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Cdt- container data types

DICTIONARYTYPESDICTIONARYCONTROLSTORAGEMETHODSDISCIPLINEOBJECTOPERATIONSDICTIONARYSTATUSHASHFUNCTIONS

Cdtmanages run-time dictionaries using standard container data types: unordered set/multiset, ordered set/multiset, list, stack, and queue.DICTIONARYTYPESVoid_t*This type is used to pass objects betweenCdtand application code. is defined as for ANSI-C and C++ and for other compilation environments.Dt_tThis is the type of a dictionary handle.Dtdisc_tThis defines the type of a discipline structure which describes object lay-out and manipulation functions.Dtmethod_tThis defines the type of a container method.Dtlink_tThis is the type of a dictionary object holder (see .)Dtstat_tThis is the type of a structure to return dictionary statistics (see .)DICTIONARYCONTROLDt_t*dtopen(Dtdisc_t*disc,Dtmethod_t*meth)This creates a new dictionary. is a discipline structure to describe object format. specifies a manipulation method. returns the new dictionary or on error.intdtclose(Dt_t*dt)This deletes and its objects. Note that fails if is being viewed by some other dictionaries (see ). returns on success and on error.voiddtclear(Dt_t*dt)This deletes all objects in without closing .Dtmethod_tdtmethod(Dt_t*dt,Dtmethod_t*meth)If is , returns the current method. Otherwise, it changes the storage method of to . Object order remains the same during a method switch among , and . Switching to and from and may cause objects to be rehashed, reordered, or removed as the case requires. returns the previous method or on error.Dtdisc_t*dtdisc(Dt_t*dt,Dtdisc_t*disc,inttype)If is , returns the current discipline. Otherwise, it changes the discipline of to . Objects may be rehashed, reordered, or removed as appropriate. can be any bit combination of and . means that objects will compare exactly the same as before thus obviating the need for reordering or removing new duplicates. means that hash values of objects remain the same thus obviating the need to rehash. returns the previous discipline on success and 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. first terminates any current view from to another dictionary. Then, if is , returns the terminated view dictionary. If is not , a viewpath from to is established. returns on success and on error. If two dictionaries on the same viewpath have the same values for the discipline fields , , , and , it is expected that key hashing will be the same. If not, undefined behaviors may result during a search or a walk.STORAGEMETHODSStorage methods are of type .Cdtsupports the following methods:DtosetDtobagObjects are ordered by comparisons. keeps unique objects. allows repeatable objects.DtsetDtbagObjects are unordered. keeps unique objects. allows repeatable objects and always keeps them together (note the effect on dictionary walking.)DtlistObjects are kept in a list. New objects are inserted either in front ofcurrentobject(see ) if this is defined or at list front if there is no current object.DtstackObjects 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.DtqueueObjects 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.DISCIPLINEObject format and associated management functions are defined in the type :intkey,sizeEach object is identified by a key used for object comparison or hashing. should be non-negative and defines an offset into . If is negative, the key is a null-terminated string with starting address . If is zero, the key is a null-terminated string with starting address . Finally, if is positive, the key is a byte array of length starting at .intlinkLet be an object to be inserted into as discussed below. If is negative, an internally allocated object holder is used to hold . Otherwise, should have a structure embedded bytes into it, i.e., at address .Void_t*(*makef)(Dt_t*dt,Void_t*obj,Dtdisc_t*disc)If is not , will call it to make a copy of suitable for insertion into . If is , itself will be inserted into .void(*freef)(Dt_t*dt,Void_t*obj,Dtdisc_t*disc)If not , is used to destroy data associated with .int(*comparf)(Dt_t*dt,Void_t*key1,Void_t*key2,Dtdisc_t*disc)If not , is used to compare two keys. Its return value should be , , or to indicate whether is smaller, equal to, or larger than . All three values are significant for method and . For other methods, a zero value indicates equality and a non-zero value indicates inequality. If is , an internal function is used to compare the keys as defined by the field.unsignedint(*hashf)(Dt_t*dt,Void_t*key,Dtdisc_t*disc)If not , is used to compute the hash value of . It is required that keys compared equal will also have same hash values. If is , an internal function is used to hash the key as defined by the field.Void_t*(*memoryf)(Dt_t*dt,Void_t*addr,size_tsize,Dtdisc_t*disc)If not , is used to allocate and free memory. When is , a memory segment of size is requested. If is not and is zero, is to be freed. If is not and is positive, is to be resized to the given size. If is ,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,inttype,Void_t*data,Dtdisc_t*disc)If not , 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: : is being opened. If returns zero, the opening process proceeds normally. A positive return value indicates that uses memory already initialized by a different dictionary. In that case, should be set to the first allocated memory segment as discussed in . may fail if this segment is not returned or if it has not been properly initialized. : is being closed. : The discipline of is being changed to a new one given in . : The method of is being changed to a new one given in .OBJECTOPERATIONSVoid_t*dtinsert(Dt_t*dt,Void_t*obj)This inserts an object prototyped by into . If there is an existing object in matching and the storage method is or , will simply return the matching object. Otherwise, a new object is inserted according to the method in use. See for object construction. returns the new object, a matching object as noted, or on error.Void_t*dtdelete(Dt_t*dt,Void_t*obj)If is not , the first object matching it is deleted. If is , methods and delete respectively stack top or queue head while other methods do nothing. See for object destruction. returns the deleted object (even if it was deallocated) or 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 or either from or from some dictionary accessible from via a viewpath (see .) and return the matching object or on failure.Void_t*dtfirst(Dt_t*dt)Void_t*dtnext(Dt_t*dt,Void_t*obj)returns the first object in . returns the object following . Objects are ordered based on the storage method in use. For and , objects are ordered by object comparisons. For , objects are ordered in reverse order of insertion. For , objects are ordered in order of insertion. For , objects are ordered by list position. For and , 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 or . Objects in a dictionary or a viewpath can be walked using a 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.Void_t*dtlast(Dt_t*dt)Void_t*dtprev(Dt_t*dt,Void_t*obj)and are like and 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 thecurrentobjectof , if any. The current object is defined after a successful call to one of , , , , , , or . As a side effect of this implementation ofCdt, when a dictionary is based on and , 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 after its key has been changed. only works if is the current object (see ).dtwalk(Dt_t*dt,int(*userf)(Dt_t*,Void_t*,Void_t*),Void_t*data)This function calls on each object in and other dictionaries viewable from it. is the dictionary containing . If returns a value, terminates and returns the same value. returns 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 or to walk a single dictionary can incur significant cost due to function calls. For efficient walking of a single directory (i.e., no viewpathing), and can be used. Objects in are made into a linked list and walked as follows: Note that returns a list of type , not . That is, it returns a dictionary holder pointer, not a user object pointer (although both are the same if the discipline field is non-negative.) The macro function returns the dictionary holder object following . The macro function returns the user object associated with , Beware that the flattened object list is unflattened on any dictionary operations other than .Dtlink_t*dtextract(Dt_t*dt)intdtrestore(Dt_t*dt,Dtlink_t*link)extracts all objects from and makes it appear empty. repopulates with objects previously obtained via . will fail if is not empty. These functions can be used to share a same 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.DICTIONARYINFORMATIONDt_t*dtvnext(Dt_t*dt)This returns the dictionary that is viewing, if any.intdtvcount(Dt_t*dt)This returns the number of dictionaries that view .Dt_t*dtvhere(Dt_t*dt)This returns the dictionary viewable from where an object was found from the most recent search or walk operation.intdtsize(Dt_t*dt)This function returns the number of objects stored in .intdtstat(Dt_t*dt,Dtstat_t*st,intall)This function reports dictionary statistics. If is non-zero, all fields of are filled. Otherwise, only the and fields are filled. It returns on success and on error. contains the below fields: : This is one of , , , , , , and . : This contains the number of objects in the dictionary. : For and , this is the number of non-empty chains in the hash table. For and , 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. and the below two fields are undefined for other methods. : For and , this is the size of a largest chain. For and , this is the size of a largest level. : For and , this is the list of counts for chains of particular sizes. For example, is the number of chains of size . For and , this is the list of sizes of the levels. For example, is the size of level .HASHFUNCTIONSunsignedintdtcharhash(unsignedinth,charc)unsignedintdtstrhash(unsignedinth,char*str,intn)These functions compute hash values from bytes or strings. computes a new hash value from byte and seed value . computes a new hash value from string and seed value . If is positive, is a byte array of length ; otherwise, is a null-terminated string.

and are based on hash tables with move-to-front collision chains. and are based on top-down splay trees. , and are based on doubly linked list.

Kiem-Phong Vo, kpv@research.att.com LIBCDT(3)