SQLite

** the multiplex VFS shim can be built as a loadable 
** module.
*/
#define UNUSED_PARAMETER(x) (void)(x)
#define MAX_PAGE_SIZE       0x10000
#define DEFAULT_SECTOR_SIZE 0x1000

/*
** For a build without mutexes, no-op the mutex calls.
*/
#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0
#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
#define sqlite3_mutex_free(X)
#define sqlite3_mutex_enter(X)
#define sqlite3_mutex_try(X)      SQLITE_OK
#define sqlite3_mutex_leave(X)
#define sqlite3_mutex_held(X)     ((void)(X),1)
#define sqlite3_mutex_notheld(X)  ((void)(X),1)
#endif /* SQLITE_THREADSAFE==0 */

/* Maximum chunk number */
#define MX_CHUNK_NUMBER 299

/* First chunk for rollback journal files */
#define SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET 400
#define SQLITE_MULTIPLEX_WAL_8_3_OFFSET 700

  int nReal;                       /* Number of chunks */
  char *zName;                     /* Base filename of this group */
  int nName;                       /* Length of base filename */
  int flags;                       /* Flags used for original opening */
  unsigned int szChunk;            /* Chunk size used for this group */
  unsigned char bEnabled;          /* TRUE to use Multiplex VFS for this file */
  unsigned char bTruncate;         /* TRUE to enable truncation of databases */
  multiplexGroup *pNext, *pPrev;   /* Doubly linked list of all group objects */
};

/*
** An instance of the following object represents each open connection
** to a file that is multiplex'ed.  This object is a 
** subclass of sqlite3_file.  The sqlite3_file object for the underlying
** VFS is appended to this structure.

  */
  sqlite3_io_methods sIoMethodsV1;
  sqlite3_io_methods sIoMethodsV2;

  /* True when this shim has been initialized.
  */
  int isInitialized;

  /* For run-time access any of the other global data structures in this
  ** shim, the following mutex must be held. In practice, all this mutex
  ** protects is add/remove operations to/from the linked list of group objects
  ** starting at pGroups below. More specifically, it protects the value of
  ** pGroups itself, and the pNext/pPrev fields of each multiplexGroup
  ** structure.  */
  sqlite3_mutex *pMutex;

  /* List of multiplexGroup objects.
  */
  multiplexGroup *pGroups;
} gMultiplex;

/************************* Utility Routines *********************************/
/*
** Acquire and release the mutex used to serialize access to the
** list of multiplexGroups.
*/
static void multiplexEnter(void){ sqlite3_mutex_enter(gMultiplex.pMutex); }
static void multiplexLeave(void){ sqlite3_mutex_leave(gMultiplex.pMutex); }

/*
** Compute a string length that is limited to what can be stored in
** lower 30 bits of a 32-bit signed integer.
**
** The value returned will never be negative.  Nor will it ever be greater
** than the actual length of the string.  For very long strings (greater
** than 1GiB) the value returned might be less than the true string length.

  UNUSED_PARAMETER(pVfs);
  memset(pConn, 0, pVfs->szOsFile);
  assert( zName || (flags & SQLITE_OPEN_DELETEONCLOSE) );

  /* We need to create a group structure and manage
  ** access to this group of files.
  */
  multiplexEnter();
  pMultiplexOpen = (multiplexConn*)pConn;

  if( rc==SQLITE_OK ){
    /* allocate space for group */
    nName = zName ? multiplexStrlen30(zName) : 0;
    sz = sizeof(multiplexGroup)                             /* multiplexGroup */
       + nName + 1;                                         /* zName */

    if( rc==SQLITE_OK ){
      if( pSubOpen->pMethods->iVersion==1 ){
        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV1;
      }else{
        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV2;
      }
      /* place this group at the head of our list */
      pGroup->pNext = gMultiplex.pGroups;
      if( gMultiplex.pGroups ) gMultiplex.pGroups->pPrev = pGroup;
      gMultiplex.pGroups = pGroup;
    }else{
      multiplexFreeComponents(pGroup);
      sqlite3_free(pGroup);
    }
  }
  multiplexLeave();
  sqlite3_free(zToFree);
  return rc;
}

/*
** This is the xDelete method used for the "multiplex" VFS.
** It attempts to delete the filename specified.

** The group structure for this file is unlinked from 
** our list of groups and freed.
*/
static int multiplexClose(sqlite3_file *pConn){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  multiplexEnter();
  multiplexFreeComponents(pGroup);
  /* remove from linked list */
  if( pGroup->pNext ) pGroup->pNext->pPrev = pGroup->pPrev;
  if( pGroup->pPrev ){
    pGroup->pPrev->pNext = pGroup->pNext;
  }else{
    gMultiplex.pGroups = pGroup->pNext;
  }
  sqlite3_free(pGroup);
  multiplexLeave();
  return rc;
}

/* Pass xRead requests thru to the original VFS after
** determining the correct chunk to operate on.
** Break up reads across chunk boundaries.
*/

** determining the correct chunk to operate on.  Delete any
** chunks above the truncate mark.
*/
static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  multiplexEnter();
  if( !pGroup->bEnabled ){
    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
    if( pSubOpen==0 ){
      rc = SQLITE_IOERR_TRUNCATE;
    }else{
      rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
    }

      pSubOpen = multiplexSubOpen(pGroup, iBaseGroup, &rc, 0, 0);
      if( pSubOpen ){
        rc = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->szChunk);
      }
    }
    if( rc ) rc = SQLITE_IOERR_TRUNCATE;
  }
  multiplexLeave();
  return rc;
}

/* Pass xSync requests through to the original VFS without change
*/
static int multiplexSync(sqlite3_file *pConn, int flags){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  int i;
  multiplexEnter();
  for(i=0; i<pGroup->nReal; i++){
    sqlite3_file *pSubOpen = pGroup->aReal[i].p;
    if( pSubOpen ){
      int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
      if( rc2!=SQLITE_OK ) rc = rc2;
    }
  }
  multiplexLeave();
  return rc;
}

/* Pass xFileSize requests through to the original VFS.
** Aggregate the size of all the chunks before returning.
*/
static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
  multiplexConn *p = (multiplexConn*)pConn;
  multiplexGroup *pGroup = p->pGroup;
  int rc = SQLITE_OK;
  int i;
  multiplexEnter();
  if( !pGroup->bEnabled ){
    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
    if( pSubOpen==0 ){
      rc = SQLITE_IOERR_FSTAT;
    }else{
      rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
    }
  }else{
    *pSize = 0;
    for(i=0; rc==SQLITE_OK; i++){
      sqlite3_int64 sz = multiplexSubSize(pGroup, i, &rc);
      if( sz==0 ) break;
      *pSize = i*(sqlite3_int64)pGroup->szChunk + sz;
    }
  }
  multiplexLeave();
  return rc;
}

/* Pass xLock requests through to the original VFS unchanged.
*/
static int multiplexLock(sqlite3_file *pConn, int lock){
  multiplexConn *p = (multiplexConn*)pConn;

*/
int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
  sqlite3_vfs *pOrigVfs;
  if( gMultiplex.isInitialized ) return SQLITE_MISUSE;
  pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
  if( pOrigVfs==0 ) return SQLITE_ERROR;
  assert( pOrigVfs!=&gMultiplex.sThisVfs );
  gMultiplex.pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
  if( !gMultiplex.pMutex ){
    return SQLITE_NOMEM;
  }
  gMultiplex.pGroups = NULL;
  gMultiplex.isInitialized = 1;
  gMultiplex.pOrigVfs = pOrigVfs;
  gMultiplex.sThisVfs = *pOrigVfs;
  gMultiplex.sThisVfs.szOsFile += sizeof(multiplexConn);
  gMultiplex.sThisVfs.zName = SQLITE_MULTIPLEX_VFS_NAME;
  gMultiplex.sThisVfs.xOpen = multiplexOpen;
  gMultiplex.sThisVfs.xDelete = multiplexDelete;

**
** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
** shutting down in order to free all remaining multiplex groups.
*/
int sqlite3_multiplex_shutdown(int eForce){
  int rc = SQLITE_OK;
  if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
  if( gMultiplex.pGroups ){
    sqlite3_log(SQLITE_MISUSE, "sqlite3_multiplex_shutdown() called "
                "while database connections are still open");
    if( !eForce ) return SQLITE_MISUSE;
    rc = SQLITE_MISUSE;
  }
  gMultiplex.isInitialized = 0;
  sqlite3_mutex_free(gMultiplex.pMutex);
  sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
  memset(&gMultiplex, 0, sizeof(gMultiplex));
  return rc;
}

/***************************** Test Code ***********************************/
#ifdef SQLITE_TEST

  /* Call sqlite3_multiplex_shutdown() */
  rc = sqlite3_multiplex_shutdown(objc==2);
  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);

  return TCL_OK;
}

/*
** tclcmd:  sqlite3_multiplex_dump
*/
static int SQLITE_TCLAPI test_multiplex_dump(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  Tcl_Obj *pResult;
  Tcl_Obj *pGroupTerm;
  multiplexGroup *pGroup;
  int i;
  int nChunks = 0;

  UNUSED_PARAMETER(clientData);
  UNUSED_PARAMETER(objc);
  UNUSED_PARAMETER(objv);

  pResult = Tcl_NewObj();
  multiplexEnter();
  for(pGroup=gMultiplex.pGroups; pGroup; pGroup=pGroup->pNext){
    pGroupTerm = Tcl_NewObj();

    if( pGroup->zName ){
      pGroup->zName[pGroup->nName] = '\0';
      Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewStringObj(pGroup->zName, -1));
    }else{
      Tcl_ListObjAppendElement(interp, pGroupTerm, Tcl_NewObj());
    }
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->nName));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->flags));

    /* count number of chunks with open handles */
    for(i=0; i<pGroup->nReal; i++){
      if( pGroup->aReal[i].p!=0 ) nChunks++;
    }
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(nChunks));

    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->szChunk));
    Tcl_ListObjAppendElement(interp, pGroupTerm,
          Tcl_NewIntObj(pGroup->nReal));

    Tcl_ListObjAppendElement(interp, pResult, pGroupTerm);
  }
  multiplexLeave();
  Tcl_SetObjResult(interp, pResult);
  return TCL_OK;
}

/*
** Tclcmd: test_multiplex_control HANDLE DBNAME SUB-COMMAND ?INT-VALUE?
*/
static int SQLITE_TCLAPI test_multiplex_control(
  ClientData cd,
  Tcl_Interp *interp,
  int objc,

int Sqlitemultiplex_Init(Tcl_Interp *interp){
  static struct {
     char *zName;
     Tcl_ObjCmdProc *xProc;
  } aCmd[] = {
    { "sqlite3_multiplex_initialize", test_multiplex_initialize },
    { "sqlite3_multiplex_shutdown", test_multiplex_shutdown },
    { "sqlite3_multiplex_dump", test_multiplex_dump },
    { "sqlite3_multiplex_control", test_multiplex_control },
  };
  int i;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }

  return TCL_OK;
}
#endif

do_test multiplex-2.3.1 {
  sqlite3 db2 test2.x
  db2 close
} {}


unset -nocomplain ::log
do_test multiplex-2.4.1 {
  sqlite3_multiplex_shutdown
} {SQLITE_MISUSE}
do_test multiplex-2.4.2 {
  execsql { INSERT INTO t1 VALUES(3, randomblob(1100)) }
} {}
do_test multiplex-2.4.3 {
  set ::log
} {SQLITE_MISUSE {sqlite3_multiplex_shutdown() called while database connections are still open}}

do_test multiplex-2.4.4 { file size [multiplex_name test.x 0] } {7168}
do_test multiplex-2.4.5 {
  db close
  sqlite3 db test.x
  db eval vacuum
  db close
  glob test.x*

#

sqlite3_multiplex_initialize "" 1
multiplex_set db main 32768 16

# Return a list of all currently defined multiplexs.
proc multiplex_list {} {
  set allq {}
  foreach q [sqlite3_multiplex_dump] {
    lappend allq [lindex $q 0]
  }
  return [lsort $allq]
}

do_test multiplex-4.1.6 {
  multiplex_delete test2.db
  sqlite3 db test2.db
  db eval {CREATE TABLE t2(x); INSERT INTO t2 VALUES('tab-t2');}
  set res [multiplex_list]

  db2 close
  set res [multiplex_list]
  list [regexp {test2.db} $res]
} {1}
do_test multiplex-4.1.12 {
  db close
  multiplex_list
} {}


#-------------------------------------------------------------------------
# The following tests test that the multiplex VFS handles malloc and IO 
# errors.
#