Fix FIONREAD for pipes

.circleci/config.yml

@@ -718,6 +718,7 @@ jobs:
             wasm2js3.test_memorygrowth_2
             wasm2js2.test_pthread_proxying
             wasmfs.test_hello_world
+            wasmfs.test_pipe_select
             wasmfs.test_unistd_links*
             wasmfs.test_atexit_standalone
             wasmfs.test_emscripten_get_now

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) {

system/lib/wasmfs/syscalls.cpp

@@ -1306,7 +1306,28 @@ int __syscall_ioctl(int fd, int request, ...) {
   if (!openFile) {
     return -EBADF;
   }
-  if (!isTTY(openFile->locked().getFile())) {
+
+  va_list args;
+  va_start(args, request);
+  void* argp = va_arg(args, void*);
+  va_end(args);
+
+  auto openHandle = openFile->locked();
+  auto file = openHandle.getFile();
+
+  if (request == FIONREAD) {
+    off_t size = file->locked().getSize();
+    if (size < 0) {
+      return (int)size;
+    }
+    if (file->isSeekable()) {
+      size -= openHandle.getPosition();
+    }
+    *static_cast<int*>(argp) = static_cast<int>(size);
+    return 0;
+  }
+
+  if (!isTTY(file)) {
     return -ENOTTY;
   }
   // TODO: Full TTY support. For now this is limited, and matches the old FS.

test/codesize/test_codesize_hello_dylink_all.json

@@ -1,7 +1,7 @@
 {
-  "a.out.js": 244260,
+  "a.out.js": 244350,
   "a.out.nodebug.wasm": 577664,
-  "total": 821924,
+  "total": 822014,
   "sent": [
     "IMG_Init",
     "IMG_Load",

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 +8,34 @@
 
 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));
 
-  close(pipe_a[0]); close(pipe_a[1]);
+  // Slightly strange behavior here that we can use FIONREAD
+  // on either the read or the write end of the pipe and get
+  // the same result, but this matches linux.
+  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;
 }