/* $Header: /cvsroot/osrs/libtiff/libtiff/tif_dirread.c,v 1.9 2002/03/27 14:46:45 warmerda 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 Read Support Routines.
 */
#include "tiffiop.h"

#define	IGNORE	0		/* tag placeholder used below */

#if HAVE_IEEEFP
#define	TIFFCvtIEEEFloatToNative(tif, n, fp)
#define	TIFFCvtIEEEDoubleToNative(tif, n, dp)
#else
extern	void TIFFCvtIEEEFloatToNative(TIFF*, uint32, float*);
extern	void TIFFCvtIEEEDoubleToNative(TIFF*, uint32, double*);
#endif

static	int EstimateStripByteCounts(TIFF*, TIFFDirEntry*, uint16);
static	void MissingRequired(TIFF*, const char*);
static	int CheckDirCount(TIFF*, TIFFDirEntry*, uint32);
static	tsize_t TIFFFetchData(TIFF*, TIFFDirEntry*, char*);
static	tsize_t TIFFFetchString(TIFF*, TIFFDirEntry*, char*);
static	float TIFFFetchRational(TIFF*, TIFFDirEntry*);
static	int TIFFFetchNormalTag(TIFF*, TIFFDirEntry*);
static	int TIFFFetchPerSampleShorts(TIFF*, TIFFDirEntry*, int*);
static	int TIFFFetchPerSampleAnys(TIFF*, TIFFDirEntry*, double*);
static	int TIFFFetchShortArray(TIFF*, TIFFDirEntry*, uint16*);
static	int TIFFFetchStripThing(TIFF*, TIFFDirEntry*, long, uint32**);
static	int TIFFFetchExtraSamples(TIFF*, TIFFDirEntry*);
static	int TIFFFetchRefBlackWhite(TIFF*, TIFFDirEntry*);
static	float TIFFFetchFloat(TIFF*, TIFFDirEntry*);
static	int TIFFFetchFloatArray(TIFF*, TIFFDirEntry*, float*);
static	int TIFFFetchDoubleArray(TIFF*, TIFFDirEntry*, double*);
static	int TIFFFetchAnyArray(TIFF*, TIFFDirEntry*, double*);
static	int TIFFFetchShortPair(TIFF*, TIFFDirEntry*);
static	void ChopUpSingleUncompressedStrip(TIFF*);

static char *
CheckMalloc(TIFF* tif, tsize_t n, const char* what)
{
	char *cp = (char*)_TIFFmalloc(n);
	if (cp == NULL)
		TIFFError(tif->tif_name, "No space %s", what);
	return (cp);
}

/*
 * Read the next TIFF directory from a file
 * and convert it to the internal format.
 * We read directories sequentially.
 */
int
TIFFReadDirectory(TIFF* tif)
{
	register TIFFDirEntry* dp;
	register int n;
	register TIFFDirectory* td;
	TIFFDirEntry* dir;
	int iv;
	long v;
	double dv;
	const TIFFFieldInfo* fip;
	int fix;
	uint16 dircount;
	toff_t nextdiroff;
	char* cp;
	int diroutoforderwarning = 0;

	tif->tif_diroff = tif->tif_nextdiroff;
	if (tif->tif_diroff == 0)		/* no more directories */
		return (0);
	/*
	 * Cleanup any previous compression state.
	 */
	(*tif->tif_cleanup)(tif);
	tif->tif_curdir++;
	nextdiroff = 0;
	if (!isMapped(tif)) {
		if (!SeekOK(tif, tif->tif_diroff)) {
			TIFFError(tif->tif_name,
			    "Seek error accessing TIFF directory");
			return (0);
		}
		if (!ReadOK(tif, &dircount, sizeof (uint16))) {
			TIFFError(tif->tif_name,
			    "Can not read TIFF directory count");
			return (0);
		}
		if (tif->tif_flags & TIFF_SWAB)
			TIFFSwabShort(&dircount);
		dir = (TIFFDirEntry *)CheckMalloc(tif,
		    dircount * sizeof (TIFFDirEntry), "to read TIFF directory");
		if (dir == NULL)
			return (0);
		if (!ReadOK(tif, dir, dircount*sizeof (TIFFDirEntry))) {
			TIFFError(tif->tif_name, "Can not read TIFF directory");
			goto bad;
		}
		/*
		 * Read offset to next directory for sequential scans.
		 */
		(void) ReadOK(tif, &nextdiroff, sizeof (uint32));
	} else {
		toff_t off = tif->tif_diroff;

		if (off + sizeof (uint16) > tif->tif_size) {
			TIFFError(tif->tif_name,
			    "Can not read TIFF directory count");
			return (0);
		} else
			_TIFFmemcpy(&dircount, tif->tif_base + off, sizeof (uint16));
		off += sizeof (uint16);
		if (tif->tif_flags & TIFF_SWAB)
			TIFFSwabShort(&dircount);
		dir = (TIFFDirEntry *)CheckMalloc(tif,
		    dircount * sizeof (TIFFDirEntry), "to read TIFF directory");
		if (dir == NULL)
			return (0);
		if (off + dircount*sizeof (TIFFDirEntry) > tif->tif_size) {
			TIFFError(tif->tif_name, "Can not read TIFF directory");
			goto bad;
		} else
			_TIFFmemcpy(dir, tif->tif_base + off,
			    dircount*sizeof (TIFFDirEntry));
		off += dircount* sizeof (TIFFDirEntry);
		if (off + sizeof (uint32) <= tif->tif_size)
			_TIFFmemcpy(&nextdiroff, tif->tif_base+off, sizeof (uint32));
	}
	if (tif->tif_flags & TIFF_SWAB)
		TIFFSwabLong(&nextdiroff);
	tif->tif_nextdiroff = nextdiroff;

	tif->tif_flags &= ~TIFF_BEENWRITING;	/* reset before new dir */
	/*
	 * Setup default value and then make a pass over
	 * the fields to check type and tag information,
	 * and to extract info required to size data
	 * structures.  A second pass is made afterwards
	 * to read in everthing not taken in the first pass.
	 */
	td = &tif->tif_dir;
	/* free any old stuff and reinit */
	TIFFFreeDirectory(tif);
	TIFFDefaultDirectory(tif);
	/*
	 * Electronic Arts writes gray-scale TIFF files
	 * without a PlanarConfiguration directory entry.
	 * Thus we setup a default value here, even though
	 * the TIFF spec says there is no default value.
	 */
	TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);

	/*
	 * Sigh, we must make a separate pass through the
	 * directory for the following reason:
	 *
	 * We must process the Compression tag in the first pass
	 * in order to merge in codec-private tag definitions (otherwise
	 * we may get complaints about unknown tags).  However, the
	 * Compression tag may be dependent on the SamplesPerPixel
	 * tag value because older TIFF specs permited Compression
	 * to be written as a SamplesPerPixel-count tag entry.
	 * Thus if we don't first figure out the correct SamplesPerPixel
	 * tag value then we may end up ignoring the Compression tag
	 * value because it has an incorrect count value (if the
	 * true value of SamplesPerPixel is not 1).
	 *
	 * It sure would have been nice if Aldus had really thought
	 * this stuff through carefully.
	 */ 
	for (dp = dir, n = dircount; n > 0; n--, dp++) {
		if (tif->tif_flags & TIFF_SWAB) {
			TIFFSwabArrayOfShort(&dp->tdir_tag, 2);
			TIFFSwabArrayOfLong(&dp->tdir_count, 2);
		}
		if (dp->tdir_tag == TIFFTAG_SAMPLESPERPIXEL) {
			if (!TIFFFetchNormalTag(tif, dp))
				goto bad;
			dp->tdir_tag = IGNORE;
		}
	}
	/*
	 * First real pass over the directory.
	 */
	fix = 0;
	for (dp = dir, n = dircount; n > 0; n--, dp++) {

                /*
                 * Find the field information entry for this tag.
		 * Added check for tags to ignore ... [BFC]
                 */
		if( TIFFReassignTagToIgnore(TIS_EXTRACT, dp->tdir_tag) )
                    dp->tdir_tag = IGNORE;

		if (dp->tdir_tag == IGNORE)
                    continue;
                
		/*
		 * Silicon Beach (at least) writes unordered
		 * directory tags (violating the spec).  Handle
		 * it here, but be obnoxious (maybe they'll fix it?).
		 */
		if (dp->tdir_tag < tif->tif_fieldinfo[fix]->field_tag) {
			if (!diroutoforderwarning) {
				TIFFWarning(tif->tif_name,
	"invalid TIFF directory; tags are not sorted in ascending order");
				diroutoforderwarning = 1;
			}
			fix = 0;			/* O(n^2) */
		}
		while (fix < tif->tif_nfields &&
		    tif->tif_fieldinfo[fix]->field_tag < dp->tdir_tag)
			fix++;
		if (fix == tif->tif_nfields ||
		    tif->tif_fieldinfo[fix]->field_tag != dp->tdir_tag) {

                    TIFFWarning(tif->tif_name,
                                "unknown field with tag %d (0x%x) encountered",
                                dp->tdir_tag,  dp->tdir_tag);

                    TIFFMergeFieldInfo( tif,
                                        _TIFFCreateAnonFieldInfo( tif,
                                              dp->tdir_tag, dp->tdir_type ),
                                        1 );
                    fix = 0;
                    while (fix < tif->tif_nfields &&
                           tif->tif_fieldinfo[fix]->field_tag < dp->tdir_tag)
			fix++;
		}
		/*
		 * Null out old tags that we ignore.
		 */
		if (tif->tif_fieldinfo[fix]->field_bit == FIELD_IGNORE) {
	ignore:
			dp->tdir_tag = IGNORE;
			continue;
		}
		/*
		 * Check data type.
		 */
		fip = tif->tif_fieldinfo[fix];
		while (dp->tdir_type != (u_short) fip->field_type) {
			if (fip->field_type == TIFF_ANY)	/* wildcard */
				break;
			fip++, fix++;
			if (fix == tif->tif_nfields ||
			    fip->field_tag != dp->tdir_tag) {
				TIFFWarning(tif->tif_name,
				   "wrong data type %d for \"%s\"; tag ignored",
				    dp->tdir_type, fip[-1].field_name);
				goto ignore;
			}
		}
		/*
		 * Check count if known in advance.
		 */
		if (fip->field_readcount != TIFF_VARIABLE) {
			uint32 expected = (fip->field_readcount == TIFF_SPP) ?
			    (uint32) td->td_samplesperpixel :
			    (uint32) fip->field_readcount;
			if (!CheckDirCount(tif, dp, expected))
				goto ignore;
		}

		switch (dp->tdir_tag) {
		case TIFFTAG_COMPRESSION:
			/*
			 * The 5.0 spec says the Compression tag has
			 * one value, while earlier specs say it has
			 * one value per sample.  Because of this, we
			 * accept the tag if one value is supplied.
			 */
			if (dp->tdir_count == 1) {
				v = TIFFExtractData(tif,
				    dp->tdir_type, dp->tdir_offset);
				if (!TIFFSetField(tif, dp->tdir_tag, (int)v))
					goto bad;
				break;
			}
			if (!TIFFFetchPerSampleShorts(tif, dp, &iv) ||
			    !TIFFSetField(tif, dp->tdir_tag, iv))
				goto bad;
			dp->tdir_tag = IGNORE;
			break;
		case TIFFTAG_STRIPOFFSETS:
		case TIFFTAG_STRIPBYTECOUNTS:
		case TIFFTAG_TILEOFFSETS:
		case TIFFTAG_TILEBYTECOUNTS:
			TIFFSetFieldBit(tif, fip->field_bit);
			break;
		case TIFFTAG_IMAGEWIDTH:
		case TIFFTAG_IMAGELENGTH:
		case TIFFTAG_IMAGEDEPTH:
		case TIFFTAG_TILELENGTH:
		case TIFFTAG_TILEWIDTH:
		case TIFFTAG_TILEDEPTH:
		case TIFFTAG_PLANARCONFIG:
		case TIFFTAG_ROWSPERSTRIP:
			if (!TIFFFetchNormalTag(tif, dp))
				goto bad;
			dp->tdir_tag = IGNORE;
			break;
		case TIFFTAG_EXTRASAMPLES:
			(void) TIFFFetchExtraSamples(tif, dp);
			dp->tdir_tag = IGNORE;
			break;
		}
	}

	/*
	 * Allocate directory structure and setup defaults.
	 */
	if (!TIFFFieldSet(tif, FIELD_IMAGEDIMENSIONS)) {
		MissingRequired(tif, "ImageLength");
		goto bad;
	}
	if (!TIFFFieldSet(tif, FIELD_PLANARCONFIG)) {
		MissingRequired(tif, "PlanarConfiguration");
		goto bad;
	}
	/* 
 	 * Setup appropriate structures (by strip or by tile)
	 */
	if (!TIFFFieldSet(tif, FIELD_TILEDIMENSIONS)) {
		td->td_nstrips = TIFFNumberOfStrips(tif);
		td->td_tilewidth = td->td_imagewidth;
		td->td_tilelength = td->td_rowsperstrip;
		td->td_tiledepth = td->td_imagedepth;
		tif->tif_flags &= ~TIFF_ISTILED;
	} else {
		td->td_nstrips = TIFFNumberOfTiles(tif);
		tif->tif_flags |= TIFF_ISTILED;
	}
	td->td_stripsperimage = td->td_nstrips;
	if (td->td_planarconfig == PLANARCONFIG_SEPARATE)
		td->td_stripsperimage /= td->td_samplesperpixel;
	if (!TIFFFieldSet(tif, FIELD_STRIPOFFSETS)) {
		MissingRequired(tif,
		    isTiled(tif) ? "TileOffsets" : "StripOffsets");
		goto bad;
	}

	/*
	 * Second pass: extract other information.
	 */
	for (dp = dir, n = dircount; n > 0; n--, dp++) {
		if (dp->tdir_tag == IGNORE)
			continue;
		switch (dp->tdir_tag) {
		case TIFFTAG_MINSAMPLEVALUE:
		case TIFFTAG_MAXSAMPLEVALUE:
		case TIFFTAG_BITSPERSAMPLE:
			/*
			 * The 5.0 spec says the Compression tag has
			 * one value, while earlier specs say it has
			 * one value per sample.  Because of this, we
			 * accept the tag if one value is supplied.
			 *
			 * The MinSampleValue, MaxSampleValue and
			 * BitsPerSample tags are supposed to be written
			 * as one value/sample, but some vendors incorrectly
			 * write one value only -- so we accept that
			 * as well (yech).
			 */
			if (dp->tdir_count == 1) {
				v = TIFFExtractData(tif,
				    dp->tdir_type, dp->tdir_offset);
				if (!TIFFSetField(tif, dp->tdir_tag, (int)v))
					goto bad;
				break;
			}
			/* fall thru... */
		case TIFFTAG_DATATYPE:
		case TIFFTAG_SAMPLEFORMAT:
			if (!TIFFFetchPerSampleShorts(tif, dp, &iv) ||
			    !TIFFSetField(tif, dp->tdir_tag, iv))
				goto bad;
			break;
		case TIFFTAG_SMINSAMPLEVALUE:
		case TIFFTAG_SMAXSAMPLEVALUE:
			if (!TIFFFetchPerSampleAnys(tif, dp, &dv) ||
			    !TIFFSetField(tif, dp->tdir_tag, dv))
				goto bad;
			break;
		case TIFFTAG_STRIPOFFSETS:
		case TIFFTAG_TILEOFFSETS:
			if (!TIFFFetchStripThing(tif, dp,
			    td->td_nstrips, &td->td_stripoffset))
				goto bad;
			break;
		case TIFFTAG_STRIPBYTECOUNTS:
		case TIFFTAG_TILEBYTECOUNTS:
			if (!TIFFFetchStripThing(tif, dp,
			    td->td_nstrips, &td->td_stripbytecount))
				goto bad;
			break;
		case TIFFTAG_COLORMAP:
		case TIFFTAG_TRANSFERFUNCTION:
			/*
			 * TransferFunction can have either 1x or 3x data
			 * values; Colormap can have only 3x items.
			 */
			v = 1L<<td->td_bitspersample;
			if (dp->tdir_tag == TIFFTAG_COLORMAP ||
			    dp->tdir_count != (uint32) v) {
				if (!CheckDirCount(tif, dp, (uint32)(3*v)))
					break;
			}
			v *= sizeof (uint16);
			cp = CheckMalloc(tif, dp->tdir_count * sizeof (uint16),
			    "to read \"TransferFunction\" tag");
			if (cp != NULL) {
				if (TIFFFetchData(tif, dp, cp)) {
					/*
					 * This deals with there being only
					 * one array to apply to all samples.
					 */
					uint32 c =
					    (uint32)1 << td->td_bitspersample;
					if (dp->tdir_count == c)
						v = 0;
					TIFFSetField(tif, dp->tdir_tag,
					    cp, cp+v, cp+2*v);
				}
				_TIFFfree(cp);
			}
			break;
		case TIFFTAG_PAGENUMBER:
		case TIFFTAG_HALFTONEHINTS:
		case TIFFTAG_YCBCRSUBSAMPLING:
		case TIFFTAG_DOTRANGE:
			(void) TIFFFetchShortPair(tif, dp);
			break;
#ifdef COLORIMETRY_SUPPORT
		case TIFFTAG_REFERENCEBLACKWHITE:
			(void) TIFFFetchRefBlackWhite(tif, dp);
			break;
#endif
/* BEGIN REV 4.0 COMPATIBILITY */
		case TIFFTAG_OSUBFILETYPE:
			v = 0;
			switch (TIFFExtractData(tif, dp->tdir_type,
			    dp->tdir_offset)) {
			case OFILETYPE_REDUCEDIMAGE:
				v = FILETYPE_REDUCEDIMAGE;
				break;
			case OFILETYPE_PAGE:
				v = FILETYPE_PAGE;
				break;
			}
			if (v)
				(void) TIFFSetField(tif,
				    TIFFTAG_SUBFILETYPE, (int)v);
			break;
/* END REV 4.0 COMPATIBILITY */
		default:
			(void) TIFFFetchNormalTag(tif, dp);
			break;
		}
	}
	/*
	 * Verify Palette image has a Colormap.
	 */
	if (td->td_photometric == PHOTOMETRIC_PALETTE &&
	    !TIFFFieldSet(tif, FIELD_COLORMAP)) {
		MissingRequired(tif, "Colormap");
		goto bad;
	}
	/*
	 * Attempt to deal with a missing StripByteCounts tag.
	 */
	if (!TIFFFieldSet(tif, FIELD_STRIPBYTECOUNTS)) {
		/*
		 * Some manufacturers violate the spec by not giving
		 * the size of the strips.  In this case, assume there
		 * is one uncompressed strip of data.
		 */
		if ((td->td_planarconfig == PLANARCONFIG_CONTIG &&
		    td->td_nstrips > 1) ||
		    (td->td_planarconfig == PLANARCONFIG_SEPARATE &&
		     td->td_nstrips != td->td_samplesperpixel)) {
		    MissingRequired(tif, "StripByteCounts");
		    goto bad;
		}
		TIFFWarning(tif->tif_name,
"TIFF directory is missing required \"%s\" field, calculating from imagelength",
		    _TIFFFieldWithTag(tif,TIFFTAG_STRIPBYTECOUNTS)->field_name);
		if (EstimateStripByteCounts(tif, dir, dircount) < 0)
		    goto bad;
#define	BYTECOUNTLOOKSBAD \
    ((td->td_stripbytecount[0] == 0 && td->td_stripoffset[0] != 0) || \
    (td->td_compression == COMPRESSION_NONE && \
     td->td_stripbytecount[0] > TIFFGetFileSize(tif) - td->td_stripoffset[0]))
	} else if (td->td_nstrips == 1 && BYTECOUNTLOOKSBAD) {
		/*
		 * Plexus (and others) sometimes give a value
		 * of zero for a tag when they don't know what
		 * the correct value is!  Try and handle the
		 * simple case of estimating the size of a one
		 * strip image.
		 */
		TIFFWarning(tif->tif_name,
	    "Bogus \"%s\" field, ignoring and calculating from imagelength",
		    _TIFFFieldWithTag(tif,TIFFTAG_STRIPBYTECOUNTS)->field_name);
		if(EstimateStripByteCounts(tif, dir, dircount) < 0)
		    goto bad;
	}
	if (dir)
		_TIFFfree((char *)dir);
	if (!TIFFFieldSet(tif, FIELD_MAXSAMPLEVALUE))
		td->td_maxsamplevalue = (uint16)((1L<<td->td_bitspersample)-1);
	/*
	 * Setup default compression scheme.
	 */
	if (!TIFFFieldSet(tif, FIELD_COMPRESSION))
		TIFFSetField(tif, TIFFTAG_COMPRESSION, COMPRESSION_NONE);
        /*
         * Some manufacturers make life difficult by writing
	 * large amounts of uncompressed data as a single strip.
	 * This is contrary to the recommendations of the spec.
         * The following makes an attempt at breaking such images
	 * into strips closer to the recommended 8k bytes.  A
	 * side effect, however, is that the RowsPerStrip tag
	 * value may be changed.
         */
	if (td->td_nstrips == 1 && td->td_compression == COMPRESSION_NONE &&
	    (tif->tif_flags & (TIFF_STRIPCHOP|TIFF_ISTILED)) == TIFF_STRIPCHOP)
		ChopUpSingleUncompressedStrip(tif);
	/*
	 * Reinitialize i/o since we are starting on a new directory.
	 */
	tif->tif_row = (uint32) -1;
	tif->tif_curstrip = (tstrip_t) -1;
	tif->tif_col = (uint32) -1;
	tif->tif_curtile = (ttile_t) -1;
	tif->tif_tilesize = TIFFTileSize(tif);
	tif->tif_scanlinesize = TIFFScanlineSize(tif);
	return (1);
bad:
	if (dir)
		_TIFFfree(dir);
	return (0);
}

static int
EstimateStripByteCounts(TIFF* tif, TIFFDirEntry* dir, uint16 dircount)
{
	register TIFFDirEntry *dp;
	register TIFFDirectory *td = &tif->tif_dir;
	uint16 i;

	if (td->td_stripbytecount)
		_TIFFfree(td->td_stripbytecount);
	td->td_stripbytecount = (uint32*)
	    CheckMalloc(tif, td->td_nstrips * sizeof (uint32),
		"for \"StripByteCounts\" array");
	if (td->td_compression != COMPRESSION_NONE) {
		uint32 space = (uint32)(sizeof (TIFFHeader)
		    + sizeof (uint16)
		    + (dircount * sizeof (TIFFDirEntry))
		    + sizeof (uint32));
		toff_t filesize = TIFFGetFileSize(tif);
		uint16 n;

		/* calculate amount of space used by indirect values */
		for (dp = dir, n = dircount; n > 0; n--, dp++)
		{
		    uint32 cc;
		    if(dp->tdir_tag == IGNORE)
		    {
		        TIFFError(tif->tif_name,
		        "Cannot determine StripByteCounts values, because of tags with unknown sizes");
			return -1;
		    }
		    cc = dp->tdir_count*TIFFDataWidth(dp->tdir_type);
		    if (cc > sizeof (uint32))
			space += cc;
		}
		space = filesize - space;
		if (td->td_planarconfig == PLANARCONFIG_SEPARATE)
			space /= td->td_samplesperpixel;
		for (i = 0; i < td->td_nstrips; i++)
			td->td_stripbytecount[i] = space;
		/*
		 * This gross hack handles the case were the offset to
		 * the last strip is past the place where we think the strip
		 * should begin.  Since a strip of data must be contiguous,
		 * it's safe to assume that we've overestimated the amount
		 * of data in the strip and trim this number back accordingly.
		 */ 
		i--;
		if (((toff_t)(td->td_stripoffset[i]+td->td_stripbytecount[i]))
                                                               > filesize)
			td->td_stripbytecount[i] =
			    filesize - td->td_stripoffset[i];
	} else {
		uint32 rowbytes = TIFFScanlineSize(tif);
		uint32 rowsperstrip = td->td_imagelength/td->td_stripsperimage;
		for (i = 0; i < td->td_nstrips; i++)
			td->td_stripbytecount[i] = rowbytes*rowsperstrip;
	}
	TIFFSetFieldBit(tif, FIELD_STRIPBYTECOUNTS);
	if (!TIFFFieldSet(tif, FIELD_ROWSPERSTRIP))
		td->td_rowsperstrip = td->td_imagelength;
	return 1;
}

static void
MissingRequired(TIFF* tif, const char* tagname)
{
	TIFFError(tif->tif_name,
	    "TIFF directory is missing required \"%s\" field", tagname);
}

/*
 * Check the count field of a directory
 * entry against a known value.  The caller
 * is expected to skip/ignore the tag if
 * there is a mismatch.
 */
static int
CheckDirCount(TIFF* tif, TIFFDirEntry* dir, uint32 count)
{
	if (count != dir->tdir_count) {
		TIFFWarning(tif->tif_name,
	"incorrect count for field \"%s\" (%lu, expecting %lu); tag ignored",
		    _TIFFFieldWithTag(tif, dir->tdir_tag)->field_name,
		    dir->tdir_count, count);
		return (0);
	}
	return (1);
}

/*
 * Fetch a contiguous directory item.
 */
static tsize_t
TIFFFetchData(TIFF* tif, TIFFDirEntry* dir, char* cp)
{
	int w = TIFFDataWidth(dir->tdir_type);
	tsize_t cc = dir->tdir_count * w;

	if (!isMapped(tif)) {
		if (!SeekOK(tif, dir->tdir_offset))
			goto bad;
		if (!ReadOK(tif, cp, cc))
			goto bad;
	} else {
		if (dir->tdir_offset + cc > tif->tif_size)
			goto bad;
		_TIFFmemcpy(cp, tif->tif_base + dir->tdir_offset, cc);
	}
	if (tif->tif_flags & TIFF_SWAB) {
		switch (dir->tdir_type) {
		case TIFF_SHORT:
		case TIFF_SSHORT:
			TIFFSwabArrayOfShort((uint16*) cp, dir->tdir_count);
			break;
		case TIFF_LONG:
		case TIFF_SLONG:
		case TIFF_FLOAT:
			TIFFSwabArrayOfLong((uint32*) cp, dir->tdir_count);
			break;
		case TIFF_RATIONAL:
		case TIFF_SRATIONAL:
			TIFFSwabArrayOfLong((uint32*) cp, 2*dir->tdir_count);
			break;
		case TIFF_DOUBLE:
			TIFFSwabArrayOfDouble((double*) cp, dir->tdir_count);
			break;
		}
	}
	return (cc);
bad:
	TIFFError(tif->tif_name, "Error fetching data for field \"%s\"",
	    _TIFFFieldWithTag(tif, dir->tdir_tag)->field_name);
	return ((tsize_t) 0);
}

/*
 * Fetch an ASCII item from the file.
 */
static tsize_t
TIFFFetchString(TIFF* tif, TIFFDirEntry* dir, char* cp)
{
	if (dir->tdir_count <= 4) {
		uint32 l = dir->tdir_offset;
		if (tif->tif_flags & TIFF_SWAB)
			TIFFSwabLong(&l);
		_TIFFmemcpy(cp, &l, dir->tdir_count);
		return (1);
	}
	return (TIFFFetchData(tif, dir, cp));
}

/*
 * Convert numerator+denominator to float.
 */
static int
cvtRational(TIFF* tif, TIFFDirEntry* dir, uint32 num, uint32 denom, float* rv)
{
	if (denom == 0) {
		TIFFError(tif->tif_name,
		    "%s: Rational with zero denominator (num = %lu)",
		    _TIFFFieldWithTag(tif, dir->tdir_tag)->field_name, num);
		return (0);
	} else {
		if (dir->tdir_type == TIFF_RATIONAL)
			*rv = ((float)num / (float)denom);
		else
			*rv = ((float)(int32)num / (float)(int32)denom);
		return (1);
	}
}

/*
 * Fetch a rational item from the file
 * at offset off and return the value
 * as a floating point number.
 */
static float
TIFFFetchRational(TIFF* tif, TIFFDirEntry* dir)
{
	uint32 l[2];
	float v;

	return (!TIFFFetchData(tif, dir, (char *)l) ||
	    !cvtRational(tif, dir, l[0], l[1], &v) ? 1.0f : v);
}

/*
 * Fetch a single floating point value
 * from the offset field and return it
 * as a native float.
 */
static float
TIFFFetchFloat(TIFF* tif, TIFFDirEntry* dir)
{
	long l = TIFFExtractData(tif, dir->tdir_type, dir->tdir_offset);
	float v = *(float*) &l;
	TIFFCvtIEEEFloatToNative(tif, 1, &v);
	return (v);
}

/*
 * Fetch an array of BYTE or SBYTE values.
 */
static int
TIFFFetchByteArray(TIFF* tif, TIFFDirEntry* dir, uint16* v)
{
    if (dir->tdir_count <= 4) {
        /*
         * Extract data from offset field.
         */
        if (tif->tif_header.tiff_magic == TIFF_BIGENDIAN) {
            switch (dir->tdir_count) {
                case 4: v[3] = (uint16)(dir->tdir_offset & 0xff);
                case 3: v[2] = (uint16)((dir->tdir_offset >> 8) & 0xff);
                case 2: v[1] = (uint16)((dir->tdir_offset >> 16) & 0xff);
                case 1: v[0] = (uint16)(dir->tdir_offset >> 24);
            }
        } else {
            switch (dir->tdir_count) {
                case 4: v[3] = (uint16)(dir->tdir_offset >> 24);
                case 3: v[2] = (uint16)((dir->tdir_offset >> 16) & 0xff);
                case 2: v[1] = (uint16)((dir->tdir_offset >> 8) & 0xff);
                case 1: v[0] = (uint16)(dir->tdir_offset & 0xff);
            }
        }
        return (1);
    } else
        return (TIFFFetchData(tif, dir, (char*) v) != 0);	/* XXX */
}

/*
 * Fetch an array of SHORT or SSHORT values.
 */
static int
TIFFFetchShortArray(TIFF* tif, TIFFDirEntry* dir, uint16* v)
{
	if (dir->tdir_count <= 2) {
		if (tif->tif_header.tiff_magic == TIFF_BIGENDIAN) {
			switch (dir->tdir_count) {
			case 2: v[1] = (uint16) (dir->tdir_offset & 0xffff);
			case 1: v[0] = (uint16) (dir->tdir_offset >> 16);
			}
		} else {
			switch (dir->tdir_count) {
			case 2: v[1] = (uint16) (dir->tdir_offset >> 16);
			case 1: v[0] = (uint16) (dir->tdir_offset & 0xffff);
			}
		}
		return (1);
	} else
		return (TIFFFetchData(tif, dir, (char *)v) != 0);
}

/*
 * Fetch a pair of SHORT or BYTE values.
 */
static int
TIFFFetchShortPair(TIFF* tif, TIFFDirEntry* dir)
{
	uint16 v[2];
	int ok = 0;

	switch (dir->tdir_type) {
	case TIFF_SHORT:
	case TIFF_SSHORT:
		ok = TIFFFetchShortArray(tif, dir, v);
		break;
	case TIFF_BYTE:
	case TIFF_SBYTE:
		ok  = TIFFFetchByteArray(tif, dir, v);
		break;
	}
	if (ok)
		TIFFSetField(tif, dir->tdir_tag, v[0], v[1]);
	return (ok);
}

/*
 * Fetch an array of LONG or SLONG values.
 */
static int
TIFFFetchLongArray(TIFF* tif, TIFFDirEntry* dir, uint32* v)
{
	if (dir->tdir_count == 1) {
		v[0] = dir->tdir_offset;
		return (1);
	} else
		return (TIFFFetchData(tif, dir, (char*) v) != 0);
}

/*
 * Fetch an array of RATIONAL or SRATIONAL values.
 */
static int
TIFFFetchRationalArray(TIFF* tif, TIFFDirEntry* dir, float* v)
{
	int ok = 0;
	uint32* l;

	l = (uint32*)CheckMalloc(tif,
	    dir->tdir_count*TIFFDataWidth(dir->tdir_type),
	    "to fetch array of rationals");
	if (l) {
		if (TIFFFetchData(tif, dir, (char *)l)) {
			uint32 i;
			for (i = 0; i < dir->tdir_count; i++) {
				ok = cvtRational(tif, dir,
				    l[2*i+0], l[2*i+1], &v[i]);
				if (!ok)
					break;
			}
		}
		_TIFFfree((char *)l);
	}
	return (ok);
}

/*
 * Fetch an array of FLOAT values.
 */
static int
TIFFFetchFloatArray(TIFF* tif, TIFFDirEntry* dir, float* v)
{

	if (dir->tdir_count == 1) {
		v[0] = *(float*) &dir->tdir_offset;
		TIFFCvtIEEEFloatToNative(tif, dir->tdir_count, v);
		return (1);
	} else	if (TIFFFetchData(tif, dir, (char*) v)) {
		TIFFCvtIEEEFloatToNative(tif, dir->tdir_count, v);
		return (1);
	} else
		return (0);
}

/*
 * Fetch an array of DOUBLE values.
 */
static int
TIFFFetchDoubleArray(TIFF* tif, TIFFDirEntry* dir, double* v)
{
	if (TIFFFetchData(tif, dir, (char*) v)) {
		TIFFCvtIEEEDoubleToNative(tif, dir->tdir_count, v);
		return (1);
	} else
		return (0);
}

/*
 * Fetch an array of ANY values.  The actual values are
 * returned as doubles which should be able hold all the
 * types.  Yes, there really should be an tany_t to avoid
 * this potential non-portability ...  Note in particular
 * that we assume that the double return value vector is
 * large enough to read in any fundamental type.  We use
 * that vector as a buffer to read in the base type vector
 * and then convert it in place to double (from end
 * to front of course).
 */
static int
TIFFFetchAnyArray(TIFF* tif, TIFFDirEntry* dir, double* v)
{
	int i;

	switch (dir->tdir_type) {
	case TIFF_BYTE:
	case TIFF_SBYTE:
		if (!TIFFFetchByteArray(tif, dir, (uint16*) v))
			return (0);
		if (dir->tdir_type == TIFF_BYTE) {
			uint16* vp = (uint16*) v;
			for (i = dir->tdir_count-1; i >= 0; i--)
				v[i] = vp[i];
		} else {
			int16* vp = (int16*) v;
			for (i = dir->tdir_count-1; i >= 0; i--)
				v[i] = vp[i];
		}
		break;
	case TIFF_SHORT:
	case TIFF_SSHORT:
		if (!TIFFFetchShortArray(tif, dir, (uint16*) v))
			return (0);
		if (dir->tdir_type == TIFF_SHORT) {
			uint16* vp = (uint16*) v;
			for (i = dir->tdir_count-1; i >= 0; i--)
				v[i] = vp[i];
		} else {
			int16* vp = (int16*) v;
			for (i = dir->tdir_count-1; i >= 0; i--)
				v[i] = vp[i];
		}
		break;
	case TIFF_LONG:
	case TIFF_SLONG:
		if (!TIFFFetchLongArray(tif, dir, (uint32*) v))
			return (0);
		if (dir->tdir_type == TIFF_LONG) {
			uint32* vp = (uint32*) v;
			for (i = dir->tdir_count-1; i >= 0; i--)
				v[i] = vp[i];
		} else {
			int32* vp = (int32*) v;
			for (i = dir->tdir_count-1; i >= 0; i--)
				v[i] = vp[i];
		}
		break;
	case TIFF_RATIONAL:
	case TIFF_SRATIONAL:
		if (!TIFFFetchRationalArray(tif, dir, (float*) v))
			return (0);
		{ float* vp = (float*) v;
		  for (i = dir->tdir_count-1; i >= 0; i--)
			v[i] = vp[i];
		}
		break;
	case TIFF_FLOAT:
		if (!TIFFFetchFloatArray(tif, dir, (float*) v))
			return (0);
		{ float* vp = (float*) v;
		  for (i = dir->tdir_count-1; i >= 0; i--)
			v[i] = vp[i];
		}
		break;
	case TIFF_DOUBLE:
		return (TIFFFetchDoubleArray(tif, dir, (double*) v));
	default:
		/* TIFF_NOTYPE */
		/* TIFF_ASCII */
		/* TIFF_UNDEFINED */
		TIFFError(tif->tif_name,
		    "cannot read TIFF_ANY type %d for field \"%s\"",
		    _TIFFFieldWithTag(tif, dir->tdir_tag)->field_name);
		return (0);
	}
	return (1);
}

/*
 * Fetch a tag that is not handled by special case code.
 */
static int
TIFFFetchNormalTag(TIFF* tif, TIFFDirEntry* dp)
{
	static const char mesg[] = "to fetch tag value";
	int ok = 0;
	const TIFFFieldInfo* fip = _TIFFFieldWithTag(tif, dp->tdir_tag);

	if (dp->tdir_count > 1) {		/* array of values */
		char* cp = NULL;

		switch (dp->tdir_type) {
		case TIFF_BYTE:
		case TIFF_SBYTE:
			/* NB: always expand BYTE values to shorts */
			cp = CheckMalloc(tif,
			    dp->tdir_count * sizeof (uint16), mesg);
			ok = cp && TIFFFetchByteArray(tif, dp, (uint16*) cp);
			break;
		case TIFF_SHORT:
		case TIFF_SSHORT:
			cp = CheckMalloc(tif,
			    dp->tdir_count * sizeof (uint16), mesg);
			ok = cp && TIFFFetchShortArray(tif, dp, (uint16*) cp);
			break;
		case TIFF_LONG:
		case TIFF_SLONG:
			cp = CheckMalloc(tif,
			    dp->tdir_count * sizeof (uint32), mesg);
			ok = cp && TIFFFetchLongArray(tif, dp, (uint32*) cp);
			break;
		case TIFF_RATIONAL:
		case TIFF_SRATIONAL:
			cp = CheckMalloc(tif,
			    dp->tdir_count * sizeof (float), mesg);
			ok = cp && TIFFFetchRationalArray(tif, dp, (float*) cp);
			break;
		case TIFF_FLOAT:
			cp = CheckMalloc(tif,
			    dp->tdir_count * sizeof (float), mesg);
			ok = cp && TIFFFetchFloatArray(tif, dp, (float*) cp);
			break;
		case TIFF_DOUBLE:
			cp = CheckMalloc(tif,
			    dp->tdir_count * sizeof (double), mesg);
			ok = cp && TIFFFetchDoubleArray(tif, dp, (double*) cp);
			break;
		case TIFF_ASCII:
		case TIFF_UNDEFINED:		/* bit of a cheat... */
			/*
			 * Some vendors write strings w/o the trailing
			 * NULL byte, so always append one just in case.
			 */
			cp = CheckMalloc(tif, dp->tdir_count+1, mesg);
			if( (ok = (cp && TIFFFetchString(tif, dp, cp))) != 0 )
				cp[dp->tdir_count] = '\0';	/* XXX */
			break;
		}
		if (ok) {
			ok = (fip->field_passcount ?
			    TIFFSetField(tif, dp->tdir_tag, dp->tdir_count, cp)
			  : TIFFSetField(tif, dp->tdir_tag, cp));
		}
		if (cp != NULL)
			_TIFFfree(cp);
	} else if (CheckDirCount(tif, dp, 1)) {	/* singleton value */
		switch (dp->tdir_type) {
		case TIFF_BYTE:
		case TIFF_SBYTE:
		case TIFF_SHORT:
		case TIFF_SSHORT:
			/*
			 * If the tag is also acceptable as a LONG or SLONG
			 * then TIFFSetField will expect an uint32 parameter
			 * passed to it (through varargs).  Thus, for machines
			 * where sizeof (int) != sizeof (uint32) we must do
			 * a careful check here.  It's hard to say if this
			 * is worth optimizing.
			 *
			 * NB: We use TIFFFieldWithTag here knowing that
			 *     it returns us the first entry in the table
			 *     for the tag and that that entry is for the
			 *     widest potential data type the tag may have.
			 */
			{ TIFFDataType type = fip->field_type;
			  if (type != TIFF_LONG && type != TIFF_SLONG) {
				uint16 v = (uint16)
			   TIFFExtractData(tif, dp->tdir_type, dp->tdir_offset);
				ok = (fip->field_passcount ?
				    TIFFSetField(tif, dp->tdir_tag, 1, &v)
				  : TIFFSetField(tif, dp->tdir_tag, v));
				break;
			  }
			}
			/* fall thru... */
		case TIFF_LONG:
		case TIFF_SLONG:
			{ uint32 v32 =
		    TIFFExtractData(tif, dp->tdir_type, dp->tdir_offset);
			  ok = (fip->field_passcount ? 
			      TIFFSetField(tif, dp->tdir_tag, 1, &v32)
			    : TIFFSetField(tif, dp->tdir_tag, v32));
			}
			break;
		case TIFF_RATIONAL:
		case TIFF_SRATIONAL:
		case TIFF_FLOAT:
			{ float v = (dp->tdir_type == TIFF_FLOAT ? 
			      TIFFFetchFloat(tif, dp)
			    : TIFFFetchRational(tif, dp));
			  ok = (fip->field_passcount ?
			      TIFFSetField(tif, dp->tdir_tag, 1, &v)
			    : TIFFSetField(tif, dp->tdir_tag, v));
			}
			break;
		case TIFF_DOUBLE:
			{ double v;
			  ok = (TIFFFetchDoubleArray(tif, dp, &v) &&
			    (fip->field_passcount ?
			      TIFFSetField(tif, dp->tdir_tag, 1, &v)
			    : TIFFSetField(tif, dp->tdir_tag, v))
			  );
			}
			break;
		case TIFF_ASCII:
		case TIFF_UNDEFINED:		/* bit of a cheat... */
			{ char c[2];
			  if( (ok = (TIFFFetchString(tif, dp, c) != 0)) != 0 ){
				c[1] = '\0';		/* XXX paranoid */
				ok = TIFFSetField(tif, dp->tdir_tag, c);
			  }
			}
			break;
		}
	}
	return (ok);
}

#define	NITEMS(x)	(sizeof (x) / sizeof (x[0]))
/*
 * Fetch samples/pixel short values for 
 * the specified tag and verify that
 * all values are the same.
 */
static int
TIFFFetchPerSampleShorts(TIFF* tif, TIFFDirEntry* dir, int* pl)
{
	int samples = tif->tif_dir.td_samplesperpixel;
	int status = 0;

	if (CheckDirCount(tif, dir, (uint32) samples)) {
		uint16 buf[10];
		uint16* v = buf;

		if (samples > NITEMS(buf))
			v = (uint16*) _TIFFmalloc(samples * sizeof (uint16));
		if (TIFFFetchShortArray(tif, dir, v)) {
			int i;
			for (i = 1; i < samples; i++)
				if (v[i] != v[0]) {
					TIFFError(tif->tif_name,
		"Cannot handle different per-sample values for field \"%s\"",
			   _TIFFFieldWithTag(tif, dir->tdir_tag)->field_name);
					goto bad;
				}
			*pl = v[0];
			status = 1;
		}
	bad:
		if (v != buf)
			_TIFFfree((char*) v);
	}
	return (status);
}

/*
 * Fetch samples/pixel ANY values for 
 * the specified tag and verify that
 * all values are the same.
 */
static int
TIFFFetchPerSampleAnys(TIFF* tif, TIFFDirEntry* dir, double* pl)
{
	int samples = (int) tif->tif_dir.td_samplesperpixel;
	int status = 0;

	if (CheckDirCount(tif, dir, (uint32) samples)) {
		double buf[10];
		double* v = buf;

		if (samples > NITEMS(buf))
			v = (double*) _TIFFmalloc(samples * sizeof (double));
		if (TIFFFetchAnyArray(tif, dir, v)) {
			int i;
			for (i = 1; i < samples; i++)
				if (v[i] != v[0]) {
					TIFFError(tif->tif_name,
		"Cannot handle different per-sample values for field \"%s\"",
			   _TIFFFieldWithTag(tif, dir->tdir_tag)->field_name);
					goto bad;
				}
			*pl = v[0];
			status = 1;
		}
	bad:
		if (v != buf)
			_TIFFfree(v);
	}
	return (status);
}
#undef NITEMS

/*
 * Fetch a set of offsets or lengths.
 * While this routine says "strips",
 * in fact it's also used for tiles.
 */
static int
TIFFFetchStripThing(TIFF* tif, TIFFDirEntry* dir, long nstrips, uint32** lpp)
{
	register uint32* lp;
	int status;

	if (!CheckDirCount(tif, dir, (uint32) nstrips))
		return (0);
	/*
	 * Allocate space for strip information.
	 */
	if (*lpp == NULL &&
	    (*lpp = (uint32 *)CheckMalloc(tif,
	      nstrips * sizeof (uint32), "for strip array")) == NULL)
		return (0);
	lp = *lpp;
	if (dir->tdir_type == (int)TIFF_SHORT) {
		/*
		 * Handle uint16->uint32 expansion.
		 */
		uint16* dp = (uint16*) CheckMalloc(tif,
		    dir->tdir_count* sizeof (uint16), "to fetch strip tag");
		if (dp == NULL)
			return (0);
		if( (status = TIFFFetchShortArray(tif, dir, dp)) != 0 ) {
			register uint16* wp = dp;
			while (nstrips-- > 0)
				*lp++ = *wp++;
		}
		_TIFFfree((char*) dp);
	} else
		status = TIFFFetchLongArray(tif, dir, lp);
	return (status);
}

#define	NITEMS(x)	(sizeof (x) / sizeof (x[0]))
/*
 * Fetch and set the ExtraSamples tag.
 */
static int
TIFFFetchExtraSamples(TIFF* tif, TIFFDirEntry* dir)
{
	uint16 buf[10];
	uint16* v = buf;
	int status;

	if (dir->tdir_count > NITEMS(buf))
		v = (uint16*) _TIFFmalloc(dir->tdir_count * sizeof (uint16));
	if (dir->tdir_type == TIFF_BYTE)
		status = TIFFFetchByteArray(tif, dir, v);
	else
		status = TIFFFetchShortArray(tif, dir, v);
	if (status)
		status = TIFFSetField(tif, dir->tdir_tag, dir->tdir_count, v);
	if (v != buf)
		_TIFFfree((char*) v);
	return (status);
}
#undef NITEMS

#ifdef COLORIMETRY_SUPPORT
/*
 * Fetch and set the RefBlackWhite tag.
 */
static int
TIFFFetchRefBlackWhite(TIFF* tif, TIFFDirEntry* dir)
{
	static const char mesg[] = "for \"ReferenceBlackWhite\" array";
	char* cp;
	int ok;

	if (dir->tdir_type == TIFF_RATIONAL)
		return (TIFFFetchNormalTag(tif, dir));
	/*
	 * Handle LONG's for backward compatibility.
	 */
	cp = CheckMalloc(tif, dir->tdir_count * sizeof (uint32), mesg);
	if( (ok = (cp && TIFFFetchLongArray(tif, dir, (uint32*) cp))) != 0) {
		float* fp = (float*)
		    CheckMalloc(tif, dir->tdir_count * sizeof (float), mesg);
		if( (ok = (fp != NULL)) != 0 ) {
			uint32 i;
			for (i = 0; i < dir->tdir_count; i++)
				fp[i] = (float)((uint32*) cp)[i];
			ok = TIFFSetField(tif, dir->tdir_tag, fp);
			_TIFFfree((char*) fp);
		}
	}
	if (cp)
		_TIFFfree(cp);
	return (ok);
}
#endif

/*
 * Replace a single strip (tile) of uncompressed data by
 * multiple strips (tiles), each approximately 8Kbytes.
 * This is useful for dealing with large images or
 * for dealing with machines with a limited amount
 * memory.
 */
static void
ChopUpSingleUncompressedStrip(TIFF* tif)
{
	register TIFFDirectory *td = &tif->tif_dir;
	uint32 bytecount = td->td_stripbytecount[0];
	uint32 offset = td->td_stripoffset[0];
	tsize_t rowbytes = TIFFVTileSize(tif, 1), stripbytes;
	tstrip_t strip, nstrips, rowsperstrip;
	uint32* newcounts;
	uint32* newoffsets;

	/*
	 * Make the rows hold at least one
	 * scanline, but fill 8k if possible.
	 */
	if (rowbytes > 8192) {
		stripbytes = rowbytes;
		rowsperstrip = 1;
	} else if (rowbytes > 0 ) {
		rowsperstrip = 8192 / rowbytes;
		stripbytes = rowbytes * rowsperstrip;
	}
        else
            return;

	/* never increase the number of strips in an image */
	if (rowsperstrip >= td->td_rowsperstrip)
		return;
	nstrips = (tstrip_t) TIFFhowmany(bytecount, stripbytes);
	newcounts = (uint32*) CheckMalloc(tif, nstrips * sizeof (uint32),
				"for chopped \"StripByteCounts\" array");
	newoffsets = (uint32*) CheckMalloc(tif, nstrips * sizeof (uint32),
				"for chopped \"StripOffsets\" array");
	if (newcounts == NULL || newoffsets == NULL) {
	        /*
		 * Unable to allocate new strip information, give
		 * up and use the original one strip information.
		 */
		if (newcounts != NULL)
			_TIFFfree(newcounts);
		if (newoffsets != NULL)
			_TIFFfree(newoffsets);
		return;
	}
	/*
	 * Fill the strip information arrays with
	 * new bytecounts and offsets that reflect
	 * the broken-up format.
	 */
	for (strip = 0; strip < nstrips; strip++) {
		if (stripbytes > (tsize_t) bytecount)
			stripbytes = bytecount;
		newcounts[strip] = stripbytes;
		newoffsets[strip] = offset;
		offset += stripbytes;
		bytecount -= stripbytes;
	}
	/*
	 * Replace old single strip info with multi-strip info.
	 */
	td->td_stripsperimage = td->td_nstrips = nstrips;
	TIFFSetField(tif, TIFFTAG_ROWSPERSTRIP, rowsperstrip);

	_TIFFfree(td->td_stripbytecount);
	_TIFFfree(td->td_stripoffset);
	td->td_stripbytecount = newcounts;
	td->td_stripoffset = newoffsets;
}
