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 */
44unsigned
45util_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