kc3-lang/libjpeg-turbo/jdmerge.h

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• Hash : 9120a247
  Author :
  Date : 2020-07-23T21:24:38
  

  Fix jpeg_skip_scanlines() segfault w/merged upsamp
  
  The additional segfault mentioned in #244 was due to the fact that
  the merged upsamplers use a different private structure than the
  non-merged upsamplers.  jpeg_skip_scanlines() was assuming the latter, so
  when merged upsampling was enabled, jpeg_skip_scanlines() clobbered one
  of the IDCT method pointers in the merged upsampler's private structure.
  
  For reasons unknown, the test image in #441 did not encounter this
  segfault (too small?), but it encountered an issue similar to the one
  fixed in 5bc43c7821df982f65aa1c738f67fbf7cba8bd69, whereby it was
  necessary to set up a dummy postprocessing function in
  read_and_discard_scanlines() when merged upsampling was enabled.
  Failing to do so caused either a segfault in merged_2v_upsample() (due
  to a NULL pointer being passed to jcopy_sample_rows()) or an error
  ("Corrupt JPEG data: premature end of data segment"), depending on the
  number of scanlines skipped and whether the first scanline skipped was
  an odd- or even-numbered row.
  
  Fixes #441
  Fixes #244 (for real this time)
  

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• jdmerge.h

• /*
   * jdmerge.h
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1994-1996, Thomas G. Lane.
   * libjpeg-turbo Modifications:
   * Copyright (C) 2020, D. R. Commander.
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   */
  
  #define JPEG_INTERNALS
  #include "jpeglib.h"
  
  #ifdef UPSAMPLE_MERGING_SUPPORTED
  
  
  /* Private subobject */
  
  typedef struct {
    struct jpeg_upsampler pub;    /* public fields */
  
    /* Pointer to routine to do actual upsampling/conversion of one row group */
    void (*upmethod) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                      JDIMENSION in_row_group_ctr, JSAMPARRAY output_buf);
  
    /* Private state for YCC->RGB conversion */
    int *Cr_r_tab;                /* => table for Cr to R conversion */
    int *Cb_b_tab;                /* => table for Cb to B conversion */
    JLONG *Cr_g_tab;              /* => table for Cr to G conversion */
    JLONG *Cb_g_tab;              /* => table for Cb to G conversion */
  
    /* For 2:1 vertical sampling, we produce two output rows at a time.
     * We need a "spare" row buffer to hold the second output row if the
     * application provides just a one-row buffer; we also use the spare
     * to discard the dummy last row if the image height is odd.
     */
    JSAMPROW spare_row;
    boolean spare_full;           /* T if spare buffer is occupied */
  
    JDIMENSION out_row_width;     /* samples per output row */
    JDIMENSION rows_to_go;        /* counts rows remaining in image */
  } my_merged_upsampler;
  
  typedef my_merged_upsampler *my_merged_upsample_ptr;
  
  #endif /* UPSAMPLE_MERGING_SUPPORTED */
  

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