/* $Header: /cvsroot/VTK/VTK/Utilities/vtktiff/tif_dir.c,v 1.1 2004/04/28 15:49:22 king Exp $ */

/*
 * Copyright (c) 1988-1997 Sam Leffler
 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and 
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the names of
 * Sam Leffler and Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Sam Leffler and Silicon Graphics.
 * 
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
 * 
 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 */

/*
 * TIFF Library.
 *
 * Directory Tag Get & Set Routines.
 * (and also some miscellaneous stuff)
 */
#include "tiffiop.h"

/*
 * These are used in the backwards compatibility code...
 */
#define DATATYPE_VOID           0       /* !untyped data */
#define DATATYPE_INT            1       /* !signed integer data */
#define DATATYPE_UINT           2       /* !unsigned integer data */
#define DATATYPE_IEEEFP         3       /* !IEEE floating point data */

void
_TIFFsetByteArray(void** vpp, void* vp, long n)
{
        if (*vpp)
                _TIFFfree(*vpp), *vpp = 0;
        if (vp && (*vpp = (void*) _TIFFmalloc(n)))
                _TIFFmemcpy(*vpp, vp, n);
}
void _TIFFsetString(char** cpp, char* cp)
    { _TIFFsetByteArray((void**) cpp, (void*) cp, (long) (strlen(cp)+1)); }
void _TIFFsetNString(char** cpp, char* cp, long n)
    { _TIFFsetByteArray((void**) cpp, (void*) cp, n); }
void _TIFFsetShortArray(uint16** wpp, uint16* wp, long n)
    { _TIFFsetByteArray((void**) wpp, (void*) wp, n*sizeof (uint16)); }
void _TIFFsetLongArray(uint32** lpp, uint32* lp, long n)
    { _TIFFsetByteArray((void**) lpp, (void*) lp, n*sizeof (uint32)); }
void _TIFFsetFloatArray(float** fpp, float* fp, long n)
    { _TIFFsetByteArray((void**) fpp, (void*) fp, n*sizeof (float)); }
void _TIFFsetDoubleArray(double** dpp, double* dp, long n)
    { _TIFFsetByteArray((void**) dpp, (void*) dp, n*sizeof (double)); }

/*
 * Install extra samples information.
 */
static int
setExtraSamples(TIFFDirectory* td, va_list ap, int* v)
{
        uint16* va;
        int i;

        *v = va_arg(ap, int);
        if ((uint16) *v > td->td_samplesperpixel)
                return (0);
        va = va_arg(ap, uint16*);
        if (*v > 0 && va == NULL)               /* typically missing param */
                return (0);
        for (i = 0; i < *v; i++)
                if (va[i] > EXTRASAMPLE_UNASSALPHA)
                        return (0);
        td->td_extrasamples = (uint16) *v;
        _TIFFsetShortArray(&td->td_sampleinfo, va, td->td_extrasamples);
        return (1);
}

#ifdef CMYK_SUPPORT
static int
checkInkNamesString(TIFF* tif, int slen, const char* s)
{
        TIFFDirectory* td = &tif->tif_dir;
        int i = td->td_samplesperpixel;

        if (slen > 0) {
                const char* ep = s+slen;
                const char* cp = s;
                for (; i > 0; i--) {
                        for (; *cp != '\0'; cp++)
                                if (cp >= ep)
                                        goto bad;
                        cp++;                           /* skip \0 */
                }
                return (cp-s);
        }
bad:
        TIFFError("TIFFSetField",
            "%s: Invalid InkNames value; expecting %d names, found %d",
            tif->tif_name,
            td->td_samplesperpixel,
            td->td_samplesperpixel-i);
        return (0);
}
#endif

static int
_TIFFVSetField(TIFF* tif, ttag_t tag, va_list ap)
{
        TIFFDirectory* td = &tif->tif_dir;
        int status = 1;
        uint32 v32;
        int i, v;
        double d;
        char* s;

        switch (tag) {
        case TIFFTAG_SUBFILETYPE:
                td->td_subfiletype = va_arg(ap, uint32);
                break;
        case TIFFTAG_IMAGEWIDTH:
                td->td_imagewidth = va_arg(ap, uint32);
                break;
        case TIFFTAG_IMAGELENGTH:
                td->td_imagelength = va_arg(ap, uint32);
                break;
        case TIFFTAG_BITSPERSAMPLE:
                td->td_bitspersample = (uint16) va_arg(ap, int);
                /*
                 * If the data require post-decoding processing
                 * to byte-swap samples, set it up here.  Note
                 * that since tags are required to be ordered,
                 * compression code can override this behaviour
                 * in the setup method if it wants to roll the
                 * post decoding work in with its normal work.
                 */
                if (tif->tif_flags & TIFF_SWAB) {
                        if (td->td_bitspersample == 16)
                                tif->tif_postdecode = _TIFFSwab16BitData;
                        else if (td->td_bitspersample == 32)
                                tif->tif_postdecode = _TIFFSwab32BitData;
                        else if (td->td_bitspersample == 64)
                                tif->tif_postdecode = _TIFFSwab64BitData;
                }
                break;
        case TIFFTAG_COMPRESSION:
                v = va_arg(ap, int) & 0xffff;
                /*
                 * If we're changing the compression scheme,
                 * the notify the previous module so that it
                 * can cleanup any state it's setup.
                 */
                if (TIFFFieldSet(tif, FIELD_COMPRESSION)) {
                        if (td->td_compression == v)
                                break;
                        (*tif->tif_cleanup)(tif);
                        tif->tif_flags &= ~TIFF_CODERSETUP;
                }
                /*
                 * Setup new compression routine state.
                 */
                if( (status = TIFFSetCompressionScheme(tif, v)) != 0 )
                    td->td_compression = v;
                else
                    status = 0;
                break;
        case TIFFTAG_PHOTOMETRIC:
                td->td_photometric = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_THRESHHOLDING:
                td->td_threshholding = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_FILLORDER:
                v = va_arg(ap, int);
                if (v != FILLORDER_LSB2MSB && v != FILLORDER_MSB2LSB)
                        goto badvalue;
                td->td_fillorder = (uint16) v;
                break;
        case TIFFTAG_DOCUMENTNAME:
                _TIFFsetString(&td->td_documentname, va_arg(ap, char*));
                break;
        case TIFFTAG_ARTIST:
                _TIFFsetString(&td->td_artist, va_arg(ap, char*));
                break;
        case TIFFTAG_DATETIME:
                _TIFFsetString(&td->td_datetime, va_arg(ap, char*));
                break;
        case TIFFTAG_HOSTCOMPUTER:
                _TIFFsetString(&td->td_hostcomputer, va_arg(ap, char*));
                break;
        case TIFFTAG_IMAGEDESCRIPTION:
                _TIFFsetString(&td->td_imagedescription, va_arg(ap, char*));
                break;
        case TIFFTAG_MAKE:
                _TIFFsetString(&td->td_make, va_arg(ap, char*));
                break;
        case TIFFTAG_MODEL:
                _TIFFsetString(&td->td_model, va_arg(ap, char*));
                break;
        case TIFFTAG_SOFTWARE:
                _TIFFsetString(&td->td_software, va_arg(ap, char*));
                break;
        case TIFFTAG_COPYRIGHT:
                _TIFFsetString(&td->td_copyright, va_arg(ap, char*));
                break;
        case TIFFTAG_ORIENTATION:
                v = va_arg(ap, int);
                if (v < ORIENTATION_TOPLEFT || ORIENTATION_LEFTBOT < v) {
                        TIFFWarning(tif->tif_name,
                            "Bad value %ld for \"%s\" tag ignored",
                            v, _TIFFFieldWithTag(tif, tag)->field_name);
                } else
                        td->td_orientation = (uint16) v;
                break;
        case TIFFTAG_SAMPLESPERPIXEL:
                /* XXX should cross check -- e.g. if pallette, then 1 */
                v = va_arg(ap, int);
                if (v == 0)
                        goto badvalue;
                td->td_samplesperpixel = (uint16) v;
                break;
        case TIFFTAG_ROWSPERSTRIP:
                v32 = va_arg(ap, uint32);
                if (v32 == 0)
                        goto badvalue32;
                td->td_rowsperstrip = v32;
                if (!TIFFFieldSet(tif, FIELD_TILEDIMENSIONS)) {
                        td->td_tilelength = v32;
                        td->td_tilewidth = td->td_imagewidth;
                }
                break;
        case TIFFTAG_MINSAMPLEVALUE:
                td->td_minsamplevalue = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_MAXSAMPLEVALUE:
                td->td_maxsamplevalue = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_SMINSAMPLEVALUE:
                td->td_sminsamplevalue = (double) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_SMAXSAMPLEVALUE:
                td->td_smaxsamplevalue = (double) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_XRESOLUTION:
                td->td_xresolution = (float) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_YRESOLUTION:
                td->td_yresolution = (float) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_PLANARCONFIG:
                v = va_arg(ap, int);
                if (v != PLANARCONFIG_CONTIG && v != PLANARCONFIG_SEPARATE)
                        goto badvalue;
                td->td_planarconfig = (uint16) v;
                break;
        case TIFFTAG_PAGENAME:
                _TIFFsetString(&td->td_pagename, va_arg(ap, char*));
                break;
        case TIFFTAG_XPOSITION:
                td->td_xposition = (float) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_YPOSITION:
                td->td_yposition = (float) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_RESOLUTIONUNIT:
                v = va_arg(ap, int);
                if (v < RESUNIT_NONE || RESUNIT_CENTIMETER < v)
                        goto badvalue;
                td->td_resolutionunit = (uint16) v;
                break;
        case TIFFTAG_PAGENUMBER:
                td->td_pagenumber[0] = (uint16) va_arg(ap, int);
                td->td_pagenumber[1] = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_HALFTONEHINTS:
                td->td_halftonehints[0] = (uint16) va_arg(ap, int);
                td->td_halftonehints[1] = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_COLORMAP:
                v32 = (uint32)(1L<<td->td_bitspersample);
                _TIFFsetShortArray(&td->td_colormap[0], va_arg(ap, uint16*), v32);
                _TIFFsetShortArray(&td->td_colormap[1], va_arg(ap, uint16*), v32);
                _TIFFsetShortArray(&td->td_colormap[2], va_arg(ap, uint16*), v32);
                break;
        case TIFFTAG_EXTRASAMPLES:
                if (!setExtraSamples(td, ap, &v))
                        goto badvalue;
                break;
        case TIFFTAG_MATTEING:
                td->td_extrasamples = (uint16) (va_arg(ap, int) != 0);
                if (td->td_extrasamples) {
                        uint16 sv = EXTRASAMPLE_ASSOCALPHA;
                        _TIFFsetShortArray(&td->td_sampleinfo, &sv, 1);
                }
                break;
        case TIFFTAG_TILEWIDTH:
                v32 = va_arg(ap, uint32);
                if (v32 % 16) {
                        if (tif->tif_mode != O_RDONLY)
                                goto badvalue32;
                        TIFFWarning(tif->tif_name,
                            "Nonstandard tile width %d, convert file", v32);
                }
                td->td_tilewidth = v32;
                tif->tif_flags |= TIFF_ISTILED;
                break;
        case TIFFTAG_TILELENGTH:
                v32 = va_arg(ap, uint32);
                if (v32 % 16) {
                        if (tif->tif_mode != O_RDONLY)
                                goto badvalue32;
                        TIFFWarning(tif->tif_name,
                            "Nonstandard tile length %d, convert file", v32);
                }
                td->td_tilelength = v32;
                tif->tif_flags |= TIFF_ISTILED;
                break;
        case TIFFTAG_TILEDEPTH:
                v32 = va_arg(ap, uint32);
                if (v32 == 0)
                        goto badvalue32;
                td->td_tiledepth = v32;
                break;
        case TIFFTAG_DATATYPE:
                v = va_arg(ap, int);
                switch (v) {
                case DATATYPE_VOID:     v = SAMPLEFORMAT_VOID;  break;
                case DATATYPE_INT:      v = SAMPLEFORMAT_INT;   break;
                case DATATYPE_UINT:     v = SAMPLEFORMAT_UINT;  break;
                case DATATYPE_IEEEFP:   v = SAMPLEFORMAT_IEEEFP;break;
                default:                goto badvalue;
                }
                td->td_sampleformat = (uint16) v;
                break;
        case TIFFTAG_SAMPLEFORMAT:
                v = va_arg(ap, int);
                if (v < SAMPLEFORMAT_UINT || SAMPLEFORMAT_COMPLEXIEEEFP < v)
                        goto badvalue;
                td->td_sampleformat = (uint16) v;
                break;
        case TIFFTAG_IMAGEDEPTH:
                td->td_imagedepth = va_arg(ap, uint32);
                break;
        case TIFFTAG_STONITS:
                d = va_arg(ap, dblparam_t);
                if (d <= 0.)
                        goto badvaluedbl;
                td->td_stonits = d;
                break;

        /* Begin Pixar Tags */
        case TIFFTAG_PIXAR_IMAGEFULLWIDTH:
                td->td_imagefullwidth = va_arg(ap, uint32);
                break;
        case TIFFTAG_PIXAR_IMAGEFULLLENGTH:
                td->td_imagefulllength = va_arg(ap, uint32);
                break;
        case TIFFTAG_PIXAR_TEXTUREFORMAT:
                _TIFFsetString(&td->td_textureformat, va_arg(ap, char*));
                break;
        case TIFFTAG_PIXAR_WRAPMODES:
                _TIFFsetString(&td->td_wrapmodes, va_arg(ap, char*));
                break;
        case TIFFTAG_PIXAR_FOVCOT:
                td->td_fovcot = (float) va_arg(ap, dblparam_t);
                break;
        case TIFFTAG_PIXAR_MATRIX_WORLDTOSCREEN:
                _TIFFsetFloatArray(&td->td_matrixWorldToScreen,
                        va_arg(ap, float*), 16);
                break;
        case TIFFTAG_PIXAR_MATRIX_WORLDTOCAMERA:
                _TIFFsetFloatArray(&td->td_matrixWorldToCamera,
                        va_arg(ap, float*), 16);
                break;
        /* End Pixar Tags */           

#if SUBIFD_SUPPORT
        case TIFFTAG_SUBIFD:
                if ((tif->tif_flags & TIFF_INSUBIFD) == 0) {
                        td->td_nsubifd = (uint16) va_arg(ap, int);
                        _TIFFsetLongArray(&td->td_subifd, va_arg(ap, uint32*),
                            (long) td->td_nsubifd);
                } else {
                        TIFFError(tif->tif_name, "Sorry, cannot nest SubIFDs");
                        status = 0;
                }
                break;
#endif
#ifdef YCBCR_SUPPORT
        case TIFFTAG_YCBCRCOEFFICIENTS:
                _TIFFsetFloatArray(&td->td_ycbcrcoeffs, va_arg(ap, float*), 3);
                break;
        case TIFFTAG_YCBCRPOSITIONING:
                td->td_ycbcrpositioning = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_YCBCRSUBSAMPLING:
                td->td_ycbcrsubsampling[0] = (uint16) va_arg(ap, int);
                td->td_ycbcrsubsampling[1] = (uint16) va_arg(ap, int);
                break;
#endif
#ifdef COLORIMETRY_SUPPORT
        case TIFFTAG_WHITEPOINT:
                _TIFFsetFloatArray(&td->td_whitepoint, va_arg(ap, float*), 2);
                break;
        case TIFFTAG_PRIMARYCHROMATICITIES:
                _TIFFsetFloatArray(&td->td_primarychromas, va_arg(ap, float*), 6);
                break;
        case TIFFTAG_TRANSFERFUNCTION:
                v = (td->td_samplesperpixel - td->td_extrasamples) > 1 ? 3 : 1;
                for (i = 0; i < v; i++)
                        _TIFFsetShortArray(&td->td_transferfunction[i],
                            va_arg(ap, uint16*), 1L<<td->td_bitspersample);
                break;
        case TIFFTAG_REFERENCEBLACKWHITE:
                /* XXX should check for null range */
                _TIFFsetFloatArray(&td->td_refblackwhite, va_arg(ap, float*), 6);
                break;
#endif
#ifdef CMYK_SUPPORT
        case TIFFTAG_INKSET:
                td->td_inkset = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_DOTRANGE:
                /* XXX should check for null range */
                td->td_dotrange[0] = (uint16) va_arg(ap, int);
                td->td_dotrange[1] = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_INKNAMES:
                i = va_arg(ap, int);
                s = va_arg(ap, char*);
                i = checkInkNamesString(tif, i, s);
                status = i > 0;
                if( i > 0 ) {
                        _TIFFsetNString(&td->td_inknames, s, i);
                        td->td_inknameslen = i;
                }
                break;
        case TIFFTAG_NUMBEROFINKS:
                td->td_ninks = (uint16) va_arg(ap, int);
                break;
        case TIFFTAG_TARGETPRINTER:
                _TIFFsetString(&td->td_targetprinter, va_arg(ap, char*));
                break;
#endif
#ifdef ICC_SUPPORT
        case TIFFTAG_ICCPROFILE:
                td->td_profileLength = (uint32) va_arg(ap, uint32);
                _TIFFsetByteArray(&td->td_profileData, va_arg(ap, void*),
                    td->td_profileLength);
                break;
#endif
#ifdef PHOTOSHOP_SUPPORT
        case TIFFTAG_PHOTOSHOP:
                td->td_photoshopLength = (uint32) va_arg(ap, uint32);
                _TIFFsetByteArray (&td->td_photoshopData, va_arg(ap, void*),
                        td->td_photoshopLength);
                break;
#endif
#ifdef IPTC_SUPPORT
    case TIFFTAG_RICHTIFFIPTC: 
                td->td_richtiffiptcLength = (uint32) va_arg(ap, uint32);
#ifdef PHOTOSHOP_SUPPORT
                _TIFFsetLongArray ((uint32**)&td->td_richtiffiptcData, va_arg(ap, uint32*),
                        td->td_richtiffiptcLength);
#else
                _TIFFsetByteArray (&td->td_photoshopData, va_arg(ap, void*),
                        td->td_photoshopLength);
#endif
                break;
#endif
        case TIFFTAG_CZ_LSMINFO:
                td->td_cz_lsminfoLength = (uint32) va_arg(ap, uint32);
                _TIFFsetByteArray (&td->td_cz_lsminfoData, va_arg(ap, void*),
                        td->td_cz_lsminfoLength);
                break;
        case TIFFTAG_UIC2TAG:
                td->td_uic2tagLength = (uint32) va_arg(ap, uint32);
                _TIFFsetLongArray (&td->td_uic2tagData, va_arg(ap, void*),
                                   td->td_uic2tagLength*6);
                break;
        default:
                /*
                 * This can happen if multiple images are open with
                 * different codecs which have private tags.  The
                 * global tag information table may then have tags
                 * that are valid for one file but not the other. 
                 * If the client tries to set a tag that is not valid
                 * for the image's codec then we'll arrive here.  This
                 * happens, for example, when tiffcp is used to convert
                 * between compression schemes and codec-specific tags
                 * are blindly copied.
                 */
                TIFFError("TIFFSetField",
                    "%s: Invalid %stag \"%s\" (not supported by codec)",
                    tif->tif_name, isPseudoTag(tag) ? "pseduo-" : "",
                    _TIFFFieldWithTag(tif, tag)->field_name);
                status = 0;
                break;
        }
        if (status) {
                TIFFSetFieldBit(tif, _TIFFFieldWithTag(tif, tag)->field_bit);
                tif->tif_flags |= TIFF_DIRTYDIRECT;
        }
        va_end(ap);
        return (status);
badvalue:
        TIFFError(tif->tif_name, "%d: Bad value for \"%s\"", v,
            _TIFFFieldWithTag(tif, tag)->field_name);
        va_end(ap);
        return (0);
badvalue32:
        TIFFError(tif->tif_name, "%ld: Bad value for \"%s\"", v32,
            _TIFFFieldWithTag(tif, tag)->field_name);
        va_end(ap);
        return (0);
badvaluedbl:
        TIFFError(tif->tif_name, "%f: Bad value for \"%s\"", d,
            _TIFFFieldWithTag(tif, tag)->field_name);
        va_end(ap);
        return (0);
}

/*
 * Return 1/0 according to whether or not
 * it is permissible to set the tag's value.
 * Note that we allow ImageLength to be changed
 * so that we can append and extend to images.
 * Any other tag may not be altered once writing
 * has commenced, unless its value has no effect
 * on the format of the data that is written.
 */
static int
OkToChangeTag(TIFF* tif, ttag_t tag)
{
        const TIFFFieldInfo* fip = _TIFFFindFieldInfo(tif, tag, TIFF_ANY);
        if (!fip) {                     /* unknown tag */
                TIFFError("TIFFSetField", "%s: Unknown %stag %u",
                    tif->tif_name, isPseudoTag(tag) ? "pseudo-" : "", tag);
                return (0);
        }
        if (tag != TIFFTAG_IMAGELENGTH && (tif->tif_flags & TIFF_BEENWRITING) &&
            !fip->field_oktochange) {
                /*
                 * Consult info table to see if tag can be changed
                 * after we've started writing.  We only allow changes
                 * to those tags that don't/shouldn't affect the
                 * compression and/or format of the data.
                 */
                TIFFError("TIFFSetField",
                    "%s: Cannot modify tag \"%s\" while writing",
                    tif->tif_name, fip->field_name);
                return (0);
        }
        return (1);
}

/*
 * Record the value of a field in the
 * internal directory structure.  The
 * field will be written to the file
 * when/if the directory structure is
 * updated.
 */
int
TIFFSetField(TIFF* tif, ttag_t tag, ...)
{
        va_list ap;
        int status;

        va_start(ap, tag);
        status = TIFFVSetField(tif, tag, ap);
        va_end(ap);
        return (status);
}

/*
 * Like TIFFSetField, but taking a varargs
 * parameter list.  This routine is useful
 * for building higher-level interfaces on
 * top of the library.
 */
int
TIFFVSetField(TIFF* tif, ttag_t tag, va_list ap)
{
        return OkToChangeTag(tif, tag) ?
            (*tif->tif_vsetfield)(tif, tag, ap) : 0;
}

static int
_TIFFVGetField(TIFF* tif, ttag_t tag, va_list ap)
{
        TIFFDirectory* td = &tif->tif_dir;

        switch (tag) {
        case TIFFTAG_SUBFILETYPE:
                *va_arg(ap, uint32*) = td->td_subfiletype;
                break;
        case TIFFTAG_IMAGEWIDTH:
                *va_arg(ap, uint32*) = td->td_imagewidth;
                break;
        case TIFFTAG_IMAGELENGTH:
                *va_arg(ap, uint32*) = td->td_imagelength;
                break;
        case TIFFTAG_BITSPERSAMPLE:
                *va_arg(ap, uint16*) = td->td_bitspersample;
                break;
        case TIFFTAG_COMPRESSION:
                *va_arg(ap, uint16*) = td->td_compression;
                break;
        case TIFFTAG_PHOTOMETRIC:
                *va_arg(ap, uint16*) = td->td_photometric;
                break;
        case TIFFTAG_THRESHHOLDING:
                *va_arg(ap, uint16*) = td->td_threshholding;
                break;
        case TIFFTAG_FILLORDER:
                *va_arg(ap, uint16*) = td->td_fillorder;
                break;
        case TIFFTAG_DOCUMENTNAME:
                *va_arg(ap, char**) = td->td_documentname;
                break;
        case TIFFTAG_ARTIST:
                *va_arg(ap, char**) = td->td_artist;
                break;
        case TIFFTAG_DATETIME:
                *va_arg(ap, char**) = td->td_datetime;
                break;
        case TIFFTAG_HOSTCOMPUTER:
                *va_arg(ap, char**) = td->td_hostcomputer;
                break;
        case TIFFTAG_IMAGEDESCRIPTION:
                *va_arg(ap, char**) = td->td_imagedescription;
                break;
        case TIFFTAG_MAKE:
                *va_arg(ap, char**) = td->td_make;
                break;
        case TIFFTAG_MODEL:
                *va_arg(ap, char**) = td->td_model;
                break;
        case TIFFTAG_SOFTWARE:
                *va_arg(ap, char**) = td->td_software;
                break;
        case TIFFTAG_COPYRIGHT:
                *va_arg(ap, char**) = td->td_copyright;
                break;
        case TIFFTAG_ORIENTATION:
                *va_arg(ap, uint16*) = td->td_orientation;
                break;
        case TIFFTAG_SAMPLESPERPIXEL:
                *va_arg(ap, uint16*) = td->td_samplesperpixel;
                break;
        case TIFFTAG_ROWSPERSTRIP:
                *va_arg(ap, uint32*) = td->td_rowsperstrip;
                break;
        case TIFFTAG_MINSAMPLEVALUE:
                *va_arg(ap, uint16*) = td->td_minsamplevalue;
                break;
        case TIFFTAG_MAXSAMPLEVALUE:
                *va_arg(ap, uint16*) = td->td_maxsamplevalue;
                break;
        case TIFFTAG_SMINSAMPLEVALUE:
                *va_arg(ap, double*) = td->td_sminsamplevalue;
                break;
        case TIFFTAG_SMAXSAMPLEVALUE:
                *va_arg(ap, double*) = td->td_smaxsamplevalue;
                break;
        case TIFFTAG_XRESOLUTION:
                *va_arg(ap, float*) = td->td_xresolution;
                break;
        case TIFFTAG_YRESOLUTION:
                *va_arg(ap, float*) = td->td_yresolution;
                break;
        case TIFFTAG_PLANARCONFIG:
                *va_arg(ap, uint16*) = td->td_planarconfig;
                break;
        case TIFFTAG_XPOSITION:
                *va_arg(ap, float*) = td->td_xposition;
                break;
        case TIFFTAG_YPOSITION:
                *va_arg(ap, float*) = td->td_yposition;
                break;
        case TIFFTAG_PAGENAME:
                *va_arg(ap, char**) = td->td_pagename;
                break;
        case TIFFTAG_RESOLUTIONUNIT:
                *va_arg(ap, uint16*) = td->td_resolutionunit;
                break;
        case TIFFTAG_PAGENUMBER:
                *va_arg(ap, uint16*) = td->td_pagenumber[0];
                *va_arg(ap, uint16*) = td->td_pagenumber[1];
                break;
        case TIFFTAG_HALFTONEHINTS:
                *va_arg(ap, uint16*) = td->td_halftonehints[0];
                *va_arg(ap, uint16*) = td->td_halftonehints[1];
                break;
        case TIFFTAG_COLORMAP:
                *va_arg(ap, uint16**) = td->td_colormap[0];
                *va_arg(ap, uint16**) = td->td_colormap[1];
                *va_arg(ap, uint16**) = td->td_colormap[2];
                break;
        case TIFFTAG_STRIPOFFSETS:
        case TIFFTAG_TILEOFFSETS:
                *va_arg(ap, uint32**) = td->td_stripoffset;
                break;
        case TIFFTAG_STRIPBYTECOUNTS:
        case TIFFTAG_TILEBYTECOUNTS:
                *va_arg(ap, uint32**) = td->td_stripbytecount;
                break;
        case TIFFTAG_MATTEING:
                *va_arg(ap, uint16*) =
                    (td->td_extrasamples == 1 &&
                     td->td_sampleinfo[0] == EXTRASAMPLE_ASSOCALPHA);
                break;
        case TIFFTAG_EXTRASAMPLES:
                *va_arg(ap, uint16*) = td->td_extrasamples;
                *va_arg(ap, uint16**) = td->td_sampleinfo;
                break;
        case TIFFTAG_TILEWIDTH:
                *va_arg(ap, uint32*) = td->td_tilewidth;
                break;
        case TIFFTAG_TILELENGTH:
                *va_arg(ap, uint32*) = td->td_tilelength;
                break;
        case TIFFTAG_TILEDEPTH:
                *va_arg(ap, uint32*) = td->td_tiledepth;
                break;
        case TIFFTAG_DATATYPE:
                switch (td->td_sampleformat) {
                case SAMPLEFORMAT_UINT:
                        *va_arg(ap, uint16*) = DATATYPE_UINT;
                        break;
                case SAMPLEFORMAT_INT:
                        *va_arg(ap, uint16*) = DATATYPE_INT;
                        break;
                case SAMPLEFORMAT_IEEEFP:
                        *va_arg(ap, uint16*) = DATATYPE_IEEEFP;
                        break;
                case SAMPLEFORMAT_VOID:
                        *va_arg(ap, uint16*) = DATATYPE_VOID;
                        break;
                }
                break;
        case TIFFTAG_SAMPLEFORMAT:
                *va_arg(ap, uint16*) = td->td_sampleformat;
                break;
        case TIFFTAG_IMAGEDEPTH:
                *va_arg(ap, uint32*) = td->td_imagedepth;
                break;
        case TIFFTAG_STONITS:
                *va_arg(ap, double*) = td->td_stonits;
                break;
#if SUBIFD_SUPPORT
        case TIFFTAG_SUBIFD:
                *va_arg(ap, uint16*) = td->td_nsubifd;
                *va_arg(ap, uint32**) = td->td_subifd;
                break;
#endif
#ifdef YCBCR_SUPPORT
        case TIFFTAG_YCBCRCOEFFICIENTS:
                *va_arg(ap, float**) = td->td_ycbcrcoeffs;
                break;
        case TIFFTAG_YCBCRPOSITIONING:
                *va_arg(ap, uint16*) = td->td_ycbcrpositioning;
                break;
        case TIFFTAG_YCBCRSUBSAMPLING:
                *va_arg(ap, uint16*) = td->td_ycbcrsubsampling[0];
                *va_arg(ap, uint16*) = td->td_ycbcrsubsampling[1];
                break;
#endif
#ifdef COLORIMETRY_SUPPORT
        case TIFFTAG_WHITEPOINT:
                *va_arg(ap, float**) = td->td_whitepoint;
                break;
        case TIFFTAG_PRIMARYCHROMATICITIES:
                *va_arg(ap, float**) = td->td_primarychromas;
                break;
        case TIFFTAG_TRANSFERFUNCTION:
                *va_arg(ap, uint16**) = td->td_transferfunction[0];
                if (td->td_samplesperpixel - td->td_extrasamples > 1) {
                        *va_arg(ap, uint16**) = td->td_transferfunction[1];
                        *va_arg(ap, uint16**) = td->td_transferfunction[2];
                }
                break;
        case TIFFTAG_REFERENCEBLACKWHITE:
                *va_arg(ap, float**) = td->td_refblackwhite;
                break;
#endif
#ifdef CMYK_SUPPORT
        case TIFFTAG_INKSET:
                *va_arg(ap, uint16*) = td->td_inkset;
                break;
        case TIFFTAG_DOTRANGE:
                *va_arg(ap, uint16*) = td->td_dotrange[0];
                *va_arg(ap, uint16*) = td->td_dotrange[1];
                break;
        case TIFFTAG_INKNAMES:
                *va_arg(ap, char**) = td->td_inknames;
                break;
        case TIFFTAG_NUMBEROFINKS:
                *va_arg(ap, uint16*) = td->td_ninks;
                break;
        case TIFFTAG_TARGETPRINTER:
                *va_arg(ap, char**) = td->td_targetprinter;
                break;
#endif
#ifdef ICC_SUPPORT
        case TIFFTAG_ICCPROFILE:
                *va_arg(ap, uint32*) = td->td_profileLength;
                *va_arg(ap, void**) = td->td_profileData;
                break;
#endif
#ifdef PHOTOSHOP_SUPPORT
        case TIFFTAG_PHOTOSHOP:
                *va_arg(ap, uint32*) = td->td_photoshopLength;
                *va_arg(ap, void**) = td->td_photoshopData;
                break;
#endif
#ifdef IPTC_SUPPORT
        case TIFFTAG_RICHTIFFIPTC:
                *va_arg(ap, uint32*) = td->td_richtiffiptcLength;
                *va_arg(ap, void**) = td->td_richtiffiptcData;
                break;
#endif
        /* Begin Pixar Tags */
        case TIFFTAG_PIXAR_IMAGEFULLWIDTH:
                *va_arg(ap, uint32*) = td->td_imagefullwidth;
                break;
        case TIFFTAG_PIXAR_IMAGEFULLLENGTH:
                *va_arg(ap, uint32*) = td->td_imagefulllength;
                break;
        case TIFFTAG_PIXAR_TEXTUREFORMAT:
                *va_arg(ap, char**) = td->td_textureformat;
                break;
        case TIFFTAG_PIXAR_WRAPMODES:
                *va_arg(ap, char**) = td->td_wrapmodes;
                break;
        case TIFFTAG_PIXAR_FOVCOT:
                *va_arg(ap, float*) = td->td_fovcot;
                break;
        case TIFFTAG_PIXAR_MATRIX_WORLDTOSCREEN:
                *va_arg(ap, float**) = td->td_matrixWorldToScreen;
                break;
        case TIFFTAG_PIXAR_MATRIX_WORLDTOCAMERA:
                *va_arg(ap, float**) = td->td_matrixWorldToCamera;
                break;
        /* End Pixar Tags */

        case TIFFTAG_CZ_LSMINFO:
          *va_arg(ap, uint32*) = td->td_cz_lsminfoLength;
          *va_arg(ap, void**) = td->td_cz_lsminfoData;
          break;
        case TIFFTAG_UIC2TAG:
          *va_arg(ap, uint32*) = td->td_uic2tagLength;
          *va_arg(ap, uint32**) = td->td_uic2tagData;
          break;
        default:
                /*
                 * This can happen if multiple images are open with
                 * different codecs which have private tags.  The
                 * global tag information table may then have tags
                 * that are valid for one file but not the other. 
                 * If the client tries to get a tag that is not valid
                 * for the image's codec then we'll arrive here.
                 */
                TIFFError("TIFFGetField",
                    "%s: Invalid %stag \"%s\" (not supported by codec)",
                    tif->tif_name, isPseudoTag(tag) ? "pseudo-" : "",
                    _TIFFFieldWithTag(tif, tag)->field_name);
                break;
        }
        return (1);
}

/*
 * Return the value of a field in the
 * internal directory structure.
 */
int
TEXPORT TIFFGetField(TIFF* tif, ttag_t tag, ...)
{
        int status;
        va_list ap;

        va_start(ap, tag);
        status = TIFFVGetField(tif, tag, ap);
        va_end(ap);
        return (status);
}

/*
 * Like TIFFGetField, but taking a varargs
 * parameter list.  This routine is useful
 * for building higher-level interfaces on
 * top of the library.
 */
int
TIFFVGetField(TIFF* tif, ttag_t tag, va_list ap)
{
        const TIFFFieldInfo* fip = _TIFFFindFieldInfo(tif, tag, TIFF_ANY);
        return (fip && (isPseudoTag(tag) || TIFFFieldSet(tif, fip->field_bit)) ?
            (*tif->tif_vgetfield)(tif, tag, ap) : 0);
}

#define CleanupField(member) {          \
    if (td->member) {                   \
        _TIFFfree(td->member);          \
        td->member = 0;                 \
    }                                   \
}

/*
 * Release storage associated with a directory.
 */
void
TIFFFreeDirectory(TIFF* tif)
{
        register TIFFDirectory *td = &tif->tif_dir;

        CleanupField(td_colormap[0]);
        CleanupField(td_colormap[1]);
        CleanupField(td_colormap[2]);
        CleanupField(td_documentname);
        CleanupField(td_artist);
        CleanupField(td_datetime);
        CleanupField(td_hostcomputer);
        CleanupField(td_imagedescription);
        CleanupField(td_make);
        CleanupField(td_model);
        CleanupField(td_software);
        CleanupField(td_copyright);
        CleanupField(td_pagename);
        CleanupField(td_sampleinfo);
#if SUBIFD_SUPPORT
        CleanupField(td_subifd);
#endif
#ifdef YCBCR_SUPPORT
        CleanupField(td_ycbcrcoeffs);
#endif
#ifdef CMYK_SUPPORT
        CleanupField(td_inknames);
        CleanupField(td_targetprinter);
#endif
#ifdef COLORIMETRY_SUPPORT
        CleanupField(td_whitepoint);
        CleanupField(td_primarychromas);
        CleanupField(td_refblackwhite);
        CleanupField(td_transferfunction[0]);
        CleanupField(td_transferfunction[1]);
        CleanupField(td_transferfunction[2]);
#endif
#ifdef ICC_SUPPORT
        CleanupField(td_profileData);
#endif
#ifdef PHOTOSHOP_SUPPORT
        CleanupField(td_photoshopData);
#endif
#ifdef IPTC_SUPPORT
        CleanupField(td_richtiffiptcData);
#endif
        CleanupField(td_cz_lsminfoData);
        CleanupField(td_uic2tagData);
        CleanupField(td_stripoffset);
        CleanupField(td_stripbytecount);
        /* Begin Pixar Tags */
        CleanupField(td_textureformat);
        CleanupField(td_wrapmodes);
        CleanupField(td_matrixWorldToScreen);
        CleanupField(td_matrixWorldToCamera);
        /* End Pixar Tags */
}
#undef CleanupField

/*
 * Client Tag extension support (from Niles Ritter).
 */
static TIFFExtendProc _TIFFextender = (TIFFExtendProc) NULL;

TIFFExtendProc
TIFFSetTagExtender(TIFFExtendProc extender)
{
        TIFFExtendProc prev = _TIFFextender;
        _TIFFextender = extender;
        return (prev);
}

/*
 * Setup for a new directory.  Should we automatically call
 * TIFFWriteDirectory() if the current one is dirty?
 *
 * The newly created directory will not exist on the file till
 * TIFFWriteDirectory(), TIFFFlush() or TIFFClose() is called.
 */
int
TIFFCreateDirectory(TIFF* tif)
{
    TIFFDefaultDirectory(tif);
    tif->tif_diroff = 0;
    tif->tif_nextdiroff = 0;
    tif->tif_curoff = 0;
    tif->tif_row = (uint32) -1;
    tif->tif_curstrip = (tstrip_t) -1;

    return 0;
}

/*
 * Setup a default directory structure.
 */
int
TIFFDefaultDirectory(TIFF* tif)
{
        register TIFFDirectory* td = &tif->tif_dir;

        _TIFFSetupFieldInfo(tif);
        _TIFFmemset(td, 0, sizeof (*td));
        td->td_fillorder = FILLORDER_MSB2LSB;
        td->td_bitspersample = 1;
        td->td_threshholding = THRESHHOLD_BILEVEL;
        td->td_orientation = ORIENTATION_TOPLEFT;
        td->td_samplesperpixel = 1;
        td->td_rowsperstrip = (uint32) -1;
        td->td_tilewidth = (uint32) -1;
        td->td_tilelength = (uint32) -1;
        td->td_tiledepth = 1;
        td->td_resolutionunit = RESUNIT_INCH;
        td->td_sampleformat = SAMPLEFORMAT_UINT;
        td->td_imagedepth = 1;
#ifdef YCBCR_SUPPORT
        td->td_ycbcrsubsampling[0] = 2;
        td->td_ycbcrsubsampling[1] = 2;
        td->td_ycbcrpositioning = YCBCRPOSITION_CENTERED;
#endif
#ifdef CMYK_SUPPORT
        td->td_inkset = INKSET_CMYK;
        td->td_ninks = 4;
#endif
        tif->tif_postdecode = _TIFFNoPostDecode;
        tif->tif_vsetfield = _TIFFVSetField;
        tif->tif_vgetfield = _TIFFVGetField;
        tif->tif_printdir = NULL;
        /*
         *  Give client code a chance to install their own
         *  tag extensions & methods, prior to compression overloads.
         */
        if (_TIFFextender)
                (*_TIFFextender)(tif);
        (void) TIFFSetField(tif, TIFFTAG_COMPRESSION, COMPRESSION_NONE);
        /*
         * NB: The directory is marked dirty as a result of setting
         * up the default compression scheme.  However, this really
         * isn't correct -- we want TIFF_DIRTYDIRECT to be set only
         * if the user does something.  We could just do the setup
         * by hand, but it seems better to use the normal mechanism
         * (i.e. TIFFSetField).
         */
        tif->tif_flags &= ~TIFF_DIRTYDIRECT;

        /*
         * As per http://bugzilla.remotesensing.org/show_bug.cgi?id=19
         * we clear the ISTILED flag when setting up a new directory.
         * Should we also be clearing stuff like INSUBIFD?
         */
        tif->tif_flags &= ~TIFF_ISTILED;

        return (1);
}

static int
TIFFAdvanceDirectory(TIFF* tif, uint32* nextdir, toff_t* off)
{
    static const char module[] = "TIFFAdvanceDirectory";
    uint16 dircount;
    if (isMapped(tif))
    {
        toff_t poff=*nextdir;
        if (poff+sizeof(uint16) > tif->tif_size)
        {
            TIFFError(module, "%s: Error fetching directory count",
                      tif->tif_name);
            return (0);
        }
        _TIFFmemcpy(&dircount, tif->tif_base+poff, sizeof (uint16));
        if (tif->tif_flags & TIFF_SWAB)
            TIFFSwabShort(&dircount);
        poff+=sizeof (uint16)+dircount*sizeof (TIFFDirEntry);
        if (off != NULL)
            *off = poff;
        if (((toff_t) (poff+sizeof (uint32))) > tif->tif_size)
        {
            TIFFError(module, "%s: Error fetching directory link",
                      tif->tif_name);
            return (0);
        }
        _TIFFmemcpy(nextdir, tif->tif_base+poff, sizeof (uint32));
        if (tif->tif_flags & TIFF_SWAB)
            TIFFSwabLong(nextdir);
        return (1);
    }
    else
    {
        if (!SeekOK(tif, *nextdir) ||
            !ReadOK(tif, &dircount, sizeof (uint16))) {
            TIFFError(module, "%s: Error fetching directory count",
                      tif->tif_name);
            return (0);
        }
        if (tif->tif_flags & TIFF_SWAB)
            TIFFSwabShort(&dircount);
        if (off != NULL)
            *off = TIFFSeekFile(tif,
                                dircount*sizeof (TIFFDirEntry), SEEK_CUR);
        else
            (void) TIFFSeekFile(tif,
                                dircount*sizeof (TIFFDirEntry), SEEK_CUR);
        if (!ReadOK(tif, nextdir, sizeof (uint32))) {
            TIFFError(module, "%s: Error fetching directory link",
                      tif->tif_name);
            return (0);
        }
        if (tif->tif_flags & TIFF_SWAB)
            TIFFSwabLong(nextdir);
        return (1);
    }
}

/*
 * Count the number of directories in a file.
 */
tdir_t
TIFFNumberOfDirectories(TIFF* tif)
{
    toff_t nextdir = tif->tif_header.tiff_diroff;
    tdir_t n = 0;
    
    while (nextdir != 0 && TIFFAdvanceDirectory(tif, &nextdir, NULL))
        n++;
    return (n);
}

/*
 * Set the n-th directory as the current directory.
 * NB: Directories are numbered starting at 0.
 */
int
TIFFSetDirectory(TIFF* tif, tdir_t dirn)
{
        toff_t nextdir;
        tdir_t n;

        nextdir = tif->tif_header.tiff_diroff;
        for (n = dirn; n > 0 && nextdir != 0; n--)
                if (!TIFFAdvanceDirectory(tif, &nextdir, NULL))
                        return (0);
        tif->tif_nextdiroff = nextdir;
        /*
         * Set curdir to the actual directory index.  The
         * -1 is because TIFFReadDirectory will increment
         * tif_curdir after successfully reading the directory.
         */
        tif->tif_curdir = (dirn - n) - 1;
        return (TIFFReadDirectory(tif));
}

/*
 * Set the current directory to be the directory
 * located at the specified file offset.  This interface
 * is used mainly to access directories linked with
 * the SubIFD tag (e.g. thumbnail images).
 */
int
TIFFSetSubDirectory(TIFF* tif, uint32 diroff)
{
        tif->tif_nextdiroff = diroff;
        return (TIFFReadDirectory(tif));
}

/*
 * Return file offset of the current directory.
 */
uint32
TIFFCurrentDirOffset(TIFF* tif)
{
        return (tif->tif_diroff);
}

/*
 * Return an indication of whether or not we are
 * at the last directory in the file.
 */
int
TIFFLastDirectory(TIFF* tif)
{
        return (tif->tif_nextdiroff == 0);
}

/*
 * Unlink the specified directory from the directory chain.
 */
int
TIFFUnlinkDirectory(TIFF* tif, tdir_t dirn)
{
        static const char module[] = "TIFFUnlinkDirectory";
        toff_t nextdir;
        toff_t off;
        tdir_t n;

        if (tif->tif_mode == O_RDONLY) {
                TIFFError(module, "Can not unlink directory in read-only file");
                return (0);
        }
        /*
         * Go to the directory before the one we want
         * to unlink and nab the offset of the link
         * field we'll need to patch.
         */
        nextdir = tif->tif_header.tiff_diroff;
        off = sizeof (uint16) + sizeof (uint16);
        for (n = dirn-1; n > 0; n--) {
                if (nextdir == 0) {
                        TIFFError(module, "Directory %d does not exist", dirn);
                        return (0);
                }
                if (!TIFFAdvanceDirectory(tif, &nextdir, &off))
                        return (0);
        }
        /*
         * Advance to the directory to be unlinked and fetch
         * the offset of the directory that follows.
         */
        if (!TIFFAdvanceDirectory(tif, &nextdir, NULL))
                return (0);
        /*
         * Go back and patch the link field of the preceding
         * directory to point to the offset of the directory
         * that follows.
         */
        (void) TIFFSeekFile(tif, off, SEEK_SET);
        if (tif->tif_flags & TIFF_SWAB)
                TIFFSwabLong(&nextdir);
        if (!WriteOK(tif, &nextdir, sizeof (uint32))) {
                TIFFError(module, "Error writing directory link");
                return (0);
        }
        /*
         * Leave directory state setup safely.  We don't have
         * facilities for doing inserting and removing directories,
         * so it's safest to just invalidate everything.  This
         * means that the caller can only append to the directory
         * chain.
         */
        (*tif->tif_cleanup)(tif);
        if ((tif->tif_flags & TIFF_MYBUFFER) && tif->tif_rawdata) {
                _TIFFfree(tif->tif_rawdata);
                tif->tif_rawdata = NULL;
                tif->tif_rawcc = 0;
        }
        tif->tif_flags &= ~(TIFF_BEENWRITING|TIFF_BUFFERSETUP|TIFF_POSTENCODE);
        TIFFFreeDirectory(tif);
        TIFFDefaultDirectory(tif);
        tif->tif_diroff = 0;                    /* force link on next write */
        tif->tif_nextdiroff = 0;                /* next write must be at end */
        tif->tif_curoff = 0;
        tif->tif_row = (uint32) -1;
        tif->tif_curstrip = (tstrip_t) -1;
        return (1);
}

/*                      [BFC]
 *
 * Author: Bruce Cameron <cameron@petris.com>
 *
 * Set a table of tags that are to be replaced during directory process by the
 * 'IGNORE' state - or return TRUE/FALSE for the requested tag such that
 * 'ReadDirectory' can use the stored information.
 */
int
TIFFReassignTagToIgnore (enum TIFFIgnoreSense task, int TIFFtagID)
{
    static int TIFFignoretags [FIELD_LAST];
    static int tagcount = 0 ;
    int         i;                                      /* Loop index */
    int         j;                                      /* Loop index */

    switch (task)
    {
      case TIS_STORE:
        if ( tagcount < (FIELD_LAST - 1) )
        {
            for ( j = 0 ; j < tagcount ; ++j )
            {                                   /* Do not add duplicate tag */
                if ( TIFFignoretags [j] == TIFFtagID )
                    return (TRUE) ;
            }
            TIFFignoretags [tagcount++] = TIFFtagID ;
            return (TRUE) ;
        }
        break ;
        
      case TIS_EXTRACT:
        for ( i = 0 ; i < tagcount ; ++i )
        {
            if ( TIFFignoretags [i] == TIFFtagID )
                return (TRUE) ;
        }
        break;
        
      case TIS_EMPTY:
        tagcount = 0 ;                  /* Clear the list */
        return (TRUE) ;
        
      default:
        break;
    }
    
    return (FALSE);
}