RWCacheManager(3C++) RWCacheManager(3C++)
NameRWCacheManager - 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
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RWCacheManager(3C++) RWCacheManager(3C++)
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.
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