/* $XConsortium: etiffpb.c,v 1.3 94/04/17 20:34:31 rws Exp $ */
/**** module etiffpb.h ****/
/******************************************************************************

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******************************************************************************

	etiffpb.c -- DDXIE module for encoding TIFF PackBits format

	Ben Fahy, AGE Logic, Sept 1993 

******************************************************************************/


#include "fax.h"
#define _PBits
#include "fencode.h"

/************************************************************************/
encode_tiffpb(state)
FaxEncodeState *state;
{
/* stuff exchanged with state variable */
register int goal;
register unsigned char *byteptr;
register unsigned char *endptr;
register int width;
register int rl;
PackBitsEncodePvt	*epvt;

/* stuff exchanged with private state variable */
int index;
int start;
int nlits;
int nvals;
register int *counts;
register int *values;


register int 	lines_coded=0;
register int	lines_to_code=0;
register int 	rlcode,lits_to_write;
register int	bytes_out;

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

	/* set up initial bitstream for the very first output strip */
	if (!state->bits.started) {
	    if (state->strip_state != StripStateNew)  {
	       	state->encoder_done = ENCODE_ERROR_StripStateNotNew;
		return(-1);
	    }
	    
	    state->bits.byteptr = (unsigned char *)state->strip;
	    state->bits.endptr  = state->bits.byteptr + state->strip_size;
	    	/* record end of output strip */

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

	/* or, reset bitstream for a new output strip */
	if (state->magic_needs)  {
	  if (state->strip_state == StripStateNew)  {
	    state->strip_state = StripStateInUse;
	    state->bits.byteptr = (unsigned char *)state->strip;
	    state->bits.endptr  = state->bits.byteptr + state->strip_size;
	    	/* record end of output strip */
	    state->bits.bitpos = 0;
	    state->bits.started = 1;
	  }
	  else {
	     /* no new strip?? But... I *need* more data! */
	      state->encoder_done = ENCODE_ERROR_BadMagic;
	      return(-1);
	  }
	  state->magic_needs = 0;
	}
	localize_state(state);


/***	Main Encoding Loop	***/
	while (1) {

	  switch(goal) {

	  case ENCODE_PB_GOAL_StartNewLine:
	    /* every new line we need to compute its runlength data */

	    { 
	    register unsigned char *ibptr=NULL;
	    register unsigned char *ebptr=NULL;
	    register int color0,color1, n_reps;

	    if (lines_coded >= state->nl_tocode) {
		/* We have read the whole input strip, need more data  */
		save_state_and_return(state);
	    }

	    ibptr = (unsigned char *) state->i_lines[lines_coded];
	    ebptr = ibptr+(width+7)/8;

	    color0 = *ibptr++;
	    n_reps = 1;
	    nvals = 0;
	    epvt->values[nvals] = color0;

	    while (ibptr < ebptr) {
		color1 = *ibptr++; if (color1 == color0) ++n_reps;
		else {
			epvt->counts[nvals++] = n_reps;
			color0 = color1;
			n_reps = 1;
			epvt->values[nvals] = color0;
		}
	    }
	    epvt->counts[nvals++] = n_reps;
	    epvt->nvals = nvals;

	    }
	    /* now that we have an encoding of the line in runlengths,
	       we need to decide what we write out as R V,  where R
	       is the runlength and V is the value, vs L V1 V2 ... VL
	       where Vi are individual values and L is the number of 
	       literal values that follow.  There isn't really any 
	       advantage to coding runlengths of size 2 or less, so
	       we will only code as a runlength for runs of 3 or more.
	    */
	    index = 0;	/* where we are in our list of runs and values */
	    start = 0;  /* where we were when we started */
	    nlits = 0;  /* number of literals we will concatenate */
	    goal = ENCODE_PB_GOAL_OutputNextRunLength;

	  case ENCODE_PB_GOAL_OutputNextRunLength:
	    /* starting from the current index, search for the first
	       runlength of three or more. Everything before then will
	       be encoded as a string of literals.
	    */

	    start = index;
	    while (index < nvals && (rl = counts[index]) < 3) {
		nlits += rl;
		++index;
	    }

	    if (start != index) {
	       /* Note: we can never call FlushLiterals when start >= nvals,
		  because index <= nvals,  and start < index if here */
	       goal = ENCODE_PB_GOAL_FlushLiterals;
	    }
	    else {
		/* found a suitable runlength */
		goal = ENCODE_PB_GOAL_FlushRunLength;
	    }
	    break;

	  case ENCODE_PB_GOAL_FlushRunLength:
	    if (!rl) {
	       state->encoder_done = ENCODE_ERROR_BadRunLength;
	       save_state_and_return(state);
	    }
	    /* Packbits represents runlengths as rl = 1 - rlcode, where */
	    /* rlcode is a negative number between -1 and -127.  So we  */
	    /* may have to break a number larger than 128 into multiple */
	    /* runlengths */
	    if (rl <= 128) {
		   rlcode = 1-rl;		/* encode the runlength */
		   rl = 0;		
	    }
	    else {
		   rlcode = -127;		/* encode the maximum 	*/
		   rl -= 128;
	    } 
	    /* before writing, make sure we aren't off end of strip 	*/
	    if ( byteptr >= endptr) {
	       goal = ENCODE_PB_GOAL_WriteCodeForRunLength;
	       state->strip_state = StripStateDone;
	       state->magic_needs = 1;
	       save_state_and_return(state);
	    }

	  case ENCODE_PB_GOAL_WriteCodeForRunLength:
	    *byteptr++ = rlcode;

	    /* before writing, make sure we aren't off end of strip 	*/
	    if ( byteptr >= endptr) {
	       goal = ENCODE_PB_GOAL_WriteValueForRunLength;
	       state->strip_state = StripStateDone;
	       state->magic_needs = 1;
	       save_state_and_return(state);
	    }
	  case ENCODE_PB_GOAL_WriteValueForRunLength:
	    *byteptr++ = values[index];
	    if (!rl) {
		if (++index >= nvals) {		/* see if done with line */
		   ++lines_coded;
		   goal = ENCODE_PB_GOAL_StartNewLine;
		}
		else
		   goal = ENCODE_PB_GOAL_OutputNextRunLength;
	    }
	    else 
	        goal = ENCODE_PB_GOAL_FlushRunLength; 
		break; 
	  case ENCODE_PB_GOAL_FlushLiterals: 
	    /* Packbits represents literal lengths as rl = 1 + rlcode, 	*/
	    /* rlcode is a number between 0 and 127.  So we have to break  */
	    /* break numbers larger than 128 into multiple runlengths	*/
	    if (nlits <= 128) {
		   rlcode = nlits-1;		/* encode the runlength */
		   nlits = 0;		
	    }
	    else {
		   rlcode = 127;		/* encode the maximum */
		   nlits -= 128;
	    } 
	    rl = 1 + rlcode;	/* need this for comparison later 	*/
	    bytes_out = 0;	/* ditto. bytes_out must be <= rl 	*/

	    /* before writing, make sure we aren't off end of strip 	*/
	    if ( byteptr >= endptr) {
	       goal = ENCODE_PB_GOAL_WriteNlits;
	       state->strip_state = StripStateDone;
	       state->magic_needs = 1;
	       save_state_and_return(state);
	    }

	  case ENCODE_PB_GOAL_WriteNlits:
	    *byteptr++ = rlcode;
	    goal = ENCODE_PB_GOAL_WriteLiterals;
		/* note that lits_to_write is always 1 or 2 */

	  case ENCODE_PB_GOAL_WriteLiterals:
	    /* this is actually a loop. 'start' gets incremented each 	*/
	    /* time through until it is equal to 'index'. We never get	*/
	    /* to this point unless start < nvals, though 		*/

	    lits_to_write = counts[start];
	    goal = ENCODE_PB_GOAL_WriteThisLiteral;

	  case ENCODE_PB_GOAL_WriteThisLiteral:
	    /* before writing, make sure we aren't off end of strip 	*/
	    if ( byteptr >= endptr) {
	       goal = ENCODE_PB_GOAL_WriteTheLiteral;
	       state->strip_state = StripStateDone;
	       state->magic_needs = 1;
	       save_state_and_return(state);
	    }

	  case ENCODE_PB_GOAL_WriteTheLiteral:
	    *byteptr++ = values[start];
	    if (++bytes_out >= 128 && nlits) {
		/* we have written the maximum amount we can	*/
		/* write at a time, yet we know there are more  */
		/* to write out. 				*/

		goal = ENCODE_PB_GOAL_FlushLiterals;

		/* If we need to write current value some more, */
		/* change count so we don't write extra		*/

		if (--lits_to_write) 
		   counts[start] = lits_to_write;
		else {
		   /* otherwise,  advance position	*/
		   ++start;
		}

		/* note that we KNOW we have to write more literals */
		/* so it is safe to increment 'start', which could  */
		/* only be equal to 'index' if we were done	    */

		break;
	    }
	    else if (--lits_to_write) {
		/* loop back and write this value again */
		goal = ENCODE_PB_GOAL_WriteThisLiteral;
		break;
	    }

	    /* If here, we are done with this literal */
	    if (++start < index)  {
	       /* if other literals to write, loop back */
	       goal = ENCODE_PB_GOAL_WriteLiterals;
	       break;
	    }

	    /* ok,  we wrote out all the literals */

	    if (index >= nvals) {		/* see if done with line */
		++lines_coded;
		goal = ENCODE_PB_GOAL_StartNewLine;
	    }
	    else
		goal = ENCODE_PB_GOAL_OutputNextRunLength;
	    break;

	  default:
	    state->encoder_done = ENCODE_ERROR_BadMagic;
	    save_state_and_return(state);
	    break;

	  } /* end of switch(goal) in main decoding loop */

	} /* end of main encoding loop */
}
/************************************************************************/