dx-doc 1:4.4.4-7 / usr / share / doc / dx / help / dxall1102

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#!N 
#!CNavyBlue #!N  #!Rcache 
Cache #!N #!EC #!N #!N The look-aside cache service stores the 
results of computations for later use. Each cache entry is uniquely 
identified by a string function name, an integer key (which the 
executive uses to store multiple outputs for a single module), the 
number of input parameters, and the set of input parameter values. 
#!N #!N The input parameters and the Object to be cached 
must be Data Explorer Objects. #!N #!N  #!F-adobe-times-bold-r-normal--18*   ASSOCIATING DATA WITH 
A CACHE ENTRY. #!EF User data not already in the form 
of an Object can be associated with ____________________________________________ a cache entry 
by means of a Private Object (see  #!Lprivsec,dxall1081 h Private Class  #!EL  ), encapsulating the 
data in an object. To associate more than one Object with 
a cache entry, use a Group to contain the Objects. #!N 
#!N  #!F-adobe-times-bold-r-normal--18*   LOSING A CACHE ENTRY. #!EF Cache entries are subject 
to deletion without notice (e.g., when the system reclaims _____________________________ memory). 
The relative cost of creating an entry (which must be specified 
when the entry is created) may be taken into account when 
deleting Objects from the cache. If an estimate is not readily 
available, specify zero (0). Specifying  #!F-adobe-times-bold-r-normal--18*   CACHE_PERMANENT #!EF as the cost 
prevents the entry from being deleted during memory reclamation. #!N #!N 
 #!F-adobe-times-bold-r-normal--18*   OBJECT REFERENCE COUNTS AND THE CACHE. #!EF It is important 
to be aware of the following: The system uses the ______________________________________________ 
cache to store intermediate results from modules. Thus inputs to modules 
often come from the cache. However: #!N #!I0 #!N  #!F-adobe-times-medium-r-normal--18*   #!N 
#!N #!I30 #!N o Once you have a pointer to a 
module's input, you can be sure it will not be deleted 
while you are processing it. #!N #!I30 #!N o If the 
input is a Group and you extract a member, that member 
will not be deleted while you are using it (because the 
Group will not be deleted). #!N #!I0 #!N #!EF #!N #!N 
#!N However, Objects other than module inputs that are put into 
or retrieved from the cache behave differently: Once an Object is 
put in the cache, the system may delete it at any 
time to reclaim memory. This last has two consequences. #!N #!I0 
#!N  #!F-adobe-times-medium-r-normal--18*   #!N #!N #!I30 #!N 1.  #!F-adobe-times-bold-r-normal--18*   DXGetCacheEntry() #!EF returns 
an Object that is referenced so that it will not be 
deleted. Thus, you must delete the Object when you are finished 
using it: #!CForestGreen #!N #!N  #!F-adobe-courier-bold-r-normal--18*   #!N o = DXGetCacheEntry(...); #!N 
... use o ... #!N DXDelete(o); #!EF #!N #!N #!EC #!N 
#!N Failure to do so will result in a memory leak, 
because the Object will always have an extra reference. #!N #!I30 
#!N 2. To continue using an Object after putting it in 
the cache, you must reference it  #!F-adobe-times-medium-i-normal--18*   before #!EF putting it 
there, and delete it when it is no longer needed: #!CForestGreen 
#!N #!N  #!F-adobe-courier-bold-r-normal--18*   #!N o = New...; #!N DXReference(o); #!N DXSetCacheEntry(..., 
o, ...); #!N ... use o ... #!N DXDelete(o); #!EF #!N 
#!N #!EC #!N #!N Conversely, if putting the Object in the 
cache is the last operation before the return, and if  #!F-adobe-times-bold-r-normal--18*   
o #!EF is not visible outside the scope of the routine, 
no reference is necessary: #!CForestGreen #!N #!N  #!F-adobe-courier-bold-r-normal--18*   #!N o = 
New...; #!N ... use o ... #!N DXSetCacheEntry(..., o, ...); #!N 
return ...; #!EF #!N #!N #!EC #!N #!N where the return 
statement does  #!F-adobe-times-medium-i-normal--18*   not #!EF return  #!F-adobe-times-bold-r-normal--18*   o #!EF . #!N 
#!I0 #!N #!EF #!N #!N #!N  #!F-adobe-times-bold-r-normal--18*   CACHE ROUTINES #!EF _____________________ 
#!N #!N #!CForestGreen #!N  #!F-adobe-courier-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   #!N #define CACHE_PERMANENT 1e32 #!EF 
#!EF #!N #!N #!EC #!N #!I0 #!N #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*   
 #!F-adobe-times-bold-r-normal--18*   Object DXGetCacheEntry() #!EF #!N Object DXGetCacheEntryV() #!EF #!I50 #!N Retrieve 
a cache entry. See  #!Ldxgcev,dxall1224 h DXGetCacheEntry, DXGetCacheEntryV  #!EL  . #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   
Error DXSetCacheEntry() #!EF #!N Error DXSetCacheEntryV() #!EF #!I50 #!N Set a 
cache entry. See  #!Ldxscev,dxall1369 h DXSetCacheEntry, DXSetCacheEntryV  #!EL  . #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Error 
DXFreeModuleId() #!EF #!N Pointer DXGetModuleId() #!EF #!I50 #!N Get a unique 
identifier for each instance of a module. See  #!Ldxfmid,dxall1216 h DXFreeModuleId  #!EL  and  #!Ldxgmid,dxall1250 h DXGetModuleId  #!EL  
. #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*    #!F-adobe-times-bold-r-normal--18*   Error DXCompareModuleId() #!EF #!EF #!I50 
#!N Returns OK if the two specified module identifiers are the 
same; otherwise returns ERROR. See  #!Ldxcmpmi,dxall1183 h DXCompareModuleId  #!EL  . #!N #!I0 #!N  #!F-adobe-times-bold-r-normal--18*   
 #!F-adobe-times-bold-r-normal--18*   Pointer DXCopyModuleId() #!EF #!EF #!I50 #!N Returns a pointer to 
a copy of the specified module identifier. See  #!Ldxcpmi,dxall1188 h DXCopyModuleId  #!EL  . #!I0 
#!N #!N #!N #!N #!N  #!F-adobe-times-medium-i-normal--18*   Next Topic #!EF #!N #!N 
 #!Lpndcmd,dxall1103 h Pending Commands  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   #!N