SQLite

    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }
#endif
  sqlite3_mutex_enter(db->mutex);
  pOld = db->pTraceArg;
  db->mTrace = xTrace ? SQLITE_TRACE_LEGACY : 0;

  db->xTrace = (int(*)(u32,void*,void*,void*))xTrace;
  db->pTraceArg = pArg;
  sqlite3_mutex_leave(db->mutex);
  return pOld;
}
#endif /* SQLITE_OMIT_DEPRECATED */

    return SQLITE_MISUSE_BKPT;
  }
#endif
  sqlite3_mutex_enter(db->mutex);
  if( mTrace==0 ) xTrace = 0;
  if( xTrace==0 ) mTrace = 0;
  db->mTrace = mTrace;



  db->xTrace = xTrace;
  db->pTraceArg = pArg;
  sqlite3_mutex_leave(db->mutex);
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_DEPRECATED

**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
**   *  Definitions of sqlite3_vfs objects for all locking methods
**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/* Turn this feature on in all builds for now */
#define SQLITE_MUTEXFREE_SHMLOCK 1
#define SQLITE_MFS_EXCLUSIVE     255
#ifndef SQLITE_MFS_NSHARD
# define SQLITE_MFS_NSHARD       8
#endif
#if SQLITE_MFS_NSHARD<1
# error "SQLITE_MFS_NSHARD must be greater than 0"
#endif

/*
** There are various methods for file locking used for concurrency
** control:
**
**   1. POSIX locking (the default),
**   2. No locking,
**   3. Dot-file locking,

  int nRef;                  /* Number of unixShm objects pointing to this */
  unixShm *pFirst;           /* All unixShm objects pointing to this */
#ifdef SQLITE_DEBUG
  u8 exclMask;               /* Mask of exclusive locks held */
  u8 sharedMask;             /* Mask of shared locks held */
  u8 nextShmId;              /* Next available unixShm.id value */
#endif

#ifdef SQLITE_MUTEXFREE_SHMLOCK
  /* In unix-excl mode, if SQLITE_MUTEXFREE_SHMLOCK is defined, all locks
  ** are stored in the following 64-bit value. There are in total 8 
  ** shm-locking slots, each of which are assigned 8-bits from the 64-bit
  ** value. The least-significant 8 bits correspond to shm-locking slot
  ** 0, and so on.
  **
  ** If the 8-bits corresponding to a shm-locking locking slot are set to
  ** 0xFF, then a write-lock is held on the slot. Or, if they are set to
  ** a non-zero value smaller than 0xFF, then they represent the total 
  ** number of read-locks held on the slot. There is no way to distinguish
  ** between a write-lock and 255 read-locks.  */
  struct LockingSlot {
    u32 nLock;
    u64 aPadding[7];
  } aMFSlot[3 + SQLITE_MFS_NSHARD*5];
#endif
};

/*
** Atomic CAS primitive used in multi-process mode. Equivalent to:
** 
**   int unixCompareAndSwap(u32 *ptr, u32 oldval, u32 newval){
**     if( *ptr==oldval ){
**       *ptr = newval;
**       return 1;
**     }
**     return 0;
**   }
*/
#define unixCompareAndSwap(ptr,oldval,newval) \
    __sync_bool_compare_and_swap(ptr,oldval,newval)


/*
** Structure used internally by this VFS to record the state of an
** open shared memory connection.
**
** The following fields are initialized when this object is created and
** are read-only thereafter:

struct unixShm {
  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
  u8 hasMutex;               /* True if holding the unixShmNode->pShmMutex */
  u8 id;                     /* Id of this connection within its unixShmNode */
  u16 sharedMask;            /* Mask of shared locks held */
  u16 exclMask;              /* Mask of exclusive locks held */
#ifdef SQLITE_MUTEXFREE_SHMLOCK
  u8 aMFCurrent[8];          /* Current slot used for each shared lock */
#endif
};

/*
** Constants used for locking
*/
#define UNIX_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */

    *pp = 0;
  }
  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
  sqlite3_mutex_leave(pShmNode->pShmMutex);
  return rc;
}

#ifdef SQLITE_MUTEXFREE_SHMLOCK
static int unixMutexFreeShmlock(
  unixFile *pFd,             /* Database file holding the shared memory */
  int ofst,                  /* First lock to acquire or release */
  int n,                     /* Number of locks to acquire or release */
  int flags                  /* What to do with the lock */
){
  struct LockMapEntry {
    int iFirst;
    int nSlot;
  } aMap[9] = {
    { 0, 1 },
    { 1, 1 },
    { 2, 1 },
    { 3+0*SQLITE_MFS_NSHARD, SQLITE_MFS_NSHARD },
    { 3+1*SQLITE_MFS_NSHARD, SQLITE_MFS_NSHARD },
    { 3+2*SQLITE_MFS_NSHARD, SQLITE_MFS_NSHARD },
    { 3+3*SQLITE_MFS_NSHARD, SQLITE_MFS_NSHARD },
    { 3+4*SQLITE_MFS_NSHARD, SQLITE_MFS_NSHARD },
    { 3+5*SQLITE_MFS_NSHARD, 0 },
  };

  unixShm *p = pFd->pShm;               /* The shared memory being locked */
  unixShm *pX;                          /* For looping over all siblings */
  unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
  int rc = SQLITE_OK;
  int iIncr;
  u16 mask;                             /* Mask of locks to take or release */

  if( flags & SQLITE_SHM_SHARED ){
    /* SHARED locks */
    u32 iOld, iNew, *ptr;
    int iIncr = -1;
    if( (flags & SQLITE_SHM_UNLOCK)==0 ){
      p->aMFCurrent[ofst] = (p->aMFCurrent[ofst] + 1) % aMap[ofst].nSlot;
      iIncr = 1;
    }
    ptr = &pShmNode->aMFSlot[aMap[ofst].iFirst + p->aMFCurrent[ofst]].nLock;
    do {
      iOld = *ptr;
      iNew = iOld + iIncr;
      if( iNew>SQLITE_MFS_EXCLUSIVE ){
        return SQLITE_BUSY;
      }
    }while( 0==unixCompareAndSwap(ptr, iOld, iNew) );
  }else{
    /* EXCLUSIVE locks */
    int iFirst = aMap[ofst].iFirst;
    int iLast = aMap[ofst+n].iFirst;
    int i;
    for(i=iFirst; i<iLast; i++){
      u32 *ptr = &pShmNode->aMFSlot[i].nLock;
      if( flags & SQLITE_SHM_UNLOCK ){
        assert( (*ptr)==SQLITE_MFS_EXCLUSIVE );
        *ptr = 0;
      }else{
        u32 iOld;
        do {
          iOld = *ptr;
          if( iOld>0 ){
            while( i>iFirst ){
              i--;
              pShmNode->aMFSlot[i].nLock = 0;
            }
            return SQLITE_BUSY;
          }
        }while( 0==unixCompareAndSwap(ptr, iOld, SQLITE_MFS_EXCLUSIVE) );
      }
    }
  }

  return SQLITE_OK;
}
#else
# define unixMutexFreeShmlock(a,b,c,d) SQLITE_OK
#endif

/*
** Change the lock state for a shared-memory segment.
**
** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
** different here than in posix.  In xShmLock(), one can go from unlocked
** to shared and back or from unlocked to exclusive and back.  But one may
** not go from shared to exclusive or from exclusive to shared.

  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
  assert( pShmNode->hShm>=0 || pDbFd->pInode->bProcessLock==1 );
  assert( pShmNode->hShm<0 || pDbFd->pInode->bProcessLock==0 );

  if( pDbFd->pInode->bProcessLock ){
    return unixMutexFreeShmlock(pDbFd, ofst, n, flags);
  }

  mask = (1<<(ofst+n)) - (1<<ofst);
  assert( n>1 || mask==(1<<ofst) );
  if( flags & SQLITE_SHM_LOCK ){
    assert( !(flags&SQLITE_SHM_SHARED) || (p->sharedMask&mask)==0 );
    assert( !(flags&SQLITE_SHM_EXCLUSIVE) || !(p->exclMask&mask) );
  }else{
    assert( !(flags&SQLITE_SHM_SHARED) || (p->sharedMask&mask)==mask );
    assert( !(flags&SQLITE_SHM_EXCLUSIVE) || (p->exclMask&mask)==mask );
  }

  sqlite3_mutex_enter(pShmNode->pShmMutex);
  if( flags & SQLITE_SHM_UNLOCK ){
    u16 allMask = 0; /* Mask of locks held by siblings */

    /* See if any siblings hold this same lock */
    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
      if( pX==p ) continue;

** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);
#ifdef SQLITE_MUTEXFREE_SHMLOCK
  __sync_synchronize();
#else
  sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
  assert( fd->pMethods->xLock==nolockLock 
       || unixFileMutexNotheld((unixFile*)fd) 
  );
  unixEnterMutex();               /* Also mutex, for redundancy */
  unixLeaveMutex();
#endif
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**
** If there is no shared memory associated with the connection then this

** ^The callback function registered by sqlite3_profile() is invoked
** as each SQL statement finishes.  ^The profile callback contains
** the original statement text and an estimate of wall-clock time
** of how long that statement took to run.  ^The profile callback
** time is in units of nanoseconds, however the current implementation
** is only capable of millisecond resolution so the six least significant
** digits in the time are meaningless.  Future versions of SQLite
** might provide greater resolution on the profiler callback.  Invoking
** either [sqlite3_trace()] or [sqlite3_trace_v2()] will cancel the
** profile callback.
*/
SQLITE_DEPRECATED void *sqlite3_trace(sqlite3*,
   void(*xTrace)(void*,const char*), void*);
SQLITE_DEPRECATED void *sqlite3_profile(sqlite3*,
   void(*xProfile)(void*,const char*,sqlite3_uint64), void*);

/*

** An instance of the following structure is allocated for each active
** superlock. The opaque handle returned by sqlite3demo_superlock() is
** actually a pointer to an instance of this structure.
*/
struct Superlock {
  sqlite3 *db;                    /* Database handle used to lock db */
  int bWal;                       /* True if db is a WAL database */
  int bRecoveryLocked;            /* True if WAL RECOVERY lock is held */
  int bReaderLocked;              /* True if WAL READER locks are held */
};
typedef struct Superlock Superlock;

/*
** The pCtx pointer passed to this function is actually a pointer to a
** SuperlockBusy structure. Invoke the busy-handler function encapsulated
** by the structure and return the result.

}

/*
** Obtain the extra locks on the database file required for WAL databases.
** Invoke the supplied busy-handler as required.
*/
static int superlockWalLock(
  Superlock *pLock,               /* Superlock handle */
  SuperlockBusy *pBusy            /* Busy handler wrapper object */
){
  int rc;                         /* Return code */
  sqlite3_file *fd = 0;           /* Main database file handle */
  void volatile *p = 0;           /* Pointer to first page of shared memory */
  sqlite3 *db = pLock->db;

  /* Obtain a pointer to the sqlite3_file object open on the main db file. */
  rc = sqlite3_file_control(db, "main", SQLITE_FCNTL_FILE_POINTER, (void *)&fd);
  if( rc!=SQLITE_OK ) return rc;

  /* Obtain the "recovery" lock. Normally, this lock is only obtained by
  ** clients running database recovery.  
  */
  assert( pLock->bRecoveryLocked==0 );
  rc = superlockShmLock(fd, 2, 1, pBusy);
  if( rc!=SQLITE_OK ) return rc;
  pLock->bRecoveryLocked = 1;

  /* Zero the start of the first shared-memory page. This means that any
  ** clients that open read or write transactions from this point on will
  ** have to run recovery before proceeding. Since they need the "recovery"
  ** lock that this process is holding to do that, no new read or write
  ** transactions may now be opened. Nor can a checkpoint be run, for the
  ** same reason.
  */
  rc = fd->pMethods->xShmMap(fd, 0, 32*1024, 1, &p);
  if( rc!=SQLITE_OK ) return rc;
  memset((void *)p, 0, 32);

  /* Obtain exclusive locks on all the "read-lock" slots. Once these locks
  ** are held, it is guaranteed that there are no active reader, writer or 
  ** checkpointer clients.
  */
  assert( pLock->bReaderLocked==0 );
  rc = superlockShmLock(fd, 3, SQLITE_SHM_NLOCK-3, pBusy);
  if( rc==SQLITE_OK ) pLock->bReaderLocked = 1;
  return rc;
}

/*
** Release a superlock held on a database file. The argument passed to 
** this function must have been obtained from a successful call to
** sqlite3demo_superlock().
*/
void sqlite3demo_superunlock(void *pLock){
  Superlock *p = (Superlock *)pLock;
  if( p->bWal ){
    int rc;                         /* Return code */
    int flags = SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE;
    sqlite3_file *fd = 0;
    rc = sqlite3_file_control(p->db, "main", SQLITE_FCNTL_FILE_POINTER, (void *)&fd);
    if( rc==SQLITE_OK ){
      if( p->bRecoveryLocked ){
        fd->pMethods->xShmLock(fd, 2, 1, flags);
        p->bRecoveryLocked = 0;
      }
      if( p->bReaderLocked ){
        fd->pMethods->xShmLock(fd, 3, SQLITE_SHM_NLOCK-3, flags);
        p->bReaderLocked = 0;
      }
    }
  }
  sqlite3_close(p->db);
  sqlite3_free(p);
}

/*

  ** to drop the WAL read and write locks currently held. Otherwise, the
  ** new WAL locks may conflict with the old.
  */
  if( rc==SQLITE_OK ){
    if( SQLITE_OK==(rc = superlockIsWal(pLock)) && pLock->bWal ){
      rc = sqlite3_exec(pLock->db, "COMMIT", 0, 0, 0);
      if( rc==SQLITE_OK ){
        rc = superlockWalLock(pLock, &busy);
      }
    }
  }

  if( rc!=SQLITE_OK ){
    sqlite3demo_superunlock(pLock);
    *ppLock = 0;

  return TCL_OK;

 bad_args:
  Tcl_WrongNumArgs(interp, 1, objv, "VFSNAME ?-noshm BOOL? ?-fullshm BOOL? ?-default BOOL? ?-mxpathname INT? ?-szosfile INT? ?-iversion INT?");
  return TCL_ERROR;
}

extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
extern const char *sqlite3ErrName(int);

/*
** tclcmd: vfs_shmlock DB DBNAME (shared|exclusive) (lock|unlock) OFFSET N
*/
static int SQLITE_TCLAPI test_vfs_shmlock(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  const char *azArg1[] = {"shared", "exclusive", 0};
  const char *azArg2[] = {"lock", "unlock", 0};
  sqlite3 *db = 0;
  int rc = SQLITE_OK;
  const char *zDbname = 0;
  int iArg1 = 0;
  int iArg2 = 0;
  int iOffset = 0;
  int n = 0;
  sqlite3_file *pFd;

  if( objc!=7 ){
    Tcl_WrongNumArgs(interp, 1, objv, 
        "DB DBNAME (shared|exclusive) (lock|unlock) OFFSET N"
    );
    return TCL_ERROR;
  }

  zDbname = Tcl_GetString(objv[2]);
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
   || Tcl_GetIndexFromObj(interp, objv[3], azArg1, "ARG", 0, &iArg1) 
   || Tcl_GetIndexFromObj(interp, objv[4], azArg2, "ARG", 0, &iArg2) 
   || Tcl_GetIntFromObj(interp, objv[5], &iOffset)
   || Tcl_GetIntFromObj(interp, objv[6], &n)
  ){
    return TCL_ERROR;
  }

  sqlite3_file_control(db, zDbname, SQLITE_FCNTL_FILE_POINTER, (void*)&pFd);
  if( pFd==0 ){
    return TCL_ERROR;
  }
  rc = pFd->pMethods->xShmLock(pFd, iOffset, n, 
      (iArg1==0 ? SQLITE_SHM_SHARED : SQLITE_SHM_EXCLUSIVE)
    | (iArg2==0 ? SQLITE_SHM_LOCK : SQLITE_SHM_UNLOCK)
  );
  Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
  return TCL_OK;
}


int Sqlitetestvfs_Init(Tcl_Interp *interp){
  Tcl_CreateObjCommand(interp, "testvfs", testvfs_cmd, 0, 0);
  Tcl_CreateObjCommand(interp, "vfs_shmlock", test_vfs_shmlock, 0, 0);
  return TCL_OK;
}

#endif

      **         checkpoint need not have completed for this to cause problems.
      */
      volatile WalCkptInfo *pInfo = walCkptInfo(pWal);

      assert( pWal->readLock>0 || pWal->hdr.mxFrame==0 );
      assert( pInfo->aReadMark[pWal->readLock]<=pSnapshot->mxFrame );

      /* If it were possible for a checkpointer thread to run concurrent 
      ** with this code, it would be a problem. In this case, it could be
      ** that the checkpointer has already determined that it will checkpoint 
      ** snapshot X, where X is later in the wal file than pSnapshot, but 
      ** has not yet set the pInfo->nBackfillAttempted variable to indicate 
      ** its intent. Fortunately this is not possible, as the call to
      ** sqlite3WalSnapshotOpen() that sets pWal->pSnapshot also takes a
      ** SHARED lock on the checkpointer slot.  */






      if( rc==SQLITE_OK ){
        /* Check that the wal file has not been wrapped. Assuming that it has
        ** not, also check that no checkpointer has attempted to checkpoint any
        ** frames beyond pSnapshot->mxFrame. If either of these conditions are
        ** true, return SQLITE_ERROR_SNAPSHOT. Otherwise, overwrite pWal->hdr
        ** with *pSnapshot and set *pChanged as appropriate for opening the
        ** snapshot.  */
        if( !memcmp(pSnapshot->aSalt, pWal->hdr.aSalt, sizeof(pWal->hdr.aSalt))
         && pSnapshot->mxFrame>=pInfo->nBackfillAttempted
        ){
          assert( pWal->readLock>0 );
          memcpy(&pWal->hdr, pSnapshot, sizeof(WalIndexHdr));
          *pChanged = bChanged;
        }else{
          rc = SQLITE_ERROR_SNAPSHOT;
        }



        pWal->minFrame = 1;
      }


      if( rc!=SQLITE_OK ){
        sqlite3WalEndReadTransaction(pWal);
      }

# This file contains code used by several different test scripts. The
# code in this file allows testfixture to control another process (or
# processes) to test locking.
#

proc do_multiclient_test {varname script} {

  foreach {tn code} [list 1 {
    if {[info exists ::G(valgrind)]} { db close ; continue }
    set ::code2_chan [launch_testfixture]
    set ::code3_chan [launch_testfixture]
    proc code2 {tcl} { testfixture $::code2_chan $tcl }
    proc code3 {tcl} { testfixture $::code3_chan $tcl }

  } 2 {
    proc code2 {tcl} { uplevel #0 $tcl }
    proc code3 {tcl} { uplevel #0 $tcl }

  }] {
    # Do not run multi-process tests with the unix-excl VFS.
    #
    if {$tn==1 && [permutation]=="unix-excl"} continue

    faultsim_delete_and_reopen

    proc code1 {tcl} { uplevel #0 $tcl }
  
    # Open connections [db2] and [db3]. Depending on which iteration this
    # is, the connections may be created in this interpreter, or in 
    # interpreters running in other OS processes. As such, the [db2] and [db3]

  Run some tests using the "test_onefile.c" demo
} -initialize {
  set ::G(perm:sqlite3_args) [list -vfs fs]
} -files {
  conflict.test  insert.test   insert2.test  insert3.test
  rollback.test  select1.test  select2.test  select3.test
}

# Run some tests using the "unix-excl" VFS.
#
test_suite "unix-excl" -description {
  Run some tests using the "unix-excl" VFS
} -initialize {
  set ::G(perm:sqlite3_args) [list -vfs unix-excl]
} -files {
  shmlock.test
}

# Run some tests using UTF-16 databases.
#
test_suite "utf16" -description {
  Run tests using UTF-16 databases
} -presql {
  pragma encoding = 'UTF-16'

# 2018 December 6
#
# 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.
#
#***********************************************************************
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

set testprefix shmlock

ifcapable !wal {finish_test ; return }

sqlite3 db2 test.db
sqlite3 db3 test.db

do_execsql_test 1.0 {
  PRAGMA journal_mode = wal;
  CREATE TABLE t1(a, b);
  INSERT INTO t1 VALUES(1, 2);
} {wal}
do_test 1.1 { execsql { SELECT * FROM t1 } db2 } {1 2}
do_test 1.2 { execsql { SELECT * FROM t1 } db3 } {1 2}

foreach {tn dbhandle cmd res} {
  1    db  {shared    lock   7 1}    OK
  2    db2 {exclusive lock   7 1}    BUSY
  3    db  {shared    unlock 7 1}    OK
  4    db2 {exclusive lock   7 1}    OK
  5    db  {shared    lock   7 1}    BUSY
  6    db  {exclusive lock   7 1}    BUSY
  7    db2 {exclusive unlock 7 1}    OK

  8    db  {exclusive lock   0 8}    OK
  9    db  {exclusive unlock 0 8}    OK
  10   db2 {exclusive lock   0 8}    OK
  11   db2 {exclusive unlock 0 8}    OK

  12   db  {shared    lock   0 1}    OK
  13   db2 {shared    lock   0 1}    OK
  14   db3 {shared    lock   0 1}    OK
  15   db3 {shared    unlock 0 1}    OK
  16   db3 {exclusive lock   0 1}    BUSY
  17   db2 {shared    unlock 0 1}    OK
  18   db3 {exclusive lock   0 1}    BUSY
  19   db  {shared    unlock 0 1}    OK
  20   db3 {exclusive lock   0 1}    OK
  21   db3 {exclusive unlock 0 1}    OK

  22   db  {shared    lock   3 1}    OK
  23   db2 {exclusive lock   2 2}    BUSY
  24   db  {shared    lock   2 1}    OK
  25   db2 {exclusive lock   0 5}    BUSY
  26   db2 {exclusive lock   0 4}    BUSY
  27   db2 {exclusive lock   0 3}    BUSY
  28   db  {shared    unlock 3 1}    OK
  29   db2 {exclusive lock   2 2}    BUSY
  28   db  {shared    unlock 2 1}    OK
  29   db2 {exclusive lock   2 2}    OK
  29   db2 {exclusive unlock 2 2}    OK
} {
  do_test 1.3.$tn [list vfs_shmlock $dbhandle main {*}$cmd] "SQLITE_$res"
}

db  close
db2 close
db3 close

if {[permutation]=="unix-excl"} {
  do_test 2.0 {
    for {set i 0} {$i < 256} {incr i} { 
      sqlite3 db$i test.db 
      execsql { SELECT * FROM t1 } db$i
    }
    for {set i 0} {$i < 255} {incr i} { 
      set rc [vfs_shmlock db$i main shared lock 4 1]
      if {$rc != "SQLITE_OK"} { error $rc }
    }

    vfs_shmlock db255 main shared lock 4 1
  } {SQLITE_BUSY}

  do_test 2.1 { vfs_shmlock db255 main exclusive lock   4 1 } SQLITE_BUSY
  do_test 2.2 { vfs_shmlock db0   main shared    unlock 4 1 } SQLITE_OK
  do_test 2.3 { vfs_shmlock db255 main shared    lock   4 1 } SQLITE_OK
  do_test 2.4 { vfs_shmlock db255 main shared    unlock 4 1 } SQLITE_OK
  do_test 2.5 { vfs_shmlock db255 main exclusive lock   4 1 } SQLITE_BUSY

  do_test 2.6 {
    for {set i 1} {$i < 255} {incr i} { 
      set rc [vfs_shmlock db255 main exclusive lock 4 1]
      if {$rc != "SQLITE_BUSY"} { error $rc }
      set rc [vfs_shmlock db$i main shared unlock 4 1]
      if {$rc != "SQLITE_OK"} { error $rc }
    }

    vfs_shmlock db255 main exclusive lock 4 1
  } {SQLITE_OK}

  vfs_shmlock db255 main exclusive unlock 4 1

  for {set i 0} {$i < 256} {incr i} {
    db$i close
  }
}

sqlite3 db0 test.db
sqlite3 db1 test.db
do_test 3.1 { execsql { SELECT * FROM t1 } db0 } {1 2}
do_test 3.2 { execsql { SELECT * FROM t1 } db1 } {1 2}

set L(0) {n n n n n n n n}
set L(1) {n n n n n n n n}
proc random_lock_test {idx} {
  global L
  set iSlot [expr int(rand()*8)]
  if {[expr int(rand()*2)]} {
    # Unlock operation
    if {[lindex $L($idx) $iSlot]!="n"} {
      vfs_shmlock db$idx main [lindex $L($idx) $iSlot] unlock $iSlot 1
      lset L($idx) $iSlot n
    }
  } else {
    # Lock operation
    if {[lindex $L($idx) $iSlot]=="n"} {
      set locktype [lindex {e s} [expr int(rand()*2)]]
      set n 1
      if {$locktype=="e"} {
        for {set l $iSlot} {$l<8 && [lindex $L($idx) $l]=="n"} {incr l} {}
        set n [expr int(rand()*($l-$iSlot))+1]
        # puts "iSlot=$iSlot l=$l L=$L($idx)"
        # puts "$iSlot $n"
      }
      set res [vfs_shmlock db$idx main $locktype lock $iSlot $n]

      set bBusy 0
      for {set i $iSlot} {$i<($iSlot+$n)} {incr i} {
        set other [lindex $L([expr ($idx+1)%2]) $i]
        if {($other!="n" && $locktype=="e")||($other=="e" && $locktype=="s")} {
          if {$res != "SQLITE_BUSY"} { error "BUSY not detected" }
          set bBusy 1
          break
        } 
      }

      if {$bBusy==0} {
        if {$res != "SQLITE_OK"} { error "BUSY false-positive" }
        for {set i $iSlot} {$i<($iSlot+$n)} {incr i} {
          lset L($idx) $i $locktype
        }
      }
    }
  }
}

set nStep 100000
for {set i 0} {$i < $nStep} {incr i} {
  random_lock_test 0
  random_lock_test 1
}

db0 close
db1 close

finish_test

#
#   3. Using connection 1, checkpoint the database. Make sure all
#      the data is present and the database is not corrupt.
#
# At one point, SQLite was failing to grow the mapping of the wal-index
# file in step 3 and the checkpoint was corrupting the database file.
#
if {[permutation]!="unix-excl"} {
  do_test wal-20.1 {
    catch {db close}
    forcedelete test.db test.db-wal test.db-journal
    sqlite3 db test.db
    execsql {
      PRAGMA journal_mode = WAL;
      CREATE TABLE t1(x);
      INSERT INTO t1 VALUES(randomblob(900));
      SELECT count(*) FROM t1;
    }
  } {wal 1}
  do_test wal-20.2 {
    set ::buddy [launch_testfixture]
    testfixture $::buddy {
      sqlite3 db test.db
      db transaction { db eval {
        PRAGMA wal_autocheckpoint = 0;
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 2 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 4 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 8 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 16 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 32 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 64 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 128 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 256 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 512 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 1024 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 2048 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 4096 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 8192 */
        INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 16384 */
      } }
    }
  } {0}
  do_test wal-20.3 {
    close $::buddy
    execsql { PRAGMA wal_checkpoint }
    execsql { SELECT count(*) FROM t1 }
  } {16384}
  do_test wal-20.4 {
    db close
    sqlite3 db test.db
    execsql { SELECT count(*) FROM t1 }
  } {16384}
  integrity_check wal-20.5
}

catch { db2 close }
catch { db close }

do_test wal-21.1 {
  faultsim_delete_and_reopen
  execsql {