minix/lib/libvtreefs/extra.c

   1 /* VTreeFS - extra.c - per-inode storage of arbitrary extra data */
   2
   3 #include "inc.h"
   4
   5 /*
   6  * Right now, we maintain the extra data (if requested) as a separate buffer,
   7  * so that we don't have to make the inode structure variable in size.  Later,
   8  * if for example the maximum node name length becomes a runtime setting, we
   9  * could reconsider this.
  10  */
  11 static char *extra_ptr = NULL;
  12 static size_t extra_size = 0; /* per inode */
  13
  14 /*
  15  * Initialize memory to store extra data.
  16  */
  17 int
  18 init_extra(unsigned int nr_inodes, size_t inode_extra)
  19 {
  20
  21         if (inode_extra == 0)
  22                 return OK;
  23
  24         if ((extra_ptr = calloc(nr_inodes, inode_extra)) == NULL)
  25                 return ENOMEM;
  26
  27         extra_size = inode_extra;
  28
  29         return OK;
  30 }
  31
  32 /*
  33  * Initialize the extra data for the given inode to zero.
  34  */
  35 void
  36 clear_inode_extra(struct inode * node)
  37 {
  38
  39         if (extra_size == 0)
  40                 return;
  41
  42         memset(&extra_ptr[node->i_num * extra_size], 0, extra_size);
  43 }
  44
  45 /*
  46  * Retrieve a pointer to the extra data for the given inode.
  47  */
  48 void *
  49 get_inode_extra(const struct inode * node)
  50 {
  51
  52         if (extra_size == 0)
  53                 return NULL;
  54
  55         return (void *)&extra_ptr[node->i_num * extra_size];
  56 }