typedef unsigned short u16;
typedef unsigned char u8;


/* Number of elements in an array object. */
#define array_size(x) (sizeof(x)/sizeof(x[0]))





/*************************************************************************
** Interface to bt_pager.c functionality.
*/
typedef struct BtPage BtPage;
typedef struct BtPager BtPager;

................................................................................
int sqlite4BtVarintGet64(const u8 *aData, i64 *piVal);
int sqlite4BtVarintLen32(int);
int sqlite4BtVarintSize(u8 c);
/*
** End of bt_varint.c interface.
*************************************************************************/

/*************************************************************************
** Interface to bt_lock.c functionality.
*/
#define BT_LOCK_NOLOCK  0x00      /* No lock held on database */
#define BT_LOCK_READER  0x01      /* Read lock held on database */
#define BT_LOCK_WRITER  0x02      /* Write lock held on database */

















typedef struct BtLock BtLock;
struct BtLock {
  /* These three are set by the bt_pager module and thereafter used by 
  ** both bt_lock and bt_pager. */
  sqlite4_env *pEnv;              /* SQLite environment */
  bt_env *pVfs;                   /* Bt environment */
  bt_file *pFd;                   /* Database file descriptor */

  /* These are used only by the bt_lock module. */
  /* todo... */
};


int sqlite4BtLockConnect(BtLock*, int (*xRecover)(BtLock*));
int sqlite4BtLockDisconnect(BtLock*, int(*xCkpt)(BtLock*), int(*xDel)(BtLock*));


int sqlite4BtLockCheckpoint(BtLock*, int(*xCkpt)(BtLock*));




int sqlite4BtLockBegin(BtLock*, int eLock);



int sqlite4BtLockEnd(BtLock*, int eLock);

/*
** End of bt_lock.c interface.
*************************************************************************/


#ifdef NDEBUG
# define btErrorBkpt(x) x
#else
int btErrorBkpt(int rc);
#endif

typedef unsigned short u16;
typedef unsigned char u8;


/* Number of elements in an array object. */
#define array_size(x) (sizeof(x)/sizeof(x[0]))

/* Number of read-lock slots in shared memory */
#define BT_NREADER 4


/*************************************************************************
** Interface to bt_pager.c functionality.
*/
typedef struct BtPage BtPage;
typedef struct BtPager BtPager;

................................................................................
int sqlite4BtVarintGet64(const u8 *aData, i64 *piVal);
int sqlite4BtVarintLen32(int);
int sqlite4BtVarintSize(u8 c);
/*
** End of bt_varint.c interface.
*************************************************************************/

/*************************************************************************
** Interface to bt_log.c functionality.
*/
typedef struct BtLog BtLog;
int sqlite4BtLogOpen(BtPager*, BtLog**, int bRecover);
int sqlite4BtLogClose(BtLog*, int bCleanup);

int sqlite4BtLogRead(BtLog*, u32 pgno, u8 *aData);
int sqlite4BtLogWrite(BtLog*, u32 pgno, u8 *aData, int bCommit);

int sqlite4BtLogSnapshotOpen(BtLog*);
int sqlite4BtLogSnapshotClose(BtLog*);
int sqlite4BtLogSnapshotWritable(BtLog*);

int sqlite4BtLogCheckpoint(BtLog*);

/*
** End of bt_log.c interface.
*************************************************************************/

/*************************************************************************
** Interface to bt_lock.c functionality.
*/
typedef struct BtLock BtLock;
struct BtLock {
  /* These three are set by the bt_pager module and thereafter used by 
  ** both bt_lock and bt_pager. */
  sqlite4_env *pEnv;              /* SQLite environment */
  bt_env *pVfs;                   /* Bt environment */
  bt_file *pFd;                   /* Database file descriptor */

  /* These are used only by the bt_lock module. */
  /* todo... */
};

/* Connect and disconnect procedures */
int sqlite4BtLockConnect(BtLock*, int (*xRecover)(BtLock*));
int sqlite4BtLockDisconnect(BtLock*, int(*xCkpt)(BtLock*), int(*xDel)(BtLock*));

/* Obtain and release the WRITER lock */
int sqlite4BtLockWriter(BtLock*);
int sqlite4BtLockWriterUnlock(BtLock*);

/* Obtain, release and query READER locks.  */
int sqlite4BtLockReader(BtLock*, u32 *aLog, u32 *aLock);
int sqlite4BtLockReaderUnlock(BtLock*);
int sqlite4BtLockReaderMin(BtLock*, u32 *aLog, u32 *aLock, u32 *piMinFrame);

/* Obtain and release CHECKPOINTER lock */
int sqlite4BtLockCkpt(BtLock*);
int sqlite4BtLockCkptUnlock(BtLock*);
/*
** End of bt_lock.c interface.
*************************************************************************/


#ifdef NDEBUG
# define btErrorBkpt(x) x
#else
int btErrorBkpt(int rc);
#endif

int sqlite4BtLockBegin(BtLock *p, int eLock){
  return SQLITE4_OK;
}

int sqlite4BtLockEnd(BtLock *p, int eLock){
  return SQLITE4_OK;
}

int sqlite4BtLockBegin(BtLock *p, int eLock){
  return SQLITE4_OK;
}

int sqlite4BtLockEnd(BtLock *p, int eLock){
  return SQLITE4_OK;
}

/* Obtain a READER lock. 
**
** Argument aLog points to an array of 6 frame addresses. These are the 
** first and last frames in each of log regions A, B and C. Argument 
** aLock points to the array of read-lock slots in shared memory.
*/
int sqlite4BtLockReader(BtLock*, u32 *aLog, u32 *aLock){
}

/*
** 2013 October 19
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
*/

#include "btInt.h"

#include <string.h>
#include <assert.h>
#include <stdio.h>

/* Magic values identifying WAL file header */
#define BT_WAL_MAGIC   0xBEE1CA62
#define BT_WAL_VERSION 0x00000001

typedef struct BtWalHdr BtWalHdr;
typedef struct BtShmHdr BtShmHdr;

/*
** WAL file header. All u32 fields are stored in big-endian order on
** disk. A single WAL file may contain two of these headers - one at
** byte offset 0 and the other at offset <sector-size> (the start of
** the second disk sector in the file, according to the xSectorSize
** VFS method).
*/
struct BtWalHdr {
  u32 iMagic;                     /* Magic number (BT_WAL_MAGIC) */
  u32 iVersion;                   /* File format version */
  u32 nSector;                    /* Sector size when header written */

  u32 iSalt1;                     /* Initial frame cksum-0 value */
  u32 iSalt2;                     /* Initial frame cksum-1 value */
  u32 iFirstFrame;                /* First frame of log (numbered from 1) */

  u32 aCksum[2];                  /* Checksum of all prior fields */
};

/*
** WAL Frame header. All fields are stored in big-endian order.
*/
struct BtFrameHdr {
  u32 pgno;                       /* Page number of this frame */
  u32 aCksum[2];                  /* Frame checksum */
};

/*
** Shared memory header. Shared memory begins with two copies of
** this structure. All fields are stored in machine byte-order.
*/
struct BtShmHdr {
  u32 aLog[6];                    /* First/last frames for each log region */
};

/*
** A single instance of this structure follows the two BtShmHdr structures 
** in shared memory.
*/
struct BtCkptHdr {
  u32 iFirstRead;                 /* First uncheckpointed frame */
  u32 iFirstRecover;              /* First recovery frame */
};


struct BtShm {
  BtShmHdr hdr1;
  BtShmHdr hdr2;
  BtCkptHdr ckpt;
  u32 aReadlock[BT_NREADER];
}

/*
** Database header.
*/
struct BtDbhdr {
  u32 pgsz;                       /* Page size in bytes */
  u32 nPg;                        /* Number of pages in database */
  u32 cookie;                     /* User cookie value */
};

/*
** Pager object.
*/
struct BtPager {
  BtLock btl;                     /* Variables shared with bt_lock module */

/*
** Database header.
*/
struct BtDbhdr {
  u32 pgsz;                       /* Page size in bytes */
  u32 nPg;                        /* Number of pages in database */
  u32 cookie;                     /* User cookie value (SQL schema cookie) */
};

/*
** Pager object.
*/
struct BtPager {
  BtLock btl;                     /* Variables shared with bt_lock module */