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);
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.
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.
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 ini‐
tialized.
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 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)
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
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.
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)
