u_draw.c revision 438d7ac146dc89d1c2943610c662c57e11a47382 
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      unsigned nr_vertex_buffers,
48      const struct pipe_vertex_element *vertex_elements,
49      unsigned nr_vertex_elements,
50      const struct pipe_draw_info *info)
51{
52   unsigned max_index;
53   unsigned i;
54
55   max_index = ~0U - 1;
56   for (i = 0; i < nr_vertex_elements; i++) {
57      const struct pipe_vertex_element *element =
58         &vertex_elements[i];
59      const struct pipe_vertex_buffer *buffer =
60         &vertex_buffers[element->vertex_buffer_index];
61      unsigned buffer_size;
62      const struct util_format_description *format_desc;
63      unsigned format_size;
64
65      assert(buffer->buffer->height0 == 1);
66      assert(buffer->buffer->depth0 == 1);
67      buffer_size = buffer->buffer->width0;
68
69      format_desc = util_format_description(element->src_format);
70      assert(format_desc->block.width == 1);
71      assert(format_desc->block.height == 1);
72      assert(format_desc->block.bits % 8 == 0);
73      format_size = format_desc->block.bits/8;
74
75      if (buffer->buffer_offset >= buffer_size) {
76         /* buffer is too small */
77         return 0;
78      }
79
80      buffer_size -= buffer->buffer_offset;
81
82      if (element->src_offset >= buffer_size) {
83         /* buffer is too small */
84         return 0;
85      }
86
87      buffer_size -= element->src_offset;
88
89      if (format_size > buffer_size) {
90         /* buffer is too small */
91         return 0;
92      }
93
94      buffer_size -= format_size;
95
96      if (buffer->stride != 0) {
97         unsigned buffer_max_index;
98
99         buffer_max_index = buffer_size / buffer->stride;
100
101         if (element->instance_divisor == 0) {
102            /* Per-vertex data */
103            max_index = MIN2(max_index, buffer_max_index);
104         }
105         else {
106            /* Per-instance data. Simply make sure the state tracker didn't
107             * request more instances than those that fit in the buffer */
108            assert((info->start_instance + info->instance_count)/element->instance_divisor
109                   <= (buffer_max_index + 1));
110         }
111      }
112   }
113
114   return max_index + 1;
115}
116