tor-browser

jddiffct.c (13396B)

---

/*
* jddiffct.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1994-1997, Thomas G. Lane.
* Lossless JPEG Modifications:
* Copyright (C) 1999, Ken Murchison.
* libjpeg-turbo Modifications:
* Copyright (C) 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains the [un]difference buffer controller for decompression.
* This controller is the top level of the lossless JPEG decompressor proper.
* The difference buffer lies between the entropy decoding and
* prediction/undifferencing steps.  The undifference buffer lies between the
* prediction/undifferencing and scaling steps.
*
* In buffered-image mode, this controller is the interface between
* input-oriented processing and output-oriented processing.
*/

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jlossls.h"            /* Private declarations for lossless codec */


#ifdef D_LOSSLESS_SUPPORTED

/* Private buffer controller object */

typedef struct {
 struct jpeg_d_coef_controller pub; /* public fields */

 /* These variables keep track of the current location of the input side. */
 /* cinfo->input_iMCU_row is also used for this. */
 JDIMENSION MCU_ctr;           /* counts MCUs processed in current row */
 unsigned int restart_rows_to_go;      /* MCU rows left in this restart
                                          interval */
 unsigned int MCU_vert_offset;         /* counts MCU rows within iMCU row */
 unsigned int MCU_rows_per_iMCU_row;   /* number of such rows needed */

 /* The output side's location is represented by cinfo->output_iMCU_row. */

 JDIFFARRAY diff_buf[MAX_COMPONENTS];  /* iMCU row of differences */
 JDIFFARRAY undiff_buf[MAX_COMPONENTS]; /* iMCU row of undiff'd samples */

#ifdef D_MULTISCAN_FILES_SUPPORTED
 /* In multi-pass modes, we need a virtual sample array for each component. */
 jvirt_sarray_ptr whole_image[MAX_COMPONENTS];
#endif
} my_diff_controller;

typedef my_diff_controller *my_diff_ptr;

/* Forward declarations */
METHODDEF(int) decompress_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf);
#ifdef D_MULTISCAN_FILES_SUPPORTED
METHODDEF(int) output_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf);
#endif


LOCAL(void)
start_iMCU_row(j_decompress_ptr cinfo)
/* Reset within-iMCU-row counters for a new row (input side) */
{
 my_diff_ptr diff = (my_diff_ptr)cinfo->coef;

 /* In an interleaved scan, an MCU row is the same as an iMCU row.
  * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
  * But at the bottom of the image, process only what's left.
  */
 if (cinfo->comps_in_scan > 1) {
   diff->MCU_rows_per_iMCU_row = 1;
 } else {
   if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
     diff->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
   else
     diff->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
 }

 diff->MCU_ctr = 0;
 diff->MCU_vert_offset = 0;
}


/*
* Initialize for an input processing pass.
*/

METHODDEF(void)
start_input_pass(j_decompress_ptr cinfo)
{
 my_diff_ptr diff = (my_diff_ptr)cinfo->coef;

 /* Because it is hitching a ride on the jpeg_inverse_dct struct,
  * start_pass_lossless() will be called at the start of the output pass.
  * This ensures that it will be called at the start of the input pass as
  * well.
  */
 (*cinfo->idct->start_pass) (cinfo);

 /* Check that the restart interval is an integer multiple of the number
  * of MCUs in an MCU row.
  */
 if (cinfo->restart_interval % cinfo->MCUs_per_row != 0)
   ERREXIT2(cinfo, JERR_BAD_RESTART,
            cinfo->restart_interval, cinfo->MCUs_per_row);

 /* Initialize restart counter */
 diff->restart_rows_to_go = cinfo->restart_interval / cinfo->MCUs_per_row;

 cinfo->input_iMCU_row = 0;
 start_iMCU_row(cinfo);
}


/*
* Check for a restart marker & resynchronize decoder, undifferencer.
* Returns FALSE if must suspend.
*/

METHODDEF(boolean)
process_restart(j_decompress_ptr cinfo)
{
 my_diff_ptr diff = (my_diff_ptr)cinfo->coef;

 if (!(*cinfo->entropy->process_restart) (cinfo))
   return FALSE;

 (*cinfo->idct->start_pass) (cinfo);

 /* Reset restart counter */
 diff->restart_rows_to_go = cinfo->restart_interval / cinfo->MCUs_per_row;

 return TRUE;
}


/*
* Initialize for an output processing pass.
*/

METHODDEF(void)
start_output_pass(j_decompress_ptr cinfo)
{
 cinfo->output_iMCU_row = 0;
}


/*
* Decompress and return some data in the supplied buffer.
* Always attempts to emit one fully interleaved MCU row ("iMCU" row).
* Input and output must run in lockstep since we have only a one-MCU buffer.
* Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
*
* NB: output_buf contains a plane for each component in image,
* which we index according to the component's SOF position.
*/

METHODDEF(int)
decompress_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf)
{
 my_diff_ptr diff = (my_diff_ptr)cinfo->coef;
 lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;
 JDIMENSION MCU_col_num;       /* index of current MCU within row */
 JDIMENSION MCU_count;         /* number of MCUs decoded */
 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 int ci, compi, row, prev_row;
 unsigned int yoffset;
 jpeg_component_info *compptr;

 /* Loop to process as much as one whole iMCU row */
 for (yoffset = diff->MCU_vert_offset; yoffset < diff->MCU_rows_per_iMCU_row;
      yoffset++) {

   /* Process restart marker if needed; may have to suspend */
   if (cinfo->restart_interval) {
     if (diff->restart_rows_to_go == 0)
       if (!process_restart(cinfo))
         return JPEG_SUSPENDED;
   }

   MCU_col_num = diff->MCU_ctr;
   /* Try to fetch an MCU row (or remaining portion of suspended MCU row). */
   MCU_count =
     (*cinfo->entropy->decode_mcus) (cinfo,
                                     diff->diff_buf, yoffset, MCU_col_num,
                                     cinfo->MCUs_per_row - MCU_col_num);
   if (MCU_count != cinfo->MCUs_per_row - MCU_col_num) {
     /* Suspension forced; update state counters and exit */
     diff->MCU_vert_offset = yoffset;
     diff->MCU_ctr += MCU_count;
     return JPEG_SUSPENDED;
   }

   /* Account for restart interval (no-op if not using restarts) */
   if (cinfo->restart_interval)
     diff->restart_rows_to_go--;

   /* Completed an MCU row, but perhaps not an iMCU row */
   diff->MCU_ctr = 0;
 }

 /*
  * Undifference and scale each scanline of the disassembled MCU row
  * separately.  We do not process dummy samples at the end of a scanline
  * or dummy rows at the end of the image.
  */
 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
   compptr = cinfo->cur_comp_info[ci];
   compi = compptr->component_index;
   for (row = 0, prev_row = compptr->v_samp_factor - 1;
        row < (cinfo->input_iMCU_row == last_iMCU_row ?
               compptr->last_row_height : compptr->v_samp_factor);
        prev_row = row, row++) {
     (*losslessd->predict_undifference[compi])
       (cinfo, compi, diff->diff_buf[compi][row],
         diff->undiff_buf[compi][prev_row], diff->undiff_buf[compi][row],
         compptr->width_in_blocks);
     (*losslessd->scaler_scale) (cinfo, diff->undiff_buf[compi][row],
                                 output_buf[compi][row],
                                 compptr->width_in_blocks);
   }
 }

 /* Completed the iMCU row, advance counters for next one.
  *
  * NB: output_data will increment output_iMCU_row.
  * This counter is not needed for the single-pass case
  * or the input side of the multi-pass case.
  */
 if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
   start_iMCU_row(cinfo);
   return JPEG_ROW_COMPLETED;
 }
 /* Completed the scan */
 (*cinfo->inputctl->finish_input_pass) (cinfo);
 return JPEG_SCAN_COMPLETED;
}


/*
* Dummy consume-input routine for single-pass operation.
*/

METHODDEF(int)
dummy_consume_data(j_decompress_ptr cinfo)
{
 return JPEG_SUSPENDED;        /* Always indicate nothing was done */
}


#ifdef D_MULTISCAN_FILES_SUPPORTED

/*
* Consume input data and store it in the full-image sample buffer.
* We read as much as one fully interleaved MCU row ("iMCU" row) per call,
* ie, v_samp_factor rows for each component in the scan.
* Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
*/

METHODDEF(int)
consume_data(j_decompress_ptr cinfo)
{
 my_diff_ptr diff = (my_diff_ptr)cinfo->coef;
 int ci, compi;
 _JSAMPARRAY buffer[MAX_COMPS_IN_SCAN];
 jpeg_component_info *compptr;

 /* Align the virtual buffers for the components used in this scan. */
 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
   compptr = cinfo->cur_comp_info[ci];
   compi = compptr->component_index;
   buffer[compi] = (_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
     ((j_common_ptr)cinfo, diff->whole_image[compi],
      cinfo->input_iMCU_row * compptr->v_samp_factor,
      (JDIMENSION)compptr->v_samp_factor, TRUE);
 }

 return decompress_data(cinfo, buffer);
}


/*
* Output some data from the full-image sample buffer in the multi-pass case.
* Always attempts to emit one fully interleaved MCU row ("iMCU" row).
* Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
*
* NB: output_buf contains a plane for each component in image.
*/

METHODDEF(int)
output_data(j_decompress_ptr cinfo, _JSAMPIMAGE output_buf)
{
 my_diff_ptr diff = (my_diff_ptr)cinfo->coef;
 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 int ci, samp_rows, row;
 _JSAMPARRAY buffer;
 jpeg_component_info *compptr;

 /* Force some input to be done if we are getting ahead of the input. */
 while (cinfo->input_scan_number < cinfo->output_scan_number ||
        (cinfo->input_scan_number == cinfo->output_scan_number &&
         cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
   if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
     return JPEG_SUSPENDED;
 }

 /* OK, output from the virtual arrays. */
 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
      ci++, compptr++) {
   /* Align the virtual buffer for this component. */
   buffer = (_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
     ((j_common_ptr)cinfo, diff->whole_image[ci],
      cinfo->output_iMCU_row * compptr->v_samp_factor,
      (JDIMENSION)compptr->v_samp_factor, FALSE);

   if (cinfo->output_iMCU_row < last_iMCU_row)
     samp_rows = compptr->v_samp_factor;
   else {
     /* NB: can't use last_row_height here; it is input-side-dependent! */
     samp_rows = (int)(compptr->height_in_blocks % compptr->v_samp_factor);
     if (samp_rows == 0) samp_rows = compptr->v_samp_factor;
   }

   for (row = 0; row < samp_rows; row++) {
     memcpy(output_buf[ci][row], buffer[row],
            compptr->width_in_blocks * sizeof(_JSAMPLE));
   }
 }

 if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
   return JPEG_ROW_COMPLETED;
 return JPEG_SCAN_COMPLETED;
}

#endif /* D_MULTISCAN_FILES_SUPPORTED */


/*
* Initialize difference buffer controller.
*/

GLOBAL(void)
_jinit_d_diff_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
{
 my_diff_ptr diff;
 int ci;
 jpeg_component_info *compptr;

 diff = (my_diff_ptr)
   (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                               sizeof(my_diff_controller));
 cinfo->coef = (struct jpeg_d_coef_controller *)diff;
 diff->pub.start_input_pass = start_input_pass;
 diff->pub.start_output_pass = start_output_pass;

 /* Create the [un]difference buffers. */
 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
      ci++, compptr++) {
   diff->diff_buf[ci] =
     ALLOC_DARRAY(JPOOL_IMAGE,
                  (JDIMENSION)jround_up((long)compptr->width_in_blocks,
                                        (long)compptr->h_samp_factor),
                  (JDIMENSION)compptr->v_samp_factor);
   diff->undiff_buf[ci] =
     ALLOC_DARRAY(JPOOL_IMAGE,
                  (JDIMENSION)jround_up((long)compptr->width_in_blocks,
                                        (long)compptr->h_samp_factor),
                  (JDIMENSION)compptr->v_samp_factor);
 }

 if (need_full_buffer) {
#ifdef D_MULTISCAN_FILES_SUPPORTED
   /* Allocate a full-image virtual array for each component. */
   int access_rows;

   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
        ci++, compptr++) {
     access_rows = compptr->v_samp_factor;
     diff->whole_image[ci] = (*cinfo->mem->request_virt_sarray)
       ((j_common_ptr)cinfo, JPOOL_IMAGE, FALSE,
        (JDIMENSION)jround_up((long)compptr->width_in_blocks,
                              (long)compptr->h_samp_factor),
        (JDIMENSION)jround_up((long)compptr->height_in_blocks,
                              (long)compptr->v_samp_factor),
        (JDIMENSION)access_rows);
   }
   diff->pub.consume_data = consume_data;
   diff->pub._decompress_data = output_data;
#else
   ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
 } else {
   diff->pub.consume_data = dummy_consume_data;
   diff->pub._decompress_data = decompress_data;
   diff->whole_image[0] = NULL; /* flag for no virtual arrays */
 }
}

#endif /* D_LOSSLESS_SUPPORTED */