squoosh/codecs/avif/enc/avif_enc_mt.worker.js

/**
 * @license
 * Copyright 2015 The Emscripten Authors
 * SPDX-License-Identifier: MIT
 */

// Pthread Web Worker startup routine:
// This is the entry point file that is loaded first by each Web Worker
// that executes pthreads on the Emscripten application.

// Thread-local:
var threadInfoStruct = 0; // Info area for this thread in Emscripten HEAP (shared). If zero, this worker is not currently hosting an executing pthread.
var selfThreadId = 0; // The ID of this thread. 0 if not hosting a pthread.
var parentThreadId = 0; // The ID of the parent pthread that launched this thread.
var initializedJS = false; // Guard variable for one-time init of the JS state (currently only embind types registration)

var Module = {};

function assert(condition, text) {
  if (!condition) abort('Assertion failed: ' + text);
}

function threadPrintErr() {
  var text = Array.prototype.slice.call(arguments).join(' ');
  console.error(text);
}
function threadAlert() {
  var text = Array.prototype.slice.call(arguments).join(' ');
  postMessage({cmd: 'alert', text: text, threadId: selfThreadId});
}
// We don't need out() for now, but may need to add it if we want to use it
// here. Or, if this code all moves into the main JS, that problem will go
// away. (For now, adding it here increases code size for no benefit.)
var out = function() {
  throw 'out() is not defined in worker.js.';
}
var err = threadPrintErr;
this.alert = threadAlert;

Module['instantiateWasm'] = function(info, receiveInstance) {
  // Instantiate from the module posted from the main thread.
  // We can just use sync instantiation in the worker.
  var instance = new WebAssembly.Instance(Module['wasmModule'], info);
  // We don't need the module anymore; new threads will be spawned from the main thread.
  Module['wasmModule'] = null;
  receiveInstance(instance); // The second 'module' parameter is intentionally null here, we don't need to keep a ref to the Module object from here.
  return instance.exports;
};

this.onmessage = function(e) {
  try {
    if (e.data.cmd === 'load') { // Preload command that is called once per worker to parse and load the Emscripten code.

      // Module and memory were sent from main thread
      Module['wasmModule'] = e.data.wasmModule;

      Module['wasmMemory'] = e.data.wasmMemory;

      Module['buffer'] = Module['wasmMemory'].buffer;

      Module['ENVIRONMENT_IS_PTHREAD'] = true;

      import(e.data.urlOrBlob).then(function(avif_enc_mt) {
        return avif_enc_mt.default(Module);
      }).then(function(instance) {
        Module = instance;
        postMessage({ 'cmd': 'loaded' });
      });
    } else if (e.data.cmd === 'objectTransfer') {
      Module['PThread'].receiveObjectTransfer(e.data);
    } else if (e.data.cmd === 'run') {
      // This worker was idle, and now should start executing its pthread entry
      // point.
      // performance.now() is specced to return a wallclock time in msecs since
      // that Web Worker/main thread launched. However for pthreads this can
      // cause subtle problems in emscripten_get_now() as this essentially
      // would measure time from pthread_create(), meaning that the clocks
      // between each threads would be wildly out of sync. Therefore sync all
      // pthreads to the clock on the main browser thread, so that different
      // threads see a somewhat coherent clock across each of them
      // (+/- 0.1msecs in testing).
      Module['__performance_now_clock_drift'] = performance.now() - e.data.time;
      threadInfoStruct = e.data.threadInfoStruct;

      // Pass the thread address inside the asm.js scope to store it for fast access that avoids the need for a FFI out.
      Module['registerPthreadPtr'](threadInfoStruct, /*isMainBrowserThread=*/0, /*isMainRuntimeThread=*/0);

      selfThreadId = e.data.selfThreadId;
      parentThreadId = e.data.parentThreadId;
      // Establish the stack frame for this thread in global scope
      // The stack grows downwards
      var max = e.data.stackBase;
      var top = e.data.stackBase + e.data.stackSize;
      assert(threadInfoStruct);
      assert(selfThreadId);
      assert(parentThreadId);
      assert(top != 0);
      assert(max != 0);
      assert(top > max);
      // Also call inside JS module to set up the stack frame for this pthread in JS module scope
      Module['establishStackSpace'](top, max);
      Module['_emscripten_tls_init']();
      Module['writeStackCookie']();

      Module['PThread'].receiveObjectTransfer(e.data);
      Module['PThread'].setThreadStatus(Module['_pthread_self'](), 1/*EM_THREAD_STATUS_RUNNING*/);

      // Embind must initialize itself on all threads, as it generates support JS.
      // We only do this once per worker since they get reused
      if (!initializedJS) {
        Module['___embind_register_native_and_builtin_types']();
        initializedJS = true;
      }

      try {
        // pthread entry points are always of signature 'void *ThreadMain(void *arg)'
        // Native codebases sometimes spawn threads with other thread entry point signatures,
        // such as void ThreadMain(void *arg), void *ThreadMain(), or void ThreadMain().
        // That is not acceptable per C/C++ specification, but x86 compiler ABI extensions
        // enable that to work. If you find the following line to crash, either change the signature
        // to "proper" void *ThreadMain(void *arg) form, or try linking with the Emscripten linker
        // flag -s EMULATE_FUNCTION_POINTER_CASTS=1 to add in emulation for this x86 ABI extension.
        var result = Module['dynCall']('ii', e.data.start_routine, [e.data.arg]);

        Module['checkStackCookie']();
        // The thread might have finished without calling pthread_exit(). If so, then perform the exit operation ourselves.
        // (This is a no-op if explicit pthread_exit() had been called prior.)
        if (!Module['getNoExitRuntime']())
          Module['PThread'].threadExit(result);
      } catch(ex) {
        if (ex === 'Canceled!') {
          Module['PThread'].threadCancel();
        } else if (ex != 'unwind') {
          Atomics.store(Module['HEAPU32'], (threadInfoStruct + 4 /*C_STRUCTS.pthread.threadExitCode*/ ) >> 2, (ex instanceof Module['ExitStatus']) ? ex.status : -2 /*A custom entry specific to Emscripten denoting that the thread crashed.*/);

          Atomics.store(Module['HEAPU32'], (threadInfoStruct + 0 /*C_STRUCTS.pthread.threadStatus*/ ) >> 2, 1); // Mark the thread as no longer running.
          if (typeof(Module['_emscripten_futex_wake']) !== "function") {
            err("Thread Initialisation failed.");
            throw ex;
          }
          Module['_emscripten_futex_wake'](threadInfoStruct + 0 /*C_STRUCTS.pthread.threadStatus*/, 0x7FFFFFFF/*INT_MAX*/); // Wake all threads waiting on this thread to finish.
          if (!(ex instanceof Module['ExitStatus'])) throw ex;
        } else {
          // else e == 'unwind', and we should fall through here and keep the pthread alive for asynchronous events.
          err('Pthread 0x' + threadInfoStruct.toString(16) + ' completed its pthread main entry point with an unwind, keeping the pthread worker alive for asynchronous operation.');
        }
      }
    } else if (e.data.cmd === 'cancel') { // Main thread is asking for a pthread_cancel() on this thread.
      if (threadInfoStruct) {
        Module['PThread'].threadCancel();
      }
    } else if (e.data.target === 'setimmediate') {
      // no-op
    } else if (e.data.cmd === 'processThreadQueue') {
      if (threadInfoStruct) { // If this thread is actually running?
        Module['_emscripten_current_thread_process_queued_calls']();
      }
    } else {
      err('worker.js received unknown command ' + e.data.cmd);
      err(e.data);
    }
  } catch(ex) {
    err('worker.js onmessage() captured an uncaught exception: ' + ex);
    if (ex && ex.stack) err(ex.stack);
    throw ex;
  }
};