Category : C Source Code
Archive   : C-TOOLBX.ZIP
Filename : BTREE.H

/* btree.h - data structures and constants for BTREE modue */
#define EOIX (-2) /* return value for end-of-index */
#define IX_FAIL (-1) /* return value for failed operation */
#define IX_OK 0 /* return value for success */

typedef long RECPOS ; /* file pos. of index block/data rec. */
#define NULLREC (-1L) /* special value for RECPOS */

#define MAXKEY 100 /* maximum length of a key */

typedef struct /* entry format in index */
{ RECPOS rptr ; /* points to lower level */
char key[MAXKEY] ; /* start of key value */
/* actual data type unknown */
} ENTRY ;

#define IXB_SIZE 1024 /* no. bytes in a block ( on disk ) */
/* IXB_SIZE = IXB_SIZE - sizeof(int)*2 - sizeof(long) */
#define IXB_SPACE 1016 /* no. bytes of entry space in block */

typedef struct /* index block format */
{ RECPOS brec ; /* index file location of block */
/* or location of next free block */
int bend ; /* first unused location in block */
int lvl ; /* records level no. (-1 = free) */
char entries[IXB_SPACE] ; /* space for entries */
} BLOCK ;

#define MAX_LEVELS 4 /* four index levels permitted */

typedef struct /* disk file index descriptor */
{ int nl ; /* number of index levels */
RECPOS rb ; /* location of root block in file */
RECPOS ff ; /* location of first free block */
ENTRY dume ; /* dummy entry */
} IX_DISK ;

typedef struct /* in-memory index descriptor */
{ int ixfile ; /* descriptor of open index file */
struct
{ RECPOS cblock ; /* current block number */
int coffset ; /* current offset within block */
} pos[MAX_LEVELS] ;
int (*pcomp) () ; /* address of compare function */
int (*psize) () ; /* address of entry size */
BLOCK cache[MAX_LEVELS] ; /* cache for current blocks */
IX_DISK dx ; /* disk resident stuff */
} IX_DESC ;