LIBCDT(3)                  Library Functions Manual                  LIBCDT(3)



NAME
       Cdt - container data types

SYNOPSIS
       #include <cdt.h>

   DICTIONARY TYPES
       Dt_t;
       Dtdisc_t;
       Dtmethod_t;
       Dtlink_t;
       Dtstat_t;

   DICTIONARY CONTROL
       Dt_t*       dtopen(const Dtdisc_t* disc, const Dtmethod_t* meth);
       int         dtclose(Dt_t* dt);
       void        dtclear(dt);
       Dtmethod_t* dtmethod(Dt_t* dt, const Dtmethod_t* meth);
       Dtdisc_t*   dtdisc(Dt_t* dt, const Dtdisc_t* disc);
       Dt_t*       dtview(Dt_t* dt, Dt_t* view);

   STORAGE METHODS
       Dtmethod_t* Dtset;
       Dtmethod_t* Dtoset;
       Dtmethod_t* Dtobag;

   DISCIPLINE
       #define DTDISC(disc,key,size,link,makef,freef,comparf)
       typedef void*      (*Dtmake_f)(void*, Dtdisc_t*);
       typedef void         (*Dtfree_f)(void*, Dtdisc_t*);
       typedef int          (*Dtcompar_f)(Dt_t*, void*, void*, Dtdisc_t*);

   OBJECT OPERATIONS
       void*   dtinsert(Dt_t* dt, void* obj);
       void*   dtdelete(Dt_t* dt, void* obj);
       void*   dtdetach(Dt_t* dt, void* obj);
       void*   dtsearch(Dt_t* dt, void* obj);
       void*   dtmatch(Dt_t* dt, void* key);
       void*   dtfirst(Dt_t* dt);
       void*   dtnext(Dt_t* dt, void* obj);
       void*   dtlast(Dt_t* dt);
       void*   dtprev(Dt_t* dt, void* obj);
       void*   dtfinger(Dt_t* dt);
       void*   dtrenew(Dt_t* dt, void* obj);
       int       dtwalk(Dt_t* dt, int (*userf)(void*, void*), void*);
       Dtlink_t* dtflatten(Dt_t* dt);
       Dtlink_t* dtlink(Dt_t*, Dtlink_t* link);
       void*   dtobj(Dt_t* dt, Dtlink_t* link);
       Dtlink_t* dtextract(Dt_t* dt);
       int       dtrestore(Dt_t* dt, Dtlink_t* link);

   DICTIONARY STATUS
       int       dtsize(Dt_t* dt);
       int       dtstat(Dt_t* dt, Dtstat_t*, int all);

   HASH FUNCTIONS
       unsigned int dtstrhash(void *str, int n);

DESCRIPTION
       Cdt manages run-time dictionaries using standard container data types:
       unordered set/multiset, ordered set/multiset, list, and stack.

   DICTIONARY TYPES
     Dt_t
       This is the type of a dictionary handle.

     Dtdisc_t
       This defines the type of a discipline structure which describes object
       lay-out and manipulation functions.

     Dtmethod_t
       This defines the type of a container method.

     Dtlink_t
       This is the type of a dictionary object holder (see dtdisc().)

     Dtstat_t
       This is the type of a structure to return dictionary statistics (see
       dtstat().)

   DICTIONARY CONTROL
     Dt_t* dtopen(const Dtdisc_t* disc, const Dtmethod_t* meth)
       This creates a new dictionary.  disc is a discipline structure to
       describe object format.  meth specifies a manipulation method.
       dtopen() returns the new dictionary or NULL on error.

     int dtclose(Dt_t* dt)
       This deletes dt and its objects.  Note that dtclose() fails if dt is
       being viewed by some other dictionaries (see dtview()).  dtclose()
       returns 0 on success and -1 on error.

     void dtclear(Dt_t* dt)
       This deletes all objects in dt without closing dt.

     Dtmethod_t dtmethod(Dt_t* dt, const Dtmethod_t* meth)
       If meth is NULL, dtmethod() returns the current method.  Otherwise, it
       changes the storage method of dt to meth.  Switching to and from Dtset
       and Dtoset/Dtobag may cause objects to be rehashed, reordered, or
       removed as the case requires.  dtmethod() returns the previous method
       or NULL on error.

     Dtdisc_t* dtdisc(Dt_t* dt, const Dtdisc_t* disc)
       If disc is NULL, dtdisc() returns the current discipline.  Otherwise,
       it changes the discipline of dt to disc.  Objects may be rehashed,
       reordered, or removed as appropriate.  dtdisc() returns the previous
       discipline on success and NULL on error.

     Dt_t* dtview(Dt_t* dt, Dt_t* view)
       A viewpath allows a search or walk starting from a dictionary to
       continue to another.  dtview() first terminates any current view from
       dt to another dictionary.  Then, if view is NULL, dtview returns the
       terminated view dictionary.  If view is not NULL, a viewpath from dt to
       view is established.  dtview() returns dt on success and NULL on error.

       It is an error to have dictionaries on a viewpath with different
       storage methods.  In addition, dictionaries on the same view path
       should treat objects in a consistent manner with respect to comparison
       or hashing.  If not, undefined behaviors may result.

   STORAGE METHODS
       Storage methods are of type Dtmethod_t*.  Cdt supports the following
       methods:

     Dtoset
     Dtobag
       Objects are ordered by comparisons.  Dtoset keeps unique objects.
       Dtobag allows repeatable objects.

     Dtset
       Objects are unordered.  Dtset keeps unique objects.  This method uses a
       hash table with chaining to manage the objects.

   DISCIPLINE
       Object format and associated management functions are defined in the
       type Dtdisc_t:
           typedef struct
           { int        key, size;
             int        link;
             Dtmake_f   makef;
             Dtfree_f   freef;
             Dtcompar_f comparf;
           } Dtdisc_t;

     int key, size
       Each object obj is identified by a key used for object comparison or
       hashing.  key should be non-negative and defines an offset into obj.
       If size is negative, the key is a null-terminated string with starting
       address *(void**)((char*)obj+key).  If size is zero, the key is a null-
       terminated string with starting address (void*)((char*)obj+key).
       Finally, if size is positive, the key is a byte array of length size
       starting at (void*)((char*)obj+key).

     int link
       Let obj be an object to be inserted into dt as discussed below.  If
       link is negative, an internally allocated object holder is used to hold
       obj. Otherwise, obj should have a Dtlink_t structure embedded link
       bytes into it, i.e., at address (Dtlink_t*)((char*)obj+link).

     void* (*makef)(void* obj, Dtdisc_t* disc)
       If makef is not NULL, dtinsert(dt,obj) will call it to make a copy of
       obj suitable for insertion into dt.  If makef is NULL, obj itself will
       be inserted into dt.

     void (*freef)(void* obj, Dtdisc_t* disc)
       If not NULL, freef is used to destroy data associated with obj.

   int (*comparf)(Dt_t* dt, void* key1, void* key2, Dtdisc_t* disc)
       If not NULL, comparf is used to compare two keys.  Its return value
       should be <0, =0, or >0 to indicate whether key1 is smaller, equal to,
       or larger than key2.  All three values are significant for method
       Dtoset and Dtobag.  For other methods, a zero value indicates equality
       and a non-zero value indicates inequality.  If (*comparf)() is NULL, an
       internal function is used to compare the keys as defined by the
       Dtdisc_t.size field.

   #define DTDISC(disc,key,size,link,makef,freef,comparf)
       This macro function initializes the discipline pointed to by disc with
       the given values.

   OBJECT OPERATIONS
     void* dtinsert(Dt_t* dt, void* obj)
       This function adds an object prototyped by obj into dt.  dtinsert()
       performs the same function for all methods.  If there is an existing
       object in dt matching obj and the storage method is Dtset or Dtoset,
       dtinsert() will simply return the matching object.  Otherwise, a new
       object is inserted according to the method in use.  See Dtdisc_t.makef
       for object construction.  The new object or a matching object as noted
       will be returned on success while NULL is returned on error.

     void* dtdelete(Dt_t* dt, void* obj)
       If obj is not NULL, there are two cases.  If the method in use is not
       Dtobag, the first object matching obj is deleted.  On the other hand,
       if the method in use is or Dtobag, the library check to see if obj is
       in the dictionary and delete it.  If obj is not in the dictionary, some
       object matching it will be deleted.  See Dtdisc_t.freef for object
       destruction.  dtdelete() returns the deleted object (even if it was
       deallocated) or NULL on error.

     void* dtdetach(Dt_t* dt, void* obj)
       This function is similar to dtdelete() but the object to be deleted
       from dt will not be freed (via the discipline freef function).

     void* dtsearch(Dt_t* dt, void* obj)
     void* dtmatch(Dt_t* dt, void* key)
       These functions find an object matching obj or key either from dt or
       from some dictionary accessible from dt via a viewpath (see dtview().)
       dtsearch() and dtmatch() return the matching object or NULL on failure.

     void* dtfirst(Dt_t* dt)
     void* dtnext(Dt_t* dt, void* obj)
       dtfirst() returns the first object in dt.  dtnext() returns the object
       following obj.  Objects are ordered based on the storage method in use.
       For Dtoset and Dtobag, objects are ordered by object comparisons.  For
       Dtset, objects are ordered by some internal order (more below).  Thus,
       objects in a dictionary or a viewpath can be walked using a for(;;)
       loop as below.
           for(obj = dtfirst(dt); obj; obj = dtnext(dt,obj))
       When a dictionary uses Dtset, the object order is determined upon a
       call to dtfirst()/dtlast().  This order is frozen until a call
       dtnext()/dtprev() returns NULL or when these same functions are called
       with a NULL object argument.  It is important that a dtfirst()/dtlast()
       call be balanced by a dtnext()/dtprev() call as described.  Nested
       loops will require multiple balancing, once per loop.  If loop
       balancing is not done carefully, either performance is degraded or
       unexpected behaviors may result.

     void* dtlast(Dt_t* dt)
     void* dtprev(Dt_t* dt, void* obj)
       dtlast() and dtprev() are like dtfirst() and dtnext() but work in
       reverse order.  Note that dictionaries on a viewpath are still walked
       in order but objects in each dictionary are walked in reverse order.

     void* dtfinger(Dt_t* dt)
       This function returns the current object of dt, if any.  The current
       object is defined after a successful call to one of dtsearch(),
       dtmatch(), dtinsert(), dtfirst(), dtnext(), dtlast(), or dtprev().  As
       a side effect of this implementation of Cdt, when a dictionary is based
       on Dtoset and Dtobag, the current object is always defined and is the
       root of the tree.

     void* dtrenew(Dt_t* dt, void* obj)
       This function repositions and perhaps rehashes an object obj after its
       key has been changed.  dtrenew() only works if obj is the current
       object (see dtfinger()).

     dtwalk(Dt_t* dt, int (*userf)(void*, void*), void* data)
       This function calls (*userf)(obj,data) on each object in dt and other
       dictionaries viewable from it.  If userf() returns a <0 value, dtwalk()
       terminates and returns the same value.  dtwalk() returns 0 on
       completion.

     Dtlink_t* dtflatten(Dt_t* dt)
     Dtlink_t* dtlink(Dt_t* dt, Dtlink_t* link)
     void* dtobj(Dt_t* dt, Dtlink_t* link)
       Using dtfirst()/dtnext() or dtlast()/dtprev() to walk a single
       dictionary can incur significant cost due to function calls.  For
       efficient walking of a single directory (i.e., no viewpathing),
       dtflatten() and dtlink() can be used.  Objects in dt are made into a
       linked list and walked as follows:
           for(link = dtflatten(dt); link; link = dtlink(dt,link) )

       Note that dtflatten() returns a list of type Dtlink_t*, not void*. That
       is, it returns a dictionary holder pointer, not a user object pointer
       (although both are the same if the discipline field link is zero.)  The
       macro function dtlink() returns the dictionary holder object following
       link.  The macro function dtobj(dt,link) returns the user object
       associated with link, Beware that the flattened object list is
       unflattened on any dictionary operations other than dtlink().

     Dtlink_t* dtextract(Dt_t* dt)
     int dtrestore(Dt_t* dt, Dtlink_t* link)
       dtextract() extracts all objects from dt and makes it appear empty.
       dtrestore() repopulates dt with objects previously obtained via
       dtextract().  dtrestore() will fail if dt is not empty.  These
       functions can be used to share a same dt handle among many sets of
       objects.  They are useful to reduce dictionary overhead in an
       application that creates many concurrent dictionaries.  It is important
       that the same discipline and method are in use at both extraction and
       restoration. Otherwise, undefined behaviors may result.

   DICTIONARY INFORMATION
     int dtsize(Dt_t* dt)
       This function returns the number of objects stored in dt.

     int dtstat(Dt_t *dt, Dtstat_t* st, int all)
       This function reports dictionary statistics.  If all is non-zero, all
       fields of st are filled.  Otherwise, only the dt_type and dt_size
       fields are filled.  It returns 0 on success and -1 on error.

       Dtstat_t contains the below fields:

       int dt_type:
              This is one of DT_SET, DT_OSET, and DT_OBAG.

       int dt_size:
              This contains the number of objects in the dictionary.

       int dt_n:
              For Dtset, this is the number of non-empty chains in the hash
              table.  For Dtoset and Dtobag, this is the deepest level in the
              tree (counting from zero.)  Each level in the tree contains all
              nodes of equal distance from the root node.  dt_n and the below
              two fields are undefined for other methods.

       int dt_max:
              For Dtset, this is the size of a largest chain.  For Dtoset and
              Dtobag, this is the size of a largest level.

       int* dt_count:
              For Dtset, this is the list of counts for chains of particular
              sizes.  For example, dt_count[1] is the number of chains of size
              1.  For Dtoset and Dtobag, this is the list of sizes of the
              levels.  For example, dt_count[1] is the size of level 1.

   HASH FUNCTIONS
     unsigned int dtstrhash(void *str, int n)
       This function computes hash values from bytes or strings.  dtstrhash()
       computes a new hash value from string str.  If n is positive, str is a
       byte array of length n; otherwise, str is a null-terminated string.

IMPLEMENTATION NOTES
       Dtset are based on hash tables with move-to-front collision chains.
       Dtoset and Dtobag are based on top-down splay trees.

AUTHOR
       Kiem-Phong Vo, kpv@research.att.com



OpenBSD                                                              LIBCDT(3)
