SQLite

This file contains notes regarding the implementation of the OTA extension.
User documentation is in sqlite3ota.h.

SQLite Hacks
------------















1) PRAGMA pager_ota_mode=1:

  This pragma sets a flag on the pager associated with the main database only.
  In a zipvfs system, this pragma is intercepted by zipvfs and the flag is set
  on the lower level pager only.

  The flag can only be set when there is no open transaction and the pager does
  not already have an open WAL file. Attempting to do so is an error.

  A pager with the pager_ota_mode flag set never runs a checkpoint.

  Other clients see a rollback-mode database on which the pager_ota_mode client
  is holding a SHARED lock. There are no locks to arbitrate between multiple
  pager_ota_mode connections. If two or more such connections attempt to write
  simultaneously, the results are undefined.

2) PRAGMA pager_ota_mode=2:

  The pager_ota_mode pragma may also be set to 2 if the main database is open 
  in WAL mode. This prevents SQLite from checkpointing the wal file as part
  of sqlite3_close().

  The effects of setting pager_ota_mode=2 if the db is not in WAL mode are
  undefined.








3) sqlite3_ckpt_open/step/close()

  API for performing (and resuming) incremental checkpoints.


The OTA extension
-----------------

    }
  } {
    reset_db
    execsql $schema

    do_test 1.$tn2.$tn.1 {
      create_ota1 ota.db
      breakpoint
      $cmd test.db ota.db
    } {SQLITE_DONE}

    do_execsql_test 1.$tn2.$tn.2 { SELECT * FROM t1 ORDER BY a ASC } {
      1 2 3 
      2 two three 
      3 {} 8.2

# progressed.
#
for {set nStep 1} {$nStep < 7} {incr nStep} {
  do_test 1.$nStep.1 {
    setup_test
    sqlite3ota ota test.db ota.db
    for {set i 0} {$i<$nStep} {incr i} {ota step}

    ota close
    sqlite3 db test.db
    execsql { INSERT INTO t1 VALUES(5, 'hello') }
    sqlite3ota ota test.db ota.db
    ota step
  } {SQLITE_BUSY}
  do_test 1.$nStep.2 {
    ota step
  } {SQLITE_BUSY}
  do_test 1.$nStep.3 {
    list [file exists test.db-oal] [file exists test.db-wal]
  } {1 0}
  do_test 1.$nStep.4 {
    list [catch { ota close } msg] $msg
  } {1 {SQLITE_BUSY - database modified during ota update}}
}

for {set nStep 7} {$nStep < 8} {incr nStep} {
  do_test 1.$nStep.1 {
    setup_test
    sqlite3ota ota test.db ota.db
    for {set i 0} {$i<$nStep} {incr i} {ota step}

  do_execsql_test 1.$nStep.5 {
    SELECT * FROM t1;
  } {1 t1 5 hello}
}



finish_test

**   Total number of sqlite3ota_step() calls made so far as part of this
**   ota update.
**
** OTA_STATE_CKPT:
**   Valid if STAGE==3. The blob to pass to sqlite3ckpt_start() to resume
**   the incremental checkpoint.
**
** OTA_STATE_COOKIE:
**   Valid if STAGE==1. The current change-counter cookie value in the 
**   target db file.
*/
#define OTA_STATE_STAGE       1
#define OTA_STATE_TBL         2
#define OTA_STATE_IDX         3
#define OTA_STATE_ROW         4
#define OTA_STATE_PROGRESS    5
#define OTA_STATE_CKPT        6
#define OTA_STATE_COOKIE      7

#define OTA_STAGE_OAL         1
#define OTA_STAGE_COPY        2
#define OTA_STAGE_CKPT        3
#define OTA_STAGE_DONE        4

  char *zOta;                     /* Path to ota db */
  int rc;                         /* Value returned by last ota_step() call */
  char *zErrmsg;                  /* Error message if rc!=SQLITE_OK */
  int nStep;                      /* Rows processed for current object */
  int nProgress;                  /* Rows processed for all objects */
  OtaObjIter objiter;             /* Iterator for skipping through tbl/idx */
  sqlite3_ckpt *pCkpt;            /* Incr-checkpoint handle */
  sqlite3_vfs *pVfs;              /* Special ota VFS object */
  unsigned int iCookie;
};

static void otaCreateVfs(sqlite3ota*, const char*);
static void otaDeleteVfs(sqlite3ota*);

/*
** Prepare the SQL statement in buffer zSql against database handle db.
** If successful, set *ppStmt to point to the new statement and return
** SQLITE_OK. 
**
** Otherwise, if an error does occur, set *ppStmt to NULL and return

  }else{
    sqlite3_free(zSql);
    zSql = 0;
  }
  va_end(ap);
  return zSql;
}

static void *otaMalloc(sqlite3ota *p, int nByte){
  void *pRet = 0;
  if( p->rc==SQLITE_OK ){
    pRet = sqlite3_malloc(nByte);
    if( pRet==0 ){
      p->rc = SQLITE_NOMEM;
    }else{
      memset(pRet, 0, nByte);
    }
  }
  return pRet;
}

/*
** This function constructs and returns a pointer to a nul-terminated 
** string containing some SQL clause or list based on one or more of the 
** column names currently stored in the pIter->azTblCol[] array.
*/
static char *otaObjIterGetCollist(

}

/*
** Open the database handle and attach the OTA database as "ota". If an
** error occurs, leave an error code and message in the OTA handle.
*/
static void otaOpenDatabase(sqlite3ota *p){
  int flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE;
  assert( p->rc==SQLITE_OK );

  assert( p->db==0 );

  p->rc = sqlite3_open_v2(p->zTarget, &p->db, flags, p->pVfs->zName);
  if( p->rc ){
    p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(p->db));
  }
  otaMPrintfExec(p, "ATTACH %Q AS ota", p->zOta);
}

/*

    ** in WAL mode). So no other connection may be writing the db.  */
    otaFileSuffix3(zBase, zWal);
    otaFileSuffix3(zBase, zOal);
    rename(zOal, zWal);

    /* Re-open the databases. */
    otaObjIterFinalize(&p->objiter);
    sqlite3_close(p->db);
    p->db = 0;
    p->eStage = OTA_STAGE_CKPT;
    otaOpenDatabase(p);
  }

  sqlite3_free(zWal);
  sqlite3_free(zOal);
}

/*

      sqlite3_mprintf(
        "INSERT OR REPLACE INTO ota.ota_state(k, v) VALUES "
        "(%d, %d), "
        "(%d, %Q), "
        "(%d, %Q), "
        "(%d, %d), "
        "(%d, %lld), "
        "(%d, ?), "
        "(%d, %lld) ",
        OTA_STATE_STAGE, p->eStage,
        OTA_STATE_TBL, p->objiter.zTbl, 
        OTA_STATE_IDX, p->objiter.zIdx, 
        OTA_STATE_ROW, p->nStep, 
        OTA_STATE_PROGRESS, p->nProgress,
        OTA_STATE_CKPT,
        OTA_STATE_COOKIE, (sqlite3_int64)p->iCookie
      )
  );
  assert( pInsert==0 || rc==SQLITE_OK );
  if( rc==SQLITE_OK ){
    if( p->pCkpt ){
      unsigned char *pCkptState = 0;
      int nCkptState = 0;

      case OTA_STATE_CKPT:
        pRet->nCkptState = sqlite3_column_bytes(pStmt, 1);
        pRet->pCkptState = (unsigned char*)otaStrndup(
            (char*)sqlite3_column_blob(pStmt, 1), pRet->nCkptState, &rc
        );
        break;

      case OTA_STATE_COOKIE:
        /* At this point (p->iCookie) contains the value of the change-counter
        ** cookie (the thing that gets incremented when a transaction is 
        ** committed in rollback mode) currently stored on page 1 of the 
        ** database file. */
        if( pRet->eStage==OTA_STAGE_OAL 
         && p->iCookie!=(unsigned int)sqlite3_column_int64(pStmt, 1) 
        ){
          rc = SQLITE_BUSY;
          p->zErrmsg = sqlite3_mprintf("database modified during ota update");
        }
        break;

      default:
        rc = SQLITE_CORRUPT;
        break;
    }
  }
  rc2 = sqlite3_finalize(pStmt);
  if( rc==SQLITE_OK ) rc = rc2;

  int nTarget = strlen(zTarget);
  int nOta = strlen(zOta);

  p = (sqlite3ota*)sqlite3_malloc(sizeof(sqlite3ota)+nTarget+1+nOta+1);
  if( p ){
    OtaState *pState = 0;

    /* Create the custom VFS */
    memset(p, 0, sizeof(sqlite3ota));
    otaCreateVfs(p, 0);

    /* Open the target database */
    if( p->rc==SQLITE_OK ){
      p->zTarget = (char*)&p[1];
      memcpy(p->zTarget, zTarget, nTarget+1);
      p->zOta = &p->zTarget[nTarget+1];
      memcpy(p->zOta, zOta, nOta+1);
      otaOpenDatabase(p);
    }

    /* If it has not already been created, create the ota_state table */
    if( p->rc==SQLITE_OK ){
      p->rc = sqlite3_exec(p->db, OTA_CREATE_STATE, 0, 0, &p->zErrmsg);
    }

    if( p->rc==SQLITE_OK ){

    }
    assert( p->rc!=SQLITE_OK || p->eStage!=0 );

    if( p->rc==SQLITE_OK ){
      if( p->eStage==OTA_STAGE_OAL ){
        const char *zScript =
          "PRAGMA journal_mode=off;"

          "BEGIN IMMEDIATE;"
        ;
        p->rc = sqlite3_exec(p->db, zScript, 0, 0, &p->zErrmsg);
  
        /* Point the object iterator at the first object */
        if( p->rc==SQLITE_OK ){
          p->rc = otaObjIterFirst(p, &p->objiter);

    otaObjIterFinalize(&p->objiter);

    /* Commit the transaction to the *-oal file. */
    if( p->rc==SQLITE_OK && p->eStage==OTA_STAGE_OAL ){
      p->rc = sqlite3_exec(p->db, "COMMIT", 0, 0, &p->zErrmsg);
    }





    /* Close the open database handle and VFS object. */
    if( p->pCkpt ) sqlite3_ckpt_close(p->pCkpt, 0, 0);
    sqlite3_close(p->db);
    otaDeleteVfs(p);

    otaEditErrmsg(p);
    rc = p->rc;
    *pzErrmsg = p->zErrmsg;
    sqlite3_free(p);
  }else{
    rc = SQLITE_NOMEM;
    *pzErrmsg = 0;
  }
  return rc;
}

/*
** Return the total number of key-value operations (inserts, deletes or 
** updates) that have been performed on the target database since the
** current OTA update was started.
*/
sqlite3_int64 sqlite3ota_progress(sqlite3ota *pOta){
  return pOta->nProgress;
}

/**************************************************************************
** Beginning of OTA VFS shim methods. The VFS shim modifies the behaviour
** of a standard VFS in the following ways:
**
**   TODO
*/

#if 0
#define OTA_FILE_VANILLA    0
#define OTA_FILE_TARGET_DB  1
#define OTA_FILE_TARGET_WAL 2
#endif

typedef struct ota_file ota_file;
typedef struct ota_vfs ota_vfs;

struct ota_file {
  sqlite3_file base;              /* sqlite3_file methods */
  sqlite3_file *pReal;            /* Underlying file handle */
  ota_vfs *pOtaVfs;               /* Pointer to the ota_vfs object */

  int nShm;                       /* Number of entries in apShm[] array */
  char **apShm;                   /* Array of mmap'd *-shm regions */
  char *zFilename;                /* Filename for *-oal file only */
};

struct ota_vfs {
  sqlite3_vfs base;             /* ota VFS shim methods */
  sqlite3_vfs *pRealVfs;        /* Underlying VFS */
  sqlite3ota *pOta;
  ota_file *pTargetDb;          /* Target database file descriptor */
  const char *zTargetDb;        /* Path that pTargetDb was opened with */
};

/*
** Close an ota file.
*/
static int otaVfsClose(sqlite3_file *pFile){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc;
  int i;

  /* Free the contents of the apShm[] array. And the array itself. */
  for(i=0; i<p->nShm; i++){
    sqlite3_free(p->apShm[i]);
  }
  sqlite3_free(p->apShm);
  p->apShm = 0;
  sqlite3_free(p->zFilename);

  if( p==pOtaVfs->pTargetDb ){
    pOtaVfs->pTargetDb = 0;
    pOtaVfs->zTargetDb = 0;
  }

  rc = p->pReal->pMethods->xClose(p->pReal);
  return rc;
}


/*
** Read and return an unsigned 32-bit big-endian integer from the buffer 
** passed as the only argument.
*/
static unsigned int otaGetU32(unsigned char *aBuf){
  return ((unsigned int)aBuf[0] << 24)
       + ((unsigned int)aBuf[1] << 16)
       + ((unsigned int)aBuf[2] <<  8)
       + ((unsigned int)aBuf[3]);
}

/*
** Read data from an otaVfs-file.
*/
static int otaVfsRead(
  sqlite3_file *pFile, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
  if( rc==SQLITE_OK && p==pOtaVfs->pTargetDb && iOfst==0 ){
    unsigned char *pBuf = (unsigned char*)zBuf;
    assert( iAmt>=100 );
    pOtaVfs->pOta->iCookie = otaGetU32(&pBuf[24]);
  }
  return rc;
}

/*
** Write data to an otaVfs-file.
*/
static int otaVfsWrite(
  sqlite3_file *pFile, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc = p->pReal->pMethods->xWrite(p->pReal, zBuf, iAmt, iOfst);
  if( rc==SQLITE_OK && p==pOtaVfs->pTargetDb && iOfst==0 ){
    unsigned char *pBuf = (unsigned char*)zBuf;
    assert( iAmt>=100 );
    pOtaVfs->pOta->iCookie = otaGetU32(&pBuf[24]);
  }
  return rc;
}

/*
** Truncate an otaVfs-file.
*/
static int otaVfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
  ota_file *p = (ota_file*)pFile;
  return p->pReal->pMethods->xTruncate(p->pReal, size);
}

/*
** Sync an otaVfs-file.
*/
static int otaVfsSync(sqlite3_file *pFile, int flags){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xSync(p->pReal, flags);
}

/*
** Return the current file-size of an otaVfs-file.
*/
static int otaVfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xFileSize(p->pReal, pSize);
}

/*
** Lock an otaVfs-file.
*/
static int otaVfsLock(sqlite3_file *pFile, int eLock){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc = SQLITE_OK;
  int eStage = pOtaVfs->pOta->eStage;

  if( pOtaVfs->pTargetDb==p 
   && (eStage==OTA_STAGE_OAL || eStage==OTA_STAGE_CKPT) 
   && eLock==SQLITE_LOCK_EXCLUSIVE
  ){
    /* Do not allow EXCLUSIVE locks. Preventing SQLite from taking this 
    ** prevents it from checkpointing the database from sqlite3_close(). */
    rc = SQLITE_BUSY;
  }else{
    rc = p->pReal->pMethods->xLock(p->pReal, eLock);
  }

  return rc;
}

/*
** Unlock an otaVfs-file.
*/
static int otaVfsUnlock(sqlite3_file *pFile, int eLock){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xUnlock(p->pReal, eLock);
}

/*
** Check if another file-handle holds a RESERVED lock on an otaVfs-file.
*/
static int otaVfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
}

/*
** File control method. For custom operations on an otaVfs-file.
*/
static int otaVfsFileControl(sqlite3_file *pFile, int op, void *pArg){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
}

/*
** Return the sector-size in bytes for an otaVfs-file.
*/
static int otaVfsSectorSize(sqlite3_file *pFile){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xSectorSize(p->pReal);
}

/*
** Return the device characteristic flags supported by an otaVfs-file.
*/
static int otaVfsDeviceCharacteristics(sqlite3_file *pFile){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
}

/*
** Shared-memory methods are all pass-thrus.
*/
static int otaVfsShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc = SQLITE_OK;

#ifdef SQLITE_AMALGAMATION
    assert( WAL_WRITE_CKPT==1 );
#endif

  if( pOtaVfs->pTargetDb==p && pOtaVfs->pOta->eStage==OTA_STAGE_OAL ){
    /* Magic number 1 is the WAL_WRITE_CKPT lock. Preventing SQLite from
    ** taking this lock also prevents any checkpoints from occurring. 
    ** todo: really, it's not clear why this might occur, as 
    ** wal_autocheckpoint ought to be turned off.  */
    if( ofst==1 && n==1 ) rc = SQLITE_BUSY;
  }else{
    assert( p->nShm==0 );
    return p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
  }

  return rc;
}

static int otaVfsShmMap(
  sqlite3_file *pFile, 
  int iRegion, 
  int szRegion, 
  int isWrite, 
  void volatile **pp
){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc = SQLITE_OK;

  /* If not in OTA_STAGE_OAL, allow this call to pass through. Or, if this
  ** ota is in the OTA_STAGE_OAL state, use heap memory for *-shm space 
  ** instead of a file on disk.  */
  if( pOtaVfs->pTargetDb==p && pOtaVfs->pOta->eStage==OTA_STAGE_OAL ){
    if( iRegion<=p->nShm ){
      int nByte = (iRegion+1) * sizeof(char*);
      char **apNew = (char**)sqlite3_realloc(p->apShm, nByte);
      if( apNew==0 ){
        rc = SQLITE_NOMEM;
      }else{
        memset(&apNew[p->nShm], 0, sizeof(char*) * (1 + iRegion - p->nShm));
        p->apShm = apNew;
        p->nShm = iRegion+1;
      }
    }

    if( rc==SQLITE_OK && p->apShm[iRegion]==0 ){
      char *pNew = (char*)sqlite3_malloc(szRegion);
      if( pNew==0 ){
        rc = SQLITE_NOMEM;
      }else{
        p->apShm[iRegion] = pNew;
      }
    }

    if( rc==SQLITE_OK ){
      *pp = p->apShm[iRegion];
    }else{
      *pp = 0;
    }
  }else{
    assert( p->apShm==0 );
    rc = p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
  }

  return rc;
}

/*
** Memory barrier.
*/
static void otaVfsShmBarrier(sqlite3_file *pFile){
  ota_file *p = (ota_file *)pFile;
  p->pReal->pMethods->xShmBarrier(p->pReal);
}

static int otaVfsShmUnmap(sqlite3_file *pFile, int delFlag){
  ota_file *p = (ota_file*)pFile;
  ota_vfs *pOtaVfs = p->pOtaVfs;
  int rc = SQLITE_OK;

  if( pOtaVfs->pTargetDb==p && pOtaVfs->pOta->eStage==OTA_STAGE_OAL ){
    /* no-op */
  }else{
    rc = p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
  }
  return rc;
}


static int otaVfsIswal(ota_vfs *pOtaVfs, const char *zPath){
  int nPath = strlen(zPath);
  int nTargetDb = strlen(pOtaVfs->zTargetDb);
  return ( nPath==(nTargetDb+4) 
        && 0==memcmp(zPath, pOtaVfs->zTargetDb, nTargetDb)
        && 0==memcmp(&zPath[nTargetDb], "-wal", 4)
  );
}


/*
** Open an ota file handle.
*/
static int otaVfsOpen(
  sqlite3_vfs *pVfs,
  const char *zName,
  sqlite3_file *pFile,
  int flags,
  int *pOutFlags
){
  static sqlite3_io_methods otavfs_io_methods = {
    2,                            /* iVersion */
    otaVfsClose,                  /* xClose */
    otaVfsRead,                   /* xRead */
    otaVfsWrite,                  /* xWrite */
    otaVfsTruncate,               /* xTruncate */
    otaVfsSync,                   /* xSync */
    otaVfsFileSize,               /* xFileSize */
    otaVfsLock,                   /* xLock */
    otaVfsUnlock,                 /* xUnlock */
    otaVfsCheckReservedLock,      /* xCheckReservedLock */
    otaVfsFileControl,            /* xFileControl */
    otaVfsSectorSize,             /* xSectorSize */
    otaVfsDeviceCharacteristics,  /* xDeviceCharacteristics */
    otaVfsShmMap,                 /* xShmMap */
    otaVfsShmLock,                /* xShmLock */
    otaVfsShmBarrier,             /* xShmBarrier */
    otaVfsShmUnmap                /* xShmUnmap */
  };
  ota_vfs *pOtaVfs = (ota_vfs*)pVfs;
  sqlite3_vfs *pRealVfs = pOtaVfs->pRealVfs;
  sqlite3ota *p = pOtaVfs->pOta;
  ota_file *pFd = (ota_file *)pFile;
  int rc = SQLITE_OK;
  const char *zOpen = zName;

  memset(pFd, 0, sizeof(ota_file));
  pFd->pReal = (sqlite3_file*)&pFd[1];
  pFd->pOtaVfs = pOtaVfs;

  if( zName && p->eStage==OTA_STAGE_OAL && otaVfsIswal(pOtaVfs, zName) ){
    char *zCopy = otaStrndup(zName, -1, &rc);
    if( zCopy ){
      int nCopy = strlen(zCopy);
      zCopy[nCopy-3] = 'o';
      zOpen = (const char*)(pFd->zFilename = zCopy);
    }
  }

  if( rc==SQLITE_OK ){
    rc = pRealVfs->xOpen(pRealVfs, zOpen, pFd->pReal, flags, pOutFlags);
  }
  if( pFd->pReal->pMethods ){
    pFile->pMethods = &otavfs_io_methods;
    if( pOtaVfs->pTargetDb==0 ){
      /* This is the target db file. */
      assert( (flags & SQLITE_OPEN_MAIN_DB) );
      assert( zOpen==zName );
      pOtaVfs->pTargetDb = pFd;
      pOtaVfs->zTargetDb = zName;
    }
  }

  return rc;
}

/*
** Delete the file located at zPath.
*/
static int otaVfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDelete(pRealVfs, zPath, dirSync);
}

/*
** Test for access permissions. Return true if the requested permission
** is available, or false otherwise.
*/
static int otaVfsAccess(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int flags, 
  int *pResOut
){
  ota_vfs *pOtaVfs = (ota_vfs*)pVfs;
  sqlite3_vfs *pRealVfs = pOtaVfs->pRealVfs;
  int rc;

  rc = pRealVfs->xAccess(pRealVfs, zPath, flags, pResOut);

  if( rc==SQLITE_OK 
   && flags==SQLITE_ACCESS_EXISTS 
   && pOtaVfs->pOta->eStage==OTA_STAGE_OAL 
   && otaVfsIswal(pOtaVfs, zPath) 
  ){
    if( *pResOut ){
      rc = SQLITE_CANTOPEN;
    }else{
      *pResOut = 1;
    }
  }

  return rc;
}

/*
** Populate buffer zOut with the full canonical pathname corresponding
** to the pathname in zPath. zOut is guaranteed to point to a buffer
** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
*/
static int otaVfsFullPathname(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int nOut, 
  char *zOut
){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xFullPathname(pRealVfs, zPath, nOut, zOut);
}

#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Open the dynamic library located at zPath and return a handle.
*/
static void *otaVfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlOpen(pRealVfs, zPath);
}

/*
** Populate the buffer zErrMsg (size nByte bytes) with a human readable
** utf-8 string describing the most recent error encountered associated 
** with dynamic libraries.
*/
static void otaVfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  pRealVfs->xDlError(pRealVfs, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*otaVfsDlSym(
  sqlite3_vfs *pVfs, 
  void *pArg, 
  const char *zSym
))(void){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlSym(pRealVfs, pArg, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void otaVfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlClose(pRealVfs, pHandle);
}
#endif /* SQLITE_OMIT_LOAD_EXTENSION */

/*
** Populate the buffer pointed to by zBufOut with nByte bytes of 
** random data.
*/
static int otaVfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xRandomness(pRealVfs, nByte, zBufOut);
}

/*
** Sleep for nMicro microseconds. Return the number of microseconds 
** actually slept.
*/
static int otaVfsSleep(sqlite3_vfs *pVfs, int nMicro){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xSleep(pRealVfs, nMicro);
}

/*
** Return the current time as a Julian Day number in *pTimeOut.
*/
static int otaVfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xCurrentTime(pRealVfs, pTimeOut);
}

static int otaVfsGetLastError(sqlite3_vfs *pVfs, int a, char *b){
  return 0;
}

static void otaCreateVfs(sqlite3ota *p, const char *zParent){

  /* Template for VFS */
  static sqlite3_vfs vfs_template = {
    1,                            /* iVersion */
    0,                            /* szOsFile */
    0,                            /* mxPathname */
    0,                            /* pNext */
    0,                            /* zName */
    0,                            /* pAppData */
    otaVfsOpen,                   /* xOpen */
    otaVfsDelete,                 /* xDelete */
    otaVfsAccess,                 /* xAccess */
    otaVfsFullPathname,           /* xFullPathname */

    otaVfsDlOpen,                 /* xDlOpen */
    otaVfsDlError,                /* xDlError */
    otaVfsDlSym,                  /* xDlSym */
    otaVfsDlClose,                /* xDlClose */

    otaVfsRandomness,             /* xRandomness */
    otaVfsSleep,                  /* xSleep */
    otaVfsCurrentTime,            /* xCurrentTime */
    otaVfsGetLastError,           /* xGetLastError */
    0,                            /* xCurrentTimeInt64 (version 2) */
    0, 0, 0                       /* Unimplemented version 3 methods */
  };

  sqlite3_vfs *pParent;           /* Parent VFS */
  ota_vfs *pNew = 0;              /* Newly allocated VFS */

  assert( p->rc==SQLITE_OK );
  pParent = sqlite3_vfs_find(zParent);
  if( pParent==0 ){
    p->rc = SQLITE_ERROR;
    p->zErrmsg = sqlite3_mprintf("no such vfs: %s", zParent);
  }else{
    int nByte = sizeof(ota_vfs) + 64;
    pNew = (ota_vfs*)otaMalloc(p, nByte);
  }

  if( pNew ){
    int rnd;
    char *zName;
    memcpy(&pNew->base, &vfs_template, sizeof(sqlite3_vfs));
    pNew->base.mxPathname = pParent->mxPathname;
    pNew->base.szOsFile = sizeof(ota_file) + pParent->szOsFile;
    pNew->pOta = p;
    pNew->pRealVfs = pParent;

    /* Give the new VFS a unique name */
    sqlite3_randomness(sizeof(int), (void*)&rnd);
    pNew->base.zName = (const char*)(zName = (char*)&pNew[1]);
    sprintf(zName, "ota_vfs_%d", rnd);

    /* Register the new VFS (not as the default) */
    assert( p->rc==SQLITE_OK );
    p->rc = sqlite3_vfs_register(&pNew->base, 0);
    if( p->rc ){
      p->zErrmsg = sqlite3_mprintf("error in sqlite3_vfs_register()");
      sqlite3_free(pNew);
    }else{
      p->pVfs = &pNew->base;
    }
  }
}

static void otaDeleteVfs(sqlite3ota *p){
  if( p->pVfs ){
    sqlite3_vfs_unregister(p->pVfs);
    sqlite3_free(p->pVfs);
    p->pVfs = 0;
  }
}


/**************************************************************************/

#ifdef SQLITE_TEST 

#include <tcl.h>

  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
  u8 walSyncFlags;            /* SYNC_NORMAL or SYNC_FULL for wal writes */
  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
  u8 tempFile;                /* zFilename is a temporary or immutable file */
  u8 noLock;                  /* Do not lock (except in WAL mode) */
  u8 readOnly;                /* True for a read-only database */
  u8 memDb;                   /* True to inhibit all file I/O */




  /**************************************************************************
  ** The following block contains those class members that change during
  ** routine operation.  Class members not in this block are either fixed
  ** when the pager is first created or else only change when there is a
  ** significant mode change (such as changing the page_size, locking_mode,
  ** or the journal_mode).  From another view, these class members describe

  PCache *pPCache;            /* Pointer to page cache object */
#ifndef SQLITE_OMIT_WAL
  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
  char *zWal;                 /* File name for write-ahead log */
#endif
};











/*
** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains
** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS 
** or CACHE_WRITE to sqlite3_db_status().
*/
#define PAGER_STAT_HIT   0
#define PAGER_STAT_MISS  1

  }

  if( rc==SQLITE_OK && bCommit && isOpen(pPager->fd) ){
    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
  }

  if( !pPager->exclusiveMode
   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
  ){
    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
    pPager->changeCountDone = 0;
  }
  pPager->eState = PAGER_READER;
  pPager->setMaster = 0;

  assert( assert_pager_state(pPager) );
  disable_simulated_io_errors();
  sqlite3BeginBenignMalloc();
  pagerFreeMapHdrs(pPager);
  /* pPager->errCode = 0; */
  pPager->exclusiveMode = 0;
#ifndef SQLITE_OMIT_WAL
  sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags, pPager->pageSize, pTmp);


  pPager->pWal = 0;
#endif
  pager_reset(pPager);
  if( MEMDB ){
    pager_unlock(pPager);
  }else{
    /* If it is open, sync the journal file before calling UnlockAndRollback.

      }
    }

    /* If there is a WAL file in the file-system, open this database in WAL
    ** mode. Otherwise, the following function call is a no-op.
    */
    rc = pagerOpenWalIfPresent(pPager);






#ifndef SQLITE_OMIT_WAL
    assert( pPager->pWal==0 || rc==SQLITE_OK );
#endif
  }

  if( pagerUseWal(pPager) ){
    assert( rc==SQLITE_OK );
    rc = pagerBeginReadTransaction(pPager);











  }

  if( pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
    rc = pagerPagecount(pPager, &pPager->dbSize);
  }

 failed:

** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
** or wal_blocking_checkpoint() API functions.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
  int rc = SQLITE_OK;
  if( pPager->pWal ){
    rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
        (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
        pPager->pBusyHandlerArg,
        pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
        pnLog, pnCkpt
    );
  }

  }

  /* Open the connection to the log file. If this operation fails, 
  ** (e.g. due to malloc() failure), return an error code.
  */
  if( rc==SQLITE_OK ){
    rc = sqlite3WalOpen(pPager->pVfs,
        pPager->fd, pPager->zWal, pPager->exclusiveMode,
        pPager->journalSizeLimit, &pPager->pWal
    );
  }
  pagerFixMaplimit(pPager);

  return rc;
}

** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
** without doing anything.
*/
int sqlite3PagerOpenWal(
  Pager *pPager,                  /* Pager object */
  int *pbOpen                     /* OUT: Set to true if call is a no-op */
){

  return pagerOpenWalInternal(pPager, pbOpen);
}

/*
** This function is called to close the connection to the log file prior
** to switching from WAL to rollback mode.
**

      pPager->pWal = 0;
      pagerFixMaplimit(pPager);
    }
  }
  return rc;
}















#endif /* !SQLITE_OMIT_WAL */

#ifdef SQLITE_ENABLE_ZIPVFS
/*
** A read-lock must be held on the pager when this function is called. If
** the pager is in WAL mode and the WAL file currently contains one or more
** frames, return the size in bytes of the page images stored within the
** WAL frames. Otherwise, if this is not a WAL database or the WAL file
** is empty, return 0.
*/
int sqlite3PagerWalFramesize(Pager *pPager){
  assert( pPager->eState>=PAGER_READER );
  return sqlite3WalFramesize(pPager->pWal);
}
#endif

#ifdef SQLITE_ENABLE_OTA












/*
** Open an incremental checkpoint handle.
*/
int sqlite3PagerWalCheckpointStart(
  sqlite3 *db, 
  Pager *pPager,

  void disable_simulated_io_errors(void);
  void enable_simulated_io_errors(void);
#else
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif



int sqlite3PagerWalCheckpointStart(sqlite3*, Pager*, u8*, int, sqlite3_ckpt**);

#endif /* _PAGER_H_ */

      pDb->pSchema->cache_size = size;
      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
    }
    break;
  }
#endif /* !SQLITE_OMIT_PAGER_PRAGMAS && !SQLITE_OMIT_DEPRECATED */













































#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
  /*
  **  PRAGMA [database.]page_size
  **  PRAGMA [database.]page_size=N
  **
  ** The first form reports the current setting for the
  ** database page size in bytes.  The second form sets the

#define PragTyp_JOURNAL_MODE                  18
#define PragTyp_JOURNAL_SIZE_LIMIT            19
#define PragTyp_LOCK_PROXY_FILE               20
#define PragTyp_LOCKING_MODE                  21
#define PragTyp_PAGE_COUNT                    22
#define PragTyp_MMAP_SIZE                     23
#define PragTyp_PAGE_SIZE                     24

#define PragTyp_SECURE_DELETE                 25
#define PragTyp_SHRINK_MEMORY                 26
#define PragTyp_SOFT_HEAP_LIMIT               27
#define PragTyp_STATS                         28
#define PragTyp_SYNCHRONOUS                   29
#define PragTyp_TABLE_INFO                    30
#define PragTyp_TEMP_STORE                    31
#define PragTyp_TEMP_STORE_DIRECTORY          32
#define PragTyp_THREADS                       33
#define PragTyp_WAL_AUTOCHECKPOINT            34
#define PragTyp_WAL_CHECKPOINT                35
#define PragTyp_ACTIVATE_EXTENSIONS           36
#define PragTyp_HEXKEY                        37
#define PragTyp_KEY                           38
#define PragTyp_REKEY                         39
#define PragTyp_LOCK_STATUS                   40
#define PragTyp_PARSER_TRACE                  41
#define PragFlag_NeedSchema           0x01
#define PragFlag_ReadOnly             0x02
static const struct sPragmaNames {
  const char *const zName;  /* Name of pragma */
  u8 ePragTyp;              /* PragTyp_XXX value */
  u8 mPragFlag;             /* Zero or more PragFlag_XXX values */
  u32 iArg;                 /* Extra argument */

    /* ePragFlag: */ PragFlag_NeedSchema,
    /* iArg:      */ 0 },
  { /* zName:     */ "page_size",
    /* ePragTyp:  */ PragTyp_PAGE_SIZE,
    /* ePragFlag: */ 0,
    /* iArg:      */ 0 },
#endif






#if defined(SQLITE_DEBUG)
  { /* zName:     */ "parser_trace",
    /* ePragTyp:  */ PragTyp_PARSER_TRACE,
    /* ePragFlag: */ 0,
    /* iArg:      */ 0 },
#endif
#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)

#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
  { /* zName:     */ "writable_schema",
    /* ePragTyp:  */ PragTyp_FLAG,
    /* ePragFlag: */ 0,
    /* iArg:      */ SQLITE_WriteSchema|SQLITE_RecoveryMode },
#endif
};
/* Number of pragmas: 59 on by default, 72 total. */

    u8 aWalHdr[WAL_HDRSIZE];      /* Buffer to assemble wal-header in */
    u32 aCksum[2];                /* Checksum for wal-header */

    sqlite3Put4byte(&aWalHdr[0], (WAL_MAGIC | SQLITE_BIGENDIAN));
    sqlite3Put4byte(&aWalHdr[4], WAL_MAX_VERSION);
    sqlite3Put4byte(&aWalHdr[8], szPage);
    sqlite3Put4byte(&aWalHdr[12], pWal->nCkpt);
    if( pWal->nCkpt==0 ) sqlite3_randomness(8, pWal->hdr.aSalt);


    memcpy(&aWalHdr[16], pWal->hdr.aSalt, 8);
    walChecksumBytes(1, aWalHdr, WAL_HDRSIZE-2*4, 0, aCksum);
    sqlite3Put4byte(&aWalHdr[24], aCksum[0]);
    sqlite3Put4byte(&aWalHdr[28], aCksum[1]);
    
    pWal->szPage = szPage;
    pWal->hdr.bigEndCksum = SQLITE_BIGENDIAN;

  NAME: activate_extensions
  IF:   defined(SQLITE_HAS_CODEC) || defined(SQLITE_ENABLE_CEROD)

  NAME: soft_heap_limit

  NAME: threads



}

# Open the output file
#
set destfile "[file dir [file dir [file normal $argv0]]]/src/pragma.h"
puts "Overwriting $destfile with new pragma table..."
set fd [open $destfile wb]