SQLite

          if(capi.SQLITE_TRACE_STMT===t){
            // x == SQL, p == sqlite3_stmt*
            console.log("SQL TRACE #"+(++this.counter)+' via sqlite3@'+c+':',
                        wasm.cstrToJs(x));
          }
        }.bind({counter: 0}));

  /**
     A map of sqlite3_vfs pointers to SQL code or a callback function
     to run when the DB constructor opens a database with the given
     VFS. In the latter case, the call signature is (theDbObject,sqlite3Namespace)
     and the callback is expected to throw on error.
  */
  const __vfsPostOpenSql = Object.create(null);

//#if enable-see
  /**
     Converts ArrayBuffer or Uint8Array ba into a string of hex
     digits.
  */
  const byteArrayToHex = function(ba){
    if( ba instanceof ArrayBuffer ){

    try{
//#if enable-see
      dbCtorApplySEEKey(this,opt);
//#endif
      // Check for per-VFS post-open SQL/callback...
      const pVfs = capi.sqlite3_js_db_vfs(pDb)
            || toss3("Internal error: cannot get VFS for new db handle.");
      const postInitSql = __vfsPostOpenSql[pVfs];
      if(postInitSql){
        /**
           Reminder: if this db is encrypted and the client did _not_ pass
           in the key, any init code will fail, causing the ctor to throw.
           We don't actually know whether the db is encrypted, so we cannot
           sensibly apply any heuristics which skip the init code only for
           encrypted databases for which no key has yet been supplied.

      }
    }catch(e){
      this.close();
      throw e;
    }
  };


  /**







     Sets SQL which should be exec()'d on a DB instance after it is

     opened with the given VFS pointer. The SQL may be any type
     supported by the "string:flexible" function argument conversion.
     Alternately, the 2nd argument may be a function, in which case it
     is called with (theOo1DbObject,sqlite3Namespace) at the end of
     the DB() constructor. The function must throw on error, in which
     case the db is closed and the exception is propagated.  This
     function is intended only for use by DB subclasses or sqlite3_vfs
     implementations.







  */
  dbCtorHelper.setVfsPostOpenSql = function(pVfs, sql){




    __vfsPostOpenSql[pVfs] = sql;
  };

  /**
     A helper for DB constructors. It accepts either a single
     config-style object or up to 3 arguments (filename, dbOpenFlags,
     dbVfsName). It returns a new object containing:

     SQLITE_OPEN_xyz types not listed here may be inadvertently
     left in OPFS but are treated as transient by this VFS and
     they will be cleaned up during VFS init. */
  const PERSISTENT_FILE_TYPES =
        capi.SQLITE_OPEN_MAIN_DB |
        capi.SQLITE_OPEN_MAIN_JOURNAL |
        capi.SQLITE_OPEN_SUPER_JOURNAL |
        capi.SQLITE_OPEN_WAL /* noting that WAL support is
                                unavailable in the WASM build.*/;

  /** Subdirectory of the VFS's space where "opaque" (randomly-named)
      files are stored. Changing this effectively invalidates the data
      stored under older names (orphaning it), so don't do that. */
  const OPAQUE_DIR_NAME = ".opaque";

  /**

          const OpfsSAHPoolDb = function(...args){
            const opt = oo1.DB.dbCtorHelper.normalizeArgs(...args);
            opt.vfs = theVfs.$zName;
            oo1.DB.dbCtorHelper.call(this, opt);
          };
          OpfsSAHPoolDb.prototype = Object.create(oo1.DB.prototype);
          poolUtil.OpfsSAHPoolDb = OpfsSAHPoolDb;
          oo1.DB.dbCtorHelper.setVfsPostOpenSql(
            theVfs.pointer,
            function(oo1Db, sqlite3){
              sqlite3.capi.sqlite3_exec(oo1Db, [
                /* See notes in sqlite3-vfs-opfs.js */
                "pragma journal_mode=DELETE;",
                "pragma cache_size=-16384;"
              ], 0, 0, 0);
            }
          );
        }/*extend sqlite3.oo1*/
        thePool.log("VFS initialized.");
        return poolUtil;
      }).catch(async (e)=>{
        await thePool.removeVfs().catch(()=>{});
        throw e;
      });

        const opt = sqlite3.oo1.DB.dbCtorHelper.normalizeArgs(...args);
        opt.vfs = opfsVfs.$zName;
        sqlite3.oo1.DB.dbCtorHelper.call(this, opt);
      };
      OpfsDb.prototype = Object.create(sqlite3.oo1.DB.prototype);
      sqlite3.oo1.OpfsDb = OpfsDb;
      OpfsDb.importDb = opfsUtil.importDb;
      sqlite3.oo1.DB.dbCtorHelper.setVfsPostOpenSql(
        opfsVfs.pointer,
        function(oo1Db, sqlite3){
          /* Set a relatively high default busy-timeout handler to
             help OPFS dbs deal with multi-tab/multi-worker
             contention. */
          sqlite3.capi.sqlite3_busy_timeout(oo1Db, 10000);
          sqlite3.capi.sqlite3_exec(oo1Db, [
            /* As of July 2023, the PERSIST journal mode on OPFS is
               somewhat slower than DELETE or TRUNCATE (it was faster
               before Chrome version 108 or 109). TRUNCATE and DELETE
               have very similar performance on OPFS.

               Roy Hashimoto notes that TRUNCATE and PERSIST modes may
               decrease OPFS concurrency because multiple connections
               can open the journal file in those modes:

               https://github.com/rhashimoto/wa-sqlite/issues/68

               Given that, and the fact that testing has not revealed
               any appreciable difference between performance of
               TRUNCATE and DELETE modes on OPFS, we currently (as of
               2023-07-13) default to DELETE mode.
            */
            "pragma journal_mode=DELETE;",
            /*
              This vfs benefits hugely from cache on moderate/large
              speedtest1 --size 50 and --size 100 workloads. We
              currently rely on setting a non-default cache size when
              building sqlite3.wasm. If that policy changes, the cache
              can be set here.
            */
            "pragma cache_size=-16384;"
          ], 0, 0, 0);
        }
      );
    }/*extend sqlite3.oo1*/

    const sanityCheck = function(){
      const scope = wasm.scopedAllocPush();
      const sq3File = new sqlite3_file();

        T.assert(0 === u1.getFileCount());
        const dbName = '/foo.db';
        let db = new u1.OpfsSAHPoolDb(dbName);
        T.assert(db instanceof sqlite3.oo1.DB)
          .assert(1 === u1.getFileCount());
        db.exec([













          'create table t(a);',
          'insert into t(a) values(1),(2),(3)'
        ]);
        T.assert(1 === u1.getFileCount());
        T.assert(3 === db.selectValue('select count(*) from t'));

        db.close();
        T.assert(1 === u1.getFileCount());
        db = new u2.OpfsSAHPoolDb(dbName);
        T.assert(1 === u1.getFileCount());
        db.close();
        const fileNames = u1.getFileNames();
        T.assert(1 === fileNames.length)
          .assert(dbName === fileNames[0])
          .assert(1 === u1.getFileCount())

        if(1){ // test exportFile() and importDb()
          const dbytes = u1.exportFile(dbName);
          T.assert(dbytes.length >= 4096);
          const dbName2 = '/exported.db';
          let nWrote = u1.importDb(dbName2, dbytes);
          T.assert( 2 == u1.getFileCount() )
            .assert( dbytes.byteLength == nWrote );
          let db2 = new u1.OpfsSAHPoolDb(dbName2);
          T.assert(db2 instanceof sqlite3.oo1.DB)

            .assert(3 === db2.selectValue('select count(*) from t'));
          db2.close();
          T.assert(true === u1.unlink(dbName2))
            .assert(false === u1.unlink(dbName2))
            .assert(1 === u1.getFileCount())
            .assert(1 === u1.getFileNames().length);
          // Try again with a function as an input source: