.TH LIBCDT 3
.SH NAME
\fBCdt\fR \- container data types
.SH SYNOPSIS
.de Tp
.fl
.ne 2
.TP
..
.de Ss
.fl
.ne 2
.SS "\\$1"
..
.de Cs
.nf
.ft 5
..
.de Ce
.ft 1
.fi
..
.ta 1.0i 2.0i 3.0i 4.0i 5.0i
.Cs
#include <graphviz/cdt.h>
.Ce
.Ss "DICTIONARY TYPES"
.Cs
Void_t*;
Dt_t;
Dtdisc_t;
Dtmethod_t;
Dtlink_t;
Dtstat_t;
.Ce
.Ss "DICTIONARY CONTROL"
.Cs
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);
.Ce
.Ss "STORAGE METHODS"
.Cs
Dtmethod_t* Dtset;
Dtmethod_t* Dtbag;
Dtmethod_t* Dtoset;
Dtmethod_t* Dtobag;
Dtmethod_t* Dtlist;
Dtmethod_t* Dtstack;
Dtmethod_t* Dtqueue;
.Ce
.Ss "DISCIPLINE"
.Cs
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*);
.Ce
.Ss "OBJECT OPERATIONS"
.Cs
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);
.Ce
.Ss "DICTIONARY STATUS"
.Cs
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);
.Ce
.Ss "HASH FUNCTIONS"
.Cs
unsigned int dtstrhash(unsigned int h, char* str, int n);
unsigned int dtcharhash(unsigned int h, unsigned char c);
.Ce
.SH DESCRIPTION
.PP
\fICdt\fP manages run-time dictionaries using standard container data types:
unordered set/multiset, ordered set/multiset, list, stack, and queue.
.PP
.Ss "DICTIONARY TYPES"
.PP
.Ss "  Void_t*"
This type is used to pass objects between \fICdt\fP and application code.
\f5Void_t\fP is defined as \f5void\fP for ANSI-C and C++
and \f5char\fP for other compilation environments.
.PP
.Ss "  Dt_t"
This is the type of a dictionary handle.
.PP
.Ss "  Dtdisc_t"
This defines the type of a discipline structure which describes
object lay-out and manipulation functions.
.PP
.Ss "  Dtmethod_t"
This defines the type of a container method.
.PP
.Ss "  Dtlink_t"
This is the type of a dictionary object holder (see \f5dtdisc()\fP.)
.PP
.Ss "  Dtstat_t"
This is the type of a structure to return dictionary statistics (see \f5dtstat()\fP.)
.PP
.Ss "DICTIONARY CONTROL"
.PP
.Ss "  Dt_t* dtopen(Dtdisc_t* disc, Dtmethod_t* meth)"
This creates a new dictionary.
\f5disc\fP is a discipline structure to describe object format.
\f5meth\fP specifies a manipulation method.
\f5dtopen()\fP returns the new dictionary or \f5NULL\fP on error.
.PP
.Ss "  int dtclose(Dt_t* dt)"
This deletes \f5dt\fP and its objects.
Note that \f5dtclose()\fP fails if \f5dt\fP is being viewed by
some other dictionaries (see \f5dtview()\fP).
\f5dtclose()\fP returns \f50\fP on success and \f5-1\fP on error.
.PP
.Ss "  void dtclear(Dt_t* dt)"
This deletes all objects in \f5dt\fP without closing \f5dt\fP.
.PP
.Ss "  Dtmethod_t dtmethod(Dt_t* dt, Dtmethod_t* meth)"
If \f5meth\fP is \f5NULL\fP, \f5dtmethod()\fP returns the current method.
Otherwise, it changes the storage method of \f5dt\fP to \f5meth\fP.
Object order remains the same during a
method switch among \f5Dtlist\fP, \f5Dtstack\fP and \f5Dtqueue\fP.
Switching to and from \f5Dtset/Dtbag\fP and \f5Dtoset/Dtobag\fP may cause
objects to be rehashed, reordered, or removed as the case requires.
\f5dtmethod()\fP returns the previous method or \f5NULL\fP on error.
.PP
.Ss "  Dtdisc_t* dtdisc(Dt_t* dt, Dtdisc_t* disc, int type)"
If \f5disc\fP is \f5NULL\fP, \f5dtdisc()\fP returns the current discipline.
Otherwise, it changes the discipline of \f5dt\fP to \f5disc\fP.
Objects may be rehashed, reordered, or removed as appropriate.
\f5type\fP can be any bit combination of \f5DT_SAMECMP\fP and \f5DT_SAMEHASH\fP.
\f5DT_SAMECMP\fP means that objects will compare exactly the same as before
thus obviating the need for reordering or removing new duplicates.
\f5DT_SAMEHASH\fP means that hash values of objects remain the same
thus obviating the need to rehash.
\f5dtdisc()\fP returns the previous discipline on success
and \f5NULL\fP on error.
.PP
.Ss "  Dt_t* dtview(Dt_t* dt, Dt_t* view)"
A viewpath allows a search or walk starting from a dictionary to continue to another.
\f5dtview()\fP first terminates any current view from \f5dt\fP to another dictionary.
Then, if \f5view\fP is \f5NULL\fP, \f5dtview\fP returns the terminated view dictionary.
If \f5view\fP is not \f5NULL\fP, a viewpath from \f5dt\fP to \f5view\fP is established.
\f5dtview()\fP returns \f5dt\fP on success and \f5NULL\fP on error.
.PP
If two dictionaries on the same viewpath have the same values for the discipline fields
\f5Dtdisc_t.link\fP, \f5Dtdisc_t.key\fP, \f5Dtdisc_t.size\fP, and \f5Dtdisc_t.hashf\fP,
it is expected that key hashing will be the same.
If not, undefined behaviors may result during a search or a walk.
.PP
.Ss "STORAGE METHODS"
.PP
Storage methods are of type \f5Dtmethod_t*\fP.
\fICdt\fP supports the following methods:
.PP
.Ss "  Dtoset"
.Ss "  Dtobag"
Objects are ordered by comparisons.
\f5Dtoset\fP keeps unique objects.
\f5Dtobag\fP allows repeatable objects.
.PP
.Ss "  Dtset"
.Ss "  Dtbag"
Objects are unordered.
\f5Dtset\fP keeps unique objects.
\f5Dtbag\fP allows repeatable objects and always keeps them together
(note the effect on dictionary walking.)
.PP
.Ss "  Dtlist"
Objects are kept in a list.
New objects are inserted either
in front of \fIcurrent object\fP (see \f5dtfinger()\fP) if this is defined
or at list front if there is no current object.
.PP
.Ss "  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.
.PP
.Ss "  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.
.PP
.Ss "DISCIPLINE"
.PP
Object format and associated management functions are
defined in the type \f5Dtdisc_t\fP:
.Cs
    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;
.Ce
.Ss "  int key, size"
Each object \f5obj\fP is identified by a key used for object comparison or hashing.
\f5key\fP should be non-negative and defines an offset into \f5obj\fP.
If \f5size\fP is negative, the key is a null-terminated
string with starting address \f5*(Void_t**)((char*)obj+key)\fP.
If \f5size\fP is zero, the key is a null-terminated string with starting address
\f5(Void_t*)((char*)obj+key)\fP.
Finally, if \f5size\fP is positive, the key is a byte array of length \f5size\fP
starting at \f5(Void_t*)((char*)obj+key)\fP.
.PP
.Ss "  int link"
Let \f5obj\fP be an object to be inserted into \f5dt\fP as discussed below.
If \f5link\fP is negative, an internally allocated object holder is used
to hold \f5obj\fP. Otherwise, \f5obj\fP should have
a \f5Dtlink_t\fP structure embedded \f5link\fP bytes into it,
i.e., at address \f5(Dtlink_t*)((char*)obj+link)\fP.
.PP
.Ss "  Void_t* (*makef)(Dt_t* dt, Void_t* obj, Dtdisc_t* disc)"
If \f5makef\fP is not \f5NULL\fP,
\f5dtinsert(dt,obj)\fP will call it
to make a copy of \f5obj\fP suitable for insertion into \f5dt\fP.
If \f5makef\fP is \f5NULL\fP, \f5obj\fP itself will be inserted into \f5dt\fP.
.PP
.Ss "  void (*freef)(Dt_t* dt, Void_t* obj, Dtdisc_t* disc)"
If not \f5NULL\fP,
\f5freef\fP is used to destroy data associated with \f5obj\fP.
.PP
.Ss "int (*comparf)(Dt_t* dt, Void_t* key1, Void_t* key2, Dtdisc_t* disc)"
If not \f5NULL\fP, \f5comparf\fP is used to compare two keys.
Its return value should be \f5<0\fP, \f5=0\fP, or \f5>0\fP to indicate
whether \f5key1\fP is smaller, equal to, or larger than \f5key2\fP.
All three values are significant for method \f5Dtoset\fP and \f5Dtobag\fP.
For other methods, a zero value
indicates equality and a non-zero value indicates inequality.
If \f5(*comparf)()\fP is \f5NULL\fP, an internal function is used
to compare the keys as defined by the \f5Dtdisc_t.size\fP field.
.PP
.Ss "  unsigned int (*hashf)(Dt_t* dt, Void_t* key, Dtdisc_t* disc)"
If not \f5NULL\fP,
\f5hashf\fP is used to compute the hash value of \f5key\fP.
It is required that keys compared equal will also have same hash values.
If \f5hashf\fP is \f5NULL\fP, an internal function is used to hash
the key as defined by the \f5Dtdisc_t.size\fP field.
.PP
.Ss "  Void_t* (*memoryf)(Dt_t* dt, Void_t* addr, size_t size, Dtdisc_t* disc)"
If not \f5NULL\fP, \f5memoryf\fP is used to allocate and free memory.
When \f5addr\fP is \f5NULL\fP, a memory segment of size \f5size\fP is requested. 
If \f5addr\fP is not \f5NULL\fP and \f5size\fP is zero, \f5addr\fP is to be freed.
If \f5addr\fP is not \f5NULL\fP and \f5size\fP is positive,
\f5addr\fP is to be resized to the given size.
If \f5memoryf\fP is \f5NULL\fP, \fImalloc(3)\fP 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.)
.PP
.Ss "  int (*eventf)(Dt_t* dt, int type, Void_t* data, Dtdisc_t* disc)"
If not \f5NULL\fP, \f5eventf\fP 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:
.Tp
\f5DT_OPEN\fP:
\f5dt\fP is being opened.
If \f5eventf\fP returns zero, the opening process proceeds normally.
A positive return value indicates that \f5dt\fP
uses memory already initialized by a different dictionary.
In that case, \f5*(Void_t**)data\fP should be set to
the first allocated memory segment as discussed in \f5memoryf\fP.
\f5dtopen()\fP may fail if this segment is not returned or
if it has not been properly initialized.
.Tp
\f5DT_CLOSE\fP:
\f5dt\fP is being closed.
.Tp
\f5DT_DISC\fP:
The discipline of \f5dt\fP is being changed to a new one given in
\f5(Dtdisc_t*)data\fP.
.Tp
\f5DT_METH\fP:
The method of \f5dt\fP is being changed to a new one given in
\f5(Dtmethod_t*)data\fP.
.PP
.Ss "OBJECT OPERATIONS"
.PP
.Ss "  Void_t* dtinsert(Dt_t* dt, Void_t* obj)"
This inserts an object prototyped by \f5obj\fP into \f5dt\fP.
If there is an existing object in \f5dt\fP matching \f5obj\fP
and the storage method is \f5Dtset\fP or \f5Dtoset\fP,
\f5dtinsert()\fP will simply return the matching object.
Otherwise, a new object is inserted according to the method in use.
See \f5Dtdisc_t.makef\fP for object construction.
\f5dtinsert()\fP returns the new object, a matching object as noted,
or \f5NULL\fP on error.
.PP
.Ss "  Void_t* dtdelete(Dt_t* dt, Void_t* obj)"
If \f5obj\fP is not \f5NULL\fP, the first object matching it is deleted.
If \f5obj\fP is \f5NULL\fP, methods \f5Dtstack\fP and \f5Dtqueue\fP
delete respectively stack top or queue head while other methods do nothing.
See \f5Dtdisc_t.freef\fP for object destruction.
\f5dtdelete()\fP returns the deleted object (even if it was deallocated)
or \f5NULL\fP on error.
.PP
.Ss "  Void_t* dtsearch(Dt_t* dt, Void_t* obj)"
.Ss "  Void_t* dtmatch(Dt_t* dt, Void_t* key)"
These functions find an object matching \f5obj\fP or \f5key\fP either from \f5dt\fP or
from some dictionary accessible from \f5dt\fP via a viewpath (see \f5dtview()\fP.)
\f5dtsearch()\fP and \f5dtmatch()\fP return the matching object or
\f5NULL\fP on failure.
.PP
.Ss "  Void_t* dtfirst(Dt_t* dt)"
.Ss "  Void_t* dtnext(Dt_t* dt, Void_t* obj)"
\f5dtfirst()\fP returns the first object in \f5dt\fP.
\f5dtnext()\fP returns the object following \f5obj\fP.
Objects are ordered based on the storage method in use.
For \f5Dtoset\fP and \f5Dtobag\fP, objects are ordered by object comparisons.
For \f5Dtstack\fP, objects are ordered in reverse order of insertion.
For \f5Dtqueue\fP, objects are ordered in order of insertion.
For \f5Dtlist\fP, objects are ordered by list position.
For \f5Dtset\fP and \f5Dtbag\fP,
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 \f5Dtset\fP or \f5Dtbag\fP.
.PP
Objects in a dictionary or a viewpath can be walked using 
a \f5for(;;)\fP 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.
.Cs
    for(obj = dtfirst(dt); obj; obj = dtnext(dt,obj))
.Ce
.Ss "  Void_t* dtlast(Dt_t* dt)"
.Ss "  Void_t* dtprev(Dt_t* dt, Void_t* obj)"
\f5dtlast()\fP and \f5dtprev()\fP are like \f5dtfirst()\fP and \f5dtnext()\fP
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.
.PP
.Ss "  Void_t* dtfinger(Dt_t* dt)"
This function returns the \fIcurrent object\fP of \f5dt\fP, if any.
The current object is defined after a successful call to one of
\f5dtsearch()\fP, \f5dtmatch()\fP, \f5dtinsert()\fP,
\f5dtfirst()\fP, \f5dtnext()\fP, \f5dtlast()\fP, or \f5dtprev()\fP.
As a side effect of this implementation of \fICdt\fP,
when a dictionary is based on \f5Dtoset\fP and \f5Dtobag\fP,
the current object is always defined and is the root of the tree.
.PP
.Ss "  Void_t* dtrenew(Dt_t* dt, Void_t* obj)"
This function repositions and perhaps rehashes
an object \f5obj\fP after its key has been changed.
\f5dtrenew()\fP only works if \f5obj\fP is the current object (see \f5dtfinger()\fP).
.PP
.Ss "  dtwalk(Dt_t* dt, int (*userf)(Dt_t*, Void_t*, Void_t*), Void_t* data)"
This function calls \f5(*userf)(walk,obj,data)\fP on each object in \f5dt\fP and
other dictionaries viewable from it.
\f5walk\fP is the dictionary containing \f5obj\fP.
If \f5userf()\fP returns a \f5<0\fP value,
\f5dtwalk()\fP terminates and returns the same value.
\f5dtwalk()\fP returns \f50\fP on completion.
.PP
.Ss "  Dtlink_t* dtflatten(Dt_t* dt)"
.Ss "  Dtlink_t* dtlink(Dt_t* dt, Dtlink_t* link)"
.Ss "  Void_t* dtobj(Dt_t* dt, Dtlink_t* link)"
Using \f5dtfirst()/dtnext()\fP or \f5dtlast()/dtprev()\fP
to walk a single dictionary can incur significant cost due to function calls.
For efficient walking of a single directory (i.e., no viewpathing),
\f5dtflatten()\fP and \f5dtlink()\fP can be used.
Objects in \f5dt\fP are made into a linked list and walked as follows:
.Cs
    for(link = dtflatten(dt); link; link = dtlink(dt,link) )
.Ce
.PP
Note that \f5dtflatten()\fP returns a list of type \f5Dtlink_t*\fP,
not \f5Void_t*\fP. That is, it returns a dictionary holder pointer,
not a user object pointer
(although both are the same if the discipline field \f5link\fP is non-negative.)
The macro function \f5dtlink()\fP
returns the dictionary holder object following \f5link\fP.
The macro function \f5dtobj(dt,link)\fP
returns the user object associated with \f5link\fP,
Beware that the flattened object list is unflattened on any
dictionary operations other than \f5dtlink()\fP.
.PP
.Ss "  Dtlink_t* dtextract(Dt_t* dt)"
.Ss "  int dtrestore(Dt_t* dt, Dtlink_t* link)"
\f5dtextract()\fP extracts all objects from \f5dt\fP and makes it appear empty.
\f5dtrestore()\fP repopulates \f5dt\fP with
objects previously obtained via \f5dtextract()\fP.
\f5dtrestore()\fP will fail if \f5dt\fP is not empty.
These functions can be used
to share a same \f5dt\fP 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.
.PP
.Ss "DICTIONARY INFORMATION"
.PP
.Ss "  Dt_t* dtvnext(Dt_t* dt)"
This returns the dictionary that \f5dt\fP is viewing, if any.
.Ss "  int dtvcount(Dt_t* dt)"
This returns the number of dictionaries that view \f5dt\fP.
.Ss "  Dt_t* dtvhere(Dt_t* dt)"
This returns the dictionary \f5v\fP viewable from \f5dt\fP
where an object was found from the most recent search or walk operation.
.Ss "  int dtsize(Dt_t* dt)"
This function returns the number of objects stored in \f5dt\fP.
.PP
.Ss "  int dtstat(Dt_t *dt, Dtstat_t* st, int all)"
This function reports dictionary statistics.
If \f5all\fP is non-zero, all fields of \f5st\fP are filled.
Otherwise, only the \f5dt_type\fP and \f5dt_size\fP fields are filled.
It returns \f50\fP on success and \f5-1\fP on error.
.PP
\f5Dtstat_t\fP contains the below fields:
.Tp
\f5int dt_type\fP:
This is one of \f5DT_SET\fP, \f5DT_BAG\fP, \f5DT_OSET\fP, \f5DT_OBAG\fP,
\f5DT_LIST\fP, \f5DT_STACK\fP, and \f5DT_QUEUE\fP.
.Tp
\f5int dt_size\fP:
This contains the number of objects in the dictionary.
.Tp
\f5int dt_n\fP:
For \f5Dtset\fP and \f5Dtbag\fP,
this is the number of non-empty chains in the hash table.
For \f5Dtoset\fP and \f5Dtobag\fP,
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.
\f5dt_n\fP and the below two fields are undefined for other methods.
.Tp
\f5int dt_max\fP:
For \f5Dtbag\fP and \f5Dtset\fP, this is the size of a largest chain.
For \f5Dtoset\fP and \f5Dtobag\fP, this is the size of a largest level.
.Tp
\f5int* dt_count\fP:
For \f5Dtset\fP and \f5Dtbag\fP,
this is the list of counts for chains of particular sizes.
For example, \f5dt_count[1]\fP is the number of chains of size \f51\fP.
For \f5Dtoset\fP and \f5Dtobag\fP, this is the list of sizes of the levels.
For example, \f5dt_count[1]\fP is the size of level \f51\fP.
.PP
.Ss "HASH FUNCTIONS"
.PP
.Ss "  unsigned int dtcharhash(unsigned int h, char c)"
.Ss "  unsigned int dtstrhash(unsigned int h, char* str, int n)"
These functions compute hash values from bytes or strings.
\f5dtcharhash()\fP computes a new hash value from byte \f5c\fP and seed value \f5h\fP.
\f5dtstrhash()\fP computes a new hash value from string \f5str\fP and seed value \f5h\fP.
If \f5n\fP is positive, \f5str\fP is a byte array of length \f5n\fP;
otherwise, \f5str\fP is a null-terminated string.
.PP
.SH IMPLEMENTATION NOTES
\f5Dtset\fP and \f5Dtbag\fP are based on hash tables with
move-to-front collision chains.
\f5Dtoset\fP and \f5Dtobag\fP are based on top-down splay trees.
\f5Dtlist\fP, \f5Dtstack\fP and \f5Dtqueue\fP are based on doubly linked list.
.PP
.SH AUTHOR
Kiem-Phong Vo, kpv@research.att.com