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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
     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