src/libstatgrab/vector.h

#include <stdlib.h>

typedef void (*vector_init_function)(void *item);
typedef void (*vector_destroy_function)(void *item);

typedef struct {
        size_t item_size;
        int used_count;
        int alloc_count;
        int block_size;
        vector_init_function init_fn;
        vector_destroy_function destroy_fn;
} vector_header;

#define VECTOR_HEADER(name, item_type, block_size, init_fn, destroy_fn) \
        vector_header name##_header = { \
                sizeof(item_type), \
                0, \
                0, \
                block_size, \
                (vector_init_function) init_fn, \
                (vector_destroy_function) destroy_fn \
        }

/* A pointer value that won't be returned by malloc, and isn't NULL, so can be
 * used as a sentinel by allocation routines that need to return NULL
 * sometimes. */
extern char statgrab_vector_sentinel_value;
static void *statgrab_vector_sentinel = &statgrab_vector_sentinel_value;

/* Internal function to resize the vector. Ideally it would take void ** as the
 * first parameter, but ANSI strict-aliasing rules would then prevent it from
 * doing anything with it, so we return a sentinel value as above instead if
 * allocation fails. */
void *statgrab_vector_resize(void *vector, vector_header *h, int count);

/* Declare a vector. Specify the init/destroy functions as NULL if you don't
 * need them. The block size is how many items to allocate at once. */
#define VECTOR_DECLARE(name, item_type, block_size, init_fn, destroy_fn) \
        item_type *name = NULL; \
        VECTOR_HEADER(name, item_type, block_size, init_fn, destroy_fn)

/* As VECTOR_DECLARE, but for a static vector. */
#define VECTOR_DECLARE_STATIC(name, item_type, block_size, init_fn, destroy_fn) \
        static item_type *name = NULL; \
        static VECTOR_HEADER(name, item_type, block_size, init_fn, destroy_fn)

/* Return the current size of a vector. */
#define VECTOR_SIZE(name) \
        name##_header.used_count

/* Resize a vector. Returns 0 on success, -1 on out-of-memory. On
 * out-of-memory, the old contents of the vector will be destroyed and the old
 * vector will be freed.
 *
 * This is ugly because it needs to check for the sentinel value.
 */
#define VECTOR_RESIZE(name, num_items) \
        (((name = statgrab_vector_resize((char *) name, &name##_header, num_items)) \
          == statgrab_vector_sentinel) ? -1 : 0)

/* Free a vector, destroying its contents. */
#define VECTOR_FREE(name) \
        VECTOR_RESIZE(name, 0)

Revision:	1.4
Committed:	Mon Apr 5 00:45:17 2004 UTC (20 years, 1 month ago) by ats
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+17 -3 lines
Log Message:	Fix the strict-aliasing warnings. This is even uglier than the previous code, since it pushes a test for a sentinel value into the VECTOR_RESIZE macro. I'm pretty certain that the pointer-to-static-used-as-sentinel is my own invention. I'm not entirely convinced that it's a good idea, but I can't see anything technically wrong with it...
#	User	Rev	Content
1	ats	1.1	#include <stdlib.h>
2
3			typedef void (vector_init_function)(void item);
4			typedef void (vector_destroy_function)(void item);
5
6			typedef struct {
7			size_t item_size;
8			int used_count;
9			int alloc_count;
10			int block_size;
11			vector_init_function init_fn;
12			vector_destroy_function destroy_fn;
13			} vector_header;
14
15	ats	1.2	#define VECTOR_HEADER(name, item_type, block_size, init_fn, destroy_fn) \
16	ats	1.1	vector_header name##_header = { \
17			sizeof(item_type), \
18			0, \
19			0, \
20			block_size, \
21			(vector_init_function) init_fn, \
22			(vector_destroy_function) destroy_fn \
23			}
24
25	ats	1.4	/* A pointer value that won't be returned by malloc, and isn't NULL, so can be
26			* used as a sentinel by allocation routines that need to return NULL
27			* sometimes. */
28			extern char statgrab_vector_sentinel_value;
29			static void *statgrab_vector_sentinel = &statgrab_vector_sentinel_value;
30
31			/* Internal function to resize the vector. Ideally it would take void ** as the
32			* first parameter, but ANSI strict-aliasing rules would then prevent it from
33			* doing anything with it, so we return a sentinel value as above instead if
34			* allocation fails. */
35			void statgrab_vector_resize(void vector, vector_header *h, int count);
36	ats	1.2
37			/* Declare a vector. Specify the init/destroy functions as NULL if you don't
38			* need them. The block size is how many items to allocate at once. */
39			#define VECTOR_DECLARE(name, item_type, block_size, init_fn, destroy_fn) \
40			item_type *name = NULL; \
41			VECTOR_HEADER(name, item_type, block_size, init_fn, destroy_fn)
42
43			/* As VECTOR_DECLARE, but for a static vector. */
44			#define VECTOR_DECLARE_STATIC(name, item_type, block_size, init_fn, destroy_fn) \
45			static item_type *name = NULL; \
46			static VECTOR_HEADER(name, item_type, block_size, init_fn, destroy_fn)
47
48	ats	1.1	/* Return the current size of a vector. */
49			#define VECTOR_SIZE(name) \
50			name##_header.used_count
51
52			/* Resize a vector. Returns 0 on success, -1 on out-of-memory. On
53			* out-of-memory, the old contents of the vector will be destroyed and the old
54	ats	1.4	* vector will be freed.
55			*
56			* This is ugly because it needs to check for the sentinel value.
57			*/
58	ats	1.1	#define VECTOR_RESIZE(name, num_items) \
59	ats	1.4	(((name = statgrab_vector_resize((char *) name, &name##_header, num_items)) \
60			== statgrab_vector_sentinel) ? -1 : 0)
61	ats	1.1
62			/* Free a vector, destroying its contents. */
63			#define VECTOR_FREE(name) \
64			VECTOR_RESIZE(name, 0)
65