text: /*
   * jdmainct.h
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1994-1996, Thomas G. Lane.
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   */
  
  #define JPEG_INTERNALS
  #include "jpeglib.h"
  #include "jpegcomp.h"
  
  
  /* Private buffer controller object */
  
  typedef struct {
    struct jpeg_d_main_controller pub; /* public fields */
  
    /* Pointer to allocated workspace (M or M+2 row groups). */
    JSAMPARRAY buffer[MAX_COMPONENTS];
  
    boolean buffer_full;          /* Have we gotten an iMCU row from decoder? */
    JDIMENSION rowgroup_ctr;      /* counts row groups output to postprocessor */
  
    /* Remaining fields are only used in the context case. */
  
    /* These are the master pointers to the funny-order pointer lists. */
    JSAMPIMAGE xbuffer[2];        /* pointers to weird pointer lists */
  
    int whichptr;                 /* indicates which pointer set is now in use */
    int context_state;            /* process_data state machine status */
    JDIMENSION rowgroups_avail;   /* row groups available to postprocessor */
    JDIMENSION iMCU_row_ctr;      /* counts iMCU rows to detect image top/bot */
  } my_main_controller;
  
  typedef my_main_controller *my_main_ptr;
  
  
  /* context_state values: */
  #define CTX_PREPARE_FOR_IMCU    0       /* need to prepare for MCU row */
  #define CTX_PROCESS_IMCU        1       /* feeding iMCU to postprocessor */
  #define CTX_POSTPONED_ROW       2       /* feeding postponed row group */
  
  
  LOCAL(void)
  set_wraparound_pointers(j_decompress_ptr cinfo)
  /* Set up the "wraparound" pointers at top and bottom of the pointer lists.
   * This changes the pointer list state from top-of-image to the normal state.
   */
  {
    my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
    int ci, i, rgroup;
    int M = cinfo->_min_DCT_scaled_size;
    jpeg_component_info *compptr;
    JSAMPARRAY xbuf0, xbuf1;
  
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
         ci++, compptr++) {
      rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
        cinfo->_min_DCT_scaled_size; /* height of a row group of component */
      xbuf0 = main_ptr->xbuffer[0][ci];
      xbuf1 = main_ptr->xbuffer[1][ci];
      for (i = 0; i < rgroup; i++) {
        xbuf0[i - rgroup] = xbuf0[rgroup * (M + 1) + i];
        xbuf1[i - rgroup] = xbuf1[rgroup * (M + 1) + i];
        xbuf0[rgroup * (M + 2) + i] = xbuf0[i];
        xbuf1[rgroup * (M + 2) + i] = xbuf1[i];
      }
    }
  }
  