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      1 /*
      2  * jdcoefct.c
      3  *
      4  * Copyright (C) 1994-1997, Thomas G. Lane.
      5  * This file is part of the Independent JPEG Group's software.
      6  * For conditions of distribution and use, see the accompanying README file.
      7  *
      8  * This file contains the coefficient buffer controller for decompression.
      9  * This controller is the top level of the JPEG decompressor proper.
     10  * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
     11  *
     12  * In buffered-image mode, this controller is the interface between
     13  * input-oriented processing and output-oriented processing.
     14  * Also, the input side (only) is used when reading a file for transcoding.
     15  */
     16 
     17 #define JPEG_INTERNALS
     18 #include "jinclude.h"
     19 #include "jpeglib.h"
     20 
     21 /* Block smoothing is only applicable for progressive JPEG, so: */
     22 #ifndef D_PROGRESSIVE_SUPPORTED
     23 #undef BLOCK_SMOOTHING_SUPPORTED
     24 #endif
     25 
     26 /* Private buffer controller object */
     27 
     28 typedef struct {
     29   struct jpeg_d_coef_controller pub; /* public fields */
     30 
     31   /* These variables keep track of the current location of the input side. */
     32   /* cinfo->input_iMCU_row is also used for this. */
     33   JDIMENSION MCU_ctr;		/* counts MCUs processed in current row */
     34   int MCU_vert_offset;		/* counts MCU rows within iMCU row */
     35   int MCU_rows_per_iMCU_row;	/* number of such rows needed */
     36 
     37   /* The output side's location is represented by cinfo->output_iMCU_row. */
     38 
     39   /* In single-pass modes, it's sufficient to buffer just one MCU.
     40    * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
     41    * and let the entropy decoder write into that workspace each time.
     42    * (On 80x86, the workspace is FAR even though it's not really very big;
     43    * this is to keep the module interfaces unchanged when a large coefficient
     44    * buffer is necessary.)
     45    * In multi-pass modes, this array points to the current MCU's blocks
     46    * within the virtual arrays; it is used only by the input side.
     47    */
     48   JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
     49 
     50 #ifdef D_MULTISCAN_FILES_SUPPORTED
     51   /* In multi-pass modes, we need a virtual block array for each component. */
     52   jvirt_barray_ptr whole_image[MAX_COMPONENTS];
     53 #endif
     54 
     55 #ifdef BLOCK_SMOOTHING_SUPPORTED
     56   /* When doing block smoothing, we latch coefficient Al values here */
     57   int * coef_bits_latch;
     58 #define SAVED_COEFS  6		/* we save coef_bits[0..5] */
     59 #endif
     60 } my_coef_controller;
     61 
     62 typedef my_coef_controller * my_coef_ptr;
     63 
     64 /* Forward declarations */
     65 METHODDEF(int) decompress_onepass
     66 	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
     67 #ifdef D_MULTISCAN_FILES_SUPPORTED
     68 METHODDEF(int) decompress_data
     69 	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
     70 #endif
     71 #ifdef BLOCK_SMOOTHING_SUPPORTED
     72 LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
     73 METHODDEF(int) decompress_smooth_data
     74 	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
     75 #endif
     76 
     77 
     78 LOCAL(void)
     79 start_iMCU_row (j_decompress_ptr cinfo)
     80 /* Reset within-iMCU-row counters for a new row (input side) */
     81 {
     82   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
     83 
     84   /* In an interleaved scan, an MCU row is the same as an iMCU row.
     85    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
     86    * But at the bottom of the image, process only what's left.
     87    */
     88   if (cinfo->comps_in_scan > 1) {
     89     coef->MCU_rows_per_iMCU_row = 1;
     90   } else {
     91     if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
     92       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
     93     else
     94       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
     95   }
     96 
     97   coef->MCU_ctr = 0;
     98   coef->MCU_vert_offset = 0;
     99 }
    100 
    101 
    102 /*
    103  * Initialize for an input processing pass.
    104  */
    105 
    106 METHODDEF(void)
    107 start_input_pass (j_decompress_ptr cinfo)
    108 {
    109   cinfo->input_iMCU_row = 0;
    110   start_iMCU_row(cinfo);
    111 }
    112 
    113 
    114 /*
    115  * Initialize for an output processing pass.
    116  */
    117 
    118 METHODDEF(void)
    119 start_output_pass (j_decompress_ptr cinfo)
    120 {
    121 #ifdef BLOCK_SMOOTHING_SUPPORTED
    122   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    123 
    124   /* If multipass, check to see whether to use block smoothing on this pass */
    125   if (coef->pub.coef_arrays != NULL) {
    126     if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
    127       coef->pub.decompress_data = decompress_smooth_data;
    128     else
    129       coef->pub.decompress_data = decompress_data;
    130   }
    131 #endif
    132   cinfo->output_iMCU_row = 0;
    133 }
    134 
    135 
    136 /*
    137  * Decompress and return some data in the single-pass case.
    138  * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
    139  * Input and output must run in lockstep since we have only a one-MCU buffer.
    140  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
    141  *
    142  * NB: output_buf contains a plane for each component in image,
    143  * which we index according to the component's SOF position.
    144  */
    145 
    146 METHODDEF(int)
    147 decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
    148 {
    149   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    150   JDIMENSION MCU_col_num;	/* index of current MCU within row */
    151   JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
    152   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
    153   int blkn, ci, xindex, yindex, yoffset, useful_width;
    154   JSAMPARRAY output_ptr;
    155   JDIMENSION start_col, output_col;
    156   jpeg_component_info *compptr;
    157   inverse_DCT_method_ptr inverse_DCT;
    158 
    159 #ifdef ANDROID_TILE_BASED_DECODE
    160   if (cinfo->tile_decode) {
    161     last_MCU_col =
    162         (cinfo->coef->MCU_column_right_boundary -
    163          cinfo->coef->MCU_column_left_boundary) - 1;
    164   }
    165 #endif
    166 
    167   /* Loop to process as much as one whole iMCU row */
    168   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
    169        yoffset++) {
    170     for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
    171 	 MCU_col_num++) {
    172       /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
    173       if (MCU_col_num < coef->pub.MCU_columns_to_skip) {
    174         (*cinfo->entropy->decode_mcu_discard_coef) (cinfo);
    175         continue;
    176       } else {
    177         jzero_far((void FAR *) coef->MCU_buffer[0],
    178 		(size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
    179         if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
    180 	  /* Suspension forced; update state counters and exit */
    181 	  coef->MCU_vert_offset = yoffset;
    182 	  coef->MCU_ctr = MCU_col_num;
    183 	  return JPEG_SUSPENDED;
    184         }
    185       }
    186       /* Determine where data should go in output_buf and do the IDCT thing.
    187        * We skip dummy blocks at the right and bottom edges (but blkn gets
    188        * incremented past them!).  Note the inner loop relies on having
    189        * allocated the MCU_buffer[] blocks sequentially.
    190        */
    191       blkn = 0;			/* index of current DCT block within MCU */
    192       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    193 	compptr = cinfo->cur_comp_info[ci];
    194 	/* Don't bother to IDCT an uninteresting component. */
    195 	if (! compptr->component_needed) {
    196 	  blkn += compptr->MCU_blocks;
    197 	  continue;
    198 	}
    199 	inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
    200 	useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
    201 						    : compptr->last_col_width;
    202 	output_ptr = output_buf[compptr->component_index] +
    203 	  yoffset * compptr->DCT_scaled_size;
    204 	start_col = MCU_col_num * compptr->MCU_sample_width;
    205 	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
    206 	  if (cinfo->input_iMCU_row < last_iMCU_row ||
    207 	      yoffset+yindex < compptr->last_row_height) {
    208 	    output_col = start_col;
    209 	    for (xindex = 0; xindex < useful_width; xindex++) {
    210 	      (*inverse_DCT) (cinfo, compptr,
    211 		        (JCOEFPTR) coef->MCU_buffer[blkn+xindex],
    212 		        output_ptr, output_col);
    213 	      output_col += compptr->DCT_scaled_size;
    214 	    }
    215 	  }
    216 	  blkn += compptr->MCU_width;
    217 	  output_ptr += compptr->DCT_scaled_size;
    218 	}
    219       }
    220     }
    221     /* Completed an MCU row, but perhaps not an iMCU row */
    222     coef->MCU_ctr = 0;
    223   }
    224   /* Completed the iMCU row, advance counters for next one */
    225   cinfo->output_iMCU_row++;
    226   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
    227     start_iMCU_row(cinfo);
    228     return JPEG_ROW_COMPLETED;
    229   }
    230   /* Completed the scan */
    231   (*cinfo->inputctl->finish_input_pass) (cinfo);
    232   return JPEG_SCAN_COMPLETED;
    233 }
    234 
    235 
    236 /*
    237  * Dummy consume-input routine for single-pass operation.
    238  */
    239 
    240 METHODDEF(int)
    241 dummy_consume_data (j_decompress_ptr cinfo)
    242 {
    243   return JPEG_SUSPENDED;	/* Always indicate nothing was done */
    244 }
    245 
    246 #ifdef D_MULTISCAN_FILES_SUPPORTED
    247 /*
    248  * Consume input data and store it in the full-image coefficient buffer.
    249  * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
    250  * ie, v_samp_factor block rows for each component in the scan.
    251  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
    252  */
    253 
    254 METHODDEF(int)
    255 consume_data (j_decompress_ptr cinfo)
    256 {
    257   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    258   JDIMENSION MCU_col_num;	/* index of current MCU within row */
    259   int blkn, ci, xindex, yindex, yoffset;
    260   JDIMENSION start_col;
    261   JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
    262   JBLOCKROW buffer_ptr;
    263   jpeg_component_info *compptr;
    264 
    265   /* Align the virtual buffers for the components used in this scan. */
    266   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    267     compptr = cinfo->cur_comp_info[ci];
    268     buffer[ci] = (*cinfo->mem->access_virt_barray)
    269       ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
    270        cinfo->tile_decode ? 0 : cinfo->input_iMCU_row * compptr->v_samp_factor,
    271        (JDIMENSION) compptr->v_samp_factor, TRUE);
    272     /* Note: entropy decoder expects buffer to be zeroed,
    273      * but this is handled automatically by the memory manager
    274      * because we requested a pre-zeroed array.
    275      */
    276   }
    277   unsigned int MCUs_per_row = cinfo->MCUs_per_row;
    278 #ifdef ANDROID_TILE_BASED_DECODE
    279   if (cinfo->tile_decode) {
    280     int iMCU_width_To_MCU_width;
    281     if (cinfo->comps_in_scan > 1) {
    282       // Interleaved
    283       iMCU_width_To_MCU_width = 1;
    284     } else {
    285       // Non-intervleaved
    286       iMCU_width_To_MCU_width = cinfo->cur_comp_info[0]->h_samp_factor;
    287     }
    288     MCUs_per_row = jmin(MCUs_per_row,
    289         (cinfo->coef->column_right_boundary - cinfo->coef->column_left_boundary)
    290         * cinfo->entropy->index->MCU_sample_size * iMCU_width_To_MCU_width);
    291   }
    292 #endif
    293 
    294   /* Loop to process one whole iMCU row */
    295   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
    296        yoffset++) {
    297    // configure huffman decoder
    298 #ifdef ANDROID_TILE_BASED_DECODE
    299     if (cinfo->tile_decode) {
    300       huffman_scan_header scan_header =
    301             cinfo->entropy->index->scan[cinfo->input_scan_number];
    302       int col_offset = cinfo->coef->column_left_boundary;
    303       (*cinfo->entropy->configure_huffman_decoder) (cinfo,
    304               scan_header.offset[cinfo->input_iMCU_row]
    305               [col_offset + yoffset * scan_header.MCUs_per_row]);
    306     }
    307 #endif
    308 
    309     // zero all blocks
    310     for (MCU_col_num = coef->MCU_ctr; MCU_col_num < MCUs_per_row;
    311           MCU_col_num++) {
    312       /* Construct list of pointers to DCT blocks belonging to this MCU */
    313       blkn = 0;			/* index of current DCT block within MCU */
    314       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    315         compptr = cinfo->cur_comp_info[ci];
    316         start_col = MCU_col_num * compptr->MCU_width;
    317         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
    318           buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
    319           for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
    320             coef->MCU_buffer[blkn++] = buffer_ptr++;
    321 #ifdef ANDROID_TILE_BASED_DECODE
    322             if (cinfo->tile_decode && cinfo->input_scan_number == 0) {
    323               // need to do pre-zero ourselves.
    324               jzero_far((void FAR *) coef->MCU_buffer[blkn-1],
    325                         (size_t) (SIZEOF(JBLOCK)));
    326             }
    327 #endif
    328           }
    329         }
    330       }
    331 
    332 
    333       /* Try to fetch the MCU. */
    334       if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
    335         /* Suspension forced; update state counters and exit */
    336         coef->MCU_vert_offset = yoffset;
    337         coef->MCU_ctr = MCU_col_num;
    338         return JPEG_SUSPENDED;
    339       }
    340     }
    341     /* Completed an MCU row, but perhaps not an iMCU row */
    342     coef->MCU_ctr = 0;
    343   }
    344   /* Completed the iMCU row, advance counters for next one */
    345   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
    346     start_iMCU_row(cinfo);
    347     return JPEG_ROW_COMPLETED;
    348   }
    349   /* Completed the scan */
    350   (*cinfo->inputctl->finish_input_pass) (cinfo);
    351   return JPEG_SCAN_COMPLETED;
    352 }
    353 
    354 /*
    355  * Consume input data and store it in the coefficient buffer.
    356  * Read one fully interleaved MCU row ("iMCU" row) per call.
    357  */
    358 
    359 METHODDEF(int)
    360 consume_data_multi_scan (j_decompress_ptr cinfo)
    361 {
    362   huffman_index *index = cinfo->entropy->index;
    363   int i, retcode, ci;
    364   int mcu = cinfo->input_iMCU_row;
    365   jinit_phuff_decoder(cinfo);
    366   for (i = 0; i < index->scan_count; i++) {
    367     (*cinfo->inputctl->finish_input_pass) (cinfo);
    368     jset_input_stream_position(cinfo, index->scan[i].bitstream_offset);
    369     cinfo->output_iMCU_row = mcu;
    370     cinfo->unread_marker = 0;
    371     // Consume SOS and DHT headers
    372     retcode = (*cinfo->inputctl->consume_markers) (cinfo, index, i);
    373     cinfo->input_iMCU_row = mcu;
    374     cinfo->input_scan_number = i;
    375     cinfo->entropy->index = index;
    376     // Consume scan block data
    377     consume_data(cinfo);
    378   }
    379   cinfo->input_iMCU_row = mcu + 1;
    380   cinfo->input_scan_number = 0;
    381   cinfo->output_scan_number = 0;
    382   return JPEG_ROW_COMPLETED;
    383 }
    384 
    385 /*
    386  * Same as consume_data, expect for saving the Huffman decode information
    387  * - bitstream offset and DC coefficient to index.
    388  */
    389 
    390 METHODDEF(int)
    391 consume_data_build_huffman_index_baseline (j_decompress_ptr cinfo,
    392         huffman_index *index, int current_scan)
    393 {
    394   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    395   JDIMENSION MCU_col_num;	/* index of current MCU within row */
    396   int ci, xindex, yindex, yoffset;
    397   JDIMENSION start_col;
    398   JBLOCKROW buffer_ptr;
    399 
    400   huffman_scan_header *scan_header = index->scan + current_scan;
    401   scan_header->MCU_rows_per_iMCU_row = coef->MCU_rows_per_iMCU_row;
    402 
    403   size_t allocate_size = coef->MCU_rows_per_iMCU_row
    404       * jdiv_round_up(cinfo->MCUs_per_row, index->MCU_sample_size)
    405       * sizeof(huffman_offset_data);
    406   scan_header->offset[cinfo->input_iMCU_row] =
    407         (huffman_offset_data*)malloc(allocate_size);
    408   index->mem_used += allocate_size;
    409 
    410   huffman_offset_data *offset_data = scan_header->offset[cinfo->input_iMCU_row];
    411 
    412   /* Loop to process one whole iMCU row */
    413   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
    414        yoffset++) {
    415     for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
    416 	 MCU_col_num++) {
    417       // Record huffman bit offset
    418       if (MCU_col_num % index->MCU_sample_size == 0) {
    419         (*cinfo->entropy->get_huffman_decoder_configuration)
    420                 (cinfo, offset_data);
    421         ++offset_data;
    422       }
    423 
    424       /* Try to fetch the MCU. */
    425       if (! (*cinfo->entropy->decode_mcu_discard_coef) (cinfo)) {
    426         /* Suspension forced; update state counters and exit */
    427         coef->MCU_vert_offset = yoffset;
    428         coef->MCU_ctr = MCU_col_num;
    429         return JPEG_SUSPENDED;
    430       }
    431     }
    432     /* Completed an MCU row, but perhaps not an iMCU row */
    433     coef->MCU_ctr = 0;
    434   }
    435   /* Completed the iMCU row, advance counters for next one */
    436   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
    437     start_iMCU_row(cinfo);
    438     return JPEG_ROW_COMPLETED;
    439   }
    440   /* Completed the scan */
    441   (*cinfo->inputctl->finish_input_pass) (cinfo);
    442   return JPEG_SCAN_COMPLETED;
    443 }
    444 
    445 /*
    446  * Same as consume_data, expect for saving the Huffman decode information
    447  * - bitstream offset and DC coefficient to index.
    448  */
    449 
    450 METHODDEF(int)
    451 consume_data_build_huffman_index_progressive (j_decompress_ptr cinfo,
    452         huffman_index *index, int current_scan)
    453 {
    454   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    455   JDIMENSION MCU_col_num;	/* index of current MCU within row */
    456   int blkn, ci, xindex, yindex, yoffset;
    457   JDIMENSION start_col;
    458   JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
    459   JBLOCKROW buffer_ptr;
    460   jpeg_component_info *compptr;
    461 
    462   int factor = 4; // maximum factor is 4.
    463   for (ci = 0; ci < cinfo->comps_in_scan; ci++)
    464     factor = jmin(factor, cinfo->cur_comp_info[ci]->h_samp_factor);
    465 
    466   int sample_size = index->MCU_sample_size * factor;
    467   huffman_scan_header *scan_header = index->scan + current_scan;
    468   scan_header->MCU_rows_per_iMCU_row = coef->MCU_rows_per_iMCU_row;
    469   scan_header->MCUs_per_row = jdiv_round_up(cinfo->MCUs_per_row, sample_size);
    470   scan_header->comps_in_scan = cinfo->comps_in_scan;
    471 
    472   size_t allocate_size = coef->MCU_rows_per_iMCU_row
    473       * scan_header->MCUs_per_row * sizeof(huffman_offset_data);
    474   scan_header->offset[cinfo->input_iMCU_row] =
    475         (huffman_offset_data*)malloc(allocate_size);
    476   index->mem_used += allocate_size;
    477 
    478   huffman_offset_data *offset_data = scan_header->offset[cinfo->input_iMCU_row];
    479 
    480   /* Align the virtual buffers for the components used in this scan. */
    481   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    482     compptr = cinfo->cur_comp_info[ci];
    483     buffer[ci] = (*cinfo->mem->access_virt_barray)
    484       ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
    485        0, // Only need one row buffer
    486        (JDIMENSION) compptr->v_samp_factor, TRUE);
    487   }
    488   /* Loop to process one whole iMCU row */
    489   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
    490        yoffset++) {
    491     for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
    492 	 MCU_col_num++) {
    493       /* For each MCU, we loop through different color components.
    494        * Then, for each color component we will get a list of pointers to DCT
    495        * blocks in the virtual buffer.
    496        */
    497       blkn = 0; /* index of current DCT block within MCU */
    498       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    499         compptr = cinfo->cur_comp_info[ci];
    500         start_col = MCU_col_num * compptr->MCU_width;
    501         /* Get the list of pointers to DCT blocks in
    502          * the virtual buffer in a color component of the MCU.
    503          */
    504         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
    505           buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
    506           for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
    507             coef->MCU_buffer[blkn++] = buffer_ptr++;
    508             if (cinfo->input_scan_number == 0) {
    509               // need to do pre-zero by ourself.
    510               jzero_far((void FAR *) coef->MCU_buffer[blkn-1],
    511                         (size_t) (SIZEOF(JBLOCK)));
    512             }
    513           }
    514         }
    515       }
    516       // Record huffman bit offset
    517       if (MCU_col_num % sample_size == 0) {
    518         (*cinfo->entropy->get_huffman_decoder_configuration)
    519                 (cinfo, offset_data);
    520         ++offset_data;
    521       }
    522       /* Try to fetch the MCU. */
    523       if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
    524 	/* Suspension forced; update state counters and exit */
    525 	coef->MCU_vert_offset = yoffset;
    526 	coef->MCU_ctr = MCU_col_num;
    527 	return JPEG_SUSPENDED;
    528       }
    529     }
    530     /* Completed an MCU row, but perhaps not an iMCU row */
    531     coef->MCU_ctr = 0;
    532   }
    533   (*cinfo->entropy->get_huffman_decoder_configuration)
    534         (cinfo, &scan_header->prev_MCU_offset);
    535   /* Completed the iMCU row, advance counters for next one */
    536   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
    537     start_iMCU_row(cinfo);
    538     return JPEG_ROW_COMPLETED;
    539   }
    540   /* Completed the scan */
    541   (*cinfo->inputctl->finish_input_pass) (cinfo);
    542   return JPEG_SCAN_COMPLETED;
    543 }
    544 
    545 /*
    546  * Decompress and return some data in the multi-pass case.
    547  * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
    548  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
    549  *
    550  * NB: output_buf contains a plane for each component in image.
    551  */
    552 
    553 METHODDEF(int)
    554 decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
    555 {
    556   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    557   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
    558   JDIMENSION block_num;
    559   int ci, block_row, block_rows;
    560   JBLOCKARRAY buffer;
    561   JBLOCKROW buffer_ptr;
    562   JSAMPARRAY output_ptr;
    563   JDIMENSION output_col;
    564   jpeg_component_info *compptr;
    565   inverse_DCT_method_ptr inverse_DCT;
    566 
    567   /* Force some input to be done if we are getting ahead of the input. */
    568   while (cinfo->input_scan_number < cinfo->output_scan_number ||
    569 	 (cinfo->input_scan_number == cinfo->output_scan_number &&
    570 	  cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
    571     if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
    572       return JPEG_SUSPENDED;
    573   }
    574 
    575   /* OK, output from the virtual arrays. */
    576   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    577        ci++, compptr++) {
    578     /* Don't bother to IDCT an uninteresting component. */
    579     if (! compptr->component_needed)
    580       continue;
    581     /* Align the virtual buffer for this component. */
    582     buffer = (*cinfo->mem->access_virt_barray)
    583       ((j_common_ptr) cinfo, coef->whole_image[ci],
    584        cinfo->tile_decode ? 0 : cinfo->output_iMCU_row * compptr->v_samp_factor,
    585        (JDIMENSION) compptr->v_samp_factor, FALSE);
    586     /* Count non-dummy DCT block rows in this iMCU row. */
    587     if (cinfo->output_iMCU_row < last_iMCU_row)
    588       block_rows = compptr->v_samp_factor;
    589     else {
    590       /* NB: can't use last_row_height here; it is input-side-dependent! */
    591       block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
    592       if (block_rows == 0) block_rows = compptr->v_samp_factor;
    593     }
    594     inverse_DCT = cinfo->idct->inverse_DCT[ci];
    595     output_ptr = output_buf[ci];
    596     int width_in_blocks = compptr->width_in_blocks;
    597     int start_block = 0;
    598 #if ANDROID_TILE_BASED_DECODE
    599     if (cinfo->tile_decode) {
    600       // width_in_blocks for a component depends on its h_samp_factor.
    601       width_in_blocks = jmin(width_in_blocks,
    602         (cinfo->coef->MCU_column_right_boundary -
    603          cinfo->coef->MCU_column_left_boundary) *
    604          compptr->h_samp_factor);
    605       start_block = coef->pub.MCU_columns_to_skip *
    606          compptr->h_samp_factor;
    607    }
    608 #endif
    609     /* Loop over all DCT blocks to be processed. */
    610     for (block_row = 0; block_row < block_rows; block_row++) {
    611       buffer_ptr = buffer[block_row];
    612       output_col = start_block * compptr->DCT_scaled_size;
    613       buffer_ptr += start_block;
    614       for (block_num = start_block; block_num < width_in_blocks; block_num++) {
    615 	(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
    616 			output_ptr, output_col);
    617 	buffer_ptr++;
    618 	output_col += compptr->DCT_scaled_size;
    619       }
    620       output_ptr += compptr->DCT_scaled_size;
    621     }
    622   }
    623 
    624   if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
    625     return JPEG_ROW_COMPLETED;
    626   return JPEG_SCAN_COMPLETED;
    627 }
    628 
    629 #endif /* D_MULTISCAN_FILES_SUPPORTED */
    630 
    631 
    632 #ifdef BLOCK_SMOOTHING_SUPPORTED
    633 
    634 /*
    635  * This code applies interblock smoothing as described by section K.8
    636  * of the JPEG standard: the first 5 AC coefficients are estimated from
    637  * the DC values of a DCT block and its 8 neighboring blocks.
    638  * We apply smoothing only for progressive JPEG decoding, and only if
    639  * the coefficients it can estimate are not yet known to full precision.
    640  */
    641 
    642 /* Natural-order array positions of the first 5 zigzag-order coefficients */
    643 #define Q01_POS  1
    644 #define Q10_POS  8
    645 #define Q20_POS  16
    646 #define Q11_POS  9
    647 #define Q02_POS  2
    648 
    649 /*
    650  * Determine whether block smoothing is applicable and safe.
    651  * We also latch the current states of the coef_bits[] entries for the
    652  * AC coefficients; otherwise, if the input side of the decompressor
    653  * advances into a new scan, we might think the coefficients are known
    654  * more accurately than they really are.
    655  */
    656 
    657 LOCAL(boolean)
    658 smoothing_ok (j_decompress_ptr cinfo)
    659 {
    660   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    661   boolean smoothing_useful = FALSE;
    662   int ci, coefi;
    663   jpeg_component_info *compptr;
    664   JQUANT_TBL * qtable;
    665   int * coef_bits;
    666   int * coef_bits_latch;
    667 
    668   if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
    669     return FALSE;
    670 
    671   /* Allocate latch area if not already done */
    672   if (coef->coef_bits_latch == NULL)
    673     coef->coef_bits_latch = (int *)
    674       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    675 				  cinfo->num_components *
    676 				  (SAVED_COEFS * SIZEOF(int)));
    677   coef_bits_latch = coef->coef_bits_latch;
    678 
    679   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    680        ci++, compptr++) {
    681     /* All components' quantization values must already be latched. */
    682     if ((qtable = compptr->quant_table) == NULL)
    683       return FALSE;
    684     /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
    685     if (qtable->quantval[0] == 0 ||
    686 	qtable->quantval[Q01_POS] == 0 ||
    687 	qtable->quantval[Q10_POS] == 0 ||
    688 	qtable->quantval[Q20_POS] == 0 ||
    689 	qtable->quantval[Q11_POS] == 0 ||
    690 	qtable->quantval[Q02_POS] == 0)
    691       return FALSE;
    692     /* DC values must be at least partly known for all components. */
    693     coef_bits = cinfo->coef_bits[ci];
    694     if (coef_bits[0] < 0)
    695       return FALSE;
    696     /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
    697     for (coefi = 1; coefi <= 5; coefi++) {
    698       coef_bits_latch[coefi] = coef_bits[coefi];
    699       if (coef_bits[coefi] != 0)
    700 	smoothing_useful = TRUE;
    701     }
    702     coef_bits_latch += SAVED_COEFS;
    703   }
    704 
    705   return smoothing_useful;
    706 }
    707 
    708 
    709 /*
    710  * Variant of decompress_data for use when doing block smoothing.
    711  */
    712 
    713 METHODDEF(int)
    714 decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
    715 {
    716   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
    717   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
    718   JDIMENSION block_num, last_block_column;
    719   int ci, block_row, block_rows, access_rows;
    720   JBLOCKARRAY buffer;
    721   JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
    722   JSAMPARRAY output_ptr;
    723   JDIMENSION output_col;
    724   jpeg_component_info *compptr;
    725   inverse_DCT_method_ptr inverse_DCT;
    726   boolean first_row, last_row;
    727   JBLOCK workspace;
    728   int *coef_bits;
    729   JQUANT_TBL *quanttbl;
    730   INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
    731   int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
    732   int Al, pred;
    733 
    734   /* Force some input to be done if we are getting ahead of the input. */
    735   while (cinfo->input_scan_number <= cinfo->output_scan_number &&
    736 	 ! cinfo->inputctl->eoi_reached) {
    737     if (cinfo->input_scan_number == cinfo->output_scan_number) {
    738       /* If input is working on current scan, we ordinarily want it to
    739        * have completed the current row.  But if input scan is DC,
    740        * we want it to keep one row ahead so that next block row's DC
    741        * values are up to date.
    742        */
    743       JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
    744       if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
    745 	break;
    746     }
    747     if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
    748       return JPEG_SUSPENDED;
    749   }
    750 
    751   /* OK, output from the virtual arrays. */
    752   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    753        ci++, compptr++) {
    754     /* Don't bother to IDCT an uninteresting component. */
    755     if (! compptr->component_needed)
    756       continue;
    757     /* Count non-dummy DCT block rows in this iMCU row. */
    758     if (cinfo->output_iMCU_row < last_iMCU_row) {
    759       block_rows = compptr->v_samp_factor;
    760       access_rows = block_rows * 2; /* this and next iMCU row */
    761       last_row = FALSE;
    762     } else {
    763       /* NB: can't use last_row_height here; it is input-side-dependent! */
    764       block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
    765       if (block_rows == 0) block_rows = compptr->v_samp_factor;
    766       access_rows = block_rows; /* this iMCU row only */
    767       last_row = TRUE;
    768     }
    769     /* Align the virtual buffer for this component. */
    770     if (cinfo->output_iMCU_row > 0) {
    771       access_rows += compptr->v_samp_factor; /* prior iMCU row too */
    772       buffer = (*cinfo->mem->access_virt_barray)
    773 	((j_common_ptr) cinfo, coef->whole_image[ci],
    774 	 (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
    775 	 (JDIMENSION) access_rows, FALSE);
    776       buffer += compptr->v_samp_factor;	/* point to current iMCU row */
    777       first_row = FALSE;
    778     } else {
    779       buffer = (*cinfo->mem->access_virt_barray)
    780 	((j_common_ptr) cinfo, coef->whole_image[ci],
    781 	 (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
    782       first_row = TRUE;
    783     }
    784     /* Fetch component-dependent info */
    785     coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
    786     quanttbl = compptr->quant_table;
    787     Q00 = quanttbl->quantval[0];
    788     Q01 = quanttbl->quantval[Q01_POS];
    789     Q10 = quanttbl->quantval[Q10_POS];
    790     Q20 = quanttbl->quantval[Q20_POS];
    791     Q11 = quanttbl->quantval[Q11_POS];
    792     Q02 = quanttbl->quantval[Q02_POS];
    793     inverse_DCT = cinfo->idct->inverse_DCT[ci];
    794     output_ptr = output_buf[ci];
    795     /* Loop over all DCT blocks to be processed. */
    796     for (block_row = 0; block_row < block_rows; block_row++) {
    797       buffer_ptr = buffer[block_row];
    798       if (first_row && block_row == 0)
    799 	prev_block_row = buffer_ptr;
    800       else
    801 	prev_block_row = buffer[block_row-1];
    802       if (last_row && block_row == block_rows-1)
    803 	next_block_row = buffer_ptr;
    804       else
    805 	next_block_row = buffer[block_row+1];
    806       /* We fetch the surrounding DC values using a sliding-register approach.
    807        * Initialize all nine here so as to do the right thing on narrow pics.
    808        */
    809       DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
    810       DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
    811       DC7 = DC8 = DC9 = (int) next_block_row[0][0];
    812       output_col = 0;
    813       last_block_column = compptr->width_in_blocks - 1;
    814       for (block_num = 0; block_num <= last_block_column; block_num++) {
    815 	/* Fetch current DCT block into workspace so we can modify it. */
    816 	jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
    817 	/* Update DC values */
    818 	if (block_num < last_block_column) {
    819 	  DC3 = (int) prev_block_row[1][0];
    820 	  DC6 = (int) buffer_ptr[1][0];
    821 	  DC9 = (int) next_block_row[1][0];
    822 	}
    823 	/* Compute coefficient estimates per K.8.
    824 	 * An estimate is applied only if coefficient is still zero,
    825 	 * and is not known to be fully accurate.
    826 	 */
    827 	/* AC01 */
    828 	if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {
    829 	  num = 36 * Q00 * (DC4 - DC6);
    830 	  if (num >= 0) {
    831 	    pred = (int) (((Q01<<7) + num) / (Q01<<8));
    832 	    if (Al > 0 && pred >= (1<<Al))
    833 	      pred = (1<<Al)-1;
    834 	  } else {
    835 	    pred = (int) (((Q01<<7) - num) / (Q01<<8));
    836 	    if (Al > 0 && pred >= (1<<Al))
    837 	      pred = (1<<Al)-1;
    838 	    pred = -pred;
    839 	  }
    840 	  workspace[1] = (JCOEF) pred;
    841 	}
    842 	/* AC10 */
    843 	if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {
    844 	  num = 36 * Q00 * (DC2 - DC8);
    845 	  if (num >= 0) {
    846 	    pred = (int) (((Q10<<7) + num) / (Q10<<8));
    847 	    if (Al > 0 && pred >= (1<<Al))
    848 	      pred = (1<<Al)-1;
    849 	  } else {
    850 	    pred = (int) (((Q10<<7) - num) / (Q10<<8));
    851 	    if (Al > 0 && pred >= (1<<Al))
    852 	      pred = (1<<Al)-1;
    853 	    pred = -pred;
    854 	  }
    855 	  workspace[8] = (JCOEF) pred;
    856 	}
    857 	/* AC20 */
    858 	if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {
    859 	  num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
    860 	  if (num >= 0) {
    861 	    pred = (int) (((Q20<<7) + num) / (Q20<<8));
    862 	    if (Al > 0 && pred >= (1<<Al))
    863 	      pred = (1<<Al)-1;
    864 	  } else {
    865 	    pred = (int) (((Q20<<7) - num) / (Q20<<8));
    866 	    if (Al > 0 && pred >= (1<<Al))
    867 	      pred = (1<<Al)-1;
    868 	    pred = -pred;
    869 	  }
    870 	  workspace[16] = (JCOEF) pred;
    871 	}
    872 	/* AC11 */
    873 	if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {
    874 	  num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
    875 	  if (num >= 0) {
    876 	    pred = (int) (((Q11<<7) + num) / (Q11<<8));
    877 	    if (Al > 0 && pred >= (1<<Al))
    878 	      pred = (1<<Al)-1;
    879 	  } else {
    880 	    pred = (int) (((Q11<<7) - num) / (Q11<<8));
    881 	    if (Al > 0 && pred >= (1<<Al))
    882 	      pred = (1<<Al)-1;
    883 	    pred = -pred;
    884 	  }
    885 	  workspace[9] = (JCOEF) pred;
    886 	}
    887 	/* AC02 */
    888 	if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {
    889 	  num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
    890 	  if (num >= 0) {
    891 	    pred = (int) (((Q02<<7) + num) / (Q02<<8));
    892 	    if (Al > 0 && pred >= (1<<Al))
    893 	      pred = (1<<Al)-1;
    894 	  } else {
    895 	    pred = (int) (((Q02<<7) - num) / (Q02<<8));
    896 	    if (Al > 0 && pred >= (1<<Al))
    897 	      pred = (1<<Al)-1;
    898 	    pred = -pred;
    899 	  }
    900 	  workspace[2] = (JCOEF) pred;
    901 	}
    902 	/* OK, do the IDCT */
    903 	(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace,
    904 			output_ptr, output_col);
    905 	/* Advance for next column */
    906 	DC1 = DC2; DC2 = DC3;
    907 	DC4 = DC5; DC5 = DC6;
    908 	DC7 = DC8; DC8 = DC9;
    909 	buffer_ptr++, prev_block_row++, next_block_row++;
    910 	output_col += compptr->DCT_scaled_size;
    911       }
    912       output_ptr += compptr->DCT_scaled_size;
    913     }
    914   }
    915 
    916   if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
    917     return JPEG_ROW_COMPLETED;
    918   return JPEG_SCAN_COMPLETED;
    919 }
    920 
    921 #endif /* BLOCK_SMOOTHING_SUPPORTED */
    922 
    923 
    924 /*
    925  * Initialize coefficient buffer controller.
    926  */
    927 
    928 GLOBAL(void)
    929 jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
    930 {
    931   my_coef_ptr coef;
    932 
    933   coef = (my_coef_ptr)
    934     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    935 				SIZEOF(my_coef_controller));
    936   cinfo->coef = (struct jpeg_d_coef_controller *) coef;
    937   coef->pub.start_input_pass = start_input_pass;
    938   coef->pub.start_output_pass = start_output_pass;
    939   coef->pub.column_left_boundary = 0;
    940   coef->pub.column_right_boundary = 0;
    941   coef->pub.MCU_columns_to_skip = 0;
    942 #ifdef BLOCK_SMOOTHING_SUPPORTED
    943   coef->coef_bits_latch = NULL;
    944 #endif
    945 
    946 #ifdef ANDROID_TILE_BASED_DECODE
    947   if (cinfo->tile_decode) {
    948     if (cinfo->progressive_mode) {
    949       /* Allocate one iMCU row virtual array, coef->whole_image[ci],
    950        * for each color component, padded to a multiple of h_samp_factor
    951        * DCT blocks in the horizontal direction.
    952        */
    953       int ci, access_rows;
    954       jpeg_component_info *compptr;
    955 
    956       for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    957 	   ci++, compptr++) {
    958         access_rows = compptr->v_samp_factor;
    959         coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
    960 	  ((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
    961 	   (JDIMENSION) jround_up((long) compptr->width_in_blocks,
    962 				(long) compptr->h_samp_factor),
    963 	   (JDIMENSION) compptr->v_samp_factor, // one iMCU row
    964 	   (JDIMENSION) access_rows);
    965       }
    966       coef->pub.consume_data_build_huffman_index =
    967             consume_data_build_huffman_index_progressive;
    968       coef->pub.consume_data = consume_data_multi_scan;
    969       coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
    970       coef->pub.decompress_data = decompress_onepass;
    971     } else {
    972       /* We only need a single-MCU buffer. */
    973       JBLOCKROW buffer;
    974       int i;
    975 
    976       buffer = (JBLOCKROW)
    977       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    978 				  D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
    979       for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
    980         coef->MCU_buffer[i] = buffer + i;
    981       }
    982       coef->pub.consume_data_build_huffman_index =
    983             consume_data_build_huffman_index_baseline;
    984       coef->pub.consume_data = dummy_consume_data;
    985       coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
    986       coef->pub.decompress_data = decompress_onepass;
    987     }
    988     return;
    989   }
    990 #endif
    991 
    992   /* Create the coefficient buffer. */
    993   if (need_full_buffer) {
    994 #ifdef D_MULTISCAN_FILES_SUPPORTED
    995     /* Allocate a full-image virtual array for each component, */
    996     /* padded to a multiple of samp_factor DCT blocks in each direction. */
    997     /* Note we ask for a pre-zeroed array. */
    998     int ci, access_rows;
    999     jpeg_component_info *compptr;
   1000 
   1001     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
   1002 	 ci++, compptr++) {
   1003       access_rows = compptr->v_samp_factor;
   1004 #ifdef BLOCK_SMOOTHING_SUPPORTED
   1005       /* If block smoothing could be used, need a bigger window */
   1006       if (cinfo->progressive_mode)
   1007 	access_rows *= 3;
   1008 #endif
   1009       coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
   1010 	((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
   1011 	 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
   1012 				(long) compptr->h_samp_factor),
   1013 	 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
   1014 				(long) compptr->v_samp_factor),
   1015 	 (JDIMENSION) access_rows);
   1016     }
   1017     coef->pub.consume_data = consume_data;
   1018     coef->pub.decompress_data = decompress_data;
   1019     coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
   1020 #else
   1021     ERREXIT(cinfo, JERR_NOT_COMPILED);
   1022 #endif
   1023   } else {
   1024     /* We only need a single-MCU buffer. */
   1025     JBLOCKROW buffer;
   1026     int i;
   1027 
   1028     buffer = (JBLOCKROW)
   1029       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
   1030 		  D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
   1031     for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
   1032       coef->MCU_buffer[i] = buffer + i;
   1033     }
   1034     coef->pub.consume_data = dummy_consume_data;
   1035     coef->pub.decompress_data = decompress_onepass;
   1036     coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
   1037   }
   1038 }
   1039