mdw@git.distorted.org.uk Git - sgt/agedu/blob - index.h

   1 /*
   2  * index.h: Manage indexes for agedu.
   3  */
   4
   5 #include <sys/types.h>
   6
   7 /*
   8  * Given the size of an existing data file and the number of
   9  * entries required in the index, return the file size required to
  10  * store the fixed initial fragment of the index before the
  11  * indexbuild functions are invoked.
  12  */
  13 off_t index_initial_size(off_t currentsize, int nodecount);
  14
  15 /*
  16  * Build an index, given the address of a memory-mapped data file
  17  * and the starting offset within it.
  18  *
  19  * trie_file structures passed to tf must of course be within the
  20  * bounds of the memory-mapped file.
  21  *
  22  * The "delta" parameter to indexbuild_new is filled in with the
  23  * maximum size by which the index can ever grow in a single
  24  * indexbuild_add call. This can be used, together with
  25  * indexbuild_realsize, to detect when the index is about to get
  26  * too big for its file and the file needs resizing.
  27  *
  28  * indexbuild_add adds a trie_file structure to the index.
  29  * indexbuild_tag, called after that, causes the current state of
  30  * the index to be preserved so that it can be queried later. It's
  31  * idempotent, and will safely do nothing if called before
  32  * indexbuild_add.
  33  *
  34  * indexbuild_realsize returns the total amount of data _actually_
  35  * written into the file, to allow it to be truncated afterwards,
  36  * and to allow the caller of the indexbuild functions to know
  37  * when the file is about to need to grow bigger during index
  38  * building.
  39  *
  40  * indexbuild_rebase is used when the file has been
  41  * re-memory-mapped at a different address (because it needs to
  42  * grow).
  43  */
  44 typedef struct indexbuild indexbuild;
  45 indexbuild *indexbuild_new(void *t, off_t startoff, int nodecount,
  46                            size_t *delta);
  47 void indexbuild_add(indexbuild *ib, const struct trie_file *tf);
  48 void indexbuild_tag(indexbuild *ib);
  49 void indexbuild_rebase(indexbuild *ib, void *t);
  50 off_t indexbuild_realsize(indexbuild *ib);
  51 void indexbuild_free(indexbuild *ib);
  52
  53 /*
  54  * Check to see if a name index has an index tree root available
  55  * (i.e. represents a directory rather than a file).
  56  */
  57 int index_has_root(const void *t, int n);
  58
  59 /*
  60  * Query an index to find the total size of records with name
  61  * index strictly less than n, with atime less than at.
  62  */
  63 unsigned long long index_query(const void *t, int n, unsigned long long at);
  64
  65 /*
  66  * Retrieve an order statistic from the index: given a fraction f,
  67  * return an atime such that (at most) the requested fraction of
  68  * the total data is older than it.
  69  */
  70 unsigned long long index_order_stat(const void *t, double f);