RWCacheManager(3C++)

Name
     RWCacheManager - Rogue Wave library class

Synopsis
              #include <rw/cacheman.h>



              RWFile f("file.dat");       // Construct a file
          RWCacheManager(&f, 100);    // Cache 100 byte blocks to file.dat




Description
     Class RWCacheManager caches fixed length blocks to and from an associated
     RWFile.  The block size can be of any length and is set at construction
     time.  The number of cached blocks can also be set at construction time.
     Writes to the file may be deferred.  Use member function flush() to have
     any pending writes performed.

Persistence
     None

Example
              #include <rw/cacheman.h>
          #include <rw/rwfile.h>
          struct Record {
            int i;
            float f;
            char str[15];
          };
          main(){
             RWoffset loc;
             RWFile file("file.dat");     // Construct a file
             // Construct a cache, using 20 slots for struct Record:
                RWCacheManager cache(&file, sizeof(Record), 20);
             Record r;
             // ...
             cache.write(loc, &r);
             // ...
             cache.read(loc, &r);
          }

Public Constructor
              RWCacheManager(RWFile* file, unsigned blocksz,
                         unsigned mxblks = 10);


     Construct a cache for the RWFile pointed to by file.  The length of the
     fixed-size blocks is given by blocksz.  The number of cached blocks is
     given by mxblks.  If the total number of bytes cached would exceed the
     maximum value of an unsigned int, then RWCacheManager will quietly decide
     to cache a smaller number of blocks.

Public Destructor
              ~RWCacheManager();


     Performs any pending I/O operations (i.e., calls flush()) and deallocates
     any allocated memory.

Public Member Functions
              RWBoolean
          flush();


     Perform any pending I/O operations.  Returns TRUE if the flush was
     successful, FALSE otherwise.

              void
          invalidate();


     Invalidate the cache.

              RWBoolean
          read(RWoffset locn, void* dat);


     Return the data located at offset locn of the associated RWFile.  The
     data is put in the buffer pointed to by dat.  This buffer must be at
     least as long as the block size specified when the cache was constructed.
     Returns TRUE if the operation was successful, otherwise FALSE.

              RWBoolean
          write(RWoffset locn, void* dat);


     Write the block of data pointed to by dat to the offset locn of the
     associated RWFile.  The number of bytes written is given by the block
     size specified when the cache was constructed.  The actual write to disk
     may be deferred.  Use member function flush() to perform any pending
     output.  Returns TRUE if the operation was successful, otherwise FALSE.