1/*
2 * jdmainct.h
3 *
4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1994-1996, Thomas G. Lane.
6 * For conditions of distribution and use, see the accompanying README file.
7 */
8
9#define JPEG_INTERNALS
10#include "jinclude.h"
11#include "jpeglib.h"
12#include "jpegcomp.h"
13
14
15/* Private buffer controller object */
16
17typedef struct {
18  struct jpeg_d_main_controller pub; /* public fields */
19
20  /* Pointer to allocated workspace (M or M+2 row groups). */
21  JSAMPARRAY buffer[MAX_COMPONENTS];
22
23  boolean buffer_full;          /* Have we gotten an iMCU row from decoder? */
24  JDIMENSION rowgroup_ctr;      /* counts row groups output to postprocessor */
25
26  /* Remaining fields are only used in the context case. */
27
28  /* These are the master pointers to the funny-order pointer lists. */
29  JSAMPIMAGE xbuffer[2];        /* pointers to weird pointer lists */
30
31  int whichptr;                 /* indicates which pointer set is now in use */
32  int context_state;            /* process_data state machine status */
33  JDIMENSION rowgroups_avail;   /* row groups available to postprocessor */
34  JDIMENSION iMCU_row_ctr;      /* counts iMCU rows to detect image top/bot */
35} my_main_controller;
36
37typedef my_main_controller * my_main_ptr;
38
39
40/* context_state values: */
41#define CTX_PREPARE_FOR_IMCU    0       /* need to prepare for MCU row */
42#define CTX_PROCESS_IMCU        1       /* feeding iMCU to postprocessor */
43#define CTX_POSTPONED_ROW       2       /* feeding postponed row group */
44
45
46LOCAL(void)
47set_wraparound_pointers (j_decompress_ptr cinfo)
48/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
49 * This changes the pointer list state from top-of-image to the normal state.
50 */
51{
52  my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
53  int ci, i, rgroup;
54  int M = cinfo->_min_DCT_scaled_size;
55  jpeg_component_info *compptr;
56  JSAMPARRAY xbuf0, xbuf1;
57
58  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
59       ci++, compptr++) {
60    rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
61      cinfo->_min_DCT_scaled_size; /* height of a row group of component */
62    xbuf0 = main_ptr->xbuffer[0][ci];
63    xbuf1 = main_ptr->xbuffer[1][ci];
64    for (i = 0; i < rgroup; i++) {
65      xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
66      xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
67      xbuf0[rgroup*(M+2) + i] = xbuf0[i];
68      xbuf1[rgroup*(M+2) + i] = xbuf1[i];
69    }
70  }
71}
72