LIBCDT(3)                  Library Functions Manual                  LIBCDT(3)



NAME
       Cdt - container data types

SYNOPSIS
       #include <cdt.h>

   DICTIONARY TYPES
       Void_t*;
       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, int type);
       Dt_t*       dtview(Dt_t* dt, Dt_t* view);
       int         dttreeset(Dt_t* dt, int minp, int balance);

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

   DISCIPLINE
       #define DTOFFSET(struct_s,member)
       #define DTDISC(disc,key,size,link,makef,freef,comparf,hashf,memoryf,eventf)
       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*   dtappend(Dt_t* dt, Void_t* obj);
       Void_t*   dtdelete(Dt_t* dt, Void_t* obj);
       Void_t*   dtattach(Dt_t* dt, Void_t* obj);
       Void_t*   dtdetach(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);

       #define   DTTREESEARCH(Dt_t* dt, Void_t* obj, action)
       #define   DTTREEMATCH(Dt_t* dt, Void_t* key, action)

   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(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.  See also the
       events DT_OPEN and DT_ENDOPEN below.

     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.  See also the events DT_CLOSE and
       DT_ENDCLOSE below.

     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.  Object order remains the
       same during a method switch among Dtlist, Dtstack, Dtqueue and Dtdeque.
       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, const 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.

       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.

     int dttreeset(Dt_t* dt, int minp, int balance)
       This function only applies to dictionaries operated under the method
       Dtoset which uses top-down splay trees (see below). It returns 0 on
       success and -1 on error.

       minp:  This parameter defines the minimum path length before a search
              path is adjusted.  For example, minp equal 0 would mean that
              search paths are always adjusted.  If minp is negative, the
              minimum search path is internally computed based on a function
              of the current dictionary size. This computed value is such that
              if the tree is balanced, it will never require adjusting.

       balance:
              If this is non-zero, the tree will be made balanced.

   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.)  These methods use a hash table with chaining to
       manage the objects.  See also the event DT_HASHSIZE below on how to
       manage hash table resizing when objects are inserted.

     Dtlist
       Objects are kept in a list.  The call dtinsert() inserts a new object
       in front of the current object (see dtfinger()) if it is defined or at
       list front if no current object is defined.  Similarly, the call
       dtappend() appends a new object after the current object (see
       dtfinger()) if it is defined or at list end if no current object is
       defined.

     Dtdeque
       Objects are kept in a deque. This is similar to Dtlist except that
       objects are always inserted at the front and appended at the tail of
       the list.

     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) or dtappend() 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.

     int (*eventf)(Dt_t* dt, int type, Void_t* data, Dtdisc_t* disc)
       If not NULL, eventf announces various events.  Each event may have
       particular handling of the return values from eventf.  But a negative
       return value typically means failure.  Following are the events:

       DT_OPEN:
              dt is being opened.  If eventf returns negative, the opening
              process terminates with failure.  If eventf returns zero, the
              opening process proceeds in a default manner.  A positive return
              value indicates special treatment of memory as follows.  If
              *(Void_t**)data is set to point to some memory segment as
              discussed in memoryf, that segment of memory is used to start
              the dictionary. If *(Void_t**)data is NULL, all memory including
              that of the dictionary handle itself will be allocated via
              memoryf.

       DT_ENDOPEN:
              This event announces that dtopen() has successfully opened a
              dictionary and is about to return. The data argument of eventf
              should be the new dictionary handle itself.

       DT_CLOSE:
              dt is about to be closed. If eventf returns negative, the
              closing process stops immediately and dtclose() returns -1.
              Objects in the dictionary are deleted only if eventf returns
              zero.  The dictionary handle itself is processed as follows.  If
              it was allocated via malloc(), it will be freed.  If it was
              allocated via memoryf (see dtopen()) and eventf returns 0, a
              call to memoryf will be issued to attempt freeing the handle.
              Otherwise, nothing will be done to its memory.

              As should be clear from their description, the events DT_OPEN
              and DT_CLOSE are designed to be used along with memoryf to
              manage the allocation and deallocation of dictionary and object
              memory across dictionaries. In fact, they can be used to manage
              dictionaries based on shared and/or persistent memory.

       DT_ENDCLOSE:
              This event announces that dtclose() has successfully closed a
              dictionary and is about to return.

       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.

       DT_HASHSIZE:
              The hash table (for Dtset and Dtbag) is being resized.  In this
              case, *(int*)data has the current size of the table.  The
              application can set the new table size by first changing
              *(int*)data to the desired size, then return a positive value.
              The application can also fix the table size at the current value
              forever by setting *(int*)data to a negative value, then again
              return a positive value. A non-positive return value from the
              event handling function means that Cdt will be responsible for
              choosing the hash table size.

   #define DTOFFSET(struct_s,member)
       This macro function computes the offset of member from the start of
       structure struct_s. It is useful for getting the offset of a Dtlink_t
       embedded inside an object.

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

   OBJECT OPERATIONS
     Void_t* dtinsert(Dt_t* dt, Void_t* obj)
     Void_t* dtappend(Dt_t* dt, Void_t* obj)
       These functions add an object prototyped by obj into dt.  dtinsert()
       and dtappend() perform the same function for all methods except for
       Dtlist. See Dtlist for details.  If there is an existing object in dt
       matching obj and the storage method is Dtset or Dtoset, dtinsert() and
       dtappend() 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_t* dtdelete(Dt_t* dt, Void_t* obj)
       If obj is NULL, methods Dtstack and Dtqueue delete respectively stack
       top or queue head while other methods do nothing.  If obj is not NULL,
       there are two cases.  If the method in use is not Dtbag or Dtobag, the
       first object matching obj is deleted.  On the other hand, if the method
       in use is Dtbag 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_t* dtattach(Dt_t* dt, Void_t* obj)
       This function is similar to dtinsert() but obj itself will be inserted
       into dt even if a discipline function makef is defined.

     Void_t* dtdetach(Dt_t* dt, Void_t* 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_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 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 or Dtbag, 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_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
       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.

     #define   DTTREESEARCH(Dt_t* dt, Void_t* obj, action)
     #define   DTTREEMATCH(Dt_t* dt, Void_t* key, action)
       These macro functions are analogues of dtsearch() and dtmatch() but
       they can only be used on a dictionary based on a binary search tree,
       i.e., Dtoset or Dtobag.

       obj or key:
              These are used to find a matching object. If there is no match,
              the result is NULL.

       action:
              The matching object o (which may be NULL) will be processed as
              follow:

                  action (o);

              Since action is used verbatim, it can be any C code fragment
              combinable with (o) to form a syntactically correct C statement.
              For example, suppose that the matching object is an integer, the
              below code accumulates the integer value in a variable total:

                  DTTREEMATCH(dt, key, total += (int));


   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)
