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vec.c
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1 /* Vector API for GDB.
2  Copyright (C) 2004-2015 Free Software Foundation, Inc.
3  Contributed by Nathan Sidwell <nathan@codesourcery.com>
4 
5  This file is part of GDB.
6 
7  This program is free software; you can redistribute it and/or modify
8  it under the terms of the GNU General Public License as published by
9  the Free Software Foundation; either version 3 of the License, or
10  (at your option) any later version.
11 
12  This program is distributed in the hope that it will be useful,
13  but WITHOUT ANY WARRANTY; without even the implied warranty of
14  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15  GNU General Public License for more details.
16 
17  You should have received a copy of the GNU General Public License
18  along with this program. If not, see <http://www.gnu.org/licenses/>. */
19 
20 #include "common-defs.h"
21 #include "vec.h"
22 
23 struct vec_prefix
24 {
25  unsigned num;
26  unsigned alloc;
27  void *vec[1];
28 };
29 
30 /* Calculate the new ALLOC value, making sure that abs(RESERVE) slots
31  are free. If RESERVE < 0 grow exactly, otherwise grow
32  exponentially. */
33 
34 static inline unsigned
35 calculate_allocation (const struct vec_prefix *pfx, int reserve)
36 {
37  unsigned alloc = 0;
38  unsigned num = 0;
39 
40  if (pfx)
41  {
42  alloc = pfx->alloc;
43  num = pfx->num;
44  }
45  else if (!reserve)
46  /* If there's no prefix, and we've not requested anything, then we
47  will create a NULL vector. */
48  return 0;
49 
50  /* We must have run out of room. */
51  gdb_assert (alloc - num < (unsigned)(reserve < 0 ? -reserve : reserve));
52 
53  if (reserve < 0)
54  /* Exact size. */
55  alloc = num + -reserve;
56  else
57  {
58  /* Exponential growth. */
59  if (!alloc)
60  alloc = 4;
61  else if (alloc < 16)
62  /* Double when small. */
63  alloc = alloc * 2;
64  else
65  /* Grow slower when large. */
66  alloc = (alloc * 3 / 2);
67 
68  /* If this is still too small, set it to the right size. */
69  if (alloc < num + reserve)
70  alloc = num + reserve;
71  }
72  return alloc;
73 }
74 
75 /* Ensure there are at least abs(RESERVE) free slots in VEC. If
76  RESERVE < 0 grow exactly, else grow exponentially. As a special
77  case, if VEC is NULL, and RESERVE is 0, no vector will be created. */
78 
79 void *
80 vec_p_reserve (void *vec, int reserve)
81 {
82  return vec_o_reserve (vec, reserve,
83  offsetof (struct vec_prefix, vec), sizeof (void *));
84 }
85 
86 /* As vec_p_reserve, but for object vectors. The vector's trailing
87  array is at VEC_OFFSET offset and consists of ELT_SIZE sized
88  elements. */
89 
90 void *
91 vec_o_reserve (void *vec, int reserve, size_t vec_offset, size_t elt_size)
92 {
93  struct vec_prefix *pfx = vec;
94  unsigned alloc = calculate_allocation (pfx, reserve);
95 
96  if (!alloc)
97  return NULL;
98 
99  vec = xrealloc (vec, vec_offset + alloc * elt_size);
100  ((struct vec_prefix *)vec)->alloc = alloc;
101  if (!pfx)
102  ((struct vec_prefix *)vec)->num = 0;
103 
104  return vec;
105 }
106 
107 #if 0
108 /* Example uses. */
109 DEF_VEC_I (int);
110 typedef struct X
111 {
112  int i;
113 } obj_t;
114 typedef obj_t *ptr_t;
115 
116 DEF_VEC_P (ptr_t);
117 DEF_VEC_O (obj_t);
118 #endif
DEF_VEC_O(btrace_block_s)
unsigned alloc
Definition: vec.c:26
DEF_VEC_I(int)
#define DEF_VEC_P(T)
Definition: vec.h:422
void * vec_o_reserve(void *vec, int reserve, size_t vec_offset, size_t elt_size)
Definition: vec.c:91
#define gdb_assert(expr)
Definition: gdb_assert.h:33
unsigned num
Definition: vec.c:25
PTR xrealloc(PTR ptr, size_t size)
Definition: common-utils.c:51
void * vec_p_reserve(void *vec, int reserve)
Definition: vec.c:80
void * vec[1]
Definition: vec.c:27
static unsigned calculate_allocation(const struct vec_prefix *pfx, int reserve)
Definition: vec.c:35
Definition: vec.c:23