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1 /* objalloc.h -- routines to allocate memory for objects
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2 Copyright (C) 1997-2020 Free Software Foundation, Inc.
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3 Written by Ian Lance Taylor, Cygnus Solutions.
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4
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5 This program is free software; you can redistribute it and/or modify it
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6 under the terms of the GNU General Public License as published by the
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7 Free Software Foundation; either version 2, or (at your option) any
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8 later version.
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9
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10 This program is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 GNU General Public License for more details.
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14
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15 You should have received a copy of the GNU General Public License
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16 along with this program; if not, write to the Free Software
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17 Foundation, 51 Franklin Street - Fifth Floor,
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18 Boston, MA 02110-1301, USA. */
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19
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20 #ifndef OBJALLOC_H
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21 #define OBJALLOC_H
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22
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23 #include "ansidecl.h"
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24
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25 /* These routines allocate space for an object. The assumption is
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26 that the object will want to allocate space as it goes along, but
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27 will never want to free any particular block. There is a function
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28 to free a block, which also frees all more recently allocated
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29 blocks. There is also a function to free all the allocated space.
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30
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31 This is essentially a specialization of obstacks. The main
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32 difference is that a block may not be allocated a bit at a time.
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33 Another difference is that these routines are always built on top
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34 of malloc, and always pass an malloc failure back to the caller,
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35 unlike more recent versions of obstacks. */
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36
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37 /* This is what an objalloc structure looks like. Callers should not
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38 refer to these fields, nor should they allocate these structure
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39 themselves. Instead, they should only create them via
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40 objalloc_init, and only access them via the functions and macros
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41 listed below. The structure is only defined here so that we can
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42 access it via macros. */
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43
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44 struct objalloc
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45 {
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46 char *current_ptr;
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47 unsigned int current_space;
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48 void *chunks;
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49 };
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50
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51 /* Work out the required alignment. */
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52
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53 struct objalloc_align { char x; double d; };
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54
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55 #if defined (__STDC__) && __STDC__
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56 #ifndef offsetof
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57 #include <stddef.h>
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58 #endif
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59 #endif
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60 #ifndef offsetof
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61 #define offsetof(TYPE, MEMBER) ((unsigned long) &((TYPE *)0)->MEMBER)
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62 #endif
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63 #define OBJALLOC_ALIGN offsetof (struct objalloc_align, d)
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64
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65 /* Create an objalloc structure. Returns NULL if malloc fails. */
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66
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67 extern struct objalloc *objalloc_create (void);
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68
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69 /* Allocate space from an objalloc structure. Returns NULL if malloc
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70 fails. */
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71
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72 extern void *_objalloc_alloc (struct objalloc *, unsigned long);
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73
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74 /* The macro version of objalloc_alloc. We only define this if using
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75 gcc, because otherwise we would have to evaluate the arguments
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76 multiple times, or use a temporary field as obstack.h does. */
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77
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78 #if defined (__GNUC__) && defined (__STDC__) && __STDC__
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79
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80 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
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81 does not implement __extension__. But that compiler doesn't define
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82 __GNUC_MINOR__. */
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83 #if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
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84 #define __extension__
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85 #endif
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86
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87 #define objalloc_alloc(o, l) \
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88 __extension__ \
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89 ({ struct objalloc *__o = (o); \
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90 unsigned long __len = (l); \
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91 if (__len == 0) \
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92 __len = 1; \
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93 __len = (__len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1); \
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94 (__len != 0 && __len <= __o->current_space \
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95 ? (__o->current_ptr += __len, \
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96 __o->current_space -= __len, \
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97 (void *) (__o->current_ptr - __len)) \
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98 : _objalloc_alloc (__o, __len)); })
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99
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100 #else /* ! __GNUC__ */
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101
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102 #define objalloc_alloc(o, l) _objalloc_alloc ((o), (l))
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103
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104 #endif /* ! __GNUC__ */
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105
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106 /* Free an entire objalloc structure. */
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107
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108 extern void objalloc_free (struct objalloc *);
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109
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110 /* Free a block allocated by objalloc_alloc. This also frees all more
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111 recently allocated blocks. */
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112
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113 extern void objalloc_free_block (struct objalloc *, void *);
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114
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115 #endif /* OBJALLOC_H */
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