OpenCores
URL https://opencores.org/ocsvn/openrisc/openrisc/trunk

Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libjava/] [classpath/] [gnu/] [java/] [awt/] [java2d/] [PixelCoverage.java] - Blame information for rev 769

Details | Compare with Previous | View Log

Line No. Rev Author Line
1 769 jeremybenn 
package gnu.java.awt.java2d;
2 
 
3 
/**
4 
 * Stores and handles the pixel converage for a scanline. The pixel coverage
5 
 * is stored as sorted list of buckets, each of which holds information about
6 
 * the coverage for the X and Y axis. This is utilized to compute the actual
7 
 * coverage for each pixel on the scanline and finding chunks of pixels with
8 
 * equal coverage.
9 
 */
10 
final class PixelCoverage
11 
{
12 
 
13 
  /**
14 
   * One bucket in the list.
15 
   */
16 
  private static final class Bucket
17 
  {
18 
    /**
19 
     * The X coordinate on the scanline to which this bucket belongs.
20 
     */
21 
    int xPos;
22 
 
23 
    /**
24 
     * The X coverage.
25 
     */
26 
    int xCov;
27 
 
28 
    /**
29 
     * The Y coverage.
30 
     */
31 
    int yCov;
32 
 
33 
    /**
34 
     * Implements a linked list. This points to the next element of the list.
35 
     */
36 
    Bucket next;
37 
 
38 
    /**
39 
     * Implements a linked list. This points to the previous element of the
40 
     * list.
41 
     */
42 
    Bucket prev;
43 
  }
44 
 
45 
  /**
46 
   * The head of the sorted list of buckets.
47 
   */
48 
  private Bucket head;
49 
 
50 
  /**
51 
   * The current bucket. We make use of the fact that the scanline converter
52 
   * always scans the scanline (and thus this list) from left to right to
53 
   * quickly find buckets or insertion points.
54 
   */
55 
  private Bucket current;
56 
 
57 
  /**
58 
   * The bucket after the last valid bucket. Unused buckets are not thrown
59 
   * away and garbage collected. Instead, we keep them at the tail of the list
60 
   * and reuse them when necessary.
61 
   */
62 
  private Bucket last;
63 
 
64 
  /**
65 
   * Indicates the the next scan of the scanline begins and that the next
66 
   * request will be at the beginning of this list. This makes searching and
67 
   * sorting of this list very quick.
68 
   */
69 
  void rewind()
70 
  {
71 
    current = head;
72 
  }
73 
 
74 
  /**
75 
   * Clears the list. This does not throw away the old buckets but only
76 
   * resets the end-pointer of the list to the first element. All buckets are
77 
   * then unused and are reused when the list is filled again.
78 
   */
79 
  void clear()
80 
  {
81 
    last = head;
82 
  }
83 
 
84 
  /**
85 
   * This adds the specified x and y coverage to the pixel at the specified
86 
   * X position.
87 
   *
88 
   * @param x the X position
89 
   * @param xc the x coverage
90 
   * @param yc the y coverage
91 
   */
92 
  void add(int x, int xc, int yc)
93 
  {
94 
    Bucket bucket = findOrInsert(x);
95 
    bucket.xCov += xc;
96 
    bucket.yCov += yc;
97 
  }
98 
 
99 
  /**
100 
   * Finds the bucket in the list with the specified X coordinate.
101 
   * If no such bucket is found, then a new one is fetched (either a cached
102 
   * bucket from the end of the list or a newly allocated one) inserted at the
103 
   * correct position and returned.
104 
   *
105 
   * @param x the X coordinate
106 
   *
107 
   * @return a bucket to hold the coverage data
108 
   */
109 
  private Bucket findOrInsert(int x)
110 
  {
111 
    // First search for a matching bucket.
112 
    if (head == null)
113 
      {
114 
        // Special case: the list is still empty.
115 
        head = new Bucket();
116 
        current = head;
117 
        return head;
118 
      }
119 
 
120 
    // This performs a linear search, starting from the current bucket.
121 
    // This is reasonably efficient because access to this list is always done
122 
    // in a linear fashion and we are not more then 1 or 2 buckets away from
123 
    // the one we're looking for.
124 
    Bucket match = current;
125 
    while (match != null && match.xPos != x)
126 
      {
127 
 
128 
      }
129 
 
130 
    return match;
131 
  }
132 
}

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.