[thirdparty/git.git] / commit-slab.h

#ifndef COMMIT_SLAB_H
#define COMMIT_SLAB_H

/*
 * define_commit_slab(slabname, elemtype) creates boilerplate code to define
 * a new struct (struct slabname) that is used to associate a piece of data
 * of elemtype to commits, and a few functions to use that struct.
 *
 * After including this header file, using:
 *
 * define_commit_slab(indegee, int);
 *
 * will let you call the following functions:
 *
 * - int *indegree_at(struct indegree *, struct commit *);
 *
 *   This function locates the data associated with the given commit in
 *   the indegree slab, and returns the pointer to it.
 *
 * - void init_indegree(struct indegree *);
 *   void init_indegree_with_stride(struct indegree *, int);
 *
 *   Initializes the indegree slab that associates an array of integers
 *   to each commit. 'stride' specifies how big each array is.  The slab
 *   that is initialized by the variant without "_with_stride" associates
 *   each commit with an array of one integer.
 *
 * - void clear_indegree(struct indegree *);
 *
 *   Empties the slab.  The slab can be reused with the same stride
 *   without calling init_indegree() again or can be reconfigured to a
 *   different stride by calling init_indegree_with_stride().
 *
 *   Call this function before the slab falls out of scope to avoid
 *   leaking memory.
 */

/* allocate ~512kB at once, allowing for malloc overhead */
#ifndef COMMIT_SLAB_SIZE
#define COMMIT_SLAB_SIZE (512*1024-32)
#endif

#define MAYBE_UNUSED __attribute__((__unused__))

#define define_commit_slab(slabname, elemtype) 				\
									\
struct slabname {							\
	unsigned slab_size;						\
	unsigned stride;						\
	unsigned slab_count;						\
	elemtype **slab;						\
};									\
static int stat_ ##slabname## realloc;					\
									\
static MAYBE_UNUSED void init_ ##slabname## _with_stride(struct slabname *s, \
						   unsigned stride)	\
{									\
	unsigned int elem_size;						\
	if (!stride)							\
		stride = 1;						\
	s->stride = stride;						\
	elem_size = sizeof(elemtype) * stride;				\
	s->slab_size = COMMIT_SLAB_SIZE / elem_size;			\
	s->slab_count = 0;						\
	s->slab = NULL;							\
}									\
									\
static MAYBE_UNUSED void init_ ##slabname(struct slabname *s)		\
{									\
	init_ ##slabname## _with_stride(s, 1);				\
}									\
									\
static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s)		\
{									\
	int i;								\
	for (i = 0; i < s->slab_count; i++)				\
		free(s->slab[i]);					\
	s->slab_count = 0;						\
	free(s->slab);							\
	s->slab = NULL;							\
}									\
									\
static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s,	\
				       const struct commit *c)		\
{									\
	int nth_slab, nth_slot;						\
									\
	nth_slab = c->index / s->slab_size;				\
	nth_slot = c->index % s->slab_size;				\
									\
	if (s->slab_count <= nth_slab) {				\
		int i;							\
		s->slab = xrealloc(s->slab,				\
				   (nth_slab + 1) * sizeof(*s->slab));	\
		stat_ ##slabname## realloc++;				\
		for (i = s->slab_count; i <= nth_slab; i++)		\
			s->slab[i] = NULL;				\
		s->slab_count = nth_slab + 1;				\
	}								\
	if (!s->slab[nth_slab])						\
		s->slab[nth_slab] = xcalloc(s->slab_size,		\
					    sizeof(**s->slab) * s->stride);		\
	return &s->slab[nth_slab][nth_slot * s->stride];				\
}									\
									\
static int stat_ ##slabname## realloc

/*
 * Note that this seemingly redundant second declaration is required
 * to allow a terminating semicolon, which makes instantiations look
 * like function declarations.  I.e., the expansion of
 *
 *    define_commit_slab(indegree, int);
 *
 * ends in 'static int stat_indegreerealloc;'.  This would otherwise
 * be a syntax error according (at least) to ISO C.  It's hard to
 * catch because GCC silently parses it by default.
 */

/*
 * Statically initialize a commit slab named "var". Note that this
 * evaluates "stride" multiple times! Example:
 *
 *   struct indegree indegrees = COMMIT_SLAB_INIT(1, indegrees);
 *
 */
#define COMMIT_SLAB_INIT(stride, var) { \
	COMMIT_SLAB_SIZE / sizeof(**((var).slab)) / (stride), \
	(stride), 0, NULL \
}

#endif /* COMMIT_SLAB_H */
Commit	Line	Data
a84b794a JH	1	#ifndef COMMIT_SLAB_H
	2	#define COMMIT_SLAB_H
	3
	4	/*
	5	* define_commit_slab(slabname, elemtype) creates boilerplate code to define
	6	* a new struct (struct slabname) that is used to associate a piece of data
	7	* of elemtype to commits, and a few functions to use that struct.
	8	*
	9	* After including this header file, using:
	10	*
	11	* define_commit_slab(indegee, int);
	12	*
	13	* will let you call the following functions:
	14	*
	15	* - int indegree_at(struct indegree , struct commit *);
	16	*
	17	* This function locates the data associated with the given commit in
	18	* the indegree slab, and returns the pointer to it.
	19	*
	20	* - void init_indegree(struct indegree *);
	21	* void init_indegree_with_stride(struct indegree *, int);
	22	*
	23	* Initializes the indegree slab that associates an array of integers
	24	* to each commit. 'stride' specifies how big each array is. The slab
dcbbc8fa	25	* that is initialized by the variant without "_with_stride" associates
a84b794a	26	* each commit with an array of one integer.
dcbbc8fa TR	27	*
	28	* - void clear_indegree(struct indegree *);
	29	*
	30	* Empties the slab. The slab can be reused with the same stride
	31	* without calling init_indegree() again or can be reconfigured to a
	32	* different stride by calling init_indegree_with_stride().
	33	*
	34	* Call this function before the slab falls out of scope to avoid
	35	* leaking memory.
a84b794a JH	36	*/
	37
	38	/* allocate ~512kB at once, allowing for malloc overhead */
	39	#ifndef COMMIT_SLAB_SIZE
	40	#define COMMIT_SLAB_SIZE (512*1024-32)
	41	#endif
	42
e9e03a77 TR	43	#define MAYBE_UNUSED __attribute__((__unused__))
e9e03a77 TR	44
a84b794a JH	45	#define define_commit_slab(slabname, elemtype) \
	46	\
	47	struct slabname { \
	48	unsigned slab_size; \
	49	unsigned stride; \
	50	unsigned slab_count; \
	51	elemtype **slab; \
	52	}; \
	53	static int stat_ ##slabname## realloc; \
	54	\
e9e03a77 TR	55	static MAYBE_UNUSED void init_ ##slabname## _with_stride(struct slabname *s, \
e9e03a77 TR	56	unsigned stride) \
a84b794a JH	57	{ \
	58	unsigned int elem_size; \
	59	if (!stride) \
	60	stride = 1; \
	61	s->stride = stride; \
d7a1d629	62	elem_size = sizeof(elemtype) * stride; \
a84b794a JH	63	s->slab_size = COMMIT_SLAB_SIZE / elem_size; \
	64	s->slab_count = 0; \
	65	s->slab = NULL; \
	66	} \
	67	\
e9e03a77	68	static MAYBE_UNUSED void init_ ##slabname(struct slabname *s) \
a84b794a JH	69	{ \
	70	init_ ##slabname## _with_stride(s, 1); \
	71	} \
	72	\
e9e03a77	73	static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s) \
a84b794a JH	74	{ \
	75	int i; \
	76	for (i = 0; i < s->slab_count; i++) \
	77	free(s->slab[i]); \
	78	s->slab_count = 0; \
	79	free(s->slab); \
	80	s->slab = NULL; \
	81	} \
	82	\
e9e03a77 TR	83	static MAYBE_UNUSED elemtype slabname## _at(struct slabname s, \
e9e03a77 TR	84	const struct commit *c) \
a84b794a	85	{ \
d7a1d629	86	int nth_slab, nth_slot; \
a84b794a	87	\
d7a1d629 RJ	88	nth_slab = c->index / s->slab_size; \
d7a1d629 RJ	89	nth_slot = c->index % s->slab_size; \
a84b794a JH	90	\
	91	if (s->slab_count <= nth_slab) { \
	92	int i; \
	93	s->slab = xrealloc(s->slab, \
cde0a057	94	(nth_slab + 1) * sizeof(*s->slab)); \
a84b794a JH	95	stat_ ##slabname## realloc++; \
	96	for (i = s->slab_count; i <= nth_slab; i++) \
	97	s->slab[i] = NULL; \
	98	s->slab_count = nth_slab + 1; \
	99	} \
	100	if (!s->slab[nth_slab]) \
	101	s->slab[nth_slab] = xcalloc(s->slab_size, \
d7a1d629 RJ	102	sizeof(*s->slab) s->stride); \
d7a1d629 RJ	103	return &s->slab[nth_slab][nth_slot * s->stride]; \
a84b794a JH	104	} \
	105	\
	106	static int stat_ ##slabname## realloc
	107
e9e03a77 TR	108	/*
	109	* Note that this seemingly redundant second declaration is required
	110	* to allow a terminating semicolon, which makes instantiations look
	111	* like function declarations. I.e., the expansion of
	112	*
	113	* define_commit_slab(indegree, int);
	114	*
	115	* ends in 'static int stat_indegreerealloc;'. This would otherwise
	116	* be a syntax error according (at least) to ISO C. It's hard to
	117	* catch because GCC silently parses it by default.
	118	*/
	119
80cdaba5 JK	120	/*
	121	* Statically initialize a commit slab named "var". Note that this
	122	* evaluates "stride" multiple times! Example:
	123	*
	124	* struct indegree indegrees = COMMIT_SLAB_INIT(1, indegrees);
	125	*
	126	*/
	127	#define COMMIT_SLAB_INIT(stride, var) { \
	128	COMMIT_SLAB_SIZE / sizeof(**((var).slab)) / (stride), \
	129	(stride), 0, NULL \
	130	}
	131
a84b794a	132	#endif /* COMMIT_SLAB_H */