1#ifndef COMMIT_SLAB_H
2#define COMMIT_SLAB_H
3/*
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
25 * that is initialized by the variant without "_with_stride" associates
26 * each commit with an array of one integer.
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.
36 */
37/* allocate ~512kB at once, allowing for malloc overhead */
39#ifndef COMMIT_SLAB_SIZE
40#define COMMIT_SLAB_SIZE (512*1024-32)
41#endif
42#define MAYBE_UNUSED __attribute__((__unused__))
44#define define_commit_slab(slabname, elemtype) \
46 \
47struct slabname { \
48 unsigned slab_size; \
49 unsigned stride; \
50 unsigned slab_count; \
51 elemtype **slab; \
52}; \
53static int stat_ ##slabname## realloc; \
54 \
55static MAYBE_UNUSED void init_ ##slabname## _with_stride(struct slabname *s, \
56 unsigned stride) \
57{ \
58 unsigned int elem_size; \
59 if (!stride) \
60 stride = 1; \
61 s->stride = stride; \
62 elem_size = sizeof(elemtype) * stride; \
63 s->slab_size = COMMIT_SLAB_SIZE / elem_size; \
64 s->slab_count = 0; \
65 s->slab = NULL; \
66} \
67 \
68static MAYBE_UNUSED void init_ ##slabname(struct slabname *s) \
69{ \
70 init_ ##slabname## _with_stride(s, 1); \
71} \
72 \
73static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s) \
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 \
83static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
84 const struct commit *c) \
85{ \
86 int nth_slab, nth_slot; \
87 \
88 nth_slab = c->index / s->slab_size; \
89 nth_slot = c->index % s->slab_size; \
90 \
91 if (s->slab_count <= nth_slab) { \
92 int i; \
93 REALLOC_ARRAY(s->slab, nth_slab + 1); \
94 stat_ ##slabname## realloc++; \
95 for (i = s->slab_count; i <= nth_slab; i++) \
96 s->slab[i] = NULL; \
97 s->slab_count = nth_slab + 1; \
98 } \
99 if (!s->slab[nth_slab]) \
100 s->slab[nth_slab] = xcalloc(s->slab_size, \
101 sizeof(**s->slab) * s->stride); \
102 return &s->slab[nth_slab][nth_slot * s->stride]; \
103} \
104 \
105static int stat_ ##slabname## realloc
106/*
108 * Note that this seemingly redundant second declaration is required
109 * to allow a terminating semicolon, which makes instantiations look
110 * like function declarations. I.e., the expansion of
111 *
112 * define_commit_slab(indegree, int);
113 *
114 * ends in 'static int stat_indegreerealloc;'. This would otherwise
115 * be a syntax error according (at least) to ISO C. It's hard to
116 * catch because GCC silently parses it by default.
117 */
118/*
120 * Statically initialize a commit slab named "var". Note that this
121 * evaluates "stride" multiple times! Example:
122 *
123 * struct indegree indegrees = COMMIT_SLAB_INIT(1, indegrees);
124 *
125 */
126#define COMMIT_SLAB_INIT(stride, var) { \
127 COMMIT_SLAB_SIZE / sizeof(**((var).slab)) / (stride), \
128 (stride), 0, NULL \
129}
130#endif /* COMMIT_SLAB_H */