object-refs.c

   1 #include "cache.h"
   2 #include "object.h"
   3
   4 int track_object_refs = 0;
   5
   6 static unsigned int refs_hash_size, nr_object_refs;
   7 static struct object_refs **refs_hash;
   8
   9 static unsigned int hash_obj(struct object *obj, unsigned int n)
  10 {
  11         unsigned int hash = *(unsigned int *)obj->sha1;
  12         return hash % n;
  13 }
  14
  15 static void insert_ref_hash(struct object_refs *ref, struct object_refs **hash, unsigned int size)
  16 {
  17         int j = hash_obj(ref->base, size);
  18
  19         while (hash[j]) {
  20                 j++;
  21                 if (j >= size)
  22                         j = 0;
  23         }
  24         hash[j] = ref;
  25 }
  26
  27 static void grow_refs_hash(void)
  28 {
  29         int i;
  30         int new_hash_size = (refs_hash_size + 1000) * 3 / 2;
  31         struct object_refs **new_hash;
  32
  33         new_hash = xcalloc(new_hash_size, sizeof(struct object_refs *));
  34         for (i = 0; i < refs_hash_size; i++) {
  35                 struct object_refs *ref = refs_hash[i];
  36                 if (!ref)
  37                         continue;
  38                 insert_ref_hash(ref, new_hash, new_hash_size);
  39         }
  40         free(refs_hash);
  41         refs_hash = new_hash;
  42         refs_hash_size = new_hash_size;
  43 }
  44
  45 static void add_object_refs(struct object *obj, struct object_refs *ref)
  46 {
  47         int nr = nr_object_refs + 1;
  48
  49         if (nr > refs_hash_size * 2 / 3)
  50                 grow_refs_hash();
  51         ref->base = obj;
  52         insert_ref_hash(ref, refs_hash, refs_hash_size);
  53         nr_object_refs = nr;
  54 }
  55
  56 struct object_refs *lookup_object_refs(struct object *obj)
  57 {
  58         struct object_refs *ref;
  59         int j;
  60
  61         /* nothing to lookup */
  62         if (!refs_hash_size)
  63                 return NULL;
  64         j = hash_obj(obj, refs_hash_size);
  65         while ((ref = refs_hash[j]) != NULL) {
  66                 if (ref->base == obj)
  67                         break;
  68                 j++;
  69                 if (j >= refs_hash_size)
  70                         j = 0;
  71         }
  72         return ref;
  73 }
  74
  75 struct object_refs *alloc_object_refs(unsigned count)
  76 {
  77         struct object_refs *refs;
  78         size_t size = sizeof(*refs) + count*sizeof(struct object *);
  79
  80         refs = xcalloc(1, size);
  81         refs->count = count;
  82         return refs;
  83 }
  84
  85 static int compare_object_pointers(const void *a, const void *b)
  86 {
  87         const struct object * const *pa = a;
  88         const struct object * const *pb = b;
  89         if (*pa == *pb)
  90                 return 0;
  91         else if (*pa < *pb)
  92                 return -1;
  93         else
  94                 return 1;
  95 }
  96
  97 void set_object_refs(struct object *obj, struct object_refs *refs)
  98 {
  99         unsigned int i, j;
 100
 101         /* Do not install empty list of references */
 102         if (refs->count < 1) {
 103                 free(refs);
 104                 return;
 105         }
 106
 107         /* Sort the list and filter out duplicates */
 108         qsort(refs->ref, refs->count, sizeof(refs->ref[0]),
 109               compare_object_pointers);
 110         for (i = j = 1; i < refs->count; i++) {
 111                 if (refs->ref[i] != refs->ref[i - 1])
 112                         refs->ref[j++] = refs->ref[i];
 113         }
 114         if (j < refs->count) {
 115                 /* Duplicates were found - reallocate list */
 116                 size_t size = sizeof(*refs) + j*sizeof(struct object *);
 117                 refs->count = j;
 118                 refs = xrealloc(refs, size);
 119         }
 120
 121         for (i = 0; i < refs->count; i++)
 122                 refs->ref[i]->used = 1;
 123         add_object_refs(obj, refs);
 124 }
 125
 126 void mark_reachable(struct object *obj, unsigned int mask)
 127 {
 128         const struct object_refs *refs;
 129
 130         if (!track_object_refs)
 131                 die("cannot do reachability with object refs turned off");
 132         /* If we've been here already, don't bother */
 133         if (obj->flags & mask)
 134                 return;
 135         obj->flags |= mask;
 136         refs = lookup_object_refs(obj);
 137         if (refs) {
 138                 unsigned i;
 139                 for (i = 0; i < refs->count; i++)
 140                         mark_reachable(refs->ref[i], mask);
 141         }
 142 }
 143
 144