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      1 /**************************************************************************
      2  *
      3  * Copyright 2017 Valve Corporation
      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 THE AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR
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     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  * @file
     30  * A simple allocator that allocates and release "numbers".
     31  *
     32  * @author Samuel Pitoiset <samuel.pitoiset (at) gmail.com>
     33  */
     34 
     35 #include "util/u_idalloc.h"
     36 #include "util/u_math.h"
     37 #include "util/u_memory.h"
     38 
     39 void
     40 util_idalloc_init(struct util_idalloc *buf)
     41 {
     42    memset(buf, 0, sizeof(*buf));
     43 }
     44 
     45 void
     46 util_idalloc_fini(struct util_idalloc *buf)
     47 {
     48    if (buf->data)
     49       free(buf->data);
     50 }
     51 
     52 void
     53 util_idalloc_resize(struct util_idalloc *buf, unsigned new_num_elements)
     54 {
     55    new_num_elements = align(new_num_elements, 32);
     56 
     57    if (new_num_elements > buf->num_elements) {
     58       unsigned i;
     59 
     60       buf->data = realloc(buf->data,
     61                           (new_num_elements / 32) * sizeof(*buf->data));
     62 
     63       for (i = buf->num_elements / 32; i < new_num_elements / 32; i++)
     64          buf->data[i] = 0;
     65       buf->num_elements = new_num_elements;
     66    }
     67 }
     68 
     69 unsigned
     70 util_idalloc_alloc(struct util_idalloc *buf)
     71 {
     72    unsigned num_elements = buf->num_elements;
     73 
     74    for (unsigned i = 0; i < num_elements / 32; i++) {
     75       if (buf->data[i] == 0xffffffff)
     76          continue;
     77 
     78       unsigned bit = ffs(~buf->data[i]) - 1;
     79       buf->data[i] |= 1u << bit;
     80       return i * 32 + bit;
     81    }
     82 
     83    /* No slots available, resize and return the first free. */
     84    util_idalloc_resize(buf, num_elements * 2);
     85 
     86    buf->data[num_elements / 32] |= 1 << (num_elements % 32);
     87 
     88    return num_elements;
     89 }
     90 
     91 void
     92 util_idalloc_free(struct util_idalloc *buf, unsigned id)
     93 {
     94    assert(id < buf->num_elements);
     95    buf->data[id / 32] &= ~(1 << (id % 32));
     96 }
     97