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(libext2fs.info)Inode count functions

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Inode count functions
---------------------

   The icount abstraction is a specialized data type used by `e2fsck'
to store how many times a particular inode is referenced by the
filesystem.  This is used twice; once to store the actual number of
times that the inode is reference; and once to store the claimed number
of times the inode is referenced according to the inode structure.

   This abstraction is designed to be extremely efficient for storing
this sort of information, by taking advantage of the following
properties of inode counts, namely (1) inode counts are very often zero
(because the inode is currrently not in use), and (2) many files have a
inode count of 1 (because they are a file which has no additional hard
links).

 - Function: errcode_t ext2fs_create_icount2 (ext2_filsys FS, int
          FLAGS, int SIZE, ext2_icount_t HINT, ext2_icount_t *RET)
     Creates an icount stucture for a filesystem FS, with initial space
     for SIZE inodes whose count is greater than 1.  The FLAGS
     parameter is either 0 or `EXT2_ICOUNT_OPT_INCREMENT', which
     indicates that icount structure should be able to increment inode
     counts quickly.  The icount structure is returned in RET.  The
     returned icount structure initially has a count of zero for all
     inodes.

     The HINT parameter allows the caller to optionally pass in another
     icount structure which is used to initialize the array of inodes
     whose count is greater than 1.  It is used purely as a speed
     optimization so that the icount structure can determine in advance
     which inodes are likely to contain a count grater than 1.

 - Function: void ext2fs_free_icount (ext2_icount_t ICOUNT)
     Frees an icount structure.

 - Function: errcode_t ext2fs_icount_fetch (ext2_icount_t ICOUNT,
          ext2_ino_t INO, __u16 *RET)
     Returns in RET fetches the count for a particular inode INO.

 - Function: errcode_t ext2fs_icount_increment (ext2_icount_t ICOUNT,
          ext2_ino_t INO, __u16 *RET)
     Increments the ref count for inode INO.

 - Function: errcode_t ext2fs_icount_decrement (ext2_icount_t ICOUNT,
          ext2_ino_t INO, __u16 *RET)
     Decrements the ref count for inode INO.

 - Function: errcode_t ext2fs_icount_store (ext2_icount_t ICOUNT,
          ext2_ino_t INO, __u16 COUNT)
     Sets the reference count for inode INO to be COUNT.

 - Function: ext2_ino_t ext2fs_get_icount_size (ext2_icount_t ICOUNT)
     Returns the current number of inodes in ICOUNT which has a count
     greater than 1.

 - Function: errcode_t ext2fs_icount_validate (ext2_icount_t ICOUNT,
          FILE *F)
     Validates the internal rep invariant of ICOUNT; if there are any
     problems, print out debugging information to F.  This function is
     intended for debugging and testing use only.