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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
  25  *   that id initialied by the variant without "_with_stride" associates
  26  *   each commit with an array of one integer.
  27  */
  28
  29 /* allocate ~512kB at once, allowing for malloc overhead */
  30 #ifndef COMMIT_SLAB_SIZE
  31 #define COMMIT_SLAB_SIZE (512*1024-32)
  32 #endif
  33
  34 #define define_commit_slab(slabname, elemtype)                          \
  35                                                                         \
  36 struct slabname {                                                       \
  37         unsigned slab_size;                                             \
  38         unsigned stride;                                                \
  39         unsigned slab_count;                                            \
  40         elemtype **slab;                                                \
  41 };                                                                      \
  42 static int stat_ ##slabname## realloc;                                  \
  43                                                                         \
  44 static void init_ ##slabname## _with_stride(struct slabname *s,         \
  45                                             unsigned stride)            \
  46 {                                                                       \
  47         unsigned int elem_size;                                         \
  48         if (!stride)                                                    \
  49                 stride = 1;                                             \
  50         s->stride = stride;                                             \
  51         elem_size = sizeof(struct slabname) * stride;                   \
  52         s->slab_size = COMMIT_SLAB_SIZE / elem_size;                    \
  53         s->slab_count = 0;                                              \
  54         s->slab = NULL;                                                 \
  55 }                                                                       \
  56                                                                         \
  57 static void init_ ##slabname(struct slabname *s)                        \
  58 {                                                                       \
  59         init_ ##slabname## _with_stride(s, 1);                          \
  60 }                                                                       \
  61                                                                         \
  62 static void clear_ ##slabname(struct slabname *s)                       \
  63 {                                                                       \
  64         int i;                                                          \
  65         for (i = 0; i < s->slab_count; i++)                             \
  66                 free(s->slab[i]);                                       \
  67         s->slab_count = 0;                                              \
  68         free(s->slab);                                                  \
  69         s->slab = NULL;                                                 \
  70 }                                                                       \
  71                                                                         \
  72 static elemtype *slabname## _at(struct slabname *s,                     \
  73                                 const struct commit *c)                 \
  74 {                                                                       \
  75         int nth_slab, nth_slot, ix;                                     \
  76                                                                         \
  77         ix = c->index * s->stride;                                      \
  78         nth_slab = ix / s->slab_size;                                   \
  79         nth_slot = ix % s->slab_size;                                   \
  80                                                                         \
  81         if (s->slab_count <= nth_slab) {                                \
  82                 int i;                                                  \
  83                 s->slab = xrealloc(s->slab,                             \
  84                                    (nth_slab + 1) * sizeof(s->slab));   \
  85                 stat_ ##slabname## realloc++;                           \
  86                 for (i = s->slab_count; i <= nth_slab; i++)             \
  87                         s->slab[i] = NULL;                              \
  88                 s->slab_count = nth_slab + 1;                           \
  89         }                                                               \
  90         if (!s->slab[nth_slab])                                         \
  91                 s->slab[nth_slab] = xcalloc(s->slab_size,               \
  92                                             sizeof(**s->slab));         \
  93         return &s->slab[nth_slab][nth_slot];                            \
  94 }                                                                       \
  95                                                                         \
  96 static int stat_ ##slabname## realloc
  97
  98 #endif /* COMMIT_SLAB_H */