SQLite

  int i;
  const char *zTarget;            /* Target database to apply OTA to */
  const char *zOta;               /* Database containing OTA */
  char *zErrmsg;                  /* Error message, if any */
  sqlite3ota *pOta;               /* OTA handle */
  int nStep = 0;                  /* Maximum number of step() calls */
  int rc;
  sqlite3_int64 nProgress = 0;

  /* Process command line arguments. Following this block local variables 
  ** zTarget, zOta and nStep are all set. */
  if( argc==5 ){
    int nArg1 = strlen(argv[1]);
    if( nArg1>5 || nArg1<2 || memcmp("-step", argv[1], nArg1) ) usage(argv[0]);
    nStep = atoi(argv[2]);

  /* Open an OTA handle. If nStep is less than or equal to zero, call
  ** sqlite3ota_step() until either the OTA has been completely applied
  ** or an error occurs. Or, if nStep is greater than zero, call
  ** sqlite3ota_step() a maximum of nStep times.  */
  pOta = sqlite3ota_open(zTarget, zOta);
  for(i=0; (nStep<=0 || i<nStep) && sqlite3ota_step(pOta)==SQLITE_OK; i++);
  nProgress = sqlite3ota_progress(pOta);
  rc = sqlite3ota_close(pOta, &zErrmsg);

  /* Let the user know what happened. */
  switch( rc ){
    case SQLITE_OK:
      fprintf(stdout, 
          "SQLITE_OK: ota update incomplete (%lld operations so far)\n",
          nProgress
      );
      break;

    case SQLITE_DONE:
      fprintf(stdout, 
          "SQLITE_DONE: ota update completed (%lld operations)\n",
          nProgress
      );
      break;

    default:
      fprintf(stderr, "error=%d: %s\n", rc, zErrmsg);
      break;
  }

  sqlite3_free(zErrmsg);
  return (rc==SQLITE_OK || rc==SQLITE_DONE) ? 0 : 1;
}

/*
** A structure to store values read from the ota_state table in memory.
*/
struct OtaState {
  char *zTbl;
  char *zIdx;
  int nRow;
  sqlite3_int64 nProgress;
};

/*
** An iterator of this type is used to iterate through all objects in
** the target database that require updating. For each such table, the
** iterator visits, in order:
**

*/
struct sqlite3ota {
  sqlite3 *db;                    /* "main" -> target db, "ota" -> ota db */
  char *zTarget;                  /* Path to target 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;
};

/*
** 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. 

        otaObjIterPrepareAll(p, pIter, 0);
        
        /* Advance to the next row to process. */
        if( p->rc==SQLITE_OK ){
          int rc = sqlite3_step(pIter->pSelect);
          if( rc==SQLITE_ROW ){
            p->nStep++;
            p->nProgress++;
            return otaStep(p);
          }
          p->rc = sqlite3_reset(pIter->pSelect);
          p->nStep = 0;
        }
      }

      otaObjIterNext(p, pIter);
    }

    if( p->rc==SQLITE_OK && pIter->zTbl==0 ){
      p->rc = SQLITE_DONE;
    }
  }
  return p->rc;
}

static void otaSaveTransactionState(sqlite3ota *p){
  otaMPrintfExec(p, 
    "INSERT OR REPLACE INTO ota.ota_state(rowid, tbl, idx, row, progress)"
    "VALUES(1, %Q, %Q, %d, %lld)",
    p->objiter.zTbl, p->objiter.zIdx, p->nStep, p->nProgress
  );
}

/*
** Allocate an OtaState object and load the contents of the ota_state 
** table into it. Return a pointer to the new object. It is the 
** responsibility of the caller to eventually free the object using

        if( zIdx ){
          pRet->zIdx = &pRet->zTbl[nTbl];
          memcpy(pRet->zIdx, zIdx, nIdx);
        }else{
          pRet->zIdx = 0;
        }
        pRet->nRow = sqlite3_column_int(pStmt, 2);
        pRet->nProgress = sqlite3_column_int64(pStmt, 3);
      }
    }else{
      pRet = (OtaState*)sqlite3_malloc(sizeof(OtaState));
      if( pRet ){
        memset(pRet, 0, sizeof(*pRet));
      }
    }

    /* Point the object iterator at the first object */
    if( p->rc==SQLITE_OK ){
      p->rc = otaObjIterFirst(p, &p->objiter);
    }

    if( p->rc==SQLITE_OK ){
      p->nProgress = pState->nProgress;
      otaLoadTransactionState(p, pState);
    }

    sqlite3_free(pState);
  }

  return p;

    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;
}


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

#ifdef SQLITE_TEST 

#include <tcl.h>

**
** Otherwise, if no error occurs, this function returns SQLITE_OK if the
** update has been partially applied, or SQLITE_DONE if it has been 
** completely applied.
*/
int sqlite3ota_close(sqlite3ota *pOta, char **pzErrmsg);

/*
** 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);

#endif /* _SQLITE3OTA_H */