Category : Files from Magazines
Archive : NOV91.ZIP
Filename : 2N11022A
Output of file : 2N11022A contained in archive : NOV91.ZIP
* LISTING 2
*
* bcache.h
*
* Header for block cache routines using
* M/LFRU algorithm.
*
* Source code Copyright (c) 1991 T.W. Nelson. May be
* used only for non-commercial purposes with
* appropriate acknowledgement of copyright.
*/
#ifndef __BCACHE_H
#define __BCACHE_H
#ifndef __STDIO_H
#include
#endif
typedef unsigned long ulong;
typedef struct cchdr far chdr_t; //block hdr object
typedef void far bufp_t; //buffer contents
typedef void far idnt_t; //cache id type
/* Block buffer header. This immediately precedes each
* block buffer in memory. Total memory required for
* each block is therefore:
* (sizeof(struct cchdr) + bsiz) bytes
*/
struct cchdr {
chdr_t *next; //next block header
chdr_t *prev; //prev block header
size_t stat; //block status
idnt_t *idnt; //cache id for proc()
ulong bnum; //block number
ulong acc; //access count
char bufp; //&bufp == buffer start
};
/* Cache descriptor type. Storage for one of these is
* allocated by the application for each cache opened.
*/
typedef struct {
idnt_t *idnt; //cache id (matches cchdr.idnt)
int bsiz; //block length in bytes
int bmax; //max number blocks in cache
ulong hits; //bc_search() finds
ulong miss; //bc_search() misses
ulong adds; //number calls to bc_addnew()
//block processing function ...
void (*proc)(idnt_t *, ulong, bufp_t *);
chdr_t *mfru; //mfru (newest) block
chdr_t *lfru; //lfru (oldest) block
chdr_t *head; //-> allocated cache memory
size_t user1; //user-defined data areas
size_t user2;
} BCACHE; //BCACHE object
#define MARK 1 //mark blocks for processing
#define RELEASE 0 //release (unmark) for reuse
#define ALLOCATE 0 //allocate memory
#define DEALLOCATE 1 //deallocate memory
#define GROUND ((chdr_t *) -1) //end of chain
#define BHDR_SIZE sizeof(struct cchdr)
#define BLOCK_PTR(type,hp) ((type *) &(hp->bufp))
//Function return values ( >= 0 ) ....
#define BC_NOTFOUND 1 //block not found
#define BC_NOERROR 0 //no error
//Function error values ( < 0 ) ....
#define BC_NOBLOCKS -1 //need >= 2 blocks
#define BC_NOMEMORY -2 //insufficient memory
//prototypes ......
int bc_open( BCACHE *c, int bmax,
int bsize, void (*proc)(), idnt_t *idnt);
int bc_alloc( BCACHE *c, int flag );
int bc_search( BCACHE *c, ulong bnum, bufp_t **bufptr);
int bc_insert( BCACHE *c, chdr_t *p );
int bc_addnew( BCACHE *c, ulong bnum, bufp_t **bufptr);
int bc_mark( BCACHE *c, ulong bnum, size_t flag );
int bc_flush( BCACHE *c );
int bc_free( BCACHE *c );
int bc_setalloc( int (*user_alloc)() );
#endif // __BCACHE_H
/* ---- End of File -------------------------------- */
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