421 lines
15 KiB
JavaScript
421 lines
15 KiB
JavaScript
/*
|
|
2022-07-22
|
|
|
|
The author disclaims copyright to this source code. In place of a
|
|
legal notice, here is a blessing:
|
|
|
|
* May you do good and not evil.
|
|
* May you find forgiveness for yourself and forgive others.
|
|
* May you share freely, never taking more than you give.
|
|
|
|
***********************************************************************
|
|
|
|
This file implements a Worker-based wrapper around SQLite3 OO API
|
|
#1.
|
|
|
|
In order to permit this API to be loaded in worker threads without
|
|
automatically registering onmessage handlers, initializing the
|
|
worker API requires calling initWorkerAPI(). If this function
|
|
is called from a non-worker thread then it throws an exception.
|
|
|
|
When initialized, it installs message listeners to receive messages
|
|
from the main thread and then it posts a message in the form:
|
|
|
|
```
|
|
{type:'sqlite3-api',data:'worker-ready'}
|
|
```
|
|
|
|
This file requires that the core C-style sqlite3 API and OO API #1
|
|
have been loaded and that self.sqlite3 contains both,
|
|
as documented for those APIs.
|
|
*/
|
|
self.sqlite3.initWorkerAPI = function(){
|
|
'use strict';
|
|
/**
|
|
UNDER CONSTRUCTION
|
|
|
|
We need an API which can proxy the DB API via a Worker message
|
|
interface. The primary quirky factor in such an API is that we
|
|
cannot pass callback functions between the window thread and a
|
|
worker thread, so we have to receive all db results via
|
|
asynchronous message-passing. That requires an asychronous API
|
|
with a distinctly different shape that the main OO API.
|
|
|
|
Certain important considerations here include:
|
|
|
|
- Support only one db connection or multiple? The former is far
|
|
easier, but there's always going to be a user out there who wants
|
|
to juggle six database handles at once. Do we add that complexity
|
|
or tell such users to write their own code using the provided
|
|
lower-level APIs?
|
|
|
|
- Fetching multiple results: do we pass them on as a series of
|
|
messages, with start/end messages on either end, or do we collect
|
|
all results and bundle them back in a single message? The former
|
|
is, generically speaking, more memory-efficient but the latter
|
|
far easier to implement in this environment. The latter is
|
|
untennable for large data sets. Despite a web page hypothetically
|
|
being a relatively limited environment, there will always be
|
|
those users who feel that they should/need to be able to work
|
|
with multi-hundred-meg (or larger) blobs, and passing around
|
|
arrays of those may quickly exhaust the JS engine's memory.
|
|
|
|
TODOs include, but are not limited to:
|
|
|
|
- The ability to manage multiple DB handles. This can
|
|
potentially be done via a simple mapping of DB.filename or
|
|
DB.pointer (`sqlite3*` handle) to DB objects. The open()
|
|
interface would need to provide an ID (probably DB.pointer) back
|
|
to the user which can optionally be passed as an argument to
|
|
the other APIs (they'd default to the first-opened DB, for
|
|
ease of use). Client-side usability of this feature would
|
|
benefit from making another wrapper class (or a singleton)
|
|
available to the main thread, with that object proxying all(?)
|
|
communication with the worker.
|
|
|
|
- Revisit how virtual files are managed. We currently delete DBs
|
|
from the virtual filesystem when we close them, for the sake of
|
|
saving memory (the VFS lives in RAM). Supporting multiple DBs may
|
|
require that we give up that habit. Similarly, fully supporting
|
|
ATTACH, where a user can upload multiple DBs and ATTACH them,
|
|
also requires the that we manage the VFS entries better.
|
|
*/
|
|
const toss = (...args)=>{throw new Error(args.join(' '))};
|
|
if('function' !== typeof importScripts){
|
|
toss("Cannot initalize the sqlite3 worker API in the main thread.");
|
|
}
|
|
const self = this.self;
|
|
const sqlite3 = this.sqlite3 || toss("Missing this.sqlite3 object.");
|
|
const SQLite3 = sqlite3.oo1 || toss("Missing this.sqlite3.oo1 OO API.");
|
|
const DB = SQLite3.DB;
|
|
|
|
/**
|
|
Returns the app-wide unique ID for the given db, creating one if
|
|
needed.
|
|
*/
|
|
const getDbId = function(db){
|
|
let id = wState.idMap.get(db);
|
|
if(id) return id;
|
|
id = 'db#'+(++wState.idSeq)+'@'+db.pointer;
|
|
/** ^^^ can't simply use db.pointer b/c closing/opening may re-use
|
|
the same address, which could map pending messages to a wrong
|
|
instance. */
|
|
wState.idMap.set(db, id);
|
|
return id;
|
|
};
|
|
|
|
/**
|
|
Helper for managing Worker-level state.
|
|
*/
|
|
const wState = {
|
|
defaultDb: undefined,
|
|
idSeq: 0,
|
|
idMap: new WeakMap,
|
|
open: function(arg){
|
|
// TODO: if arg is a filename, look for a db in this.dbs with the
|
|
// same filename and close/reopen it (or just pass it back as is?).
|
|
if(!arg && this.defaultDb) return this.defaultDb;
|
|
//???if(this.defaultDb) this.defaultDb.close();
|
|
let db;
|
|
db = (Array.isArray(arg) ? new DB(...arg) : new DB(arg));
|
|
this.dbs[getDbId(db)] = db;
|
|
if(!this.defaultDb) this.defaultDb = db;
|
|
return db;
|
|
},
|
|
close: function(db,alsoUnlink){
|
|
if(db){
|
|
delete this.dbs[getDbId(db)];
|
|
db.close(alsoUnlink);
|
|
if(db===this.defaultDb) this.defaultDb = undefined;
|
|
}
|
|
},
|
|
post: function(type,data,xferList){
|
|
if(xferList){
|
|
self.postMessage({type, data},xferList);
|
|
xferList.length = 0;
|
|
}else{
|
|
self.postMessage({type, data});
|
|
}
|
|
},
|
|
/** Map of DB IDs to DBs. */
|
|
dbs: Object.create(null),
|
|
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. */
|
|
const affirmDbOpen = function(db = wState.defaultDb){
|
|
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.defaultDb;
|
|
return affirmExists ? affirmDbOpen(db) : db;
|
|
};
|
|
|
|
const getDefaultDbId = function(){
|
|
return wState.defaultDb && getDbId(wState.defaultDb);
|
|
};
|
|
|
|
/**
|
|
A level of "organizational abstraction" for the Worker
|
|
API. Each method in this object must map directly to a Worker
|
|
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 response
|
|
state, which the dispatcher may amend. All methods must throw
|
|
on error.
|
|
*/
|
|
const wMsgHandler = {
|
|
xfer: [/*Temp holder for "transferable" postMessage() state.*/],
|
|
/**
|
|
Proxy for DB.exec() which expects a single argument of type
|
|
string (SQL to execute) or an options object in the form
|
|
expected by exec(). The notable differences from exec()
|
|
include:
|
|
|
|
- The default value for options.rowMode is 'array' because
|
|
the normal default cannot cross the window/Worker boundary.
|
|
|
|
- A function-type options.callback property cannot cross
|
|
the window/Worker boundary, so is not useful here. If
|
|
options.callback is a string then it is assumed to be a
|
|
message type key, in which case a callback function will be
|
|
applied which posts each row result via:
|
|
|
|
postMessage({type: thatKeyType, data: theRow})
|
|
|
|
And, at the end of the result set (whether or not any
|
|
result rows were produced), it will post an identical
|
|
message with data:null to alert the caller than the result
|
|
set is completed.
|
|
|
|
The callback proxy must not recurse into this interface, or
|
|
results are undefined. (It hypothetically cannot recurse
|
|
because an exec() call will be tying up the Worker thread,
|
|
causing any recursion attempt to wait until the first
|
|
exec() is completed.)
|
|
|
|
The response is the input options object (or a synthesized
|
|
one if passed only a string), noting that
|
|
options.resultRows and options.columnNames may be populated
|
|
by the call to exec().
|
|
|
|
This opens/creates the Worker's db if needed.
|
|
*/
|
|
exec: function(ev){
|
|
const opt = (
|
|
'string'===typeof ev.data
|
|
) ? {sql: ev.data} : (ev.data || Object.create(null));
|
|
if(undefined===opt.rowMode){
|
|
/* Since the default rowMode of 'stmt' is not useful
|
|
for the Worker interface, we'll default to
|
|
something else. */
|
|
opt.rowMode = 'array';
|
|
}else if('stmt'===opt.rowMode){
|
|
toss("Invalid rowMode for exec(): stmt mode",
|
|
"does not work in the Worker API.");
|
|
}
|
|
const db = getMsgDb(ev);
|
|
if(opt.callback || Array.isArray(opt.resultRows)){
|
|
// Part of a copy-avoidance optimization for blobs
|
|
db._blobXfer = this.xfer;
|
|
}
|
|
const callbackMsgType = opt.callback;
|
|
if('string' === typeof callbackMsgType){
|
|
/* Treat this as a worker message type and post each
|
|
row as a message of that type. */
|
|
const that = this;
|
|
opt.callback =
|
|
(row)=>wState.post(callbackMsgType,row,this.xfer);
|
|
}
|
|
try {
|
|
db.exec(opt);
|
|
if(opt.callback instanceof Function){
|
|
opt.callback = callbackMsgType;
|
|
wState.post(callbackMsgType, null);
|
|
}
|
|
}/*catch(e){
|
|
console.warn("Worker is propagating:",e);throw e;
|
|
}*/finally{
|
|
delete db._blobXfer;
|
|
if(opt.callback){
|
|
opt.callback = callbackMsgType;
|
|
}
|
|
}
|
|
return opt;
|
|
}/*exec()*/,
|
|
/**
|
|
TO(re)DO, once we can abstract away access to the
|
|
JS environment's virtual filesystem. Currently this
|
|
always throws.
|
|
|
|
Response is (should be) an object:
|
|
|
|
{
|
|
buffer: Uint8Array (db file contents),
|
|
filename: the current db filename,
|
|
mimetype: 'application/x-sqlite3'
|
|
}
|
|
|
|
TODO is to determine how/whether this feature can support
|
|
exports of ":memory:" and "" (temp file) DBs. The latter is
|
|
ostensibly easy because the file is (potentially) on disk, but
|
|
the former does not have a structure which maps directly to a
|
|
db file image.
|
|
*/
|
|
export: function(ev){
|
|
toss("export() requires reimplementing for portability reasons.");
|
|
/**const db = getMsgDb(ev);
|
|
const response = {
|
|
buffer: db.exportBinaryImage(),
|
|
filename: db.filename,
|
|
mimetype: 'application/x-sqlite3'
|
|
};
|
|
this.xfer.push(response.buffer.buffer);
|
|
return response;**/
|
|
}/*export()*/,
|
|
/**
|
|
Proxy for the DB constructor. Expects to be passed a single
|
|
object or a falsy value to use defaults. The object may
|
|
have a filename property to name the db file (see the DB
|
|
constructor for peculiarities and transformations) and/or a
|
|
buffer property (a Uint8Array holding a complete database
|
|
file's contents). The response is an object:
|
|
|
|
{
|
|
filename: db filename (possibly differing from the input),
|
|
|
|
id: an opaque ID value intended for future distinction
|
|
between multiple db handles. Messages including a specific
|
|
ID will use the DB for that ID.
|
|
|
|
}
|
|
|
|
If the Worker's db is currently opened, this call closes it
|
|
before proceeding.
|
|
*/
|
|
open: function(ev){
|
|
wState.close(/*true???*/);
|
|
const args = [], data = (ev.data || {});
|
|
if(data.simulateError){
|
|
toss("Throwing because of open.simulateError flag.");
|
|
}
|
|
if(data.filename) args.push(data.filename);
|
|
if(data.buffer){
|
|
args.push(data.buffer);
|
|
this.xfer.push(data.buffer.buffer);
|
|
}
|
|
const db = wState.open(args);
|
|
return {
|
|
filename: db.filename,
|
|
dbId: getDbId(db)
|
|
};
|
|
},
|
|
/**
|
|
Proxy for DB.close(). If ev.data may either be a boolean or
|
|
an object with an `unlink` property. If that value is
|
|
truthy then the db file (if the db is currently open) will
|
|
be unlinked from the virtual filesystem, else it will be
|
|
kept intact. The response object is:
|
|
|
|
{
|
|
filename: db filename _if_ the db is opened when this
|
|
is called, else the undefined value
|
|
}
|
|
*/
|
|
close: function(ev){
|
|
const db = getMsgDb(ev,false);
|
|
const response = {
|
|
filename: db && db.filename
|
|
};
|
|
if(db){
|
|
wState.close(db, !!((ev.data && 'object'===typeof ev.data)
|
|
? ev.data.unlink : ev.data));
|
|
}
|
|
return response;
|
|
},
|
|
toss: function(ev){
|
|
toss("Testing worker exception");
|
|
}
|
|
}/*wMsgHandler*/;
|
|
|
|
/**
|
|
UNDER CONSTRUCTION!
|
|
|
|
A subset of the DB API is accessible via Worker messages in the
|
|
form:
|
|
|
|
{ type: apiCommand,
|
|
dbId: optional DB ID value (else uses a default db handle)
|
|
data: apiArguments
|
|
}
|
|
|
|
As a rule, these commands respond with a postMessage() of their
|
|
own in the same form, but will, if needed, transform the `data`
|
|
member to an object and may add state to it. The responses
|
|
always have an object-format `data` part. If the inbound `data`
|
|
is an object which has a `messageId` property, that property is
|
|
always mirrored in the result object, for use in client-side
|
|
dispatching of these asynchronous results. Exceptions thrown
|
|
during processing result in an `error`-type event with a
|
|
payload in the form:
|
|
|
|
{
|
|
message: error string,
|
|
errorClass: class name of the error type,
|
|
dbId: DB handle ID,
|
|
input: ev.data,
|
|
[messageId: if set in the inbound message]
|
|
}
|
|
|
|
The individual APIs are documented in the wMsgHandler object.
|
|
*/
|
|
self.onmessage = function(ev){
|
|
ev = ev.data;
|
|
let response, dbId = ev.dbId, evType = ev.type;
|
|
const arrivalTime = performance.now();
|
|
try {
|
|
if(wMsgHandler.hasOwnProperty(evType) &&
|
|
wMsgHandler[evType] instanceof Function){
|
|
response = wMsgHandler[evType](ev);
|
|
}else{
|
|
toss("Unknown db worker message type:",ev.type);
|
|
}
|
|
}catch(err){
|
|
evType = 'error';
|
|
response = {
|
|
message: err.message,
|
|
errorClass: err.name,
|
|
input: ev
|
|
};
|
|
if(err.stack){
|
|
response.stack = ('string'===typeof err.stack)
|
|
? err.stack.split('\n') : err.stack;
|
|
}
|
|
if(0) console.warn("Worker is propagating an exception to main thread.",
|
|
"Reporting it _here_ for the stack trace:",err,response);
|
|
}
|
|
if(!response.messageId && ev.data
|
|
&& 'object'===typeof ev.data && ev.data.messageId){
|
|
response.messageId = ev.data.messageId;
|
|
}
|
|
if(!dbId){
|
|
dbId = response.dbId/*from 'open' cmd*/
|
|
|| getDefaultDbId();
|
|
}
|
|
if(!response.dbId) response.dbId = dbId;
|
|
// Timing info is primarily for use in testing this API. It's not part of
|
|
// the public API. arrivalTime = when the worker got the message.
|
|
response.workerReceivedTime = arrivalTime;
|
|
response.workerRespondTime = performance.now();
|
|
response.departureTime = ev.departureTime;
|
|
wState.post(evType, response, wMsgHandler.xfer);
|
|
};
|
|
setTimeout(()=>self.postMessage({type:'sqlite3-api',data:'worker-ready'}), 0);
|
|
}.bind({self, sqlite3: self.sqlite3});
|