Fix FIONREAD for pipes

Fixes: #26711

Author: sbc100

src/audio_worklet.js

@@ -273,6 +273,7 @@ var port = globalThis.port || {};
 class BootstrapMessages extends AudioWorkletProcessor {
   constructor(arg) {
     super();
+    console.log("BootstrapMessages CTOR", arg);
     startWasmWorker(arg.processorOptions)
     // Listen to messages from the main thread. These messages will ask this
     // scope to create the real AudioWorkletProcessors that call out to Wasm to

src/lib/libpipefs.js

@@ -117,7 +117,16 @@ addToLibrary({
       dup(stream) {
         stream.node.pipe.refcnt++;
       },
-      ioctl(stream, request, varargs) {
+      ioctl(stream, request, argp) {
+        if (request == {{{ cDefs.FIONREAD }}}) {
+          var pipe = stream.node.pipe;
+          var currentLength = 0;
+          for (var bucket of pipe.buckets) {
+            currentLength += bucket.offset - bucket.roffset;
+          }
+          {{{ makeSetValue('argp', 0, 'currentLength', 'i32') }}};
+          return 0;
+        }
         return {{{ cDefs.EINVAL }}};
       },
       fsync(stream) {

src/lib/libwebaudio.js

@@ -227,6 +227,7 @@ var LibraryWebAudio = {
         audioWorklet['port'] = {
           postMessage: (msg) => {
             if (msg['_boot']) {
+              console.log("creating em-bootstrap", Object.keys(msg));
               audioWorklet.bootstrapMessage = new AudioWorkletNode(audioContext, 'em-bootstrap', {
                 processorOptions: msg
               });

test/core/test_pipe_select.c

@@ -1,4 +1,5 @@
 #include <sys/select.h>
+#include <sys/ioctl.h>
 #include <time.h>
 #include <assert.h>
 #include <stdio.h>
@@ -7,18 +8,29 @@
 
 int pipe_a[2];
 
+int get_available(int fd) {
+  int avail = 0;
+  assert(ioctl(fd, FIONREAD, &avail) == 0);
+  printf("FIONREAD %d -> %d\n", fd, avail);
+  return avail;
+}
+
 int main() {
   fd_set readfds;
   const char *t = "test\n";
 
   assert(pipe(pipe_a) == 0);
+  assert(get_available(pipe_a[0]) == 0);
+  assert(get_available(pipe_a[1]) == 0);
+
   FD_ZERO(&readfds);
   FD_SET(pipe_a[0], &readfds);
   write(pipe_a[1], t, strlen(t));
   assert(select(pipe_a[0] + 1, &readfds, NULL, NULL, NULL) == 1);
   assert(FD_ISSET(pipe_a[0], &readfds));
+  assert(get_available(pipe_a[0]) == strlen(t));
+  assert(get_available(pipe_a[1]) == strlen(t));
 
   close(pipe_a[0]); close(pipe_a[1]);
-
   return 0;
 }