1 /* Type-safe arrays which grow dynamically.  Shared definitions.
2    Copyright (C) 2017-2022 Free Software Foundation, Inc.
3    This file is part of the GNU C Library.
4 
5    The GNU C Library is free software; you can redistribute it and/or
6    modify it under the terms of the GNU Lesser General Public
7    License as published by the Free Software Foundation; either
8    version 2.1 of the License, or (at your option) any later version.
9 
10    The GNU C Library is distributed in the hope that it will be useful,
11    but WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13    Lesser General Public License for more details.
14 
15    You should have received a copy of the GNU Lesser General Public
16    License along with the GNU C Library; if not, see
17    <https://www.gnu.org/licenses/>.  */
18 
19 /* To use the dynarray facility, you need to include
20    <malloc/dynarray-skeleton.c> and define the parameter macros
21    documented in that file.
22 
23    A minimal example which provides a growing list of integers can be
24    defined like this:
25 
26      struct int_array
27      {
28        // Pointer to result array followed by its length,
29        // as required by DYNARRAY_FINAL_TYPE.
30        int *array;
31        size_t length;
32      };
33 
34      #define DYNARRAY_STRUCT dynarray_int
35      #define DYNARRAY_ELEMENT int
36      #define DYNARRAY_PREFIX dynarray_int_
37      #define DYNARRAY_FINAL_TYPE struct int_array
38      #include <malloc/dynarray-skeleton.c>
39 
40    To create a three-element array with elements 1, 2, 3, use this
41    code:
42 
43      struct dynarray_int dyn;
44      dynarray_int_init (&dyn);
45      for (int i = 1; i <= 3; ++i)
46        {
47          int *place = dynarray_int_emplace (&dyn);
48          assert (place != NULL);
49          *place = i;
50        }
51      struct int_array result;
52      bool ok = dynarray_int_finalize (&dyn, &result);
53      assert (ok);
54      assert (result.length == 3);
55      assert (result.array[0] == 1);
56      assert (result.array[1] == 2);
57      assert (result.array[2] == 3);
58      free (result.array);
59 
60    If the elements contain resources which must be freed, define
61    DYNARRAY_ELEMENT_FREE appropriately, like this:
62 
63      struct str_array
64      {
65        char **array;
66        size_t length;
67      };
68 
69      #define DYNARRAY_STRUCT dynarray_str
70      #define DYNARRAY_ELEMENT char *
71      #define DYNARRAY_ELEMENT_FREE(ptr) free (*ptr)
72      #define DYNARRAY_PREFIX dynarray_str_
73      #define DYNARRAY_FINAL_TYPE struct str_array
74      #include <malloc/dynarray-skeleton.c>
75 
76    Compared to scratch buffers, dynamic arrays have the following
77    features:
78 
79    - They have an element type, and are not just an untyped buffer of
80      bytes.
81 
82    - When growing, previously stored elements are preserved.  (It is
83      expected that scratch_buffer_grow_preserve and
84      scratch_buffer_set_array_size eventually go away because all
85      current users are moved to dynamic arrays.)
86 
87    - Scratch buffers have a more aggressive growth policy because
88      growing them typically means a retry of an operation (across an
89      NSS service module boundary), which is expensive.
90 
91    - For the same reason, scratch buffers have a much larger initial
92      stack allocation.  */
93 
94 #ifndef _DYNARRAY_H
95 #define _DYNARRAY_H
96 
97 #include <stdbool.h>
98 #include <stddef.h>
99 #include <string.h>
100 
101 struct dynarray_header
102 {
103   size_t used;
104   size_t allocated;
105   void *array;
106 };
107 
108 /* Marker used in the allocated member to indicate that an error was
109    encountered.  */
110 static inline size_t
__dynarray_error_marker(void)111 __dynarray_error_marker (void)
112 {
113   return -1;
114 }
115 
116 /* Internal function.  See the has_failed function in
117    dynarray-skeleton.c.  */
118 static inline bool
__dynarray_error(struct dynarray_header * list)119 __dynarray_error (struct dynarray_header *list)
120 {
121   return list->allocated == __dynarray_error_marker ();
122 }
123 
124 /* Internal function.  Enlarge the dynamically allocated area of the
125    array to make room for one more element.  SCRATCH is a pointer to
126    the scratch area (which is not heap-allocated and must not be
127    freed).  ELEMENT_SIZE is the size, in bytes, of one element.
128    Return false on failure, true on success.  */
129 bool __libc_dynarray_emplace_enlarge (struct dynarray_header *,
130                                       void *scratch, size_t element_size);
131 
132 /* Internal function.  Enlarge the dynamically allocated area of the
133    array to make room for at least SIZE elements (which must be larger
134    than the existing used part of the dynamic array).  SCRATCH is a
135    pointer to the scratch area (which is not heap-allocated and must
136    not be freed).  ELEMENT_SIZE is the size, in bytes, of one element.
137    Return false on failure, true on success.  */
138 bool __libc_dynarray_resize (struct dynarray_header *, size_t size,
139                              void *scratch, size_t element_size);
140 
141 /* Internal function.  Like __libc_dynarray_resize, but clear the new
142    part of the dynamic array.  */
143 bool __libc_dynarray_resize_clear (struct dynarray_header *, size_t size,
144                                    void *scratch, size_t element_size);
145 
146 /* Internal type.  */
147 struct dynarray_finalize_result
148 {
149   void *array;
150   size_t length;
151 };
152 
153 /* Internal function.  Copy the dynamically-allocated area to an
154    explicitly-sized heap allocation.  SCRATCH is a pointer to the
155    embedded scratch space.  ELEMENT_SIZE is the size, in bytes, of the
156    element type.  On success, true is returned, and pointer and length
157    are written to *RESULT.  On failure, false is returned.  The caller
158    has to take care of some of the memory management; this function is
159    expected to be called from dynarray-skeleton.c.  */
160 bool __libc_dynarray_finalize (struct dynarray_header *list, void *scratch,
161                                size_t element_size,
162                                struct dynarray_finalize_result *result);
163 
164 
165 /* Internal function.  Terminate the process after an index error.
166    SIZE is the number of elements of the dynamic array.  INDEX is the
167    lookup index which triggered the failure.  */
168 _Noreturn void __libc_dynarray_at_failure (size_t size, size_t index);
169 
170 #ifndef _ISOMAC
171 libc_hidden_proto (__libc_dynarray_emplace_enlarge)
172 libc_hidden_proto (__libc_dynarray_resize)
173 libc_hidden_proto (__libc_dynarray_resize_clear)
174 libc_hidden_proto (__libc_dynarray_finalize)
175 libc_hidden_proto (__libc_dynarray_at_failure)
176 #endif
177 
178 #endif /* _DYNARRAY_H */
179