Merge pull request #11343 from DeterminateSystems/no-framedsink-threads

withFramedSink(): Don't use a thread to monitor the other side

src/libutil/serialise.cc

@@ -10,6 +10,8 @@
 #ifdef _WIN32
 # include <fileapi.h>
 # include "windows-error.hh"
+#else
+# include <poll.h>
 #endif
 
 
@@ -158,6 +160,29 @@ bool FdSource::good()
 }
 
 
+bool FdSource::hasData()
+{
+    if (BufferedSource::hasData()) return true;
+
+    while (true) {
+        fd_set fds;
+        FD_ZERO(&fds);
+        FD_SET(fd, &fds);
+
+        struct timeval timeout;
+        timeout.tv_sec = 0;
+        timeout.tv_usec = 0;
+
+        auto n = select(fd + 1, &fds, nullptr, nullptr, &timeout);
+        if (n < 0) {
+            if (errno == EINTR) continue;
+            throw SysError("polling file descriptor");
+        }
+        return FD_ISSET(fd, &fds);
+    }
+}
+
+
 size_t StringSource::read(char * data, size_t len)
 {
     if (pos == s.size()) throw EndOfFile("end of string reached");