Initial project import

tools/v/vlib/os/signal.c.v

@@ -0,0 +1,45 @@
+module os
+
+#include <signal.h>
+
+// v_signal_with_handler_cast wraps signal() with a cast to avoid
+// clang -Werror=incompatible-function-pointer-types between
+// void (*)(os__Signal) and void (*)(int).
+#define v_signal_with_handler_cast(sig, handler) signal((sig), (void (*)(int))(handler))
+
+fn C.v_signal_with_handler_cast(signal i32, handlercb SignalHandler) voidptr
+
+// signal will assign `handler` callback to be called when `signum` signal is received.
+pub fn signal_opt(signum Signal, handler SignalHandler) !SignalHandler {
+	C.errno = 0
+	prev_handler := C.v_signal_with_handler_cast(int(signum), handler)
+	if prev_handler == C.SIG_ERR {
+		// errno isn't correctly set on Windows, but EINVAL is this only possible value it can take anyway
+		return error_with_code(posix_get_error_msg(C.EINVAL), C.EINVAL)
+	}
+	return SignalHandler(prev_handler)
+}
+
+// A convenient way to ignore certain system signals when there is no need to process certain system signals,
+// Masking of system signals under posix systems requires a distinction between main and background threads.
+// Since there is no good way to easily tell whether the current thread is the main or background thread,
+// So a global variable is introduced to make the distinction.
+
+// An empty system signal handler (callback function) used to mask the specified system signal.
+fn ignore_signal_handler(_signal Signal) {
+}
+
+// signal_ignore to mask system signals, e.g.: signal_ignore(.pipe, .urg, ...).
+pub fn signal_ignore(args ...Signal) {
+	if is_main_thread() {
+		// for main thread.
+		$if !windows {
+			for arg in args {
+				signal_opt(arg, ignore_signal_handler) or {}
+			}
+		}
+	} else {
+		// for background threads.
+		signal_ignore_internal(...args)
+	}
+}