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 "git-compat-util.h"
  12 #include "object.h"
  13 #include "blob.h"
  14 #include "tree.h"
  15 #include "commit.h"
  16 #include "repository.h"
  17 #include "tag.h"
  18 #include "alloc.h"
  19
  20 #define BLOCKING 1024
  21
  22 union any_object {
  23         struct object object;
  24         struct blob blob;
  25         struct tree tree;
  26         struct commit commit;
  27         struct tag tag;
  28 };
  29
  30 struct alloc_state {
  31         int nr;    /* number of nodes left in current allocation */
  32         void *p;   /* first free node in current allocation */
  33
  34         /* bookkeeping of allocations */
  35         void **slabs;
  36         int slab_nr, slab_alloc;
  37 };
  38
  39 struct alloc_state *allocate_alloc_state(void)
  40 {
  41         return xcalloc(1, sizeof(struct alloc_state));
  42 }
  43
  44 void clear_alloc_state(struct alloc_state *s)
  45 {
  46         while (s->slab_nr > 0) {
  47                 s->slab_nr--;
  48                 free(s->slabs[s->slab_nr]);
  49         }
  50
  51         FREE_AND_NULL(s->slabs);
  52 }
  53
  54 static inline void *alloc_node(struct alloc_state *s, size_t node_size)
  55 {
  56         void *ret;
  57
  58         if (!s->nr) {
  59                 s->nr = BLOCKING;
  60                 s->p = xmalloc(BLOCKING * node_size);
  61
  62                 ALLOC_GROW(s->slabs, s->slab_nr + 1, s->slab_alloc);
  63                 s->slabs[s->slab_nr++] = s->p;
  64         }
  65         s->nr--;
  66         ret = s->p;
  67         s->p = (char *)s->p + node_size;
  68         memset(ret, 0, node_size);
  69
  70         return ret;
  71 }
  72
  73 void *alloc_blob_node(struct repository *r)
  74 {
  75         struct blob *b = alloc_node(r->parsed_objects->blob_state, sizeof(struct blob));
  76         b->object.type = OBJ_BLOB;
  77         return b;
  78 }
  79
  80 void *alloc_tree_node(struct repository *r)
  81 {
  82         struct tree *t = alloc_node(r->parsed_objects->tree_state, sizeof(struct tree));
  83         t->object.type = OBJ_TREE;
  84         return t;
  85 }
  86
  87 void *alloc_tag_node(struct repository *r)
  88 {
  89         struct tag *t = alloc_node(r->parsed_objects->tag_state, sizeof(struct tag));
  90         t->object.type = OBJ_TAG;
  91         return t;
  92 }
  93
  94 void *alloc_object_node(struct repository *r)
  95 {
  96         struct object *obj = alloc_node(r->parsed_objects->object_state, sizeof(union any_object));
  97         obj->type = OBJ_NONE;
  98         return obj;
  99 }
 100
 101 /*
 102  * The returned count is to be used as an index into commit slabs,
 103  * that are *NOT* maintained per repository, and that is why a single
 104  * global counter is used.
 105  */
 106 static unsigned int alloc_commit_index(void)
 107 {
 108         static unsigned int parsed_commits_count;
 109         return parsed_commits_count++;
 110 }
 111
 112 void init_commit_node(struct commit *c)
 113 {
 114         c->object.type = OBJ_COMMIT;
 115         c->index = alloc_commit_index();
 116 }
 117
 118 void *alloc_commit_node(struct repository *r)
 119 {
 120         struct commit *c = alloc_node(r->parsed_objects->commit_state, sizeof(struct commit));
 121         init_commit_node(c);
 122         return c;
 123 }