src/gallium/auxiliary/util/u_draw.c

   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 for the current set of bound vertex
  37  * buffers.  Regardless of any other consideration, all vertex lookups need to
  38  * be clamped to 0..max_index to prevent an out-of-bound access.
  39  */
  40 unsigned
  41 util_draw_max_index(
  42       const struct pipe_vertex_buffer *vertex_buffers,
  43       unsigned nr_vertex_buffers,
  44       const struct pipe_vertex_element *vertex_elements,
  45       unsigned nr_vertex_elements,
  46       const struct pipe_draw_info *info)
  47 {
  48    unsigned max_index;
  49    unsigned i;
  50
  51    max_index = ~0;
  52    for (i = 0; i < nr_vertex_elements; i++) {
  53       const struct pipe_vertex_element *element =
  54          &vertex_elements[i];
  55       const struct pipe_vertex_buffer *buffer =
  56          &vertex_buffers[element->vertex_buffer_index];
  57       unsigned buffer_size;
  58       const struct util_format_description *format_desc;
  59       unsigned format_size;
  60
  61       assert(buffer->buffer->height0 == 1);
  62       assert(buffer->buffer->depth0 == 1);
  63       buffer_size = buffer->buffer->width0;
  64
  65       format_desc = util_format_description(element->src_format);
  66       assert(format_desc->block.width == 1);
  67       assert(format_desc->block.height == 1);
  68       assert(format_desc->block.bits % 8 == 0);
  69       format_size = format_desc->block.bits/8;
  70
  71       assert(buffer_size - buffer->buffer_offset <= buffer_size);
  72       buffer_size -= buffer->buffer_offset;
  73
  74       assert(buffer_size - element->src_offset <= buffer_size);
  75       buffer_size -= element->src_offset;
  76
  77       assert(buffer_size - format_size <= buffer_size);
  78       buffer_size -= format_size;
  79
  80       if (buffer->stride != 0) {
  81          unsigned buffer_max_index;
  82
  83          buffer_max_index = buffer_size / buffer->stride;
  84
  85          if (element->instance_divisor == 0) {
  86             /* Per-vertex data */
  87             max_index = MIN2(max_index, buffer_max_index);
  88          }
  89          else {
  90             /* Per-instance data. Simply make sure the state tracker didn't
  91              * request more instances than those that fit in the buffer */
  92             assert((info->start_instance + info->instance_count)/element->instance_divisor
  93                    <= (buffer_max_index + 1));
  94          }
  95       }
  96    }
  97
  98    return max_index;
  99 }