dx-doc 1:4.4.4-9 / usr / share / doc / dx / help / dxall1121

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#!N 
#!CNavyBlue #!N  #!Rhash Hashing 
#!N #!EC #!N #!N This section describes a set of routines 
for storing an arbitrary number of elements with a fixed access 
time. This implementation is designed for general-purpose use in many applications. 
Copies of the elements are stored in a hash table. #!N 
#!N The elements may be of any fixed size, set at 
the time that the hash table is created. Each element contains 
a key identifying the element, along with whatever data you choose 
to associate with that key. For example, a key might be 
an x, y, z point, with an associated data value for 
that point. #!N #!N Elements are stored in the table using 
long integer pseudokeys. These pseudokeys should be uniformly distributed in any 
range beginning at zero. #!N Note: Pseudokey 0xFFFFFFFF is reserved. Items 
cannot not be placed in the hash table using this pseudokey 
value. #!N #!N #!N The elements themselves may contain the pseudokey 
as their first long integer word. Alternatively, the pseudokey may be 
derived from the element through a call-back function provided at the 
time the hash table is created. #!N #!N More than one 
element may be stored under the same pseudokey if a compare 
function is provided at the time the hash table was created. 
Whenever the hash table query function is called with the same 
search key, the hash table is searched for an element whose 
pseudokey matches the key either in or derived from the search 
key. If no compare function has been provided, the found element 
is returned. However, if a compare function has been provided, it 
is called by the hash table query routine to match the 
search key against each element in the hash table that matches 
the pseudokey. When the compare function succeeds (returns a 0), the 
element is returned. #!N #!N A similar sequence is used to 
either insert a unique element (if a compare function was provided) 
or to overwrite a previously inserted element of the same key 
(if a compare function was not provided). #!N Note: Only 16 
elements may be stored using the same pseudokey. #!N #!N #!I0 
#!N #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   HashTable DXCreateHash() #!EF #!EF #!I50 
#!N Creates a hash table. See  #!Lun10,dxall1122 h Examples  #!EL  . See  #!Ldxch,dxall1190 h DXCreateHash  #!EL  . 
#!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Element DXQueryHashElement() #!EF #!EF #!I50 #!N 
Searches a hash table for an element matching a specified key. 
See  #!Lun10,dxall1122 h Examples  #!EL  . See  #!Ldxqhe,dxall1345 h DXQueryHashElement  #!EL  . #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   
Error DXInsertHashElement() #!EF #!EF #!I50 #!N Inserts an element into a 
hash table. See  #!Lun10,dxall1122 h Examples  #!EL  . See  #!Ldxihe,dxall1283 h DXInsertHashElement  #!EL  . #!N #!I0 #!N 
 #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Error DXDeleteHashElement() #!EF #!EF #!I50 #!N Removes any element 
that matches a search key. See  #!Ldxdhe,dxall1197 h DXDeleteHashElement  #!EL  . #!N #!I0 #!N 
 #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Error DXInitGetNextHashElement() #!EF #!EF #!I50 #!N Initializes the pointer 
to the next element for  #!F-adobe-times-bold-r-normal--18*   GetNextHashElement #!EF . See  #!Ldxignhe,dxall1279 h DXInitGetNextHashElement  #!EL  
. #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Error DXGetNextHashElement() #!EF #!EF #!I50 
#!N Returns the next element in a hash table. See  #!Ldxgnhe,dxall1251 h DXGetNextHashElement  #!EL  
. #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Error DXDestroyHash() #!EF #!EF #!I50 
#!N Deletes a hash table. See  #!Ldxdhsh,dxall1198 h DXDestroyHash  #!EL  . #!I0 #!N #!N 
#!N #!N Optional routines provided by the caller at the time 
of creation of the hash table follow: #!N #!N #!I0 #!N 
#!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   hashFunc() #!EF #!EF #!I50 #!N Converts 
a search key to a long integer pseudokey. Called on insertion 
and query. #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   cmpFunc() #!EF #!EF #!I50 
#!N Determines whether elements with the same pseudokey are unique. Called 
on insertion and query. #!I0 #!N #!N #!N #!N #!N  #!F-adobe-times-medium-i-normal--18*   
Next Topic #!EF #!N #!N  #!Lun10,dxall1122 h Examples  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   #!N