/* $Xorg: dg4.c,v 1.4 2001/02/09 02:04:25 xorgcvs Exp $ */
/* AGE Logic - Oct 15 1995 - Larry Hare */
/**** module fax/g4.c ****/
/******************************************************************************

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*****************************************************************************
  
	fax/g4.c -- DDXIE G4 fax decode technique/element
  
	Ben Fahy -- AGE Logic, Inc. May, 1993
  
*****************************************************************************/


#define _G4
#include "fax.h"
#include "faxint.h"
#include "bits.h"

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


/**********************************************************************/
int decode_g4(state)
FaxState *state;
{
register int bitpos;
register unsigned char *byteptr;
register unsigned char *endptr;
register int a0_color;
register int a0_pos;
register int goal;
register int mode;	/* could overload goal, but will resist */
register int length;
register int width;

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 	rl;

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

	/* set up initial bitstream for the very first strip */
	if (!state->bits.started) {
	    if (state->strip_state != StripStateNew) {
		state->decoder_done = FAX_DECODE_DONE_ErrorBadStripper;
		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) {
	  switch(goal) {
	  case FAX_GOAL_StartNewLine:

	    /* if any data produced by previous states, write it out */
	    if (lines_found >= state->nl_sought) 
		    save_state_and_return(state);

	    /* normal line initialization stuff */
	    a0_pos   = -1;
	    a0_color = WHITE;
	    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) 
	         adjust_bitstream_8(length,byteptr,bitpos,endptr);
	    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;
	    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;
	    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++] = a0a1;
		new_trans[n_new_trans] = a0_pos = a0a1 + a1a2;
		++n_new_trans;
	    } 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++] = a0_pos + a0a1;
		new_trans[n_new_trans]   = a0_pos = a0_pos + a0a1 + a1a2;
		++n_new_trans;
	    }
	    if (a0_pos >= width) {
		if (a0_pos > width) {
		   state->decoder_done = FAX_DECODE_DONE_ErrorPastWidth;
		   save_state_and_return(state);
		}
		goal = FAX_GOAL_StartNewLine;
		FlushLineData();
		break;
	    }
	    else 
	        goal = FAX_GOAL_DetermineMode;
	    break;

	  case FAX_MODE_Pass:
	    if (!n_old_trans) {	/* line above all white */
		state->decoder_done = FAX_DECODE_DONE_ErrorPassAboveAllWhite;
		save_state_and_return(state);
	    }
	    find_b2pos(a0_pos,a0_color,n_old_trans,old_trans);

	    a0_pos = b2_pos;
	    if (a0_pos < 0) {
		FlushLineData();
	       	goal = FAX_GOAL_StartNewLine;
	       	break;
	    }
	    if (a0_pos >= width) {
		state->decoder_done = FAX_DECODE_DONE_ErrorBadA0pos;
		save_state_and_return(state);
	    }
	    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) {
		     state->decoder_done = FAX_DECODE_DONE_ErrorBadGoal;
		     save_state_and_return(state);
		   }
		   b1_pos = width;
		}
	    } else {		
	       /* line above was all white. Since b1 was first non-white */
	       /* b1 is imaginary transition off right edge.		 */
		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;
	    new_trans[n_new_trans++] = a0_pos > 0 ? a0_pos : 0;
	    if (a0_pos >= width) {
	        FlushLineData();
	        goal = FAX_GOAL_StartNewLine;
	    }
	    else  {
		/* not at eol yet */
		goal = FAX_GOAL_DetermineMode;
	    }
	    break;

	  default:
	    state->decoder_done = FAX_DECODE_DONE_ErrorBadGoal;
	    save_state_and_return(state);
	  break;
	  }  /* end of switch */
	}
/***	End, Main Decoding Loop	***/
}
/**** module fax/g4.c ****/
