#ifndef BLKIO_H         /* prevent multiple includes */
#define BLKIO_H

#include <stddef.h>
#include <stdio.h>

/* blkio constants */
#define BOPEN_MAX       FOPEN_MAX       /* max # block files open at once */

/* blkio type definitions */
typedef size_t  bpos_t;         /* block file position */

typedef struct {                /* block buffer control structure */
        bpos_t bn;              /* block number [1...] */
        int flags;              /* block status flags */
        size_t more;            /* link to more recently used block */
        size_t less;            /* link to less recently used block */
} block_t;

typedef struct {                /* block file control structure */
        int fd;                 /* file descriptor */
        int flags;              /* status flags */
        size_t hdrsize;         /* size of file header */
        size_t blksize;         /* size of blocks */
        size_t bufcnt;          /* number blocks to buffer (0 if unbuffered) */
        bpos_t endblk;          /* first block past end of file */
        size_t most;            /* most recently accessed block [1..bufcnt] */
        size_t least;           /* least recently accessed block [1..bufcnt] */
        block_t *block_p;       /* doubly linked list of blocks */
        void *blkbuf;           /* buffer storage for header and blocks */
} BLKFILE;
extern BLKFILE biob[BOPEN_MAX]; /* BLKFILE control struct table declaration */

/* block_t flag bits */
#define BLKREAD           (01)  /* block can be read */
#define BLKWRITE          (02)  /* block needs to be written to disk */

/* biob flag bits */
#define BIOOPEN           (03)  /* open status bits */
#define BIOREAD           (01)  /* block file is open for reading */
#define BIOWRITE          (02)  /* block file is open for writing */
#define BIOUSRBUF         (04)  /* user supplied buffer */

/* block file error codes */
#define BEOS            (0)             /* start of blkio error code domain */
#define BEMFILE         (BEOS - 1)      /* too many block files open */
#define BENOPEN         (BEOS - 2)      /* block file is not open */
#define BENBUF          (BEOS - 3)      /* buffering is off */
#define BEBUF           (BEOS - 4)      /* buffering is on */
#define BEBOUND         (BEOS - 5)      /* block boundary error */
#define BEEOF           (BEOS - 6)      /* past end of file */
#define BENFL           (BEOS - 7)      /* no free list */
#define BEPANIC         (BEOS - 10)     /* internal blkio error */

#endif  /* #ifndef BLKIO_H */