text: /*
   * jdmaster.c
   *
   * Copyright (C) 1991-1998, Thomas G. Lane.
   * This file is part of the Independent JPEG Group's software.
   * For conditions of distribution and use, see the accompanying README file.
   *
   * This file contains master control logic for the JPEG decompressor.
   * These routines are concerned with selecting the modules to be executed
   * and with determining the number of passes and the work to be done in each
   * pass.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude12.h"
  #include "jpeglib12.h"
  
  
  /* Private state */
  
  typedef struct {
    struct jpeg_decomp_master pub; /* public fields */
  
    int pass_number;		/* # of passes completed */
  
    boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */
  
    /* Saved references to initialized quantizer modules,
     * in case we need to switch modes.
     */
    struct jpeg_color_quantizer * quantizer_1pass;
    struct jpeg_color_quantizer * quantizer_2pass;
  } my_decomp_master;
  
  typedef my_decomp_master * my_master_ptr;
  
  
  /*
   * Determine whether merged upsample/color conversion should be used.
   * CRUCIAL: this must match the actual capabilities of jdmerge.c!
   */
  
  LOCAL(boolean)
  use_merged_upsample (j_decompress_ptr cinfo)
  {
  #ifdef UPSAMPLE_MERGING_SUPPORTED
    /* Merging is the equivalent of plain box-filter upsampling */
    if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
      return FALSE;
    /* jdmerge.c only supports YCC=>RGB color conversion */
    if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 ||
        cinfo->out_color_space != JCS_RGB ||
        cinfo->out_color_components != RGB_PIXELSIZE)
      return FALSE;
    /* and it only handles 2h1v or 2h2v sampling ratios */
    if (cinfo->comp_info[0].h_samp_factor != 2 ||
        cinfo->comp_info[1].h_samp_factor != 1 ||
        cinfo->comp_info[2].h_samp_factor != 1 ||
        cinfo->comp_info[0].v_samp_factor >  2 ||
        cinfo->comp_info[1].v_samp_factor != 1 ||
        cinfo->comp_info[2].v_samp_factor != 1)
      return FALSE;
    /* furthermore, it doesn't work if each component has been
       processed differently */
    if (cinfo->comp_info[0].codec_data_unit != cinfo->min_codec_data_unit ||
        cinfo->comp_info[1].codec_data_unit != cinfo->min_codec_data_unit ||
        cinfo->comp_info[2].codec_data_unit != cinfo->min_codec_data_unit)
      return FALSE;
    /* ??? also need to test for upsample-time rescaling, when & if supported */
    return TRUE;			/* by golly, it'll work... */
  #else
    return FALSE;
  #endif
  }
  
  
  /*
   * Compute output image dimensions and related values.
   * NOTE: this is exported for possible use by application.
   * Hence it mustn't do anything that can't be done twice.
   * Also note that it may be called before the master module is initialized!
   */
  
  GLOBAL(void)
  jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
  /* Do computations that are needed before master selection phase */
  {
    /* Prevent application from calling me at wrong times */
    if (cinfo->global_state != DSTATE_READY)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    (*cinfo->codec->calc_output_dimensions) (cinfo);
  
    /* Report number of components in selected colorspace. */
    /* Probably this should be in the color conversion module... */
    switch (cinfo->out_color_space) {
    case JCS_GRAYSCALE:
      cinfo->out_color_components = 1;
      break;
    case JCS_RGB:
  #if RGB_PIXELSIZE != 3
      cinfo->out_color_components = RGB_PIXELSIZE;
      break;
  #endif /* else share code with YCbCr */
    case JCS_YCbCr:
      cinfo->out_color_components = 3;
      break;
    case JCS_CMYK:
    case JCS_YCCK:
      cinfo->out_color_components = 4;
      break;
    default:			/* else must be same colorspace as in file */
      cinfo->out_color_components = cinfo->num_components;
      break;
    }
    cinfo->output_components = (cinfo->quantize_colors ? 1 :
  			      cinfo->out_color_components);
  
    /* See if upsampler will want to emit more than one row at a time */
    if (use_merged_upsample(cinfo))
      cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
    else
      cinfo->rec_outbuf_height = 1;
  }
  
  
  /*
   * Several decompression processes need to range-limit values to the range
   * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
   * due to noise introduced by quantization, roundoff error, etc.  These
   * processes are inner loops and need to be as fast as possible.  On most
   * machines, particularly CPUs with pipelines or instruction prefetch,
   * a (subscript-check-less) C table lookup
   *		x = sample_range_limit[x];
   * is faster than explicit tests
   *		if (x < 0)  x = 0;
   *		else if (x > MAXJSAMPLE)  x = MAXJSAMPLE;
   * These processes all use a common table prepared by the routine below.
   *
   * For most steps we can mathematically guarantee that the initial value
   * of x is within MAXJSAMPLE+1 of the legal range, so a table running from
   * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient.  But for the initial
   * limiting step (just after the IDCT), a wildly out-of-range value is 
   * possible if the input data is corrupt.  To avoid any chance of indexing
   * off the end of memory and getting a bad-pointer trap, we perform the
   * post-IDCT limiting thus:
   *		x = range_limit[x & MASK];
   * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
   * samples.  Under normal circumstances this is more than enough range and
   * a correct output will be generated; with bogus input data the mask will
   * cause wraparound, and we will safely generate a bogus-but-in-range output.
   * For the post-IDCT step, we want to convert the data from signed to unsigned
   * representation by adding CENTERJSAMPLE at the same time that we limit it.
   * So the post-IDCT limiting table ends up looking like this:
   *   CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
   *   MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
   *   0          (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
   *   0,1,...,CENTERJSAMPLE-1
   * Negative inputs select values from the upper half of the table after
   * masking.
   *
   * We can save some space by overlapping the start of the post-IDCT table
   * with the simpler range limiting table.  The post-IDCT table begins at
   * sample_range_limit + CENTERJSAMPLE.
   *
   * Note that the table is allocated in near data space on PCs; it's small
   * enough and used often enough to justify this.
   */
  
  LOCAL(void)
  prepare_range_limit_table (j_decompress_ptr cinfo)
  /* Allocate and fill in the sample_range_limit table */
  {
    JSAMPLE * table;
    int i;
  
    table = (JSAMPLE *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  		(5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE));
    table += (MAXJSAMPLE+1);	/* allow negative subscripts of simple table */
    cinfo->sample_range_limit = table;
    /* First segment of "simple" table: limit[x] = 0 for x < 0 */
    MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE));
    /* Main part of "simple" table: limit[x] = x */
    for (i = 0; i <= MAXJSAMPLE; i++)
      table[i] = (JSAMPLE) i;
    table += CENTERJSAMPLE;	/* Point to where post-IDCT table starts */
    /* End of simple table, rest of first half of post-IDCT table */
    for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++)
      table[i] = MAXJSAMPLE;
    /* Second half of post-IDCT table */
    MEMZERO(table + (2 * (MAXJSAMPLE+1)),
  	  (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE));
    MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE),
  	  cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE));
  }
  
  
  /*
   * Master selection of decompression modules.
   * This is done once at jpeg_start_decompress time.  We determine
   * which modules will be used and give them appropriate initialization calls.
   * We also initialize the decompressor input side to begin consuming data.
   *
   * Since jpeg_read_header has finished, we know what is in the SOF
   * and (first) SOS markers.  We also have all the application parameter
   * settings.
   */
  
  LOCAL(void)
  master_selection (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
    long samplesperrow;
    JDIMENSION jd_samplesperrow;
  
    /* Initialize dimensions and other stuff */
    jpeg_calc_output_dimensions(cinfo);
    prepare_range_limit_table(cinfo);
  
    /* Width of an output scanline must be representable as JDIMENSION. */
    samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
    jd_samplesperrow = (JDIMENSION) samplesperrow;
    if ((long) jd_samplesperrow != samplesperrow)
      ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
  
    /* Initialize my private state */
    master->pass_number = 0;
    master->using_merged_upsample = use_merged_upsample(cinfo);
  
    /* Color quantizer selection */
    master->quantizer_1pass = NULL;
    master->quantizer_2pass = NULL;
    /* No mode changes if not using buffered-image mode. */
    if (! cinfo->quantize_colors || ! cinfo->buffered_image) {
      cinfo->enable_1pass_quant = FALSE;
      cinfo->enable_external_quant = FALSE;
      cinfo->enable_2pass_quant = FALSE;
    }
    if (cinfo->quantize_colors) {
      if (cinfo->raw_data_out)
        ERREXIT(cinfo, JERR_NOTIMPL);
      /* 2-pass quantizer only works in 3-component color space. */
      if (cinfo->out_color_components != 3) {
        cinfo->enable_1pass_quant = TRUE;
        cinfo->enable_external_quant = FALSE;
        cinfo->enable_2pass_quant = FALSE;
        cinfo->colormap = NULL;
      } else if (cinfo->colormap != NULL) {
        cinfo->enable_external_quant = TRUE;
      } else if (cinfo->two_pass_quantize) {
        cinfo->enable_2pass_quant = TRUE;
      } else {
        cinfo->enable_1pass_quant = TRUE;
      }
  
      if (cinfo->enable_1pass_quant) {
  #ifdef QUANT_1PASS_SUPPORTED
        jinit_1pass_quantizer(cinfo);
        master->quantizer_1pass = cinfo->cquantize;
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      }
  
      /* We use the 2-pass code to map to external colormaps. */
      if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
  #ifdef QUANT_2PASS_SUPPORTED
        jinit_2pass_quantizer(cinfo);
        master->quantizer_2pass = cinfo->cquantize;
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      }
      /* If both quantizers are initialized, the 2-pass one is left active;
       * this is necessary for starting with quantization to an external map.
       */
    }
  
    /* Post-processing: in particular, color conversion first */
    if (! cinfo->raw_data_out) {
      if (master->using_merged_upsample) {
  #ifdef UPSAMPLE_MERGING_SUPPORTED
        jinit_merged_upsampler(cinfo); /* does color conversion too */
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      } else {
        jinit_color_deconverter(cinfo);
        jinit_upsampler(cinfo);
      }
      jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
    }
  
    /* Initialize principal buffer controllers. */
    if (! cinfo->raw_data_out)
      jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
  
    /* We can now tell the memory manager to allocate virtual arrays. */
    (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
  
    /* Initialize input side of decompressor to consume first scan. */
    (*cinfo->inputctl->start_input_pass) (cinfo);
  
  #ifdef D_MULTISCAN_FILES_SUPPORTED
    /* If jpeg_start_decompress will read the whole file, initialize
     * progress monitoring appropriately.  The input step is counted
     * as one pass.
     */
    if (cinfo->progress != NULL && ! cinfo->buffered_image &&
        cinfo->inputctl->has_multiple_scans) {
      int nscans;
      /* Estimate number of scans to set pass_limit. */
      if (cinfo->process == JPROC_PROGRESSIVE) {
        /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
        nscans = 2 + 3 * cinfo->num_components;
      } else {
        /* For a nonprogressive multiscan file, estimate 1 scan per component. */
        nscans = cinfo->num_components;
      }
      cinfo->progress->pass_counter = 0L;
      cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
      cinfo->progress->completed_passes = 0;
      cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
      /* Count the input pass as done */
      master->pass_number++;
    }
  #endif /* D_MULTISCAN_FILES_SUPPORTED */
  }
  
  
  /*
   * Per-pass setup.
   * This is called at the beginning of each output pass.  We determine which
   * modules will be active during this pass and give them appropriate
   * start_pass calls.  We also set is_dummy_pass to indicate whether this
   * is a "real" output pass or a dummy pass for color quantization.
   * (In the latter case, jdapistd.c will crank the pass to completion.)
   */
  
  METHODDEF(void)
  prepare_for_output_pass (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
  
    if (master->pub.is_dummy_pass) {
  #ifdef QUANT_2PASS_SUPPORTED
      /* Final pass of 2-pass quantization */
      master->pub.is_dummy_pass = FALSE;
      (*cinfo->cquantize->start_pass) (cinfo, FALSE);
      (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
      (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
  #else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif /* QUANT_2PASS_SUPPORTED */
    } else {
      if (cinfo->quantize_colors && cinfo->colormap == NULL) {
        /* Select new quantization method */
        if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
  	cinfo->cquantize = master->quantizer_2pass;
  	master->pub.is_dummy_pass = TRUE;
        } else if (cinfo->enable_1pass_quant) {
  	cinfo->cquantize = master->quantizer_1pass;
        } else {
  	ERREXIT(cinfo, JERR_MODE_CHANGE);
        }
      }
      (*cinfo->codec->start_output_pass) (cinfo);
      if (! cinfo->raw_data_out) {
        if (! master->using_merged_upsample)
  	(*cinfo->cconvert->start_pass) (cinfo);
        (*cinfo->upsample->start_pass) (cinfo);
        if (cinfo->quantize_colors)
  	(*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
        (*cinfo->post->start_pass) (cinfo,
  	    (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
        (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
      }
    }
  
    /* Set up progress monitor's pass info if present */
    if (cinfo->progress != NULL) {
      cinfo->progress->completed_passes = master->pass_number;
      cinfo->progress->total_passes = master->pass_number +
  				    (master->pub.is_dummy_pass ? 2 : 1);
      /* In buffered-image mode, we assume one more output pass if EOI not
       * yet reached, but no more passes if EOI has been reached.
       */
      if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) {
        cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
      }
    }
  }
  
  
  /*
   * Finish up at end of an output pass.
   */
  
  METHODDEF(void)
  finish_output_pass (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
  
    if (cinfo->quantize_colors)
      (*cinfo->cquantize->finish_pass) (cinfo);
    master->pass_number++;
  }
  
  
  #ifdef D_MULTISCAN_FILES_SUPPORTED
  
  /*
   * Switch to a new external colormap between output passes.
   */
  
  GLOBAL(void)
  jpeg_new_colormap (j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr) cinfo->master;
  
    /* Prevent application from calling me at wrong times */
    if (cinfo->global_state != DSTATE_BUFIMAGE)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    if (cinfo->quantize_colors && cinfo->enable_external_quant &&
        cinfo->colormap != NULL) {
      /* Select 2-pass quantizer for external colormap use */
      cinfo->cquantize = master->quantizer_2pass;
      /* Notify quantizer of colormap change */
      (*cinfo->cquantize->new_color_map) (cinfo);
      master->pub.is_dummy_pass = FALSE; /* just in case */
    } else
      ERREXIT(cinfo, JERR_MODE_CHANGE);
  }
  
  #endif /* D_MULTISCAN_FILES_SUPPORTED */
  
  
  /*
   * Initialize master decompression control and select active modules.
   * This is performed at the start of jpeg_start_decompress.
   */
  
  GLOBAL(void)
  jinit_master_decompress (j_decompress_ptr cinfo)
  {
    my_master_ptr master;
  
    master = (my_master_ptr)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  				  SIZEOF(my_decomp_master));
    cinfo->master = (struct jpeg_decomp_master *) master;
    master->pub.prepare_for_output_pass = prepare_for_output_pass;
    master->pub.finish_output_pass = finish_output_pass;
  
    master->pub.is_dummy_pass = FALSE;
  
    master_selection(cinfo);
  }
  