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.ijg
7  * file.
8  */
9 
10 #define JPEG_INTERNALS
11 #include "jpeglib.h"
12 #include "jpegcomp.h"
13 
14 
15 /* Private buffer controller object */
16 
17 typedef 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 
37 typedef 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 
46 LOCAL(void)
set_wraparound_pointers(j_decompress_ptr cinfo)47 set_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