SQLite

      const kvvfsMakeKey = wasm.exports.sqlite3_wasm_kvvfsMakeKeyOnPstack,
            pstack = wasm.pstack,
            pAllocRaw = wasm.exports.sqlite3_wasm_pstack_alloc;

      const kvvfsStorage = (zClass)=>
            ((115/*=='s'*/===wasm.getMemValue(zClass))
             ? sessionStorage : localStorage);

      /**
         Implementations for members of the object referred to by
         sqlite3_wasm_kvvfs_methods(). We swap out the native
         implementations with these, which use localStorage or
         sessionStorage for their backing store.
      */
      const kvvfsImpls = {
        xRead: (zClass, zKey, zBuf, nBuf)=>{
          const stack = pstack.pointer,
                astack = wasm.scopedAllocPush();
          try {
            const zXKey = kvvfsMakeKey(zClass,zKey);
            if(!zXKey) return -3/*OOM*/;

            console.error("kvstorageDelete()",e);
            return capi.SQLITE_IOERR;
          }finally{
            pstack.restore(stack);
          }
        }
      }/*kvvfsImpls*/;
      for(const k of Object.keys(kvvfsImpls)){
        kvvfsMethods[kvvfsMethods.memberKey(k)] =
          wasm.installFunction(
            kvvfsMethods.memberSignature(k),
            kvvfsImpls[k]
          );
      }
    }else{

    messageId: ...as above...,
    result: {
      filename: db filename, possibly differing from the input.

      dbId: an opaque ID value which must be passed in the message
      envelope to other calls in this API to tell them which db to
      use. If it is not provided to future calls, they will default to
      operating on the least-recently-opened db. This property is, for
      API consistency's sake, also part of the containing message
      envelope.  Only the `open` operation includes it in the `result`
      property.

      persistent: true if the given filename resides in the
      known-persistent storage, else false.

   }
  }
  ```

    return id;
  };

  /**
     Internal helper for managing Worker-level state.
  */
  const wState = {
    /**
       Each opened DB is added to this.dbList, and the first entry in
       that list is the default db. As each db is closed, its entry is
       removed from the list.
    */
    dbList: [],
    /** Sequence number of dbId generation. */
    idSeq: 0,
    /** Map of DB instances to dbId. */
    idMap: new WeakMap,
    /** Temp holder for "transferable" postMessage() state. */
    xfer: [],
    open: function(opt){
      const db = new DB(opt.filename);
      this.dbs[getDbId(db)] = db;
      if(this.dbList.indexOf(db)<0) this.dbList.push(db);
      return db;
    },
    close: function(db,alsoUnlink){
      if(db){
        delete this.dbs[getDbId(db)];
        const filename = db.filename;
        const pVfs = sqlite3.wasm.sqlite3_wasm_db_vfs(db.pointer, 0);
        db.close();
        const ddNdx = this.dbList.indexOf(db);
        if(ddNdx>=0) this.dbList.splice(ddNdx, 1);
        if(alsoUnlink && filename && pVfs){
          sqlite3.wasm.sqlite3_wasm_vfs_unlink(pVfs, filename);
        }
      }
    },
    /**
       Posts the given worker message value. If xferList is provided,

        id is not valid, else return the db or undefined. */
    getDb: function(id,require=true){
      return this.dbs[id]
        || (require ? toss("Unknown (or closed) DB ID:",id) : undefined);
    }
  };

  /** Throws if the given db is falsy or not opened, else returns its
      argument. */
  const affirmDbOpen = function(db = wState.dbList[0]){
    return (db && db.pointer) ? db : toss("DB is not opened.");
  };

  /** Extract dbId from the given message payload. */
  const getMsgDb = function(msgData,affirmExists=true){
    const db = wState.getDb(msgData.dbId,false) || wState.dbList[0];
    return affirmExists ? affirmDbOpen(db) : db;
  };

  const getDefaultDbId = function(){
    return wState.dbList[0] && getDbId(wState.dbList[0]);
  };

  /**
     A level of "organizational abstraction" for the Worker1
     API. Each method in this object must map directly to a Worker1
     message type key. The onmessage() dispatcher attempts to
     dispatch all inbound messages to a method of this object,
     passing it the event.data part of the inbound event object. All
     methods must return a plain Object containing any result
     state, which the dispatcher may amend. All methods must throw
     on error.
  */

        oargs.filename = args.filename || '';
      }else{
        oargs.filename = args.filename;
      }
      const db = wState.open(oargs);
      rc.filename = db.filename;
      rc.persistent = (!!pDir && db.filename.startsWith(pDir+'/'))
        || !!sqlite3.capi.sqlite3_js_db_uses_vfs(db.pointer, "opfs");
      rc.dbId = getDbId(db);
      return rc;
    },

    close: function(ev){
      const db = getMsgDb(ev,false);
      const response = {

      rc.wasmfsOpfsEnabled = !!sqlite3.capi.sqlite3_wasmfs_opfs_dir();
      rc.version = sqlite3.version;
      rc.vfsList = sqlite3.capi.sqlite3_js_vfs_list();
      return rc;
    },

    /**



       Exports the database to a byte array, as per
       sqlite3_serialize(). Response is an object:

       {
         bytearray: Uint8Array (db file contents),
         filename: the current db filename,
         mimetype: 'application/x-sqlite3'
       }





    */
    export: function(ev){

      /**
         We need to reimplement this to use the Emscripten FS
         interface. That part used to be in the OO#1 API but that
         dependency was removed from that level of the API.
      */
      const db = getMsgDb(ev);
      const response = {
        bytearray: sqlite3.capi.sqlite3_js_db_export(db.pointer),
        filename: db.filename,
        mimetype: 'application/x-sqlite3'
      };
      wState.xfer.push(response.bytearray.buffer);
      return response;
    }/*export()*/,

    toss: function(ev){
      toss("Testing worker exception");
    }
  }/*wMsgHandler*/;