1 files changed, 74 insertions, 0 deletions
diff --git a/src/shared/fdsignal.inc/eventfd.c b/src/shared/fdsignal.inc/eventfd.c
new file mode 100644
index 0000000..358d41c
--- /dev/null
+++ b/src/shared/fdsignal.inc/eventfd.c
@@ -0,0 +1,74 @@
+#include <sys/eventfd.h>
+#include <poll.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <unistd.h>
+
+/*
+ * Linux implementation of signals.
+ * Internally, eventfds are used for signalling, as they
+ * provide the least overhead. We don't allocate any struct
+ * ever, but cast the event fd+1 to dnbd3_signal_t*
+ * to save all the malloc() and free() calls.
+ */
+
+dnbd3_signal_t* signal_new()
+{
+	// On error, eventfd() returns -1, so essentially we return NULL on error.
+	// (Yes, NULL doesn't have to be 0 everywhere, but cmon)
+	return (dnbd3_signal_t*)(intptr_t)( eventfd( 0, EFD_NONBLOCK ) + 1 );
+}
+
+dnbd3_signal_t* signal_newBlocking()
+{
+	return (dnbd3_signal_t*)(intptr_t)( eventfd( 0, 0 ) + 1 );
+}
+
+int signal_call(const dnbd3_signal_t* const signal)
+{
+	if ( signal == NULL ) return SIGNAL_ERROR;
+	static const uint64_t one = 1;
+	const int signalFd = ( (int)(intptr_t)signal ) - 1;
+	return write( signalFd, &one, sizeof one ) == sizeof one ? SIGNAL_OK : SIGNAL_ERROR;
+}
+
+int signal_wait(const dnbd3_signal_t* const signal, int timeoutMs)
+{
+	if ( signal == NULL ) return SIGNAL_ERROR;
+	const int signalFd = ( (int)(intptr_t)signal ) - 1;
+	struct pollfd ps = {
+		.fd = signalFd,
+		.events = POLLIN
+	};
+	int ret = poll( &ps, 1, timeoutMs );
+	if ( ret == 0 ) return SIGNAL_TIMEOUT;
+	if ( ret == -1 ) return SIGNAL_ERROR;
+	if ( ps.revents & ( POLLERR | POLLNVAL ) ) return SIGNAL_ERROR;
+	return signal_clear( signal );
+}
+
+int signal_clear(const dnbd3_signal_t* const signal)
+{
+	if ( signal == NULL ) return SIGNAL_ERROR;
+	uint64_t ret;
+	const int signalFd = ( (int)(intptr_t)signal ) - 1;
+	if ( read( signalFd, &ret, sizeof ret ) != sizeof ret ) {
+		if ( errno == EAGAIN ) return 0;
+		return SIGNAL_ERROR;
+	}
+	return (int)ret;
+}
+
+void signal_close(const dnbd3_signal_t* const signal)
+{
+	const int signalFd = ( (int)(intptr_t)signal ) - 1;
+	close( signalFd );
+}
+
+int signal_getWaitFd(const dnbd3_signal_t* const signal)
+{
+	if ( signal == NULL ) return -1;
+	const int signalFd = ( (int)(intptr_t)signal ) - 1;
+	return signalFd;
+}
+