Add jpeg_skip_scanlines() API to libjpeg-turbo

jdcoefct.c

 /*
  * jdcoefct.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
+ * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
  * Copyright (C) 2010, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains the coefficient buffer controller for decompression.
  * This controller is the top level of the JPEG decompressor proper.
  * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
  *
  * In buffered-image mode, this controller is the interface between
  * input-oriented processing and output-oriented processing.
  * Also, the input side (only) is used when reading a file for transcoding.
  */
 
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "jpeglib.h"
+#include "jdcoefct.h"
 #include "jpegcomp.h"
 
-/* Block smoothing is only applicable for progressive JPEG, so: */
-#ifndef D_PROGRESSIVE_SUPPORTED
-#undef BLOCK_SMOOTHING_SUPPORTED
-#endif
-
-/* 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 */
-  int MCU_vert_offset;          /* counts MCU rows within iMCU row */
-  int MCU_rows_per_iMCU_row;    /* number of such rows needed */
-
-  /* The output side's location is represented by cinfo->output_iMCU_row. */
-
-  /* In single-pass modes, it's sufficient to buffer just one MCU.
-   * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
-   * and let the entropy decoder write into that workspace each time.
-   * (On 80x86, the workspace is FAR even though it's not really very big;
-   * this is to keep the module interfaces unchanged when a large coefficient
-   * buffer is necessary.)
-   * In multi-pass modes, this array points to the current MCU's blocks
-   * within the virtual arrays; it is used only by the input side.
-   */
-  JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
-
-  /* Temporary workspace for one MCU */
-  JCOEF * workspace;
-
-#ifdef D_MULTISCAN_FILES_SUPPORTED
-  /* In multi-pass modes, we need a virtual block array for each component. */
-  jvirt_barray_ptr whole_image[MAX_COMPONENTS];
-#endif
-
-#ifdef BLOCK_SMOOTHING_SUPPORTED
-  /* When doing block smoothing, we latch coefficient Al values here */
-  int * coef_bits_latch;
-#define SAVED_COEFS  6          /* we save coef_bits[0..5] */
-#endif
-} my_coef_controller;
-
-typedef my_coef_controller * my_coef_ptr;
 
 /* Forward declarations */
 METHODDEF(int) decompress_onepass
         JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 #ifdef D_MULTISCAN_FILES_SUPPORTED
 METHODDEF(int) decompress_data
         JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 #endif
 #ifdef BLOCK_SMOOTHING_SUPPORTED
 LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
 METHODDEF(int) decompress_smooth_data
         JPP((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_coef_ptr coef = (my_coef_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) {
-    coef->MCU_rows_per_iMCU_row = 1;
-  } else {
-    if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
-      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
-    else
-      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
-  }
-
-  coef->MCU_ctr = 0;
-  coef->MCU_vert_offset = 0;
-}
-
-
 /*
  * Initialize for an input processing pass.
  */
 
 METHODDEF(void)
 start_input_pass (j_decompress_ptr cinfo)
 {
   cinfo->input_iMCU_row = 0;
   start_iMCU_row(cinfo);
 }
@@ skipping 623 matching lines @@
     coef->pub.consume_data = dummy_consume_data;
     coef->pub.decompress_data = decompress_onepass;
     coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
   }
 
   /* Allocate the workspace buffer */
   coef->workspace = (JCOEF *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 SIZEOF(JCOEF) * DCTSIZE2);
 }