LIBCDT(3)                 OpenBSD Programmer's Manual                LIBCDT(3)



NAME
       Cdt - container data types

SYNOPSIS
       #include <graphviz/cdt.h>

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

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

   STORAGE METHODS
       Dtmethod_t* Dtset;
       Dtmethod_t* Dtbag;
       Dtmethod_t* Dtoset;
       Dtmethod_t* Dtobag;
       Dtmethod_t* Dtlist;
       Dtmethod_t* Dtstack;
       Dtmethod_t* Dtqueue;

   DISCIPLINE
       typedef Void_t*      (*Dtmake_f)(Dt_t*, Void_t*, Dtdisc_t*);
       typedef void         (*Dtfree_f)(Dt_t*, Void_t*, Dtdisc_t*);
       typedef int          (*Dtcompar_f)(Dt_t*, Void_t*, Void_t*, Dtdisc_t*);
       typedef unsigned int (*Dthash_f)(Dt_t*, Void_t*, Dtdisc_t*);
       typedef Void_t*      (*Dtmemory_f)(Dt_t*, Void_t*, size_t, Dtdisc_t*);
       typedef int          (*Dtevent_f)(Dt_t*, int, Void_t*, Dtdisc_t*);

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

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

   HASH FUNCTIONS
       unsigned int dtstrhash(unsigned int h, char* str, int n);
       unsigned int dtcharhash(unsigned int h, unsigned char c);

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

   DICTIONARY TYPES
     Void_t*
       This type is used to pass objects between Cdt and application code.
       Void_t is defined as void for ANSI-C and C++ and char for other
       compilation environments.

     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(Dtdisc_t* disc, 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, Dtmethod_t* meth)
       If meth is NULL, dtmethod() returns the current method.  Otherwise, it
       changes the storage method of dt to meth.  Object order remains the
       same during a method switch among Dtlist, Dtstack and Dtqueue.
       Switching to and from Dtset/Dtbag 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, Dtdisc_t* disc, int type)
       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.  type can be any bit combination
       of DT_SAMECMP and DT_SAMEHASH.  DT_SAMECMP means that objects will
       compare exactly the same as before thus obviating the need for
       reordering or removing new duplicates.  DT_SAMEHASH means that hash
       values of objects remain the same thus obviating the need to rehash.
       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.

       If two dictionaries on the same viewpath have the same values for the
       discipline fields Dtdisc_t.link, Dtdisc_t.key, Dtdisc_t.size, and
       Dtdisc_t.hashf, it is expected that key hashing will be the same.  If
       not, undefined behaviors may result during a search or a walk.

   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
     Dtbag
       Objects are unordered.  Dtset keeps unique objects.  Dtbag allows
       repeatable objects and always keeps them together (note the effect on
       dictionary walking.)

     Dtlist
       Objects are kept in a list.  New objects are inserted either in front
       of current object (see dtfinger()) if this is defined or at list front
       if there is no current object.

     Dtstack
       Objects are kept in a stack, i.e., in reverse order of insertion.
       Thus, the last object inserted is at stack top and will be the first to
       be deleted.

     Dtqueue
       Objects are kept in a queue, i.e., in order of insertion.  Thus, the
       first object inserted is at queue head and will be the first to be
       deleted.

   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;
             Dthash_f   hashf;
             Dtmemory_f memoryf;
             Dtevent_f  eventf;
           } 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_t**)((char*)obj+key).  If size is zero, the key is a
       null-terminated string with starting address (Void_t*)((char*)obj+key).
       Finally, if size is positive, the key is a byte array of length size
       starting at (Void_t*)((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_t* (*makef)(Dt_t* dt, Void_t* 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)(Dt_t* dt, Void_t* obj, Dtdisc_t* disc)
       If not NULL, freef is used to destroy data associated with obj.

   int (*comparf)(Dt_t* dt, Void_t* key1, Void_t* 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.

     unsigned int (*hashf)(Dt_t* dt, Void_t* key, Dtdisc_t* disc)
       If not NULL, hashf is used to compute the hash value of key.  It is
       required that keys compared equal will also have same hash values.  If
       hashf is NULL, an internal function is used to hash the key as defined
       by the Dtdisc_t.size field.

     Void_t* (*memoryf)(Dt_t* dt, Void_t* addr, size_t size, Dtdisc_t* disc)
       If not NULL, memoryf is used to allocate and free memory.  When addr is
       NULL, a memory segment of size size is requested.  If addr is not NULL
       and size is zero, addr is to be freed.  If addr is not NULL and size is
       positive, addr is to be resized to the given size.  If memoryf is NULL,
       malloc(3) is used.  When dictionaries share memory, a record of the
       first allocated memory segment should be kept so that it can be used to
       initialize new dictionaries (see below.)

     int (*eventf)(Dt_t* dt, int type, Void_t* data, Dtdisc_t* disc)
       If not NULL, eventf announces various events.  If it returns a negative
       value, the calling operation will terminate with failure.  Unless noted
       otherwise, a non-negative return value let the calling function proceed
       normally. Following are the events:

       DT_OPEN:
              dt is being opened.  If eventf returns zero, the opening process
              proceeds normally.  A positive return value indicates that dt
              uses memory already initialized by a different dictionary.  In
              that case, *(Void_t**)data should be set to the first allocated
              memory segment as discussed in memoryf.  dtopen() may fail if
              this segment is not returned or if it has not been properly
              initialized.

       DT_CLOSE:
              dt is being closed.

       DT_DISC:
              The discipline of dt is being changed to a new one given in
              (Dtdisc_t*)data.

       DT_METH:
              The method of dt is being changed to a new one given in
              (Dtmethod_t*)data.

   OBJECT OPERATIONS
     Void_t* dtinsert(Dt_t* dt, Void_t* obj)
       This inserts an object prototyped by obj into dt.  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.  dtinsert() returns the new
       object, a matching object as noted, or NULL on error.

     Void_t* dtdelete(Dt_t* dt, Void_t* obj)
       If obj is not NULL, the first object matching it is deleted.  If obj is
       NULL, methods Dtstack and Dtqueue delete respectively stack top or
       queue head while other methods do nothing.  See Dtdisc_t.freef for
       object destruction.  dtdelete() returns the deleted object (even if it
       was deallocated) or NULL on error.

     Void_t* dtsearch(Dt_t* dt, Void_t* obj)
     Void_t* dtmatch(Dt_t* dt, Void_t* 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_t* dtfirst(Dt_t* dt)
     Void_t* dtnext(Dt_t* dt, Void_t* 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
       Dtstack, objects are ordered in reverse order of insertion.  For
       Dtqueue, objects are ordered in order of insertion.  For Dtlist,
       objects are ordered by list position.  For Dtset and Dtbag, objects use
       some internal ordering which may change on any search, insert, or
       delete operations.  Therefore, these operations should not be used
       during a walk on a dictionary using either Dtset or Dtbag.

       Objects in a dictionary or a viewpath can be walked using a for(;;)
       loop as below.  Note that only one loop can be used at a time per
       dictionary.  Concurrent or nested loops may result in unexpected
       behaviors.
           for(obj = dtfirst(dt); obj; obj = dtnext(dt,obj))

     Void_t* dtlast(Dt_t* dt)
     Void_t* dtprev(Dt_t* dt, Void_t* 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_t* 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_t* dtrenew(Dt_t* dt, Void_t* 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)(Dt_t*, Void_t*, Void_t*), Void_t* data)
       This function calls (*userf)(walk,obj,data) on each object in dt and
       other dictionaries viewable from it.  walk is the dictionary containing
       obj.  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_t* 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_t*.
       That is, it returns a dictionary holder pointer, not a user object
       pointer (although both are the same if the discipline field link is
       non-negative.)  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 concurrently many 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
     Dt_t* dtvnext(Dt_t* dt)
       This returns the dictionary that dt is viewing, if any.

     int dtvcount(Dt_t* dt)
       This returns the number of dictionaries that view dt.

     Dt_t* dtvhere(Dt_t* dt)
       This returns the dictionary v viewable from dt where an object was
       found from the most recent search or walk operation.

     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_BAG, DT_OSET, DT_OBAG, DT_LIST,
              DT_STACK, and DT_QUEUE.

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

       int dt_n:
              For Dtset and Dtbag, 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 Dtbag and 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 and Dtbag, 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 dtcharhash(unsigned int h, char c)
     unsigned int dtstrhash(unsigned int h, char* str, int n)
       These functions compute hash values from bytes or strings.
       dtcharhash() computes a new hash value from byte c and seed value h.
       dtstrhash() computes a new hash value from string str and seed value h.
       If n is positive, str is a byte array of length n; otherwise, str is a
       null-terminated string.

IMPLEMENTATION NOTES
       Dtset and Dtbag are based on hash tables with move-to-front collision
       chains.  Dtoset and Dtobag are based on top-down splay trees.  Dtlist,
       Dtstack and Dtqueue are based on doubly linked list.

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



                                                                     LIBCDT(3)
