#pragma warn -use
static char 	*sccsid = "@(#)TIFF/tif_thunder.c 1.11, Copyright (c) Sam Leffler, Dieter Linde, "__DATE__;
#pragma warn .use
/*
 * Copyright (c) 1988, 1990 by Sam Leffler, Oct 8 1990
 * All rights reserved.
 *
 * This file is provided for unrestricted use provided that this legend is included on all tape media and as a part of the
 * software program in whole or part.  Users may copy, modify or distribute this file at will.
 *
 * TIFF Library.
 *
 * ThunderScan 4-bit Compression Algorithm Support
 */
#include "tiffio.h"

/*
 * ThunderScan uses an encoding scheme designed for 4-bit pixel values.  Data is encoded in bytes, with
 * each byte split into a 2-bit code word and a 6-bit data value.  The encoding gives raw data, runs of
 * pixels, or pixel values encoded as a delta from the previous pixel value.  For the latter, either 2-bit
 * or 3-bit delta values are used, with the deltas packed into a single byte.
 */
#define THUNDER_DATA		0x3	/* mask for 6-bit data */
#define THUNDER_CODE            0xc0    /* mask for 2-bit code word */
/*** code values ***/
#define THUNDER_RUN             0x00    /* run of pixels w/ encoded count */
#define THUNDER_2BITDELTAS      0x40    /* 3 pixels w/ encoded 2-bit deltas */
#define     DELTA2_SKIP         2       /* skip code for 2-bit deltas */
#define THUNDER_3BITDELTAS      0x80    /* 2 pixels w/ encoded 3-bit deltas */
#define     DELTA3_SKIP         4       /* skip code for 3-bit deltas */
#define THUNDER_RAW             0xc0    /* raw data encoded */

#define SETPIXEL(op, v)	{ \
        			lastpixel = (v) & 0xf; \
        			if (npixels++ & 1) \
            				*op++ |= lastpixel; \
        			else \
            				op[0] = lastpixel << 4; \
			}

static int	twobitdeltas[4] = { 0, 1, 0, -1 };
static int 	threebitdeltas[8] = { 0, 1, 2, 3, 0, -3, -2, -1 };

#pragma warn -par
/****************************************************************************
 *
 */
static int
ThunderScanEncode(
        TIFF 	*tif,
        u_char 	*pp,
        int 	cc
        )
{
        TIFFError(tif->tif_name, "ThunderScan encoding is not implemented");
        return(-1);
}
#pragma warn .par

#pragma warn -par
/****************************************************************************
 *
 */
static int
ThunderScanDecode(
        TIFF 		*tif,
        register u_char	*op,
        int 		occ
        )
{
        register u_char	*bp;
        register int 	n, lastpixel, npixels, delta;
        register long	cc;
        int 		imagewidth;

        bp = (u_char *)tif->tif_rawcp;
        cc = tif->tif_rawcc;
        imagewidth = tif->tif_dir.td_imagewidth;
        lastpixel = npixels = 0;
        while (cc > 0 && npixels < imagewidth) {
                n = *bp++, cc--;
                switch (n & THUNDER_CODE) {
                	case THUNDER_RUN:	/* pixel run */

    	/*
         * Replicate the last pixel n times, where n is the lower-order 6 bits.
         */
                        	if (npixels & 1) {
                                	op[0] |= lastpixel;
                                	lastpixel = *op++; 
                                	npixels++; 
                                	n--;
                        	} 
                        	else
                                	lastpixel |= lastpixel << 4;
                        		npixels += n;
                        		for (; n > 0; n -= 2)
                                		*op++ = lastpixel;
                        		if (n == -1)
                                		*--op &= 0xf0;
                        		lastpixel &= 0xf;
                        		break;

                	case THUNDER_2BITDELTAS:	/* 2-bit deltas */
                        	if ((delta = ((n >> 4) & 3)) != DELTA2_SKIP)
                                	SETPIXEL(op, lastpixel + twobitdeltas[delta]);
                        	if ((delta = ((n >> 2) & 3)) != DELTA2_SKIP)
                                	SETPIXEL(op, lastpixel + twobitdeltas[delta]);
                        	if ((delta = (n & 3)) != DELTA2_SKIP)
                                	SETPIXEL(op, lastpixel + twobitdeltas[delta]);
                        	break;

                	case THUNDER_3BITDELTAS:	/* 3-bit deltas */
                        	if ((delta = ((n >> 3) & 7)) != DELTA3_SKIP)
                                	SETPIXEL(op, lastpixel + threebitdeltas[delta]);
                        	if ((delta = (n & 7)) != DELTA3_SKIP)
                                	SETPIXEL(op, lastpixel + threebitdeltas[delta]);
                        	break;

                	case THUNDER_RAW:	/* raw data */
                        	SETPIXEL(op, n);
                        	break;
               	}
      	}
        tif->tif_rawcp = (u_char *)bp;
        tif->tif_rawcc = cc;
        if (npixels != imagewidth) {
                TIFFError(tif->tif_name, "ThunderScanDecode: %s data for scanline %d (npixels = %d)", npixels < imagewidth ? "Not enough" : "Too much", tif->tif_row, npixels);
                return(0);
        }
        return(1);
}
#pragma warn .par

/****************************************************************************
 *
 */
int
TIFFInitThunderScan(
       	TIFF 	*tif
       	)
{
        tif->tif_decoderow = ThunderScanDecode;
        tif->tif_encoderow = ThunderScanEncode;
        return(1);
}