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Diffstat (limited to 'commit-slab.h')
| -rw-r--r-- | commit-slab.h | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/commit-slab.h b/commit-slab.h new file mode 100644 index 0000000000..f37ec3831f --- /dev/null +++ b/commit-slab.h @@ -0,0 +1,131 @@ +#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; \ + REALLOC_ARRAY(s->slab, nth_slab + 1); \ + 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 */ |