45 lines
2.0 KiB
JavaScript
45 lines
2.0 KiB
JavaScript
/*
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2022-05-23
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The author disclaims copyright to this source code. In place of a
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legal notice, here is a blessing:
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* May you do good and not evil.
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* May you find forgiveness for yourself and forgive others.
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* May you share freely, never taking more than you give.
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***********************************************************************
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This is a JS Worker file for the main sqlite3 api. It loads
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sqlite3.js, initializes the module, and postMessage()'s a message
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after the module is initialized:
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{type: 'sqlite3-api', data: 'ready'}
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This seemingly superfluous level of indirection is necessary when
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loading sqlite3.js via a Worker. Loading sqlite3.js from the main
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window thread elides the Worker-specific API. Instantiating a worker
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with new Worker("sqlite.js") will not (cannot) call
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initSqlite3Module() to initialize the module due to a
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timing/order-of-operations conflict (and that symbol is not exported
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in a way that a Worker loading it that way can see it). Thus JS
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code wanting to load the sqlite3 Worker-specific API needs to pass
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_this_ file (or equivalent) to the Worker constructor and then
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listen for an event in the form shown above in order to know when
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the module has completed initialization. sqlite3.js will fire a
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similar event, with data:'loaded' as the final step in its loading
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process. Whether or not we _really_ need both 'loaded' and 'ready'
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events is unclear, but they are currently separate events primarily
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for the sake of clarity in the timing of when it's okay to use the
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loaded module. At the time the 'loaded' event is fired, it's
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possible (but unknown and unknowable) that the emscripten-generated
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module-setup infrastructure still has work to do. Thus it is
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hypothesized that client code is better off waiting for the 'ready'
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even before using the API.
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*/
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"use strict";
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importScripts('sqlite3.js');
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initSqlite3Module().then(function(){
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setTimeout(()=>self.postMessage({type:'sqlite3-api',data:'ready'}), 0);
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});
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