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1  /**************************************************************************
2   *
3   * Copyright 2011 VMware, Inc.
4   * All Rights Reserved.
5   *
6   * Permission is hereby granted, free of charge, to any person obtaining a
7   * copy of this software and associated documentation files (the
8   * "Software"), to deal in the Software without restriction, including
9   * without limitation the rights to use, copy, modify, merge, publish,
10   * distribute, sub license, and/or sell copies of the Software, and to
11   * permit persons to whom the Software is furnished to do so, subject to
12   * the following conditions:
13   *
14   * The above copyright notice and this permission notice (including the
15   * next paragraph) shall be included in all copies or substantial portions
16   * of the Software.
17   *
18   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19   * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21   * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
22   * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23   * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24   * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25   *
26   **************************************************************************/
27  
28  
29  #include "util/u_debug.h"
30  #include "util/u_math.h"
31  #include "util/u_format.h"
32  #include "util/u_draw.h"
33  
34  
35  /**
36   * Returns the largest legal index value plus one for the current set
37   * of bound vertex buffers.  Regardless of any other consideration,
38   * all vertex lookups need to be clamped to 0..max_index-1 to prevent
39   * an out-of-bound access.
40   *
41   * Note that if zero is returned it means that one or more buffers is
42   * too small to contain any valid vertex data.
43   */
44  unsigned
util_draw_max_index(const struct pipe_vertex_buffer * vertex_buffers,const struct pipe_vertex_element * vertex_elements,unsigned nr_vertex_elements,const struct pipe_draw_info * info)45  util_draw_max_index(
46        const struct pipe_vertex_buffer *vertex_buffers,
47        const struct pipe_vertex_element *vertex_elements,
48        unsigned nr_vertex_elements,
49        const struct pipe_draw_info *info)
50  {
51     unsigned max_index;
52     unsigned i;
53  
54     max_index = ~0U - 1;
55     for (i = 0; i < nr_vertex_elements; i++) {
56        const struct pipe_vertex_element *element =
57           &vertex_elements[i];
58        const struct pipe_vertex_buffer *buffer =
59           &vertex_buffers[element->vertex_buffer_index];
60        unsigned buffer_size;
61        const struct util_format_description *format_desc;
62        unsigned format_size;
63  
64        if (!buffer->buffer) {
65           continue;
66        }
67  
68        assert(buffer->buffer->height0 == 1);
69        assert(buffer->buffer->depth0 == 1);
70        buffer_size = buffer->buffer->width0;
71  
72        format_desc = util_format_description(element->src_format);
73        assert(format_desc->block.width == 1);
74        assert(format_desc->block.height == 1);
75        assert(format_desc->block.bits % 8 == 0);
76        format_size = format_desc->block.bits/8;
77  
78        if (buffer->buffer_offset >= buffer_size) {
79           /* buffer is too small */
80           return 0;
81        }
82  
83        buffer_size -= buffer->buffer_offset;
84  
85        if (element->src_offset >= buffer_size) {
86           /* buffer is too small */
87           return 0;
88        }
89  
90        buffer_size -= element->src_offset;
91  
92        if (format_size > buffer_size) {
93           /* buffer is too small */
94           return 0;
95        }
96  
97        buffer_size -= format_size;
98  
99        if (buffer->stride != 0) {
100           unsigned buffer_max_index;
101  
102           buffer_max_index = buffer_size / buffer->stride;
103  
104           if (element->instance_divisor == 0) {
105              /* Per-vertex data */
106              max_index = MIN2(max_index, buffer_max_index);
107           }
108           else {
109              /* Per-instance data. Simply make sure the state tracker didn't
110               * request more instances than those that fit in the buffer */
111              assert((info->start_instance + info->instance_count)/element->instance_divisor
112                     <= (buffer_max_index + 1));
113           }
114        }
115     }
116  
117     return max_index + 1;
118  }
119