


LIBCDT(3)                                               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);



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LIBCDT(3)                                               LIBCDT(3)


       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 compi-
       lation 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.




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LIBCDT(3)                                               LIBCDT(3)


     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.  Switch-
       ing  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 com-
       pare  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  con-
       tinue  to  another.  dtview() first terminates any current view from dt
       to another dictionary.  Then, if view is NULL, dtview returns the  ter-
       minated  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.  Dto-
       bag allows repeatable objects.





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LIBCDT(3)                                               LIBCDT(3)


     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).



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LIBCDT(3)                                               LIBCDT(3)


     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 ini-
              tialized.

       DT_CLOSE:
              dt is being closed.



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LIBCDT(3)                                               LIBCDT(3)


       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 dur-
       ing 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 dic-
       tionary.  Concurrent or nested loops may result  in  unexpected  behav-
       iors.
           for(obj = dtfirst(dt); obj; obj = dtnext(dt,obj))

     Void_t* dtlast(Dt_t* dt)




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LIBCDT(3)                                               LIBCDT(3)


     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 dictio-
       nary 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 dtex-
       tract().  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



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LIBCDT(3)                                               LIBCDT(3)


       are useful to reduce dictionary overhead in an application that creates
       concurrently  many  dictionaries.  It is important that the same disci-
       pline and method are in use at both extraction and restoration.  Other-
       wise, 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.





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LIBCDT(3)                                               LIBCDT(3)


   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







































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