/* $XConsortium: dg32d.c,v 1.5 94/04/17 20:34:27 rws Exp $ */
/**** module fax/dg32d.c ****/
/******************************************************************************

Copyright (c) 1993, 1994  X Consortium

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				NOTICE
                              
This software is being provided by AGE Logic, Inc. under the
following license.  By obtaining, using and/or copying this software,
you agree that you have read, understood, and will comply with these
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     Permission to use, copy, modify, distribute and sell this
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     "Copyright 1993, 1994 by AGE Logic, Inc."
     
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     Title to this software shall at all times remain with AGE
     Logic, Inc.
*****************************************************************************
  
	fax/dg32d.c -- DDXIE G32D fax decode technique/element
  
	Ben Fahy -- AGE Logic, Inc. May, 1993
  
*****************************************************************************/

#define lenient_decoder

/* the folling define causes extra stuff to be saved in state recorder */
#define _G32D

#include "fax.h"
#include "faxint.h"
#include "bits.h"

#include <servermd.h> /* pick up the BITMAP_BIT_ORDER from Core X*/


/**********************************************************************/
int decode_g32d(state)
FaxState *state;
{
register int bitpos;
register unsigned char *byteptr;
register unsigned char *endptr;
register int a0_color;
register int a0_pos,a1_pos;
register int goal;
register int mode;	/* could overload goal, but will resist */
register int length;
register int width;
register int g32d_horiz;
register int rl;

int 	lines_found=0;
int	n_old_trans;
int	n_new_trans;
int	*old_trans;
int	*new_trans;
int 	a0a1,a1a2;
int 	length_acc=0;
int 	last_b1_idx=0;
int 	b1_pos,b2_pos;
int 	code,nbits;

	if (state == (FaxState *)NULL)
		return(-1);

	/* set up initial bitstream for the very first strip */
	if (!state->bits.started) {
	    if (state->strip_state != StripStateNew) {
	       return(-1);
	    }
	    state->bits.byteptr = (unsigned char *)state->strip;
	    state->bits.endptr  = state->bits.byteptr + state->strip_size-4;
	       /* we will panic with four bytes to go */

	    state->bits.bitpos = 0;
	    state->bits.started = 1;
	}

	localize_state(state);

	if (state->magic_needs) 
	    finish_magic(state->final);
		/* a magic strip was waiting for 1st word of next strip */


/***	Main Decoding Loop	***/
	while(1) {
	  if (endptr < byteptr) {
	      return(-1);
	  }
	  switch(goal) {

	  case FAX_GOAL_SkipPastAnyToEOL:
		code = 0;	/* get Gnu cc to shut up. */
		while (byteptr < endptr) {
	    	  /* look for EOL code */
	    	  code = get_wcode(byteptr,bitpos,endptr);
	    	  rl     = _WhiteFaxTable[code].run_length;
	      	  if (rl == EOL_RUN_LENGTH) 
			break;
#if defined(lenient_decoder)
		  else
			/* move bitstream one bit further and try again */
 		 	adjust_1bit(byteptr,bitpos,endptr);
#else
		  else if (!state->o_line && !lines_found) {
			/* we'll be lenient starting out */
 		 	adjust_1bit(byteptr,bitpos,endptr);
		  }
		  else {
			state->decoder_done = FAX_DECODE_DONE_ErrorSkipPast;
	    		save_state_and_return(state);
		  }
#endif
		}
		if (byteptr >= endptr) {
			state->decoder_done = FAX_DECODE_DONE_ErrorSkipPast;
	    		save_state_and_return(state);
		}
	    	nbits  = _WhiteFaxTable[code].n_bits;
	    	goal = FAX_GOAL_SeekTagBit;
	    	adjust_bitstream(nbits,byteptr,bitpos,endptr);
		break;

	  case FAX_GOAL_SeekEOLandTag:
	    goal =  FAX_GOAL_SkipPastAnyToEOL;
	    break;

	    case FAX_GOAL_SeekTagBit:
	    if (get_bit(byteptr,bitpos,endptr)) {
		g32d_horiz = 1;
	    }
	    else {
		g32d_horiz = 0;
	    }
	    goal = FAX_GOAL_AdjustTag;
		/* have to set this goal in case adjusting throws us 
		   back to the caller in order  to get more data. */

	    adjust_1bit(byteptr,bitpos,endptr);
	    case FAX_GOAL_AdjustTag:

		
	    /*** ok, now start a new line ***/
	    goal = FAX_GOAL_StartNewLine;
	    break;

	  case FAX_GOAL_StartNewLine:

	    /* if we got all the data we want, write it out */
	    if (lines_found >= state->nl_sought)
		    save_state_and_return(state);

	    /* normal line initialization stuff */
	    a0_pos   = -1;
	    a0_color = WHITE;
	    if (g32d_horiz)
		goal = FAX_GOAL_HandleHoriz;
	    else
	        goal = FAX_GOAL_DetermineMode;

	    reset_transitions();
	    break;
	  case FAX_GOAL_DetermineMode:
	    get_mode_and_length(mode,length,byteptr,bitpos,endptr); 
	    goal = mode;
		/* our goal is now to handle whatever mode we're in! */

	    if (mode == FAX_MODE_Unknown)  {
		/* hopefully, we just hit the first 0 in an EOL */
		goal = FAX_GOAL_SeekEOLandTag;
	    }
	    else
	         adjust_bitstream_8(length,byteptr,bitpos,endptr);
	    break;

	  case  FAX_GOAL_RecoverZero:

	    /* have to set new goal in case adjusting throws us	*/
	    /* back to the caller (to get more data) 		*/
	    goal = FAX_GOAL_AdjustedButStillRecovering;
	    adjust_bitstream(nbits,byteptr,bitpos,endptr);

	  case FAX_GOAL_AdjustedButStillRecovering:
	    {
	    int next_goal = FAX_GOAL_FoundOneEOL;

	    while (1) {
	       if (*byteptr) {
		register int mask;
	        /* important assumption: we only get here if we have */
	        /* found at least twelve bits of zero leading up to  */
	        /* the current bitposition.  Therefore, there can't  */
		/* be any bits in the byte before the one we want    */

		mask = 1 << (7-bitpos);
		while (bitpos < 8) {
		   if (mask & (*byteptr))
			break;
		   mask >>= 1;
		   ++bitpos;
		 }	     /* can't really reach bitpos = 8 above */
		 goal = next_goal;
 		 adjust_1bit(byteptr,bitpos,endptr);
		 break;
			/* break out of while (1) */
	       }
	       else {
		 bitpos = 0;
		 if (++byteptr >= endptr)
	           do_magic(byteptr,bitpos,endptr);
		 /* loop around to search some more */
	       }
	    } /* end of while */

	    }
	    break;

	  case  FAX_GOAL_FoundOneEOL:
	    /* found an EOL.  If this is RTC, there will be five more EOL's */
	    /* one the way.  If this is a normal EOL,  next code will not   */
	    /* be an EOL,  and we should interpret the next bit as tag bit  */


	    /* look for second EOL code */
	    code = get_wcode(byteptr,bitpos,endptr);
	    rl = _WhiteFaxTable[code].run_length;
	    if (rl != EOL_RUN_LENGTH) {
	        goal =  FAX_GOAL_SeekTagBit;
		break;
	    }

	    /* Got a second EOL code */
	    return(-1);
	    break;

	  case  FAX_GOAL_HandleHoriz: 
	    length_acc=0;
	    goal = FAX_GOAL_AccumulateA0A1;
		/* in case I run out of data while getting a0-a1 distance */


	  case FAX_GOAL_AccumulateA0A1:
	    get_a0a1(FAX_GOAL_RecordA0A1);
		/* If we have to return for data before getting the 	*/
		/* whole a0a1 distance, we want to return to the a0a1	*/
		/* accumulate state when we reenter the decoder. If	*/
		/* adjusting the bitstream forces us to return after	*/
		/* getting the last part of the a0a1 distance, then	*/
		/* we want to jump to state FAX_GOAL_RecordA0A1 when	*/
		/* we reenter the decoder.				*/

	  case  FAX_GOAL_RecordA0A1:
	    a0a1 = length_acc;
	    if (a0_pos < 0) {
		/* at start of line, a0a1 is the number of white pixels,  */
		/* which is also the index on the line where white->black */
		new_trans[n_new_trans++] = a1_pos = a0a1;
	    } else {
		/* in middle of the line, a0a1 is run-length, so
		 * a1_pos = a0_pos + a0a1, a2_pos = a1_pos + a1a2
		 *
		 *  0  1  2  3  4  5  6  7  8  9  A  B  C  D 
		 *    |w |w |w |b |b |b |b |b |w |  |  |  |  |
		 *     a0       a1             a2
		 */ 
		new_trans[n_new_trans++] = a1_pos = a0_pos + a0a1;
	    }
	    if (a1_pos >= width) {
		if (a1_pos > width) {
#if defined(lenient_decoder)
		   /* we went too far, but we'll be forgiving */
		  a1_pos = width;
#else  /* not so lenient */
		  state->decoder_done = FAX_DECODE_DONE_ErrorPastWidth;
		  return(lines_found);
#endif
		}
		FlushLineData();
		goal = FAX_GOAL_SeekEOLandTag;
		break;
	    }

	    if (goal == FAX_GOAL_RecoverZero) {
	        /* it's possible we got here by reading a zero in get_a0a1, */
	        /* in which case 'goal' was set to FAX_GOAL_RecoverZero. We */
	        /* must assume that the zero is an EOL pre-padded with a    */
	        /* variable number of zeros, which is legal according to    */
	        /* the coding spec.  So we will record the increment in     */
	        /* line number and then attempt to recover.		    */
		FlushLineData();
	  	goal = FAX_GOAL_SkipPastAnyToEOL;
	        break;
			/* break out of the switch, loop with the while */
	    }

	    if (rl == EOL_RUN_LENGTH) {
		FlushLineData();
	        goal =  FAX_GOAL_SeekTagBit;
		/* if we got a non-zero length, remember the transition */
		/* in case the next line is coded in vertical mode	*/
		if (a0a1)
		   new_trans[n_new_trans++] = a0a1;

		/* notice we don't have to worry about a0_pos - 
		   it will be reset when we start the new line
		*/
		break;
			/* break out of the switch, loop with the while */
	    }
	    length_acc=0;
	    goal = FAX_GOAL_AccumulateA1A2;
		/* in case I run out of data while getting a1-a2 distance */

	  case  FAX_GOAL_AccumulateA1A2:
	    get_a1a2(FAX_GOAL_FinishHoriz);
		/* If we have to return for data before getting the 	*/
		/* whole a1a2 distance, we want to return to the a1a2	*/
		/* accumulate state when we reenter the decoder. If	*/
		/* adjusting the bitstream forces us to return after	*/
		/* getting the last part of the a1a2 distance, then	*/
		/* we want to jump to state FAX_GOAL_FinishHoriz when	*/
		/* we reenter the decoder.				*/

	  case  FAX_GOAL_FinishHoriz:
	    a1a2 = length_acc;
	    /* XXX - I may regret not checking for a1a2 > 0 later... */
	    new_trans[n_new_trans] = a0_pos = new_trans[n_new_trans-1]+a1a2;
	    n_new_trans++;


	    /* it's possible we got here by reading a zero in get_a1a2, */
	    /* in which case 'goal' was set to FAX_GOAL_RecoverZero. We */
	    /* must assume that the zero is an EOL pre-padded with a 	*/
	    /* variable number of zeros, which is legal according to	*/
	    /* the coding spec.  So we will update the line count and	*/
	    /* then attempt to recover.					*/
	    if (goal == FAX_GOAL_RecoverZero) {
	        /* assume we have hit the begining of an EOL */
		FlushLineData();
	  	goal = FAX_GOAL_SkipPastAnyToEOL;
	        break;
	    }
	    if (rl == EOL_RUN_LENGTH) {
		FlushLineData();
	        goal =  FAX_GOAL_SeekTagBit;
		break;
	    }
	    if (a0_pos >= width) {
		if (a0_pos > width) {
#if defined(lenient_decoder)
		   /* we went too far, but we'll be forgiving */
		   a0_pos = width;
#else
		   state->decoder_done = FAX_DECODE_DONE_ErrorPastWidth;
		   return(lines_found);
#endif
		}
		FlushLineData();
		goal = FAX_GOAL_SeekEOLandTag;
		break;
	    }
	    else {
		if (g32d_horiz)
	            goal = FAX_GOAL_HandleHoriz;
		else
	            goal = FAX_GOAL_DetermineMode;
	    }
	    break;

	  case FAX_MODE_Pass:
	    if (!n_old_trans) {	/* line above all white */
	      return(-1);
	    }
	    find_b2pos(a0_pos,a0_color,n_old_trans,old_trans);

	    a0_pos = b2_pos;
	    if (a0_pos < 0) {
		FlushLineData();
	       	goal = FAX_GOAL_SeekEOLandTag;
	       	break;
	    }
	    if (a0_pos >= width) {
		return(-1);
	    }
	    goal = FAX_GOAL_DetermineMode;
	    break;

	  case FAX_GOAL_HandleVertL3:
	  case FAX_GOAL_HandleVertL2:
	  case FAX_GOAL_HandleVertL1:
	  case FAX_GOAL_HandleVert0:
	  case FAX_GOAL_HandleVertR1:
	  case FAX_GOAL_HandleVertR2:
	  case FAX_GOAL_HandleVertR3:
	    if (n_old_trans) {	/* line above not all white */
		find_b1pos(a0_pos,a0_color,n_old_trans,old_trans);

		if (b1_pos < 0) {
		   if (goal > FAX_GOAL_HandleVert0) {
		     return(-1);	/* error! */
		   }
		   b1_pos = width;
		}
		/* ok, we are guaranteed that 0 <= b1_pos <= width */
		/* set a0_pos = a1_pos,  which is relative to b1_pos */
		a0_pos   = b1_pos + (goal-FAX_GOAL_HandleVert0);
		a0_color = 1-a0_color;
	        if (a0_pos >= width) {
		    FlushLineData();
		    goal = FAX_GOAL_SeekEOLandTag;
		}
		else  {
		    /* not at eol yet */
		    goal = FAX_GOAL_DetermineMode;
		    new_trans[n_new_trans++] = a0_pos;
		}
	    }
	    else {		
	       /* line above was all white. Since b1 was first non-white */
	       /* b1 is imaginary transition off right edge.  In other   */
	       /* words, there are no more transitions! Done with line	 */

		FlushLineData();
		goal = FAX_GOAL_SeekEOLandTag;
	    }
	    break;

	  default:
	    return(-1);
	  break;
	  }  /* end of switch */
	}
/***	End, Main Decoding Loop	***/
}
/**** module fax/g32d.c ****/