gdb/vec.c

   1 /* Vector API for GDB.
   2    Copyright (C) 2004, 2005, 2006, 2007 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 2 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, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20    Boston, MA 02110-1301, USA.  */
  21
  22 #include "defs.h"
  23 #include "vec.h"
  24
  25 struct vec_prefix
  26 {
  27   unsigned num;
  28   unsigned alloc;
  29   void *vec[1];
  30 };
  31
  32 /* Calculate the new ALLOC value, making sure that abs(RESERVE) slots
  33    are free.  If RESERVE < 0 grow exactly, otherwise grow
  34    exponentially.  */
  35
  36 static inline unsigned
  37 calculate_allocation (const struct vec_prefix *pfx, int reserve)
  38 {
  39   unsigned alloc = 0;
  40   unsigned num = 0;
  41
  42   if (pfx)
  43     {
  44       alloc = pfx->alloc;
  45       num = pfx->num;
  46     }
  47   else if (!reserve)
  48     /* If there's no prefix, and we've not requested anything, then we
  49        will create a NULL vector.  */
  50     return 0;
  51
  52   /* We must have run out of room.  */
  53   gdb_assert (alloc - num < (unsigned)(reserve < 0 ? -reserve : reserve));
  54
  55   if (reserve < 0)
  56     /* Exact size.  */
  57     alloc = num + -reserve;
  58   else
  59     {
  60       /* Exponential growth. */
  61       if (!alloc)
  62         alloc = 4;
  63       else if (alloc < 16)
  64         /* Double when small.  */
  65         alloc = alloc * 2;
  66       else
  67         /* Grow slower when large.  */
  68         alloc = (alloc * 3 / 2);
  69
  70       /* If this is still too small, set it to the right size. */
  71       if (alloc < num + reserve)
  72         alloc = num + reserve;
  73     }
  74   return alloc;
  75 }
  76
  77 /* Ensure there are at least abs(RESERVE) free slots in VEC.  If
  78    RESERVE < 0 grow exactly, else grow exponentially.  As a special
  79    case, if VEC is NULL, and RESERVE is 0, no vector will be created. */
  80
  81 void *
  82 vec_p_reserve (void *vec, int reserve)
  83 {
  84   return vec_o_reserve (vec, reserve,
  85                         offsetof (struct vec_prefix, vec), sizeof (void *));
  86 }
  87
  88 /* As vec_p_reserve, but for object vectors.  The vector's trailing
  89    array is at VEC_OFFSET offset and consists of ELT_SIZE sized
  90    elements.  */
  91
  92 void *
  93 vec_o_reserve (void *vec, int reserve, size_t vec_offset, size_t elt_size)
  94 {
  95   struct vec_prefix *pfx = vec;
  96   unsigned alloc = calculate_allocation (pfx, reserve);
  97
  98   if (!alloc)
  99     return NULL;
 100
 101   vec = xrealloc (vec, vec_offset + alloc * elt_size);
 102   ((struct vec_prefix *)vec)->alloc = alloc;
 103   if (!pfx)
 104     ((struct vec_prefix *)vec)->num = 0;
 105
 106   return vec;
 107 }
 108
 109 #if 0
 110 /* Example uses.  */
 111 DEF_VEC_I (int);
 112 typedef struct X
 113 {
 114   int i;
 115 } obj_t;
 116 typedef obj_t *ptr_t;
 117
 118 DEF_VEC_P (ptr_t);
 119 DEF_VEC_O (obj_t);
 120 #endif