u_idalloc.c revision b8e80941 
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2 *
3 * Copyright 2017 Valve Corporation
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27
28/**
29 * @file
30 * A simple allocator that allocates and release "numbers".
31 *
32 * @author Samuel Pitoiset <samuel.pitoiset@gmail.com>
33 */
34
35#include "util/u_idalloc.h"
36#include "util/u_math.h"
37#include "util/u_memory.h"
38
39void
40util_idalloc_init(struct util_idalloc *buf)
41{
42   memset(buf, 0, sizeof(*buf));
43}
44
45void
46util_idalloc_fini(struct util_idalloc *buf)
47{
48   if (buf->data)
49      free(buf->data);
50}
51
52void
53util_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
69unsigned
70util_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
91void
92util_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