commit-slab: document clear_$slabname()
[git/git.git] / commit-slab.h
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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.
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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.
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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
43#define define_commit_slab(slabname, elemtype) \
44 \
45struct slabname { \
46 unsigned slab_size; \
47 unsigned stride; \
48 unsigned slab_count; \
49 elemtype **slab; \
50}; \
51static int stat_ ##slabname## realloc; \
52 \
53static void init_ ##slabname## _with_stride(struct slabname *s, \
54 unsigned stride) \
55{ \
56 unsigned int elem_size; \
57 if (!stride) \
58 stride = 1; \
59 s->stride = stride; \
d7a1d629 60 elem_size = sizeof(elemtype) * stride; \
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61 s->slab_size = COMMIT_SLAB_SIZE / elem_size; \
62 s->slab_count = 0; \
63 s->slab = NULL; \
64} \
65 \
66static void init_ ##slabname(struct slabname *s) \
67{ \
68 init_ ##slabname## _with_stride(s, 1); \
69} \
70 \
71static void clear_ ##slabname(struct slabname *s) \
72{ \
73 int i; \
74 for (i = 0; i < s->slab_count; i++) \
75 free(s->slab[i]); \
76 s->slab_count = 0; \
77 free(s->slab); \
78 s->slab = NULL; \
79} \
80 \
81static elemtype *slabname## _at(struct slabname *s, \
82 const struct commit *c) \
83{ \
d7a1d629 84 int nth_slab, nth_slot; \
a84b794a 85 \
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86 nth_slab = c->index / s->slab_size; \
87 nth_slot = c->index % s->slab_size; \
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88 \
89 if (s->slab_count <= nth_slab) { \
90 int i; \
91 s->slab = xrealloc(s->slab, \
92 (nth_slab + 1) * sizeof(s->slab)); \
93 stat_ ##slabname## realloc++; \
94 for (i = s->slab_count; i <= nth_slab; i++) \
95 s->slab[i] = NULL; \
96 s->slab_count = nth_slab + 1; \
97 } \
98 if (!s->slab[nth_slab]) \
99 s->slab[nth_slab] = xcalloc(s->slab_size, \
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100 sizeof(**s->slab) * s->stride); \
101 return &s->slab[nth_slab][nth_slot * s->stride]; \
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102} \
103 \
104static int stat_ ##slabname## realloc
105
106#endif /* COMMIT_SLAB_H */