Two workers & worker termination (#198)

* Refactoring codecs

* Plugging in new processor

* Fixing decorator

* MozJPEG free issue

* Better worker aborting, and terminate workers that aren't used for 10 seconds

* Better comment

* Ooops, half-typed comment

* Uncommenting problematic line

* Surma fixed it!

* Abstracting WASM initialisation

* Better comment

* Don't need this.

* Adding ticket

* noInitalRun

* Reverting MozJPEG issue demo

* Making a const for worker timeout

* Inline docs

* Bail early rather than nesting

* Addressing nits

src/codecs/mozjpeg/encoder.ts

@@ -1,49 +1,18 @@
-import EncoderWorker from './Encoder.worker';
+import mozjpeg_enc, { MozJPEGModule } from '../../../codecs/mozjpeg_enc/mozjpeg_enc';
+import wasmUrl from '../../../codecs/mozjpeg_enc/mozjpeg_enc.wasm';
+import { EncodeOptions } from './encoder-meta';
+import { initWasmModule } from '../util';
 
-export enum MozJpegColorSpace {
-  GRAYSCALE = 1,
-  RGB,
-  YCbCr,
-}
-
-export interface EncodeOptions {
-  quality: number;
-  baseline: boolean;
-  arithmetic: boolean;
-  progressive: boolean;
-  optimize_coding: boolean;
-  smoothing: number;
-  color_space: MozJpegColorSpace;
-  quant_table: number;
-  trellis_multipass: boolean;
-  trellis_opt_zero: boolean;
-  trellis_opt_table: boolean;
-  trellis_loops: number;
-}
-
-export interface EncoderState { type: typeof type; options: EncodeOptions; }
-
-export const type = 'mozjpeg';
-export const label = 'MozJPEG';
-export const mimeType = 'image/jpeg';
-export const extension = 'jpg';
-export const defaultOptions: EncodeOptions = {
-  quality: 75,
-  baseline: false,
-  arithmetic: false,
-  progressive: true,
-  optimize_coding: true,
-  smoothing: 0,
-  color_space: MozJpegColorSpace.YCbCr,
-  quant_table: 3,
-  trellis_multipass: false,
-  trellis_opt_zero: false,
-  trellis_opt_table: false,
-  trellis_loops: 1,
-};
-
-export async function encode(data: ImageData, options: EncodeOptions) {
-  // We need to await this because it's been comlinked.
-  const encoder = await new EncoderWorker();
-  return encoder.encode(data, options);
+let emscriptenModule: Promise<MozJPEGModule>;
+
+export async function encode(data: ImageData, options: EncodeOptions): Promise<ArrayBuffer> {
+  if (!emscriptenModule) emscriptenModule = initWasmModule(mozjpeg_enc, wasmUrl);
+
+  const module = await emscriptenModule;
+  const resultView = module.encode(data.data, data.width, data.height, options);
+  const result = new Uint8Array(resultView);
+  module.free_result();
+
+  // wasm can’t run on SharedArrayBuffers, so we hard-cast to ArrayBuffer.
+  return result.buffer as ArrayBuffer;
 }