commit-slab.h

   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 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
  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                                                                         \
  45 struct slabname {                                                       \
  46         unsigned slab_size;                                             \
  47         unsigned stride;                                                \
  48         unsigned slab_count;                                            \
  49         elemtype **slab;                                                \
  50 };                                                                      \
  51 static int stat_ ##slabname## realloc;                                  \
  52                                                                         \
  53 static 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;                                             \
  60         elem_size = sizeof(elemtype) * stride;                          \
  61         s->slab_size = COMMIT_SLAB_SIZE / elem_size;                    \
  62         s->slab_count = 0;                                              \
  63         s->slab = NULL;                                                 \
  64 }                                                                       \
  65                                                                         \
  66 static void init_ ##slabname(struct slabname *s)                        \
  67 {                                                                       \
  68         init_ ##slabname## _with_stride(s, 1);                          \
  69 }                                                                       \
  70                                                                         \
  71 static 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                                                                         \
  81 static elemtype *slabname## _at(struct slabname *s,                     \
  82                                 const struct commit *c)                 \
  83 {                                                                       \
  84         int nth_slab, nth_slot;                                         \
  85                                                                         \
  86         nth_slab = c->index / s->slab_size;                             \
  87         nth_slot = c->index % s->slab_size;                             \
  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,               \
 100                                             sizeof(**s->slab) * s->stride);             \
 101         return &s->slab[nth_slab][nth_slot * s->stride];                                \
 102 }                                                                       \
 103                                                                         \
 104 static int stat_ ##slabname## realloc
 105
 106 #endif /* COMMIT_SLAB_H */