alloc.c

   1 /*
   2  * alloc.c  - specialized allocator for internal objects
   3  *
   4  * Copyright (C) 2006 Linus Torvalds
   5  *
   6  * The standard malloc/free wastes too much space for objects, partly because
   7  * it maintains all the allocation infrastructure, but even more because it ends
   8  * up with maximal alignment because it doesn't know what the object alignment
   9  * for the new allocation is.
  10  */
  11 #include "cache.h"
  12 #include "object.h"
  13 #include "blob.h"
  14 #include "tree.h"
  15 #include "commit.h"
  16 #include "tag.h"
  17 #include "alloc.h"
  18
  19 #define BLOCKING 1024
  20
  21 union any_object {
  22         struct object object;
  23         struct blob blob;
  24         struct tree tree;
  25         struct commit commit;
  26         struct tag tag;
  27 };
  28
  29 struct alloc_state {
  30         int nr;    /* number of nodes left in current allocation */
  31         void *p;   /* first free node in current allocation */
  32
  33         /* bookkeeping of allocations */
  34         void **slabs;
  35         int slab_nr, slab_alloc;
  36 };
  37
  38 struct alloc_state *allocate_alloc_state(void)
  39 {
  40         return xcalloc(1, sizeof(struct alloc_state));
  41 }
  42
  43 void clear_alloc_state(struct alloc_state *s)
  44 {
  45         while (s->slab_nr > 0) {
  46                 s->slab_nr--;
  47                 free(s->slabs[s->slab_nr]);
  48         }
  49
  50         FREE_AND_NULL(s->slabs);
  51 }
  52
  53 static inline void *alloc_node(struct alloc_state *s, size_t node_size)
  54 {
  55         void *ret;
  56
  57         if (!s->nr) {
  58                 s->nr = BLOCKING;
  59                 s->p = xmalloc(BLOCKING * node_size);
  60
  61                 ALLOC_GROW(s->slabs, s->slab_nr + 1, s->slab_alloc);
  62                 s->slabs[s->slab_nr++] = s->p;
  63         }
  64         s->nr--;
  65         ret = s->p;
  66         s->p = (char *)s->p + node_size;
  67         memset(ret, 0, node_size);
  68
  69         return ret;
  70 }
  71
  72 void *alloc_blob_node(struct repository *r)
  73 {
  74         struct blob *b = alloc_node(r->parsed_objects->blob_state, sizeof(struct blob));
  75         b->object.type = OBJ_BLOB;
  76         return b;
  77 }
  78
  79 void *alloc_tree_node(struct repository *r)
  80 {
  81         struct tree *t = alloc_node(r->parsed_objects->tree_state, sizeof(struct tree));
  82         t->object.type = OBJ_TREE;
  83         return t;
  84 }
  85
  86 void *alloc_tag_node(struct repository *r)
  87 {
  88         struct tag *t = alloc_node(r->parsed_objects->tag_state, sizeof(struct tag));
  89         t->object.type = OBJ_TAG;
  90         return t;
  91 }
  92
  93 void *alloc_object_node(struct repository *r)
  94 {
  95         struct object *obj = alloc_node(r->parsed_objects->object_state, sizeof(union any_object));
  96         obj->type = OBJ_NONE;
  97         return obj;
  98 }
  99
 100 /*
 101  * The returned count is to be used as an index into commit slabs,
 102  * that are *NOT* maintained per repository, and that is why a single
 103  * global counter is used.
 104  */
 105 static unsigned int alloc_commit_index(void)
 106 {
 107         static unsigned int parsed_commits_count;
 108         return parsed_commits_count++;
 109 }
 110
 111 void init_commit_node(struct commit *c)
 112 {
 113         c->object.type = OBJ_COMMIT;
 114         c->index = alloc_commit_index();
 115 }
 116
 117 void *alloc_commit_node(struct repository *r)
 118 {
 119         struct commit *c = alloc_node(r->parsed_objects->commit_state, sizeof(struct commit));
 120         init_commit_node(c);
 121         return c;
 122 }