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src/Source/LibJPEG/jcarith.c  view on Meta::CPAN

      e->c += e->a;
      e->a = qe;
    }
    *st = (sv & 0x80) ^ nm;	/* Estimate_after_MPS */
  }

  /* Renormalization & data output per section D.1.6 */
  do {
    e->a <<= 1;
    e->c <<= 1;
    if (--e->ct == 0) {
      /* Another byte is ready for output */
      temp = e->c >> 19;
      if (temp > 0xFF) {
	/* Handle overflow over all stacked 0xFF bytes */
	if (e->buffer >= 0) {
	  if (e->zc)
	    do emit_byte(0x00, cinfo);
	    while (--e->zc);
	  emit_byte(e->buffer + 1, cinfo);
	  if (e->buffer + 1 == 0xFF)
	    emit_byte(0x00, cinfo);
	}
	e->zc += e->sc;  /* carry-over converts stacked 0xFF bytes to 0x00 */
	e->sc = 0;
	/* Note: The 3 spacer bits in the C register guarantee
	 * that the new buffer byte can't be 0xFF here
	 * (see page 160 in the P&M JPEG book). */
	e->buffer = temp & 0xFF;  /* new output byte, might overflow later */
      } else if (temp == 0xFF) {
	++e->sc;  /* stack 0xFF byte (which might overflow later) */
      } else {
	/* Output all stacked 0xFF bytes, they will not overflow any more */
	if (e->buffer == 0)
	  ++e->zc;
	else if (e->buffer >= 0) {
	  if (e->zc)
	    do emit_byte(0x00, cinfo);
	    while (--e->zc);
	  emit_byte(e->buffer, cinfo);
	}
	if (e->sc) {
	  if (e->zc)
	    do emit_byte(0x00, cinfo);
	    while (--e->zc);
	  do {
	    emit_byte(0xFF, cinfo);
	    emit_byte(0x00, cinfo);
	  } while (--e->sc);
	}
	e->buffer = temp & 0xFF;  /* new output byte (can still overflow) */
      }
      e->c &= 0x7FFFFL;
      e->ct += 8;
    }
  } while (e->a < 0x8000L);
}


/*
 * Emit a restart marker & resynchronize predictions.
 */

LOCAL(void)
emit_restart (j_compress_ptr cinfo, int restart_num)
{
  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
  int ci;
  jpeg_component_info * compptr;

  finish_pass(cinfo);

  emit_byte(0xFF, cinfo);
  emit_byte(JPEG_RST0 + restart_num, cinfo);

  /* Re-initialize statistics areas */
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    /* DC needs no table for refinement scan */
    if (cinfo->Ss == 0 && cinfo->Ah == 0) {
      MEMZERO(entropy->dc_stats[compptr->dc_tbl_no], DC_STAT_BINS);
      /* Reset DC predictions to 0 */
      entropy->last_dc_val[ci] = 0;
      entropy->dc_context[ci] = 0;
    }
    /* AC needs no table when not present */
    if (cinfo->Se) {
      MEMZERO(entropy->ac_stats[compptr->ac_tbl_no], AC_STAT_BINS);
    }
  }

  /* Reset arithmetic encoding variables */
  entropy->c = 0;
  entropy->a = 0x10000L;
  entropy->sc = 0;
  entropy->zc = 0;
  entropy->ct = 11;
  entropy->buffer = -1;  /* empty */
}


/*
 * MCU encoding for DC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF(boolean)
encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
  unsigned char *st;
  int blkn, ci, tbl;
  int v, v2, m;
  ISHIFT_TEMPS

  /* Emit restart marker if needed */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      emit_restart(cinfo, entropy->next_restart_num);
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;