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(indegree, 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. The location to
19 * store the data is allocated as necessary.
20 *
21 * - int *indegree_peek(struct indegree *, struct commit *);
22 *
23 * This function is similar to indegree_at(), but it will return NULL
24 * until a call to indegree_at() was made for the commit.
25 *
26 * - void init_indegree(struct indegree *);
27 * void init_indegree_with_stride(struct indegree *, int);
28 *
29 * Initializes the indegree slab that associates an array of integers
30 * to each commit. 'stride' specifies how big each array is. The slab
31 * that is initialized by the variant without "_with_stride" associates
32 * each commit with an array of one integer.
33 *
34 * - void clear_indegree(struct indegree *);
35 *
36 * Empties the slab. The slab can be reused with the same stride
37 * without calling init_indegree() again or can be reconfigured to a
38 * different stride by calling init_indegree_with_stride().
39 *
40 * Call this function before the slab falls out of scope to avoid
41 * leaking memory.
42 */
43/* allocate ~512kB at once, allowing for malloc overhead */
45#ifndef COMMIT_SLAB_SIZE
46#define COMMIT_SLAB_SIZE (512*1024-32)
47#endif
48#define MAYBE_UNUSED __attribute__((__unused__))
50#define define_commit_slab(slabname, elemtype) \
52 \
53struct slabname { \
54 unsigned slab_size; \
55 unsigned stride; \
56 unsigned slab_count; \
57 elemtype **slab; \
58}; \
59static int stat_ ##slabname## realloc; \
60 \
61static MAYBE_UNUSED void init_ ##slabname## _with_stride(struct slabname *s, \
62 unsigned stride) \
63{ \
64 unsigned int elem_size; \
65 if (!stride) \
66 stride = 1; \
67 s->stride = stride; \
68 elem_size = sizeof(elemtype) * stride; \
69 s->slab_size = COMMIT_SLAB_SIZE / elem_size; \
70 s->slab_count = 0; \
71 s->slab = NULL; \
72} \
73 \
74static MAYBE_UNUSED void init_ ##slabname(struct slabname *s) \
75{ \
76 init_ ##slabname## _with_stride(s, 1); \
77} \
78 \
79static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s) \
80{ \
81 int i; \
82 for (i = 0; i < s->slab_count; i++) \
83 free(s->slab[i]); \
84 s->slab_count = 0; \
85 free(s->slab); \
86 s->slab = NULL; \
87} \
88 \
89static MAYBE_UNUSED elemtype *slabname## _at_peek(struct slabname *s, \
90 const struct commit *c, \
91 int add_if_missing) \
92{ \
93 int nth_slab, nth_slot; \
94 \
95 nth_slab = c->index / s->slab_size; \
96 nth_slot = c->index % s->slab_size; \
97 \
98 if (s->slab_count <= nth_slab) { \
99 int i; \
100 if (!add_if_missing) \
101 return NULL; \
102 REALLOC_ARRAY(s->slab, nth_slab + 1); \
103 stat_ ##slabname## realloc++; \
104 for (i = s->slab_count; i <= nth_slab; i++) \
105 s->slab[i] = NULL; \
106 s->slab_count = nth_slab + 1; \
107 } \
108 if (!s->slab[nth_slab]) { \
109 if (!add_if_missing) \
110 return NULL; \
111 s->slab[nth_slab] = xcalloc(s->slab_size, \
112 sizeof(**s->slab) * s->stride); \
113 } \
114 return &s->slab[nth_slab][nth_slot * s->stride]; \
115} \
116 \
117static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
118 const struct commit *c) \
119{ \
120 return slabname##_at_peek(s, c, 1); \
121} \
122 \
123static MAYBE_UNUSED elemtype *slabname## _peek(struct slabname *s, \
124 const struct commit *c) \
125{ \
126 return slabname##_at_peek(s, c, 0); \
127} \
128 \
129struct slabname
130/*
132 * Note that this redundant forward declaration is required
133 * to allow a terminating semicolon, which makes instantiations look
134 * like function declarations. I.e., the expansion of
135 *
136 * define_commit_slab(indegree, int);
137 *
138 * ends in 'struct indegree;'. This would otherwise
139 * be a syntax error according (at least) to ISO C. It's hard to
140 * catch because GCC silently parses it by default.
141 */
142/*
144 * Statically initialize a commit slab named "var". Note that this
145 * evaluates "stride" multiple times! Example:
146 *
147 * struct indegree indegrees = COMMIT_SLAB_INIT(1, indegrees);
148 *
149 */
150#define COMMIT_SLAB_INIT(stride, var) { \
151 COMMIT_SLAB_SIZE / sizeof(**((var).slab)) / (stride), \
152 (stride), 0, NULL \
153}
154#endif /* COMMIT_SLAB_H */