                                len += strlen (val+len);
                        }
                        v_rat = exif_get_rational (
                                e->data + 8 * i, o);
                        if (v_rat.denominator) {
                                /*
                                 * Choose the number of significant digits to
                                 * display based on the size of the denominator.
                                 * It is scaled so that denominators within the
                                 * range 13..120 will show 2 decimal points.
                                 */
                                int decimals = (int)(log10(v_rat.denominator)-0.08+1.0);
                                snprintf (val+len, maxlen-len, "%2.*f",
                                          decimals,
                                          (double) v_rat.numerator /
                                          (double) v_rat.denominator);
                        } else
                                snprintf (val+len, maxlen-len, "%lu/%lu",
                                  (unsigned long) v_rat.numerator,
                                  (unsigned long) v_rat.denominator);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_SRATIONAL:
                len = 0;
                for (i = 0; i < e->components; i++) {
                        if (i > 0) {
                                snprintf (val+len, maxlen-len, ", ");
                                len += strlen (val+len);
                        }
                        v_srat = exif_get_srational (
                                e->data + 8 * i, o);
                        if (v_srat.denominator) {
                                int decimals = (int)(log10(fabs(v_srat.denominator))-0.08+1.0);
                                snprintf (val+len, maxlen-len, "%2.*f",
                                          decimals,
                                          (double) v_srat.numerator /
                                          (double) v_srat.denominator);
                        } else
                                snprintf (val+len, maxlen-len, "%li/%li",
                                  (long) v_srat.numerator,
                                  (long) v_srat.denominator);
                        len += strlen (val+len);
                        if (len >= maxlen-1) break;
                }
                break;
        case EXIF_FORMAT_DOUBLE:
        case EXIF_FORMAT_FLOAT:
        default:
                snprintf (val, maxlen, _("%i bytes unsupported data type"),
                          e->size);
                break;
        }
}

void
exif_entry_dump (ExifEntry *e, unsigned int indent)
{
        char buf[1024];
        char value[1024];
        unsigned int i;

        for (i = 0; i < 2 * indent; i++)
                buf[i] = ' ';
        buf[i] = '\0';

        if (!e)
                return;

        printf ("%sTag: 0x%x ('%s')\n", buf, e->tag,
                exif_tag_get_name_in_ifd (e->tag, exif_entry_get_ifd(e)));
        printf ("%s  Format: %i ('%s')\n", buf, e->format,
                exif_format_get_name (e->format));
        printf ("%s  Components: %i\n", buf, (int) e->components);
        printf ("%s  Size: %i\n", buf, e->size);
        printf ("%s  Value: %s\n", buf, exif_entry_get_value (e, value, sizeof(value)));
}

static int
match_repeated_char(const unsigned char *data, unsigned char ch, size_t n)
{
        int i;
        for (i=n; i; --i, ++data) {
                if (*data == 0) {
                        i = 0;  /* all bytes before NUL matched */
                        break;
                }
                if (*data != ch)
                        break;
        }
        return i;
}

#define CF(entry,target,v,maxlen)                                       \
{                                                                       \
        if (entry->format != target) {                                  \
                exif_entry_log (entry, EXIF_LOG_CODE_CORRUPT_DATA,      \
                        _("The tag '%s' contains data of an invalid "   \
                        "format ('%s', expected '%s')."),               \
                        exif_tag_get_name (entry->tag),                 \
                        exif_format_get_name (entry->format),           \
                        exif_format_get_name (target));                 \
                break;                                                  \
        }                                                               \
}

#define CC(entry,target,v,maxlen)                                       \
{                                                                       \
        if (entry->components != target) {                              \
                exif_entry_log (entry, EXIF_LOG_CODE_CORRUPT_DATA,      \
                        _("The tag '%s' contains an invalid number of " \
                          "components (%i, expected %i)."),             \
                        exif_tag_get_name (entry->tag),         \
                        (int) entry->components, (int) target);         \
                break;                                                  \
        }                                                               \
}

static const struct {
        ExifTag tag;
        const char *strings[10];
} list[] = {
#ifndef NO_VERBOSE_TAG_DATA
  { EXIF_TAG_PLANAR_CONFIGURATION,
    { N_("Chunky format"), N_("Planar format"), NULL}},
  { EXIF_TAG_SENSING_METHOD,
    { "", N_("Not defined"), N_("One-chip color area sensor"),
      N_("Two-chip color area sensor"), N_("Three-chip color area sensor"),
      N_("Color sequential area sensor"), "", N_("Trilinear sensor"),
      N_("Color sequential linear sensor"), NULL}},
  { EXIF_TAG_ORIENTATION,
    { "", N_("Top-left"), N_("Top-right"), N_("Bottom-right"),
      N_("Bottom-left"), N_("Left-top"), N_("Right-top"),
      N_("Right-bottom"), N_("Left-bottom"), NULL}},
  { EXIF_TAG_YCBCR_POSITIONING,
    { "", N_("Centered"), N_("Co-sited"), NULL}},
  { EXIF_TAG_PHOTOMETRIC_INTERPRETATION,
    { N_("Reversed mono"), N_("Normal mono"), N_("RGB"), N_("Palette"), "",
      N_("CMYK"), N_("YCbCr"), "", N_("CieLAB"), NULL}},
  { EXIF_TAG_CUSTOM_RENDERED,
    { N_("Normal process"), N_("Custom process"), NULL}},
  { EXIF_TAG_EXPOSURE_MODE,
    { N_("Auto exposure"), N_("Manual exposure"), N_("Auto bracket"), NULL}},
  { EXIF_TAG_WHITE_BALANCE,
    { N_("Auto white balance"), N_("Manual white balance"), NULL}},
  { EXIF_TAG_SCENE_CAPTURE_TYPE,
    { N_("Standard"), N_("Landscape"), N_("Portrait"),
      N_("Night scene"), NULL}},
  { EXIF_TAG_GAIN_CONTROL,
    { N_("Normal"), N_("Low gain up"), N_("High gain up"),
      N_("Low gain down"), N_("High gain down"), NULL}},
  { EXIF_TAG_SATURATION,
    { N_("Normal"), N_("Low saturation"), N_("High saturation"), NULL}},
  { EXIF_TAG_CONTRAST , {N_("Normal"), N_("Soft"), N_("Hard"), NULL}},
  { EXIF_TAG_SHARPNESS, {N_("Normal"), N_("Soft"), N_("Hard"), NULL}},
#endif
  { 0, {NULL}}
};

static const struct {
  ExifTag tag;
  struct {
    int index;
    const char *values[4]; 
  } elem[25];
} list2[] = {
#ifndef NO_VERBOSE_TAG_DATA
  { EXIF_TAG_METERING_MODE,
    { {  0, {N_("Unknown"), NULL}},
      {  1, {N_("Average"), N_("Avg"), NULL}},
      {  2, {N_("Center-weighted average"), N_("Center-weight"), NULL}},
      {  3, {N_("Spot"), NULL}},
      {  4, {N_("Multi spot"), NULL}},
      {  5, {N_("Pattern"), NULL}},
      {  6, {N_("Partial"), NULL}},
      {255, {N_("Other"), NULL}},
      {  0, {NULL}}}},
  { EXIF_TAG_COMPRESSION,
    { {1, {N_("Uncompressed"), NULL}},
      {5, {N_("LZW compression"), NULL}},
      {6, {N_("JPEG compression"), NULL}},
      {7, {N_("JPEG compression"), NULL}},
      {8, {N_("Deflate/ZIP compression"), NULL}},
      {32773, {N_("PackBits compression"), NULL}},
      {0, {NULL}}}},
  { EXIF_TAG_LIGHT_SOURCE,
    { {  0, {N_("Unknown"), NULL}},
      {  1, {N_("Daylight"), NULL}},
      {  2, {N_("Fluorescent"), NULL}},
      {  3, {N_("Tungsten incandescent light"), N_("Tungsten"), NULL}},
      {  4, {N_("Flash"), NULL}},
      {  9, {N_("Fine weather"), NULL}},
      { 10, {N_("Cloudy weather"), N_("Cloudy"), NULL}},
      { 11, {N_("Shade"), NULL}},
      { 12, {N_("Daylight fluorescent"), NULL}},
      { 13, {N_("Day white fluorescent"), NULL}},
      { 14, {N_("Cool white fluorescent"), NULL}},
      { 15, {N_("White fluorescent"), NULL}},
      { 17, {N_("Standard light A"), NULL}},
      { 18, {N_("Standard light B"), NULL}},
      { 19, {N_("Standard light C"), NULL}},
      { 20, {N_("D55"), NULL}},
      { 21, {N_("D65"), NULL}},
      { 22, {N_("D75"), NULL}},
      { 24, {N_("ISO studio tungsten"),NULL}},
      {255, {N_("Other"), NULL}},
      {  0, {NULL}}}},
  { EXIF_TAG_FOCAL_PLANE_RESOLUTION_UNIT,
    { {2, {N_("Inch"), N_("in"), NULL}},
      {3, {N_("Centimeter"), N_("cm"), NULL}},
      {0, {NULL}}}},
  { EXIF_TAG_RESOLUTION_UNIT,
    { {2, {N_("Inch"), N_("in"), NULL}},
      {3, {N_("Centimeter"), N_("cm"), NULL}}, 
      {0, {NULL}}}},
  { EXIF_TAG_EXPOSURE_PROGRAM,
    { {0, {N_("Not defined"), NULL}},
      {1, {N_("Manual"), NULL}},
      {2, {N_("Normal program"), N_("Normal"), NULL}},
      {3, {N_("Aperture priority"), N_("Aperture"), NULL}},
      {4, {N_("Shutter priority"),N_("Shutter"), NULL}},
      {5, {N_("Creative program (biased toward depth of field)"),
           N_("Creative"), NULL}},
      {6, {N_("Creative program (biased toward fast shutter speed)"),
           N_("Action"), NULL}},
      {7, {N_("Portrait mode (for closeup photos with the background out "
              "of focus)"), N_("Portrait"), NULL}},
      {8, {N_("Landscape mode (for landscape photos with the background "
              "in focus)"), N_("Landscape"), NULL}},
      {0, {NULL}}}},
  { EXIF_TAG_FLASH,
    { {0x0000, {N_("Flash did not fire"), N_("No flash"), NULL}},
      {0x0001, {N_("Flash fired"), N_("Flash"), N_("Yes"), NULL}},
      {0x0005, {N_("Strobe return light not detected"), N_("Without strobe"),
                NULL}},
      {0x0007, {N_("Strobe return light detected"), N_("With strobe"), NULL}},
      {0x0008, {N_("Flash did not fire"), NULL}}, /* Olympus E-330 */
      {0x0009, {N_("Flash fired, compulsory flash mode"), NULL}},
      {0x000d, {N_("Flash fired, compulsory flash mode, return light "
                   "not detected"), NULL}},
      {0x000f, {N_("Flash fired, compulsory flash mode, return light "
                   "detected"), NULL}},
      {0x0010, {N_("Flash did not fire, compulsory flash mode"), NULL}},
      {0x0018, {N_("Flash did not fire, auto mode"), NULL}},
      {0x0019, {N_("Flash fired, auto mode"), NULL}},
      {0x001d, {N_("Flash fired, auto mode, return light not detected"),
                NULL}},
      {0x001f, {N_("Flash fired, auto mode, return light detected"), NULL}},
      {0x0020, {N_("No flash function"),NULL}},
      {0x0041, {N_("Flash fired, red-eye reduction mode"), NULL}},
      {0x0045, {N_("Flash fired, red-eye reduction mode, return light "
                   "not detected"), NULL}},
      {0x0047, {N_("Flash fired, red-eye reduction mode, return light "
                   "detected"), NULL}},
      {0x0049, {N_("Flash fired, compulsory flash mode, red-eye reduction "
                   "mode"), NULL}},
      {0x004d, {N_("Flash fired, compulsory flash mode, red-eye reduction "
                  "mode, return light not detected"), NULL}},
      {0x004f, {N_("Flash fired, compulsory flash mode, red-eye reduction mode, "
                   "return light detected"), NULL}},
      {0x0058, {N_("Flash did not fire, auto mode, red-eye reduction mode"), NULL}},
      {0x0059, {N_("Flash fired, auto mode, red-eye reduction mode"), NULL}},
      {0x005d, {N_("Flash fired, auto mode, return light not detected, "
                   "red-eye reduction mode"), NULL}},
      {0x005f, {N_("Flash fired, auto mode, return light detected, "
                   "red-eye reduction mode"), NULL}},
      {0x0000, {NULL}}}},
  { EXIF_TAG_SUBJECT_DISTANCE_RANGE, 
    { {0, {N_("Unknown"), N_("?"), NULL}},
      {1, {N_("Macro"), NULL}},
      {2, {N_("Close view"), N_("Close"), NULL}},
      {3, {N_("Distant view"), N_("Distant"), NULL}},
      {0, {NULL}}}},
  { EXIF_TAG_COLOR_SPACE,
    { {1, {N_("sRGB"), NULL}},
      {2, {N_("Adobe RGB"), NULL}},
      {0xffff, {N_("Uncalibrated"), NULL}},
      {0x0000, {NULL}}}},
#endif
  {0, { { 0, {NULL}}} }
};

const char *
exif_entry_get_value (ExifEntry *e, char *val, unsigned int maxlen)
{
        unsigned int i, j, k;
        ExifShort v_short, v_short2, v_short3, v_short4;
        ExifByte v_byte;
        ExifRational v_rat;
        ExifSRational v_srat;
        char b[64];
        const char *c;
        ExifByteOrder o;
        double d;
        ExifEntry *entry;
        static const struct {
                char label[5];
                char major, minor;
        } versions[] = {
                {"0110", 1,  1},
                {"0120", 1,  2},
                {"0200", 2,  0},
                {"0210", 2,  1},
                {"0220", 2,  2},
                {"0221", 2, 21},
                {"0230", 2,  3},
                {""    , 0,  0}
        };

        /* FIXME: This belongs to somewhere else. */
        /* libexif should use the default system locale.
         * If an application specifically requires UTF-8, then we
         * must give the application a way to tell libexif that.
         * 
         * bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
         */
        bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);

        if (!e || !e->parent || !e->parent->parent || !maxlen)
                return val;

        /* make sure the returned string is zero terminated */
        memset (val, 0, maxlen);
        maxlen--;
        memset (b, 0, sizeof (b));

        /* We need the byte order */
        o = exif_data_get_byte_order (e->parent->parent);

        /* Sanity check */
        if (e->size != e->components * exif_format_get_size (e->format)) {
                snprintf (val, maxlen, _("Invalid size of entry (%i, "
                        "expected %li x %i)."), e->size, e->components,
                                exif_format_get_size (e->format));
                return val;
        }

        switch (e->tag) {
        case EXIF_TAG_USER_COMMENT:

                /*
                 * The specification says UNDEFINED, but some
                 * manufacturers don't care and use ASCII. If this is the
                 * case here, only refuse to read it if there is no chance
                 * of finding readable data.
                 */
                if ((e->format != EXIF_FORMAT_ASCII) || 
                    (e->size <= 8) ||
                    ( memcmp (e->data, "ASCII\0\0\0"  , 8) &&
                      memcmp (e->data, "UNICODE\0"    , 8) &&
                      memcmp (e->data, "JIS\0\0\0\0\0", 8) &&
                      memcmp (e->data, "\0\0\0\0\0\0\0\0", 8)))
                        CF (e, EXIF_FORMAT_UNDEFINED, val, maxlen);

                /*
                 * Note that, according to the specification (V2.1, p 40),
                 * the user comment field does not have to be 
                 * NULL terminated.
                 */
                if ((e->size >= 8) && !memcmp (e->data, "ASCII\0\0\0", 8)) {
                        strncpy (val, (char *) e->data + 8, MIN (e->size - 8, maxlen));
                        break;
                }
                if ((e->size >= 8) && !memcmp (e->data, "UNICODE\0", 8)) {
                        strncpy (val, _("Unsupported UNICODE string"), maxlen);
                /* FIXME: use iconv to convert into the locale encoding.
                 * EXIF 2.2 implies (but does not say) that this encoding is
                 * UCS-2.
                 */
                        break;
                }
                if ((e->size >= 8) && !memcmp (e->data, "JIS\0\0\0\0\0", 8)) {
                        strncpy (val, _("Unsupported JIS string"), maxlen);
                /* FIXME: use iconv to convert into the locale encoding */
                        break;
                }

                /* Check if there is really some information in the tag. */
                for (i = 0; (i < e->size) &&
                            (!e->data[i] || (e->data[i] == ' ')); i++);
                if (i == e->size) break;

                /*
                 * If we reach this point, the tag does not
                 * comply with the standard but seems to contain data.
                 * Print as much as possible.
                 */
                exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                        _("Tag UserComment contains data but is "
                          "against specification."));
                for (j = 0; (i < e->size) && (j < maxlen); i++, j++) {
                        exif_entry_log (e, EXIF_LOG_CODE_DEBUG,
                                _("Byte at position %i: 0x%02x"), i, e->data[i]);
                        val[j] = isprint (e->data[i]) ? e->data[i] : '.';
                }
                break;

        case EXIF_TAG_EXIF_VERSION:
                CF (e, EXIF_FORMAT_UNDEFINED, val, maxlen);
                CC (e, 4, val, maxlen);
                strncpy (val, _("Unknown Exif Version"), maxlen);
                for (i = 0; *versions[i].label; i++) {
                        if (!memcmp (e->data, versions[i].label, 4)) {
                                snprintf (val, maxlen,
                                        _("Exif Version %d.%d"),
                                        versions[i].major,
                                        versions[i].minor);
                                break;
                        }
                }
                break;
        case EXIF_TAG_FLASH_PIX_VERSION:
                CF (e, EXIF_FORMAT_UNDEFINED, val, maxlen);
                CC (e, 4, val, maxlen);
                if (!memcmp (e->data, "0100", 4))
                        strncpy (val, _("FlashPix Version 1.0"), maxlen);
                else if (!memcmp (e->data, "0101", 4))
                        strncpy (val, _("FlashPix Version 1.01"), maxlen);
                else
                        strncpy (val, _("Unknown FlashPix Version"), maxlen);
                break;
        case EXIF_TAG_COPYRIGHT:
                CF (e, EXIF_FORMAT_ASCII, val, maxlen);

                /*
                 * First part: Photographer.
                 * Some cameras store a string like "   " here. Ignore it.
                 * Remember that a corrupted tag might not be NUL-terminated
                 */
                if (e->size && e->data && match_repeated_char(e->data, ' ', e->size))
                        strncpy (val, (char *) e->data, MIN (maxlen, e->size));
                else
                        strncpy (val, _("[None]"), maxlen);
                strncat (val, " ", maxlen - strlen (val));
                strncat (val, _("(Photographer)"), maxlen - strlen (val));

                /* Second part: Editor. */
                strncat (val, " - ", maxlen - strlen (val));
                k = 0;
                if (e->size && e->data) {
                        const unsigned char *tagdata = memchr(e->data, 0, e->size);
                        if (tagdata++) {
                                int editor_ofs = tagdata - e->data;
                                int remaining = e->size - editor_ofs;
                                if (match_repeated_char(tagdata, ' ', remaining)) {
                                        strncat (val, (const char*)tagdata, MIN (maxlen - strlen (val), remaining));
                                        ++k;
                                }
                        }
                }
                if (!k)
                        strncat (val, _("[None]"), maxlen - strlen (val));
                strncat (val, " ", maxlen - strlen (val));
                strncat (val, _("(Editor)"), maxlen - strlen (val));

                break;
        case EXIF_TAG_FNUMBER:
                CF (e, EXIF_FORMAT_RATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_rat = exif_get_rational (e->data, o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_rat.numerator / (double) v_rat.denominator;
                snprintf (val, maxlen, "f/%.01f", d);
                break;
        case EXIF_TAG_APERTURE_VALUE:
        case EXIF_TAG_MAX_APERTURE_VALUE:
                CF (e, EXIF_FORMAT_RATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_rat = exif_get_rational (e->data, o);
                if (!v_rat.denominator || (0x80000000 == v_rat.numerator)) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_rat.numerator / (double) v_rat.denominator;
                snprintf (val, maxlen, _("%.02f EV"), d);
                snprintf (b, sizeof (b), _(" (f/%.01f)"), pow (2, d / 2.));
                if (maxlen > strlen (val) + strlen (b))
                        strncat (val, b, maxlen - strlen (val));
                break;
        case EXIF_TAG_FOCAL_LENGTH:
                CF (e, EXIF_FORMAT_RATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_rat = exif_get_rational (e->data, o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }

                /*
                 * For calculation of the 35mm equivalent,
                 * Minolta cameras need a multiplier that depends on the
                 * camera model.
                 */
                d = 0.;
                entry = exif_content_get_entry (
                        e->parent->parent->ifd[EXIF_IFD_0], EXIF_TAG_MAKE);
                if (entry && entry->data &&
                    !strncmp ((char *)entry->data, "Minolta", 7)) {
                        entry = exif_content_get_entry (
                                        e->parent->parent->ifd[EXIF_IFD_0],
                                        EXIF_TAG_MODEL);
                        if (entry && entry->data) {
                                if (!strncmp ((char *)entry->data, "DiMAGE 7", 8))
                                        d = 3.9;
                                else if (!strncmp ((char *)entry->data, "DiMAGE 5", 8))
                                        d = 4.9;
                        }
                }
                if (d)
                        snprintf (b, sizeof (b), _(" (35 equivalent: %d mm)"),
                                  (int) (d * (double) v_rat.numerator /
                                             (double) v_rat.denominator));

                d = (double) v_rat.numerator / (double) v_rat.denominator;
                snprintf (val, maxlen, "%.1f mm", d);
                if (maxlen > strlen (val) + strlen (b))
                        strncat (val, b, maxlen - strlen (val));
                break;
        case EXIF_TAG_SUBJECT_DISTANCE:
                CF (e, EXIF_FORMAT_RATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_rat = exif_get_rational (e->data, o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_rat.numerator / (double) v_rat.denominator;
                snprintf (val, maxlen, "%.1f m", d);
                break;
        case EXIF_TAG_EXPOSURE_TIME:
                CF (e, EXIF_FORMAT_RATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_rat = exif_get_rational (e->data, o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_rat.numerator / (double) v_rat.denominator;
                if (d < 1)
                        snprintf (val, maxlen, _("1/%i"), (int) (0.5 + 1. / d));
                else
                        snprintf (val, maxlen, "%i", (int) d);
                if (maxlen > strlen (val) + strlen (_(" sec.")))
                        strncat (val, _(" sec."), maxlen - strlen (val));
                break;
        case EXIF_TAG_SHUTTER_SPEED_VALUE:
                CF (e, EXIF_FORMAT_SRATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_srat = exif_get_srational (e->data, o);
                if (!v_srat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_srat.numerator / (double) v_srat.denominator;
                snprintf (val, maxlen, _("%.02f EV"), d);
                d = 1. / pow (2, d);
                if (d < 1)
                  snprintf (b, sizeof (b), _(" (1/%d sec.)"), (int) (1. / d));
                else
                  snprintf (b, sizeof (b), _(" (%d sec.)"), (int) d);
                strncat (val, b, maxlen - strlen (val));
                break;
        case EXIF_TAG_BRIGHTNESS_VALUE:
                CF (e, EXIF_FORMAT_SRATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_srat = exif_get_srational (e->data, o);
                if (!v_srat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_srat.numerator / (double) v_srat.denominator;
                snprintf (val, maxlen, _("%.02f EV"), d);
                snprintf (b, sizeof (b), _(" (%.02f cd/m^2)"),
                        1. / (M_PI * 0.3048 * 0.3048) * pow (2, d));
                if (maxlen > strlen (val) + strlen (b))
                        strncat (val, b, maxlen - strlen (val));
                break;
        case EXIF_TAG_FILE_SOURCE:
                CF (e, EXIF_FORMAT_UNDEFINED, val, maxlen);
                CC (e, 1, val, maxlen);
                v_byte = e->data[0];
                if (v_byte == 3)
                        strncpy (val, _("DSC"), maxlen);
                else
                        snprintf (val, maxlen, _("Internal error (unknown "
                                  "value %i)"), v_byte);
                break;
        case EXIF_TAG_COMPONENTS_CONFIGURATION:
                CF (e, EXIF_FORMAT_UNDEFINED, val, maxlen);
                CC (e, 4, val, maxlen);
                for (i = 0; i < 4; i++) {
                        switch (e->data[i]) {
                        case 0: c = _("-"); break;
                        case 1: c = _("Y"); break;
                        case 2: c = _("Cb"); break;
                        case 3: c = _("Cr"); break;
                        case 4: c = _("R"); break;
                        case 5: c = _("G"); break;
                        case 6: c = _("B"); break;
                        default: c = _("Reserved"); break;
                        }
                        strncat (val, c, maxlen - strlen (val));
                        if (i < 3)
                                strncat (val, " ", maxlen - strlen (val));
                }
                break;
        case EXIF_TAG_EXPOSURE_BIAS_VALUE:
                CF (e, EXIF_FORMAT_SRATIONAL, val, maxlen);
                CC (e, 1, val, maxlen);
                v_srat = exif_get_srational (e->data, o);
                if (!v_srat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_srat.numerator / (double) v_srat.denominator;
                snprintf (val, maxlen, _("%.02f EV"), d);
                break;
        case EXIF_TAG_SCENE_TYPE:
                CF (e, EXIF_FORMAT_UNDEFINED, val, maxlen);
                CC (e, 1, val, maxlen);
                v_byte = e->data[0];
                if (v_byte == 1)
                        strncpy (val, _("Directly photographed"), maxlen);
                else
                        snprintf (val, maxlen, _("Internal error (unknown "
                                  "value %i)"), v_byte);
                break;
        case EXIF_TAG_YCBCR_SUB_SAMPLING:
                CF (e, EXIF_FORMAT_SHORT, val, maxlen);
                CC (e, 2, val, maxlen);
                v_short  = exif_get_short (e->data, o);
                v_short2 = exif_get_short (
                        e->data + exif_format_get_size (e->format),
                        o);
                if ((v_short == 2) && (v_short2 == 1))
                        strncpy (val, _("YCbCr4:2:2"), maxlen);
                else if ((v_short == 2) && (v_short2 == 2))
                        strncpy (val, _("YCbCr4:2:0"), maxlen);
                else
                        snprintf (val, maxlen, "%u, %u", v_short, v_short2);
                break;
        case EXIF_TAG_SUBJECT_AREA:
                CF (e, EXIF_FORMAT_SHORT, val, maxlen);
                switch (e->components) {
                case 2:
                        v_short  = exif_get_short (e->data, o);
                        v_short2 = exif_get_short (e->data + 2, o);
                        snprintf (val, maxlen, "(x,y) = (%i,%i)",
                                  v_short, v_short2);
                        break;
                case 3:
                        v_short  = exif_get_short (e->data, o);
                        v_short2 = exif_get_short (e->data + 2, o);
                        v_short3 = exif_get_short (e->data + 4, o);
                        snprintf (val, maxlen, _("Within distance %i of "
                                "(x,y) = (%i,%i)"), v_short3, v_short,
                                v_short2);
                        break;
                case 4:
                        v_short  = exif_get_short (e->data, o);
                        v_short2 = exif_get_short (e->data + 2, o);
                        v_short3 = exif_get_short (e->data + 4, o);
                        v_short4 = exif_get_short (e->data + 6, o);
                        snprintf (val, maxlen, _("Within rectangle "
                                "(width %i, height %i) around "
                                "(x,y) = (%i,%i)"), v_short3, v_short4,
                                v_short, v_short2);
                        break;
                default:
                        snprintf (val, maxlen, _("Unexpected number "
                                "of components (%li, expected 2, 3, or 4)."),
                                e->components); 
                }
                break;
        case EXIF_TAG_GPS_VERSION_ID:
                /* This is only valid in the GPS IFD */
                CF (e, EXIF_FORMAT_BYTE, val, maxlen);
                CC (e, 4, val, maxlen);
                v_byte = e->data[0];
                snprintf (val, maxlen, "%u", v_byte);
                maxlen -= strlen (val);
                for (i = 1; i < e->components; i++) {
                        v_byte = e->data[i];
                        snprintf (b, sizeof (b), ".%u", v_byte);
                        strncat (val, b, maxlen);
                        maxlen -= strlen (b);
                        if ((signed)maxlen <= 0) break;
                }
                break;
        case EXIF_TAG_INTEROPERABILITY_VERSION:
        /* a.k.a. case EXIF_TAG_GPS_LATITUDE: */
                /* This tag occurs in EXIF_IFD_INTEROPERABILITY */
                if (e->format == EXIF_FORMAT_UNDEFINED) {
                        strncpy (val, (char *) e->data, MIN (maxlen, e->size));
                        break;
                }
                /* EXIF_TAG_GPS_LATITUDE is the same numerically as
                 * EXIF_TAG_INTEROPERABILITY_VERSION but in EXIF_IFD_GPS
                 */
                exif_entry_format_value(e, val, maxlen);
                break;
        case EXIF_TAG_GPS_ALTITUDE_REF:
                /* This is only valid in the GPS IFD */
                CF (e, EXIF_FORMAT_BYTE, val, maxlen);
                CC (e, 1, val, maxlen);
                v_byte = e->data[0];
                if (v_byte == 0)
                        strncpy (val, _("Sea level"), maxlen);
                else if (v_byte == 1)
                        strncpy (val, _("Sea level reference"), maxlen);
                else
                        snprintf (val, maxlen, _("Internal error (unknown "
                                  "value %i)"), v_byte);
                break;
        case EXIF_TAG_GPS_TIME_STAMP:
                /* This is only valid in the GPS IFD */
                CF (e, EXIF_FORMAT_RATIONAL, val, maxlen);
                CC (e, 3, val, maxlen);

                v_rat  = exif_get_rational (e->data, o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                i = v_rat.numerator / v_rat.denominator;

                v_rat = exif_get_rational (e->data +
                                             exif_format_get_size (e->format),
                                           o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                j = v_rat.numerator / v_rat.denominator;

                v_rat = exif_get_rational (e->data +
                                             2*exif_format_get_size (e->format),
                                             o);
                if (!v_rat.denominator) {
                        exif_entry_format_value(e, val, maxlen);
                        break;
                }
                d = (double) v_rat.numerator / (double) v_rat.denominator;
                snprintf (val, maxlen, "%02u:%02u:%05.2f", i, j, d);
                break;

        case EXIF_TAG_METERING_MODE:
        case EXIF_TAG_COMPRESSION:
        case EXIF_TAG_LIGHT_SOURCE:
        case EXIF_TAG_FOCAL_PLANE_RESOLUTION_UNIT:
        case EXIF_TAG_RESOLUTION_UNIT:
        case EXIF_TAG_EXPOSURE_PROGRAM:
        case EXIF_TAG_FLASH:
        case EXIF_TAG_SUBJECT_DISTANCE_RANGE:
        case EXIF_TAG_COLOR_SPACE:
                CF (e,EXIF_FORMAT_SHORT, val, maxlen);
                CC (e, 1, val, maxlen);
                v_short = exif_get_short (e->data, o);

                /* Search the tag */
                for (i = 0; list2[i].tag && (list2[i].tag != e->tag); i++);
                if (!list2[i].tag) {
                        snprintf (val, maxlen, _("Internal error (unknown "
                                  "value %i)"), v_short);
                        break;
                }

                /* Find the value */
                for (j = 0; list2[i].elem[j].values[0] &&
                            (list2[i].elem[j].index < v_short); j++);
                if (list2[i].elem[j].index != v_short) {
                        snprintf (val, maxlen, _("Internal error (unknown "
                                  "value %i)"), v_short);
                        break;
                }

                /* Find a short enough value */
                memset (val, 0, maxlen);
                for (k = 0; list2[i].elem[j].values[k]; k++) {
                        size_t l = strlen (_(list2[i].elem[j].values[k]));
                        if ((maxlen > l) && (strlen (val) < l))
                                strncpy (val, _(list2[i].elem[j].values[k]), maxlen);
                }
                if (!val[0]) snprintf (val, maxlen, "%i", v_short);

                break;

        case EXIF_TAG_PLANAR_CONFIGURATION:
        case EXIF_TAG_SENSING_METHOD:
        case EXIF_TAG_ORIENTATION:
        case EXIF_TAG_YCBCR_POSITIONING:
        case EXIF_TAG_PHOTOMETRIC_INTERPRETATION:
        case EXIF_TAG_CUSTOM_RENDERED:
        case EXIF_TAG_EXPOSURE_MODE:
        case EXIF_TAG_WHITE_BALANCE:
        case EXIF_TAG_SCENE_CAPTURE_TYPE:
        case EXIF_TAG_GAIN_CONTROL:
        case EXIF_TAG_SATURATION:
        case EXIF_TAG_CONTRAST:
        case EXIF_TAG_SHARPNESS:
                CF (e, EXIF_FORMAT_SHORT, val, maxlen);
                CC (e, 1, val, maxlen);
                v_short = exif_get_short (e->data, o);

                /* Search the tag */
                for (i = 0; list[i].tag && (list[i].tag != e->tag); i++);
                if (!list[i].tag) {
                        snprintf (val, maxlen, _("Internal error (unknown "
                                  "value %i)"), v_short);
                        break;
                }

                /* Find the value */
                for (j = 0; list[i].strings[j] && (j < v_short); j++);
                if (!list[i].strings[j])
                        snprintf (val, maxlen, "%i", v_short);
                else if (!*list[i].strings[j])
                        snprintf (val, maxlen, _("Unknown value %i"), v_short);
                else
                        strncpy (val, _(list[i].strings[j]), maxlen);
                break;

        case EXIF_TAG_XP_TITLE:
        case EXIF_TAG_XP_COMMENT:
        case EXIF_TAG_XP_AUTHOR:
        case EXIF_TAG_XP_KEYWORDS:
        case EXIF_TAG_XP_SUBJECT:
        {
                /* Sanity check the size to prevent overflow */
                if (e->size+sizeof(unsigned short) < e->size) break;

                /* The tag may not be U+0000-terminated , so make a local
                   U+0000-terminated copy before converting it */
                unsigned short *utf16 = exif_mem_alloc (e->priv->mem, e->size+sizeof(unsigned short));
                if (!utf16) break;
                memcpy(utf16, e->data, e->size);
                utf16[e->size/sizeof(unsigned short)] = 0;

                /* Warning! The texts are converted from UTF16 to UTF8 */
                /* FIXME: use iconv to convert into the locale encoding */
                exif_convert_utf16_to_utf8(val, utf16, maxlen);
                exif_mem_free(e->priv->mem, utf16);
                break;
        }

        default:
                /* Use a generic value formatting */
                exif_entry_format_value(e, val, maxlen);
        }

        return val;
}


void
exif_entry_initialize (ExifEntry *e, ExifTag tag)
{
        ExifRational r;
        ExifByteOrder o;

        /* We need the byte order */
        if (!e || !e->parent || e->data || !e->parent->parent)
                return;
        o = exif_data_get_byte_order (e->parent->parent);

        e->tag = tag;
        switch (tag) {

        /* LONG, 1 component, no default */
        case EXIF_TAG_PIXEL_X_DIMENSION:
        case EXIF_TAG_PIXEL_Y_DIMENSION:
        case EXIF_TAG_EXIF_IFD_POINTER:
        case EXIF_TAG_GPS_INFO_IFD_POINTER:
        case EXIF_TAG_INTEROPERABILITY_IFD_POINTER:
        case EXIF_TAG_JPEG_INTERCHANGE_FORMAT_LENGTH:
        case EXIF_TAG_JPEG_INTERCHANGE_FORMAT:
                e->components = 1;
                e->format = EXIF_FORMAT_LONG;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                break;

        /* SHORT, 1 component, no default */
        case EXIF_TAG_SUBJECT_LOCATION:
        case EXIF_TAG_SENSING_METHOD:
        case EXIF_TAG_PHOTOMETRIC_INTERPRETATION:
        case EXIF_TAG_COMPRESSION:
        case EXIF_TAG_EXPOSURE_MODE:
        case EXIF_TAG_WHITE_BALANCE:
        case EXIF_TAG_FOCAL_LENGTH_IN_35MM_FILM:
        case EXIF_TAG_GAIN_CONTROL:
        case EXIF_TAG_SUBJECT_DISTANCE_RANGE:
        case EXIF_TAG_FLASH:
        case EXIF_TAG_ISO_SPEED_RATINGS:

        /* SHORT, 1 component, default 0 */
        case EXIF_TAG_IMAGE_WIDTH:
        case EXIF_TAG_IMAGE_LENGTH:
        case EXIF_TAG_EXPOSURE_PROGRAM:
        case EXIF_TAG_LIGHT_SOURCE:
        case EXIF_TAG_METERING_MODE:
        case EXIF_TAG_CUSTOM_RENDERED:
        case EXIF_TAG_SCENE_CAPTURE_TYPE:
        case EXIF_TAG_CONTRAST:
        case EXIF_TAG_SATURATION:
        case EXIF_TAG_SHARPNESS:
                e->components = 1;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 0);
                break;

        /* SHORT, 1 component, default 1 */
        case EXIF_TAG_ORIENTATION:
        case EXIF_TAG_PLANAR_CONFIGURATION:
        case EXIF_TAG_YCBCR_POSITIONING:
                e->components = 1;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 1);
                break;

        /* SHORT, 1 component, default 2 */
        case EXIF_TAG_RESOLUTION_UNIT:
        case EXIF_TAG_FOCAL_PLANE_RESOLUTION_UNIT:
                e->components = 1;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 2);
                break;

        /* SHORT, 1 component, default 3 */
        case EXIF_TAG_SAMPLES_PER_PIXEL:
                e->components = 1;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 3);
                break;

        /* SHORT, 1 component, default 0xffff */
        case EXIF_TAG_COLOR_SPACE:
                e->components = 1;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 0xffff);
                break;

        /* SHORT, 3 components, default 8 8 8 */
        case EXIF_TAG_BITS_PER_SAMPLE:
                e->components = 3;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 8);
                exif_set_short (
                        e->data + exif_format_get_size (e->format),
                        o, 8);
                exif_set_short (
                        e->data + 2 * exif_format_get_size (e->format),
                        o, 8);
                break;

        /* SHORT, 2 components, default 2 1 */
        case EXIF_TAG_YCBCR_SUB_SAMPLING:
                e->components = 2;
                e->format = EXIF_FORMAT_SHORT;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                exif_set_short (e->data, o, 2);
                exif_set_short (
                        e->data + exif_format_get_size (e->format),
                        o, 1);
                break;

        /* SRATIONAL, 1 component, no default */
        case EXIF_TAG_EXPOSURE_BIAS_VALUE:
        case EXIF_TAG_BRIGHTNESS_VALUE:
        case EXIF_TAG_SHUTTER_SPEED_VALUE:
                e->components = 1;
                e->format = EXIF_FORMAT_SRATIONAL;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                break;

        /* RATIONAL, 1 component, no default */
        case EXIF_TAG_EXPOSURE_TIME:
        case EXIF_TAG_FOCAL_PLANE_X_RESOLUTION:
        case EXIF_TAG_FOCAL_PLANE_Y_RESOLUTION:
        case EXIF_TAG_EXPOSURE_INDEX:
        case EXIF_TAG_FLASH_ENERGY:
        case EXIF_TAG_FNUMBER:
        case EXIF_TAG_FOCAL_LENGTH:
        case EXIF_TAG_SUBJECT_DISTANCE:
        case EXIF_TAG_MAX_APERTURE_VALUE:
        case EXIF_TAG_APERTURE_VALUE:
        case EXIF_TAG_COMPRESSED_BITS_PER_PIXEL:
        case EXIF_TAG_PRIMARY_CHROMATICITIES:
        case EXIF_TAG_DIGITAL_ZOOM_RATIO:
                e->components = 1;
                e->format = EXIF_FORMAT_RATIONAL;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                break;

        /* RATIONAL, 1 component, default 72/1 */
        case EXIF_TAG_X_RESOLUTION:
        case EXIF_TAG_Y_RESOLUTION:
                e->components = 1;
                e->format = EXIF_FORMAT_RATIONAL;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                r.numerator = 72;
                r.denominator = 1;
                exif_set_rational (e->data, o, r);
                break;

        /* RATIONAL, 2 components, no default */
        case EXIF_TAG_WHITE_POINT:
                e->components = 2;
                e->format = EXIF_FORMAT_RATIONAL;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                break;

        /* RATIONAL, 6 components */
        case EXIF_TAG_REFERENCE_BLACK_WHITE:
                e->components = 6;
                e->format = EXIF_FORMAT_RATIONAL;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                r.denominator = 1;
                r.numerator = 0;
                exif_set_rational (e->data, o, r);
                r.numerator = 255;
                exif_set_rational (
                        e->data + exif_format_get_size (e->format), o, r);
                r.numerator = 0;
                exif_set_rational (
                        e->data + 2 * exif_format_get_size (e->format), o, r);
                r.numerator = 255;
                exif_set_rational (
                        e->data + 3 * exif_format_get_size (e->format), o, r);
                r.numerator = 0;
                exif_set_rational (
                        e->data + 4 * exif_format_get_size (e->format), o, r);
                r.numerator = 255;
                exif_set_rational (
                        e->data + 5 * exif_format_get_size (e->format), o, r);
                break;

        /* ASCII, 20 components */
        case EXIF_TAG_DATE_TIME:
        case EXIF_TAG_DATE_TIME_ORIGINAL:
        case EXIF_TAG_DATE_TIME_DIGITIZED:
        {
                time_t t;
#ifdef HAVE_LOCALTIME_R
                struct tm tms;
#endif
                struct tm *tm;

                t = time (NULL);
#ifdef HAVE_LOCALTIME_R
                tm = localtime_r (&t, &tms);
#else
                tm = localtime (&t);
#endif
                e->components = 20;
                e->format = EXIF_FORMAT_ASCII;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                snprintf ((char *) e->data, e->size,
                          "%04i:%02i:%02i %02i:%02i:%02i",
                          tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
                          tm->tm_hour, tm->tm_min, tm->tm_sec);
                break;
        }

        /* ASCII, no default */
        case EXIF_TAG_SUB_SEC_TIME:
        case EXIF_TAG_SUB_SEC_TIME_ORIGINAL:
        case EXIF_TAG_SUB_SEC_TIME_DIGITIZED:
                e->components = 0;
                e->format = EXIF_FORMAT_ASCII;
                e->size = 0;
                e->data = NULL;
                break;

        /* ASCII, default "[None]" */
        case EXIF_TAG_IMAGE_DESCRIPTION:
        case EXIF_TAG_MAKE:
        case EXIF_TAG_MODEL:
        case EXIF_TAG_SOFTWARE:
        case EXIF_TAG_ARTIST:
                e->components = strlen (_("[None]")) + 1;
                e->format = EXIF_FORMAT_ASCII;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                strncpy ((char *)e->data, _("[None]"), e->size);
                break;
        /* ASCII, default "[None]\0[None]\0" */
        case EXIF_TAG_COPYRIGHT:
                e->components = (strlen (_("[None]")) + 1) * 2;
                e->format = EXIF_FORMAT_ASCII;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                strcpy (((char *)e->data) + 0, _("[None]"));
                strcpy (((char *)e->data) + strlen (_("[None]")) + 1, _("[None]"));
                break;

        /* UNDEFINED, 1 component, default 1 */
        case EXIF_TAG_SCENE_TYPE:
                e->components = 1;
                e->format = EXIF_FORMAT_UNDEFINED;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                e->data[0] = 0x01;
                break;

        /* UNDEFINED, 1 component, default 3 */
        case EXIF_TAG_FILE_SOURCE:
                e->components = 1;
                e->format = EXIF_FORMAT_UNDEFINED;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                e->data[0] = 0x03;
                break;

        /* UNDEFINED, 4 components, default 48 49 48 48 */
        case EXIF_TAG_FLASH_PIX_VERSION:
                e->components = 4;
                e->format = EXIF_FORMAT_UNDEFINED;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                memcpy (e->data, "0100", 4);
                break;

        /* UNDEFINED, 4 components, default 48 50 49 48 */
        case EXIF_TAG_EXIF_VERSION:
                e->components = 4;
                e->format = EXIF_FORMAT_UNDEFINED;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                memcpy (e->data, "0210", 4);
                break;

        /* UNDEFINED, 4 components, default 1 2 3 0 */
        case EXIF_TAG_COMPONENTS_CONFIGURATION:
                e->components = 4;
                e->format = EXIF_FORMAT_UNDEFINED;
                e->size = exif_format_get_size (e->format) * e->components;
                e->data = exif_entry_alloc (e, e->size);
                if (!e->data) break;
                e->data[0] = 1;
                e->data[1] = 2;
                e->data[2] = 3;
                e->data[3] = 0;
                break;

        /* UNDEFINED, no components, no default */
        /* Use this if the tag is otherwise unsupported */
        case EXIF_TAG_MAKER_NOTE:
        case EXIF_TAG_USER_COMMENT:
        default:
                e->components = 0;
                e->format = EXIF_FORMAT_UNDEFINED;
                e->size = 0;
                e->data = NULL;
                break;
        }
}

---