select()

2 files changed, 39 insertions, 2 deletions

diff --git a/src/library.js b/src/library.js
index 42eb951f..75a8a90a 100644
--- a/src/library.js
+++ b/src/library.js
@@ -7058,6 +7058,26 @@ LibraryManager.library = {
     return fd;
   },
 
+  select: function(nfds, readfds, writefds, exceptfds, timeout) {
+    // only readfds are supported, not writefds or exceptfds
+    // timeout is always 0 - fully async
+    assert(!writefds && !exceptfds);
+    var ret = 0;
+    var l = {{{ makeGetValue('readfds', 0, 'i32') }}};
+    var h = {{{ makeGetValue('readfds', 4, 'i32') }}};
+    nfds = Math.min(64, nfds); // fd sets have 64 bits
+    for (var fd = 0; fd < nfds; fd++) {
+      var bit = fd % 32, int = fd < 32 ? l : h;
+      if (int & (1 << bit)) {
+        // index is in the set, check if it is ready for read
+        var info = Sockets.fds[fd];
+        if (!info) continue;
+        if (info.bufferWrite != info.bufferRead) ret++;
+      }
+    }
+    return ret;
+  },
+
   // ==========================================================================
   // emscripten.h
   // ==========================================================================
diff --git a/tests/websockets.c b/tests/websockets.c
index 8a8a0919..57549e94 100644
--- a/tests/websockets.c
+++ b/tests/websockets.c
@@ -8,6 +8,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
+#include <assert.h>
 #if EMSCRIPTEN
 #include <emscripten.h>
 #endif
@@ -16,11 +17,25 @@
 
 int SocketFD;
 
+int not_always_data = 0;
+
 unsigned int get_all_buf(int sock, char* output, unsigned int maxsize)
 {
+  // select check for IO
+  fd_set sett;
+  FD_ZERO(&sett);
+  assert(select(64, &sett, NULL, NULL, NULL) == 0); // empty set
+  FD_SET(sock, &sett);
+  assert(select(0, &sett, NULL, NULL, NULL) == 0); // max FD to check is 0
+  int select_says_yes = select(64, &sett, NULL, NULL, NULL);
+
+  // ioctl check for IO
   int bytes;
-  if (ioctl(sock, FIONREAD, &bytes)) return 0;
-  if (bytes == 0) return 0;
+  if (ioctl(sock, FIONREAD, &bytes) || bytes == 0) {
+    not_always_data = 1;
+    return 0;
+  }
+  assert(select_says_yes); // ioctl must agree with select
 
   char buffer[1024];
   int n;
@@ -67,6 +82,8 @@ void iter(void *arg) {
     printf("sum: %d\n", sum);
 
 #if EMSCRIPTEN
+    assert(not_always_data == 1);
+
     int result = sum;
     REPORT_RESULT();
 #endif