LCOV - code coverage report
Current view: directory - media/libjpeg - jdmainct.c (source / functions) Found Hit Coverage
Test: app.info Lines: 149 139 93.3 %
Date: 2012-06-02 Functions: 9 8 88.9 %

       1                 : /*
       2                 :  * jdmainct.c
       3                 :  *
       4                 :  * Copyright (C) 1994-1996, Thomas G. Lane.
       5                 :  * Copyright (C) 2010, D. R. Commander.
       6                 :  * This file is part of the Independent JPEG Group's software.
       7                 :  * For conditions of distribution and use, see the accompanying README file.
       8                 :  *
       9                 :  * This file contains the main buffer controller for decompression.
      10                 :  * The main buffer lies between the JPEG decompressor proper and the
      11                 :  * post-processor; it holds downsampled data in the JPEG colorspace.
      12                 :  *
      13                 :  * Note that this code is bypassed in raw-data mode, since the application
      14                 :  * supplies the equivalent of the main buffer in that case.
      15                 :  */
      16                 : 
      17                 : #define JPEG_INTERNALS
      18                 : #include "jinclude.h"
      19                 : #include "jpeglib.h"
      20                 : #include "jpegcomp.h"
      21                 : 
      22                 : 
      23                 : /*
      24                 :  * In the current system design, the main buffer need never be a full-image
      25                 :  * buffer; any full-height buffers will be found inside the coefficient or
      26                 :  * postprocessing controllers.  Nonetheless, the main controller is not
      27                 :  * trivial.  Its responsibility is to provide context rows for upsampling/
      28                 :  * rescaling, and doing this in an efficient fashion is a bit tricky.
      29                 :  *
      30                 :  * Postprocessor input data is counted in "row groups".  A row group
      31                 :  * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
      32                 :  * sample rows of each component.  (We require DCT_scaled_size values to be
      33                 :  * chosen such that these numbers are integers.  In practice DCT_scaled_size
      34                 :  * values will likely be powers of two, so we actually have the stronger
      35                 :  * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
      36                 :  * Upsampling will typically produce max_v_samp_factor pixel rows from each
      37                 :  * row group (times any additional scale factor that the upsampler is
      38                 :  * applying).
      39                 :  *
      40                 :  * The coefficient controller will deliver data to us one iMCU row at a time;
      41                 :  * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
      42                 :  * exactly min_DCT_scaled_size row groups.  (This amount of data corresponds
      43                 :  * to one row of MCUs when the image is fully interleaved.)  Note that the
      44                 :  * number of sample rows varies across components, but the number of row
      45                 :  * groups does not.  Some garbage sample rows may be included in the last iMCU
      46                 :  * row at the bottom of the image.
      47                 :  *
      48                 :  * Depending on the vertical scaling algorithm used, the upsampler may need
      49                 :  * access to the sample row(s) above and below its current input row group.
      50                 :  * The upsampler is required to set need_context_rows TRUE at global selection
      51                 :  * time if so.  When need_context_rows is FALSE, this controller can simply
      52                 :  * obtain one iMCU row at a time from the coefficient controller and dole it
      53                 :  * out as row groups to the postprocessor.
      54                 :  *
      55                 :  * When need_context_rows is TRUE, this controller guarantees that the buffer
      56                 :  * passed to postprocessing contains at least one row group's worth of samples
      57                 :  * above and below the row group(s) being processed.  Note that the context
      58                 :  * rows "above" the first passed row group appear at negative row offsets in
      59                 :  * the passed buffer.  At the top and bottom of the image, the required
      60                 :  * context rows are manufactured by duplicating the first or last real sample
      61                 :  * row; this avoids having special cases in the upsampling inner loops.
      62                 :  *
      63                 :  * The amount of context is fixed at one row group just because that's a
      64                 :  * convenient number for this controller to work with.  The existing
      65                 :  * upsamplers really only need one sample row of context.  An upsampler
      66                 :  * supporting arbitrary output rescaling might wish for more than one row
      67                 :  * group of context when shrinking the image; tough, we don't handle that.
      68                 :  * (This is justified by the assumption that downsizing will be handled mostly
      69                 :  * by adjusting the DCT_scaled_size values, so that the actual scale factor at
      70                 :  * the upsample step needn't be much less than one.)
      71                 :  *
      72                 :  * To provide the desired context, we have to retain the last two row groups
      73                 :  * of one iMCU row while reading in the next iMCU row.  (The last row group
      74                 :  * can't be processed until we have another row group for its below-context,
      75                 :  * and so we have to save the next-to-last group too for its above-context.)
      76                 :  * We could do this most simply by copying data around in our buffer, but
      77                 :  * that'd be very slow.  We can avoid copying any data by creating a rather
      78                 :  * strange pointer structure.  Here's how it works.  We allocate a workspace
      79                 :  * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
      80                 :  * of row groups per iMCU row).  We create two sets of redundant pointers to
      81                 :  * the workspace.  Labeling the physical row groups 0 to M+1, the synthesized
      82                 :  * pointer lists look like this:
      83                 :  *                   M+1                          M-1
      84                 :  * master pointer --> 0         master pointer --> 0
      85                 :  *                    1                            1
      86                 :  *                   ...                          ...
      87                 :  *                   M-3                          M-3
      88                 :  *                   M-2                           M
      89                 :  *                   M-1                          M+1
      90                 :  *                    M                           M-2
      91                 :  *                   M+1                          M-1
      92                 :  *                    0                            0
      93                 :  * We read alternate iMCU rows using each master pointer; thus the last two
      94                 :  * row groups of the previous iMCU row remain un-overwritten in the workspace.
      95                 :  * The pointer lists are set up so that the required context rows appear to
      96                 :  * be adjacent to the proper places when we pass the pointer lists to the
      97                 :  * upsampler.
      98                 :  *
      99                 :  * The above pictures describe the normal state of the pointer lists.
     100                 :  * At top and bottom of the image, we diddle the pointer lists to duplicate
     101                 :  * the first or last sample row as necessary (this is cheaper than copying
     102                 :  * sample rows around).
     103                 :  *
     104                 :  * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1.  In that
     105                 :  * situation each iMCU row provides only one row group so the buffering logic
     106                 :  * must be different (eg, we must read two iMCU rows before we can emit the
     107                 :  * first row group).  For now, we simply do not support providing context
     108                 :  * rows when min_DCT_scaled_size is 1.  That combination seems unlikely to
     109                 :  * be worth providing --- if someone wants a 1/8th-size preview, they probably
     110                 :  * want it quick and dirty, so a context-free upsampler is sufficient.
     111                 :  */
     112                 : 
     113                 : 
     114                 : /* Private buffer controller object */
     115                 : 
     116                 : typedef struct {
     117                 :   struct jpeg_d_main_controller pub; /* public fields */
     118                 : 
     119                 :   /* Pointer to allocated workspace (M or M+2 row groups). */
     120                 :   JSAMPARRAY buffer[MAX_COMPONENTS];
     121                 : 
     122                 :   boolean buffer_full;          /* Have we gotten an iMCU row from decoder? */
     123                 :   JDIMENSION rowgroup_ctr;      /* counts row groups output to postprocessor */
     124                 : 
     125                 :   /* Remaining fields are only used in the context case. */
     126                 : 
     127                 :   /* These are the master pointers to the funny-order pointer lists. */
     128                 :   JSAMPIMAGE xbuffer[2];        /* pointers to weird pointer lists */
     129                 : 
     130                 :   int whichptr;                 /* indicates which pointer set is now in use */
     131                 :   int context_state;            /* process_data state machine status */
     132                 :   JDIMENSION rowgroups_avail;   /* row groups available to postprocessor */
     133                 :   JDIMENSION iMCU_row_ctr;      /* counts iMCU rows to detect image top/bot */
     134                 : } my_main_controller;
     135                 : 
     136                 : typedef my_main_controller * my_main_ptr;
     137                 : 
     138                 : /* context_state values: */
     139                 : #define CTX_PREPARE_FOR_IMCU    0       /* need to prepare for MCU row */
     140                 : #define CTX_PROCESS_IMCU        1       /* feeding iMCU to postprocessor */
     141                 : #define CTX_POSTPONED_ROW       2       /* feeding postponed row group */
     142                 : 
     143                 : 
     144                 : /* Forward declarations */
     145                 : METHODDEF(void) process_data_simple_main
     146                 :         JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
     147                 :              JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
     148                 : METHODDEF(void) process_data_context_main
     149                 :         JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
     150                 :              JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
     151                 : #ifdef QUANT_2PASS_SUPPORTED
     152                 : METHODDEF(void) process_data_crank_post
     153                 :         JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
     154                 :              JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
     155                 : #endif
     156                 : 
     157                 : 
     158                 : LOCAL(void)
     159               3 : alloc_funny_pointers (j_decompress_ptr cinfo)
     160                 : /* Allocate space for the funny pointer lists.
     161                 :  * This is done only once, not once per pass.
     162                 :  */
     163                 : {
     164               3 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     165                 :   int ci, rgroup;
     166               3 :   int M = cinfo->_min_DCT_scaled_size;
     167                 :   jpeg_component_info *compptr;
     168                 :   JSAMPARRAY xbuf;
     169                 : 
     170                 :   /* Get top-level space for component array pointers.
     171                 :    * We alloc both arrays with one call to save a few cycles.
     172                 :    */
     173               3 :   main_ptr->xbuffer[0] = (JSAMPIMAGE)
     174               6 :     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
     175               3 :                                 cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
     176               3 :   main_ptr->xbuffer[1] = main_ptr->xbuffer[0] + cinfo->num_components;
     177                 : 
     178              15 :   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     179               9 :        ci++, compptr++) {
     180              18 :     rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
     181               9 :       cinfo->_min_DCT_scaled_size; /* height of a row group of component */
     182                 :     /* Get space for pointer lists --- M+4 row groups in each list.
     183                 :      * We alloc both pointer lists with one call to save a few cycles.
     184                 :      */
     185               9 :     xbuf = (JSAMPARRAY)
     186               9 :       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
     187                 :                                   2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
     188               9 :     xbuf += rgroup;             /* want one row group at negative offsets */
     189               9 :     main_ptr->xbuffer[0][ci] = xbuf;
     190               9 :     xbuf += rgroup * (M + 4);
     191               9 :     main_ptr->xbuffer[1][ci] = xbuf;
     192                 :   }
     193               3 : }
     194                 : 
     195                 : 
     196                 : LOCAL(void)
     197               3 : make_funny_pointers (j_decompress_ptr cinfo)
     198                 : /* Create the funny pointer lists discussed in the comments above.
     199                 :  * The actual workspace is already allocated (in main_ptr->buffer),
     200                 :  * and the space for the pointer lists is allocated too.
     201                 :  * This routine just fills in the curiously ordered lists.
     202                 :  * This will be repeated at the beginning of each pass.
     203                 :  */
     204                 : {
     205               3 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     206                 :   int ci, i, rgroup;
     207               3 :   int M = cinfo->_min_DCT_scaled_size;
     208                 :   jpeg_component_info *compptr;
     209                 :   JSAMPARRAY buf, xbuf0, xbuf1;
     210                 : 
     211              15 :   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     212               9 :        ci++, compptr++) {
     213              18 :     rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
     214               9 :       cinfo->_min_DCT_scaled_size; /* height of a row group of component */
     215               9 :     xbuf0 = main_ptr->xbuffer[0][ci];
     216               9 :     xbuf1 = main_ptr->xbuffer[1][ci];
     217                 :     /* First copy the workspace pointers as-is */
     218               9 :     buf = main_ptr->buffer[ci];
     219             129 :     for (i = 0; i < rgroup * (M + 2); i++) {
     220             120 :       xbuf0[i] = xbuf1[i] = buf[i];
     221                 :     }
     222                 :     /* In the second list, put the last four row groups in swapped order */
     223              33 :     for (i = 0; i < rgroup * 2; i++) {
     224              24 :       xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i];
     225              24 :       xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i];
     226                 :     }
     227                 :     /* The wraparound pointers at top and bottom will be filled later
     228                 :      * (see set_wraparound_pointers, below).  Initially we want the "above"
     229                 :      * pointers to duplicate the first actual data line.  This only needs
     230                 :      * to happen in xbuffer[0].
     231                 :      */
     232              21 :     for (i = 0; i < rgroup; i++) {
     233              12 :       xbuf0[i - rgroup] = xbuf0[0];
     234                 :     }
     235                 :   }
     236               3 : }
     237                 : 
     238                 : 
     239                 : LOCAL(void)
     240               2 : set_wraparound_pointers (j_decompress_ptr cinfo)
     241                 : /* Set up the "wraparound" pointers at top and bottom of the pointer lists.
     242                 :  * This changes the pointer list state from top-of-image to the normal state.
     243                 :  */
     244                 : {
     245               2 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     246                 :   int ci, i, rgroup;
     247               2 :   int M = cinfo->_min_DCT_scaled_size;
     248                 :   jpeg_component_info *compptr;
     249                 :   JSAMPARRAY xbuf0, xbuf1;
     250                 : 
     251              10 :   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     252               6 :        ci++, compptr++) {
     253              12 :     rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
     254               6 :       cinfo->_min_DCT_scaled_size; /* height of a row group of component */
     255               6 :     xbuf0 = main_ptr->xbuffer[0][ci];
     256               6 :     xbuf1 = main_ptr->xbuffer[1][ci];
     257              14 :     for (i = 0; i < rgroup; i++) {
     258               8 :       xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
     259               8 :       xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
     260               8 :       xbuf0[rgroup*(M+2) + i] = xbuf0[i];
     261               8 :       xbuf1[rgroup*(M+2) + i] = xbuf1[i];
     262                 :     }
     263                 :   }
     264               2 : }
     265                 : 
     266                 : 
     267                 : LOCAL(void)
     268               3 : set_bottom_pointers (j_decompress_ptr cinfo)
     269                 : /* Change the pointer lists to duplicate the last sample row at the bottom
     270                 :  * of the image.  whichptr indicates which xbuffer holds the final iMCU row.
     271                 :  * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
     272                 :  */
     273                 : {
     274               3 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     275                 :   int ci, i, rgroup, iMCUheight, rows_left;
     276                 :   jpeg_component_info *compptr;
     277                 :   JSAMPARRAY xbuf;
     278                 : 
     279              15 :   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     280               9 :        ci++, compptr++) {
     281                 :     /* Count sample rows in one iMCU row and in one row group */
     282               9 :     iMCUheight = compptr->v_samp_factor * compptr->_DCT_scaled_size;
     283               9 :     rgroup = iMCUheight / cinfo->_min_DCT_scaled_size;
     284                 :     /* Count nondummy sample rows remaining for this component */
     285               9 :     rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight);
     286               9 :     if (rows_left == 0) rows_left = iMCUheight;
     287                 :     /* Count nondummy row groups.  Should get same answer for each component,
     288                 :      * so we need only do it once.
     289                 :      */
     290               9 :     if (ci == 0) {
     291               3 :       main_ptr->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1);
     292                 :     }
     293                 :     /* Duplicate the last real sample row rgroup*2 times; this pads out the
     294                 :      * last partial rowgroup and ensures at least one full rowgroup of context.
     295                 :      */
     296               9 :     xbuf = main_ptr->xbuffer[main_ptr->whichptr][ci];
     297              33 :     for (i = 0; i < rgroup * 2; i++) {
     298              24 :       xbuf[rows_left + i] = xbuf[rows_left-1];
     299                 :     }
     300                 :   }
     301               3 : }
     302                 : 
     303                 : 
     304                 : /*
     305                 :  * Initialize for a processing pass.
     306                 :  */
     307                 : 
     308                 : METHODDEF(void)
     309               5 : start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
     310                 : {
     311               5 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     312                 : 
     313               5 :   switch (pass_mode) {
     314                 :   case JBUF_PASS_THRU:
     315               5 :     if (cinfo->upsample->need_context_rows) {
     316               3 :       main_ptr->pub.process_data = process_data_context_main;
     317               3 :       make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
     318               3 :       main_ptr->whichptr = 0;        /* Read first iMCU row into xbuffer[0] */
     319               3 :       main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
     320               3 :       main_ptr->iMCU_row_ctr = 0;
     321                 :     } else {
     322                 :       /* Simple case with no context needed */
     323               2 :       main_ptr->pub.process_data = process_data_simple_main;
     324                 :     }
     325               5 :     main_ptr->buffer_full = FALSE;   /* Mark buffer empty */
     326               5 :     main_ptr->rowgroup_ctr = 0;
     327               5 :     break;
     328                 : #ifdef QUANT_2PASS_SUPPORTED
     329                 :   case JBUF_CRANK_DEST:
     330                 :     /* For last pass of 2-pass quantization, just crank the postprocessor */
     331               0 :     main_ptr->pub.process_data = process_data_crank_post;
     332               0 :     break;
     333                 : #endif
     334                 :   default:
     335               0 :     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
     336               0 :     break;
     337                 :   }
     338               5 : }
     339                 : 
     340                 : 
     341                 : /*
     342                 :  * Process some data.
     343                 :  * This handles the simple case where no context is required.
     344                 :  */
     345                 : 
     346                 : METHODDEF(void)
     347             164 : process_data_simple_main (j_decompress_ptr cinfo,
     348                 :                           JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
     349                 :                           JDIMENSION out_rows_avail)
     350                 : {
     351             164 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     352                 :   JDIMENSION rowgroups_avail;
     353                 : 
     354                 :   /* Read input data if we haven't filled the main buffer yet */
     355             164 :   if (! main_ptr->buffer_full) {
     356              11 :     if (! (*cinfo->coef->decompress_data) (cinfo, main_ptr->buffer))
     357               0 :       return;                   /* suspension forced, can do nothing more */
     358              11 :     main_ptr->buffer_full = TRUE;    /* OK, we have an iMCU row to work with */
     359                 :   }
     360                 : 
     361                 :   /* There are always min_DCT_scaled_size row groups in an iMCU row. */
     362             164 :   rowgroups_avail = (JDIMENSION) cinfo->_min_DCT_scaled_size;
     363                 :   /* Note: at the bottom of the image, we may pass extra garbage row groups
     364                 :    * to the postprocessor.  The postprocessor has to check for bottom
     365                 :    * of image anyway (at row resolution), so no point in us doing it too.
     366                 :    */
     367                 : 
     368                 :   /* Feed the postprocessor */
     369             164 :   (*cinfo->post->post_process_data) (cinfo, main_ptr->buffer,
     370                 :                                      &main_ptr->rowgroup_ctr, rowgroups_avail,
     371                 :                                      output_buf, out_row_ctr, out_rows_avail);
     372                 : 
     373                 :   /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
     374             164 :   if (main_ptr->rowgroup_ctr >= rowgroups_avail) {
     375              10 :     main_ptr->buffer_full = FALSE;
     376              10 :     main_ptr->rowgroup_ctr = 0;
     377                 :   }
     378                 : }
     379                 : 
     380                 : 
     381                 : /*
     382                 :  * Process some data.
     383                 :  * This handles the case where context rows must be provided.
     384                 :  */
     385                 : 
     386                 : METHODDEF(void)
     387              69 : process_data_context_main (j_decompress_ptr cinfo,
     388                 :                            JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
     389                 :                            JDIMENSION out_rows_avail)
     390                 : {
     391              69 :   my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
     392                 : 
     393                 :   /* Read input data if we haven't filled the main buffer yet */
     394              69 :   if (! main_ptr->buffer_full) {
     395              14 :     if (! (*cinfo->coef->decompress_data) (cinfo,
     396               7 :                                            main_ptr->xbuffer[main_ptr->whichptr]))
     397               2 :       return;                   /* suspension forced, can do nothing more */
     398               5 :     main_ptr->buffer_full = TRUE;    /* OK, we have an iMCU row to work with */
     399               5 :     main_ptr->iMCU_row_ctr++;        /* count rows received */
     400                 :   }
     401                 : 
     402                 :   /* Postprocessor typically will not swallow all the input data it is handed
     403                 :    * in one call (due to filling the output buffer first).  Must be prepared
     404                 :    * to exit and restart.  This switch lets us keep track of how far we got.
     405                 :    * Note that each case falls through to the next on successful completion.
     406                 :    */
     407              67 :   switch (main_ptr->context_state) {
     408                 :   case CTX_POSTPONED_ROW:
     409                 :     /* Call postprocessor using previously set pointers for postponed row */
     410               4 :     (*cinfo->post->post_process_data) (cinfo, main_ptr->xbuffer[main_ptr->whichptr],
     411                 :                         &main_ptr->rowgroup_ctr, main_ptr->rowgroups_avail,
     412                 :                         output_buf, out_row_ctr, out_rows_avail);
     413               4 :     if (main_ptr->rowgroup_ctr < main_ptr->rowgroups_avail)
     414               2 :       return;                   /* Need to suspend */
     415               2 :     main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
     416               2 :     if (*out_row_ctr >= out_rows_avail)
     417               2 :       return;                   /* Postprocessor exactly filled output buf */
     418                 :     /*FALLTHROUGH*/
     419                 :   case CTX_PREPARE_FOR_IMCU:
     420                 :     /* Prepare to process first M-1 row groups of this iMCU row */
     421               5 :     main_ptr->rowgroup_ctr = 0;
     422               5 :     main_ptr->rowgroups_avail = (JDIMENSION) (cinfo->_min_DCT_scaled_size - 1);
     423                 :     /* Check for bottom of image: if so, tweak pointers to "duplicate"
     424                 :      * the last sample row, and adjust rowgroups_avail to ignore padding rows.
     425                 :      */
     426               5 :     if (main_ptr->iMCU_row_ctr == cinfo->total_iMCU_rows)
     427               3 :       set_bottom_pointers(cinfo);
     428               5 :     main_ptr->context_state = CTX_PROCESS_IMCU;
     429                 :     /*FALLTHROUGH*/
     430                 :   case CTX_PROCESS_IMCU:
     431                 :     /* Call postprocessor using previously set pointers */
     432              63 :     (*cinfo->post->post_process_data) (cinfo, main_ptr->xbuffer[main_ptr->whichptr],
     433                 :                         &main_ptr->rowgroup_ctr, main_ptr->rowgroups_avail,
     434                 :                         output_buf, out_row_ctr, out_rows_avail);
     435              63 :     if (main_ptr->rowgroup_ctr < main_ptr->rowgroups_avail)
     436              59 :       return;                   /* Need to suspend */
     437                 :     /* After the first iMCU, change wraparound pointers to normal state */
     438               4 :     if (main_ptr->iMCU_row_ctr == 1)
     439               2 :       set_wraparound_pointers(cinfo);
     440                 :     /* Prepare to load new iMCU row using other xbuffer list */
     441               4 :     main_ptr->whichptr ^= 1; /* 0=>1 or 1=>0 */
     442               4 :     main_ptr->buffer_full = FALSE;
     443                 :     /* Still need to process last row group of this iMCU row, */
     444                 :     /* which is saved at index M+1 of the other xbuffer */
     445               4 :     main_ptr->rowgroup_ctr = (JDIMENSION) (cinfo->_min_DCT_scaled_size + 1);
     446               4 :     main_ptr->rowgroups_avail = (JDIMENSION) (cinfo->_min_DCT_scaled_size + 2);
     447               4 :     main_ptr->context_state = CTX_POSTPONED_ROW;
     448                 :   }
     449                 : }
     450                 : 
     451                 : 
     452                 : /*
     453                 :  * Process some data.
     454                 :  * Final pass of two-pass quantization: just call the postprocessor.
     455                 :  * Source data will be the postprocessor controller's internal buffer.
     456                 :  */
     457                 : 
     458                 : #ifdef QUANT_2PASS_SUPPORTED
     459                 : 
     460                 : METHODDEF(void)
     461               0 : process_data_crank_post (j_decompress_ptr cinfo,
     462                 :                          JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
     463                 :                          JDIMENSION out_rows_avail)
     464                 : {
     465               0 :   (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL,
     466                 :                                      (JDIMENSION *) NULL, (JDIMENSION) 0,
     467                 :                                      output_buf, out_row_ctr, out_rows_avail);
     468               0 : }
     469                 : 
     470                 : #endif /* QUANT_2PASS_SUPPORTED */
     471                 : 
     472                 : 
     473                 : /*
     474                 :  * Initialize main buffer controller.
     475                 :  */
     476                 : 
     477                 : GLOBAL(void)
     478               5 : jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
     479                 : {
     480                 :   my_main_ptr main_ptr;
     481                 :   int ci, rgroup, ngroups;
     482                 :   jpeg_component_info *compptr;
     483                 : 
     484               5 :   main_ptr = (my_main_ptr)
     485               5 :     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
     486                 :                                 SIZEOF(my_main_controller));
     487               5 :   cinfo->main = (struct jpeg_d_main_controller *) main_ptr;
     488               5 :   main_ptr->pub.start_pass = start_pass_main;
     489                 : 
     490               5 :   if (need_full_buffer)         /* shouldn't happen */
     491               0 :     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
     492                 : 
     493                 :   /* Allocate the workspace.
     494                 :    * ngroups is the number of row groups we need.
     495                 :    */
     496               5 :   if (cinfo->upsample->need_context_rows) {
     497               3 :     if (cinfo->_min_DCT_scaled_size < 2) /* unsupported, see comments above */
     498               0 :       ERREXIT(cinfo, JERR_NOTIMPL);
     499               3 :     alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
     500               3 :     ngroups = cinfo->_min_DCT_scaled_size + 2;
     501                 :   } else {
     502               2 :     ngroups = cinfo->_min_DCT_scaled_size;
     503                 :   }
     504                 : 
     505              25 :   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     506              15 :        ci++, compptr++) {
     507              30 :     rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
     508              15 :       cinfo->_min_DCT_scaled_size; /* height of a row group of component */
     509              30 :     main_ptr->buffer[ci] = (*cinfo->mem->alloc_sarray)
     510              45 :                         ((j_common_ptr) cinfo, JPOOL_IMAGE,
     511              15 :                          compptr->width_in_blocks * compptr->_DCT_scaled_size,
     512              15 :                          (JDIMENSION) (rgroup * ngroups));
     513                 :   }
     514               5 : }

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