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

	    break;
	  k += 15;
	}
      }

      EndOfBlock: ;
    }

    /* Completed MCU, so update state */
    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
    ASSIGN_STATE(entropy->saved, state);
  }

  /* Account for restart interval (no-op if not using restarts) */
  entropy->restarts_to_go--;

  return TRUE;
}


/*
 * Initialize for a Huffman-compressed scan.
 */

METHODDEF(void)
start_pass_huff_decoder (j_decompress_ptr cinfo)
{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  int ci, blkn, tbl, i;
  jpeg_component_info * compptr;

  if (cinfo->progressive_mode) {
    /* Validate progressive scan parameters */
    if (cinfo->Ss == 0) {
      if (cinfo->Se != 0)
	goto bad;
    } else {
      /* need not check Ss/Se < 0 since they came from unsigned bytes */
      if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
	goto bad;
      /* AC scans may have only one component */
      if (cinfo->comps_in_scan != 1)
	goto bad;
    }
    if (cinfo->Ah != 0) {
      /* Successive approximation refinement scan: must have Al = Ah-1. */
      if (cinfo->Ah-1 != cinfo->Al)
	goto bad;
    }
    if (cinfo->Al > 13) {	/* need not check for < 0 */
      /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
       * but the spec doesn't say so, and we try to be liberal about what we
       * accept.  Note: large Al values could result in out-of-range DC
       * coefficients during early scans, leading to bizarre displays due to
       * overflows in the IDCT math.  But we won't crash.
       */
      bad:
      ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
	       cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
    }
    /* Update progression status, and verify that scan order is legal.
     * Note that inter-scan inconsistencies are treated as warnings
     * not fatal errors ... not clear if this is right way to behave.
     */
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
      int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
      if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
	WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
      for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
	int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
	if (cinfo->Ah != expected)
	  WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
	coef_bit_ptr[coefi] = cinfo->Al;
      }
    }

    /* Select MCU decoding routine */
    if (cinfo->Ah == 0) {
      if (cinfo->Ss == 0)
	entropy->pub.decode_mcu = decode_mcu_DC_first;
      else
	entropy->pub.decode_mcu = decode_mcu_AC_first;
    } else {
      if (cinfo->Ss == 0)
	entropy->pub.decode_mcu = decode_mcu_DC_refine;
      else
	entropy->pub.decode_mcu = decode_mcu_AC_refine;
    }

    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      /* Make sure requested tables are present, and compute derived tables.
       * We may build same derived table more than once, but it's not expensive.
       */
      if (cinfo->Ss == 0) {
	if (cinfo->Ah == 0) {	/* DC refinement needs no table */
	  tbl = compptr->dc_tbl_no;
	  jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
				  & entropy->derived_tbls[tbl]);
	}
      } else {
	tbl = compptr->ac_tbl_no;
	jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
				& entropy->derived_tbls[tbl]);
	/* remember the single active table */
	entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
      }
      /* Initialize DC predictions to 0 */
      entropy->saved.last_dc_val[ci] = 0;
    }

    /* Initialize private state variables */
    entropy->saved.EOBRUN = 0;
  } else {
    /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
     * This ought to be an error condition, but we make it a warning because
     * there are some baseline files out there with all zeroes in these bytes.
     */
    if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
	((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&