SQLite

int sqlite3BtreeExclusiveLock(Btree *p){
  int rc;
  Pgno pgno = 0;
  BtShared *pBt = p->pBt;
  assert( p->inTrans==TRANS_WRITE && pBt->pPage1 );
  sqlite3BtreeEnter(p);
  rc = sqlite3PagerExclusiveLock(pBt->pPager, pBt->pPage1->pDbPage, &pgno);
#ifdef SQLITE_OMIT_CONCURRENT
  assert( pgno==0 );
#else
  if( rc==SQLITE_BUSY_SNAPSHOT && pgno ){
    PgHdr *pPg = 0;
    int rc2 = sqlite3PagerGet(pBt->pPager, pgno, &pPg, 0);
    if( rc2==SQLITE_OK ){
      int bWrite = -1;
      const char *zObj = 0;
      const char *zTab = 0;

          (int)pgno,
          (bWrite==0?"read-only":(bWrite>0?"read/write":"unknown")),
          (zTab ? "index" : "table"),
          (zTab ? zTab : ""), (zTab ? "." : ""), (zObj ? zObj : "UNKNOWN")
      );
    }
  }
#endif
  sqlite3BtreeLeave(p);
  return rc;
}

#if !defined(SQLITE_OMIT_SHARED_CACHE)
/*
** Return true if the Btree passed as the only argument is sharable.

*/
struct MemPage {
  u8 isInit;           /* True if previously initialized. MUST BE FIRST! */
  u8 bBusy;            /* Prevent endless loops on corrupt database files */
  u8 intKey;           /* True if table b-trees.  False for index b-trees */
  u8 intKeyLeaf;       /* True if the leaf of an intKey table */
  Pgno pgno;           /* Page number for this page */
#ifndef SQLITE_OMIT_CONCURRENT
  Pgno pgnoRoot;       /* Root page of b-tree that this page belongs to */
#endif
  /* Only the first 8 bytes (above) are zeroed by pager.c when a new page
  ** is allocated. All fields that follow must be initialized before use */
  u8 leaf;             /* True if a leaf page */
  u8 hdrOffset;        /* 100 for page 1.  0 otherwise */
  u8 childPtrSize;     /* 0 if leaf==1.  4 if leaf==0 */
  u8 max1bytePayload;  /* min(maxLocal,127) */
  u8 nOverflow;        /* Number of overflow cell bodies in aCell[] */

  u8 *aData;           /* Pointer to disk image of the page data */
  u8 *aDataEnd;        /* One byte past the end of usable data */
  u8 *aCellIdx;        /* The cell index area */
  u8 *aDataOfst;       /* Same as aData for leaves.  aData+4 for interior */
  DbPage *pDbPage;     /* Pager page handle */
  u16 (*xCellSize)(MemPage*,u8*);             /* cellSizePtr method */
  void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */



};

/*
** A linked list of the following structures is stored at BtShared.pLock.
** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
** is opened on the table with root page BtShared.iTable. Locks are removed
** from this list when a transaction is committed or rolled back, or when

int sqlite3PagerUpgradeSnapshot(Pager *pPager, DbPage*);
void sqlite3PagerSetDbsize(Pager *pPager, Pgno);
int sqlite3PagerIsWal(Pager*);
#else
# define sqlite3PagerEndConcurrent(x)
#endif

#if !defined(SQLITE_DEBUG) && !defined(SQLITE_OMIT_CONCURRENT)
int sqlite3PagerIswriteable(DbPage*);
#endif

int sqlite3PagerWalInfo(Pager*, u32 *pnPrior, u32 *pnFrame);

#if defined(SQLITE_HAS_CODEC) && !defined(SQLITE_OMIT_WAL)
void *sqlite3PagerCodec(DbPage *);
#endif